Network Manager Reference Guide - Avaya...

Avaya MultiService Network Manager Reference Guide

April 2002

Avaya MultiService Network Manager Reference Guide

Copyright Avaya Inc. 2002 ALL RIGHTS RESERVED

The products, specifications, and other technical information regarding the products contained in this document are subject to change without notice. All information in this document is believed to be accurate and reliable, but is presented without warranty of any kind, express or implied, and users must take full responsibility for their application of any products specified in this document. Avaya disclaims responsibility for errors which may appear in this document, and it reserves the right, in its sole discretion and without notice, to make substitutions and modifications in the products and practices described in this document.

Avaya™, Cajun™, P550™, LANstack™, CajunView™, and SMON™ are trademarks of Avaya Inc.

ALL OTHER TRADEMARKS MENTIONED IN THIS DOCUMENT ARE PROPERTY OF THEIR RESPECTIVE OWNERS.

Release 3.012

Table of Contents

Preface . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . vi

Chapter 1 — LAN Protocols. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 1

Ethernet Standards . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1Ethernet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .1Fast Ethernet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2Gigabit Ethernet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2Power Over Ethernet . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2

Benefits Of PoE . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .2FDDI . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3Auto-Negotiation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3IP Multicast . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3

IP Multicast Filtering . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4IP Telephony . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .4

What is IP Telephony . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5Voice over IP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5

Benefits of VoIP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .5IP Telephony Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . .6

Chapter 2 — VLANs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7

Why Are They Called VLANs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .7When to Use VLANs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8Benefits of VLANs . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8

Security . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .8Bandwidth . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .9Configuration and Maintenance . . . . . . . . . . . . . . . . . . . . . . . . .9VIDP (VLAN Information Distribution Protocol) . . . . . . . . . . . . .9

VLAN Tagging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .10

Chapter 3 — ATM - Asynchronous Transfer Mode . . . . . . . . . . . . . . 11

Call Setup and Termination . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12Data Transfer . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12The ATM Cell . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12LAN Emulation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .12LAN Emulation Components . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .13

LEC . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .14LES . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15BUS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15LECS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15

Avaya MultiService Network Manager Reference Guide iii

Table of Contents

Connections . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .15Proprietary Redundant Services . . . . . . . . . . . . . . . . . . . . . . . . . . . .16

Redundant LES/BUS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16Distributed LES/BUS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .16Resilient LECS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17LEC to LES Assignment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .17

Chapter 4 — Routing, Bridging, and Switching . . . . . . . . . . . . . . . . 19

Routing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .19Bridging . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .21

Relaying and Filtering Frames . . . . . . . . . . . . . . . . . . . . . . . . . .22Advantages an\\d Disadvantages of Bridging . . . . . . . . . . . . . .23Spanning Tree Algorithm (STA) . . . . . . . . . . . . . . . . . . . . . . . .23

Switching Technology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25Switching vs. Routing and Bridging . . . . . . . . . . . . . . . . . . . . .25How Switching Works . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .25Benefits of Switching Technology . . . . . . . . . . . . . . . . . . . . . . .26Segment Switching . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .26Compatibility . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .27

Chapter 5 — Network Management Applications . . . . . . . . . . . . . . 28

Network Agents . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .28In-Band Transmission . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .29Side-Band Transmission . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .30Out-of-Band Transmission . . . . . . . . . . . . . . . . . . . . . . . . . . . .31

Switch Monitoring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .31RMON . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .32SMON . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .32

Port Mirroring . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .34Port Classification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .34Severity Degrees . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .34Link Aggregation Groups (LAGs) . . . . . . . . . . . . . . . . . . . . . . . . . . .36Policy Based Management . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .36

Rules . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .37QoS . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .37

DSCP . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .37Class of Service . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .38Trust . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .38

iv Avaya MultiService Network Manager Reference Guide

Table of Contents

Chapter 6 — Network Features . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39

Redundancy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .39Switching Redundancy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .39Port Redundancy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .40

Security . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .40Security Methods . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .40Security Nullification . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .40

Load Balancing . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .41Load Balancing Elements . . . . . . . . . . . . . . . . . . . . . . . . . . . . .42Load Balancing Applications . . . . . . . . . . . . . . . . . . . . . . . . . . .43

Firewall Load Balancing . . . . . . . . . . . . . . . . . . . . . . . . . . .43Server Load Balancing . . . . . . . . . . . . . . . . . . . . . . . . . . . .44Application Redirection . . . . . . . . . . . . . . . . . . . . . . . . . . .45

Persistency . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .46Load Balancing Metrics . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .47

Round Robin . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .47Hash . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .47MinMiss Hash . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .48

Chapter 7 — Glossary . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49

Index. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 65

Avaya MultiService Network Manager Reference Guide v

Preface

This Reference Guide is designed to provide general reference material on issues and technologies that are common to Avaya Inc.’s products. The Reference Guide includes the following chapters:

• LAN Protocols - Explains several types of protocols commonly used in LANs, including Ethernet and FDDI.

• VLANs - Explains VLANs, as well as their benefits and the VLAN Tagging method.

• ATM - Asynchronous Transfer Mode - Explains the ATM data transfer method, including a section on ELANs (Emulated LANs), and ELAN to VLAN association.

• Routing, Bridging, and Switching - Explains these three methods of routing data from source to destination.

• Network Management Applications - Describes several applications used in network management that are supplied or supported by Avaya Inc.’s hardware and software products. These include Network Agents, the RMON and SMON monitoring protocols, and several other items.

• Network Features - Describes redundancy and network security, as applied in a switched network environment.

• Glossary - A glossary of networking terms.

Avaya MultiService Network Manager Reference Guide vi

1

Avaya MultiService Netw

LAN Protocols

This chapter describes the following topics:

• Ethernet Standards - One of the most widely implemented LAN standards.

• FDDI - Mainly used in WAN (Wide Area Network) backbones.

• Auto-Negotiation - An Ethernet protocol for negotiating port speed and duplex mode between stations.

• IP Multicast - A method for efficient distribution of high-bandwidth applications, such as video conferencing.

• IP Telephony - A method for using IP as a medium for voice data.

Ethernet Standards

The Ethernet standards include standards for the following:

• Ethernet

• Fast Ethernet

• Gigabit Ethernet

• Power Over Ethernet

Ethernet

Ethernet is one of the most widely implemented LAN standards. It supports data transfer rates of 10 Mbps, and is therefore also known as 10 Base-T.

Ethernet uses the Carrier Sense Multiple Access with Collision Detection (CSMA/CD) access method to handle simultaneous demands. CSMA/CD is a multi-user network allocation procedure in which every station can receive the transmissions of every other station. Each station waits for the network to be idle before transmitting and each station can detect collisions by other stations.

ork Manager Reference Guide 1

Chapter 1

Ethernet is standardized as IEEE 802.3.

Fast Ethernet

Fast Ethernet is a newer version of Ethernet, supporting data transfer rates of 100 Mbps. Fast Ethernet is similar enough to Ethernet to support the use of most existing Ethernet applications and network management tools. Fast Ethernet is also known as 100 Base-T.

Fast Ethernet is standardized as IEEE 802.3u.

Gigabit Ethernet

Gigabit Ethernet is the newest version of Ethernet, supporting data rates of 1 Gbps. It is also known as 1000 Base-T.

Gigabit Ethernet is standardized as IEEE 802.3z.

Power Over Ethernet

A Power over Ethernet (PoE) module is a power injector add-on device that provides power to IP telephones over an Ethernet line. The power is transmitted via the device’s ports to the IP telephones over the same cable carrying the IP packets. There are currently two types of PoE adapters, a module jack or a hub-like device for multiple access points.

Avaya devices that support PoE automatically discover the connection and removal of IP telephones from the inline powered ports and provide power accordingly. The power is provided using an internal 225 watt power supply over a 48 volt feed. It is possible to attach external power as an alternative power supply, should the internal power supply fail.

In addition, you can configure power priorities per port ensuring that important equipment is guaranteed power whenever necessary.

Benefits Of PoE

Power over Ethernet modules provide the following benefits:

• Power over Ethernet modules can end wireless LAN installation costs. This is because installers only have to run a single Ethernet cable to each access point base station, instead of running separate power and data cables for each device.

• Power over Ethernet modules reduce installation complexity. Enterprises no longer need to employ electricians to install dedicated AC power lines to each access point in the network.

2 Avaya MultiService Network Manager Reference Guide

LAN Protocols

FDDI

FDDI (Fiber Distributed Data Interface) is a set of ANSI protocols for sending digital data over fiber optic cable. FDDI networks are token-passing networks that support data rates of up to 100 Mbps. FDDI networks are typically used as backbones for WANs.

FDDI-2, an extension to FDDI, supports the transmission of voice and video information as well as data. Another variation of FDDI, called FDDI Full Duplex Technology (FFDT), uses the same network infrastructure, but can potentially support data rates of up to 200 Mbps.

Auto-Negotiation

Auto-Negotiation is a protocol that runs between two stations. When enabled, Auto-Negotiation negotiates port speed and duplex mode by detecting the highest common denominator port connection for the endstations. For example, if one workstation supports both 10Mbps and 100Mbps speed ports, while the other workstation only supports 10Mbps, then Auto-Negotiation sets the port speed to 10Mbps.

For Gigabit ports, Auto-Negotiation determines the Flow Control configuration of the port.

IP Multicast

IP Multicast is a method of sending a single copy of an IP packet to multiple destinations. It can be used by different applications including video streaming and video conferencing.

The Multicast packet is forwarded from the sender to the recipients, duplicated only when needed by routers along the way and sent in multiple directions so that it reaches all the members of the Multicast group. Multicast addresses are a special kind of IP address (class D), each identifying a multicast group. Stations join and leave multicast groups using IGMP. This is a control-plane protocol through which IP hosts register with their router to receive packets for certain multicast addresses. In addition, routers support one or more multicast routing protocols (e.g., DVMRP, PIM) that construct multicast delivery trees on which the multicast traffic is forwarded.

Avaya MultiService Network Manager Reference Guide 3

Chapter 1

IP multicast packets are transmitted on LANs in MAC multicast frames. Traditional LAN switches flood these multicast packets like broadcast packets to all stations in the VLAN. In order to avoid sending multicast packets where they are not required, multicast filtering functions may be added to the Layer 2 switches, as described in the IEEE standard 802.1D (aka 802.1p). Layer 2 switches capable of multicast filtering send the multicast packets only to ports connecting members of that multicast group. This is typically based on IGMP snooping, GMRP, or CGMP.

IP Multicast Filtering

Some of Avaya Inc.'s device managers include a multicast filtering application. This application learns which switch ports need to receive which multicast packets. Based on IGMP snooping, the application then configures the necessary information into the switch's hardware tables. Using the learned information, IP multicast packets are forwarded only to ports connecting members of that multicast group.

The multicast filtering function in Avaya Inc.'s devices is transparent to the IP hosts and routers. Apart from filtering multicast packets from certain ports where they are not needed, it does not affect the forwarding behavior. Forwarding is performed for ports that get the multicast as if there was no filtering. The multicast packet will not be sent to any ports that do not receive it when there is no filtering.

The multicast filtering function operates per VLAN. A multicast packet arriving at the device on a certain VLAN will be forwarded only to a subset of the ports of that VLAN. If VLAN tagging mode is used on the output port, then the multicast packet will be tagged with the same VLAN number with which it arrived. This is interoperable with multicast routers that expect Layer 2 switching to be done independently for each VLAN.

Avaya Inc's IP multicast filtering applications currently support IGMP snooping for IGMP versions 1 and 2.

IP Telephony

This section provides information about IP telephony and includes the following topics:

• What is IP Telephony

• Voice over IP

• IP Telephony Components


LAN Protocols

What is IP Telephony

IP Telephony refers to the use of packet-switched connections to exchange voice, fax, and other forms of information that have traditionally been carried over the dedicated circuit-switched connections of the public switched telephone network (PSTN). Using the Internet, calls travel as packets of data on shared lines, avoiding the tolls of the PSTN. IP telephony is an important part of the convergence of computers, telephones, and television into a single integrated information environment. The challenge in IP telephony is to deliver the voice, fax, or video packets in a dependable flow to the user.

Voice over IP

Voice over IP (VoIP) is an organized effort to standardize IP telephony. VoIP is a set of facilities for managing the delivery of voice information using the Internet Protocol (IP). This means that voice information is sent in digital form in discrete packets rather than in the traditional circuit-committed protocols of the PSTN.

VoIP consists of several interconnected processes that convert a voice signal into a stream of packets on a packet network and back again. VoIP allows the human voice to travel simultaneously over a single packet network line with both fax information and modem data.

VoIP devices are positioned at the enterprise gateway. The gateway receives packetized voice transmissions from users within the company and then routes them to other parts of its intranet (LAN or WAN) or, using a T-carrier system or E-carrier interface, sends them over the PSTN.

Using public networks, it is currently difficult to guarantee Quality of Service (QoS). Better service is possible with private networks managed by an enterprise or by an Internet telephony service provider (ITSP).

Benefits of VoIP

VoIP provides rich benefits for networking equipment manufacturers, service providers, businesses, and home users.

• Avoiding the tolls charged by ordinary telephone service provides a more cost-effective traditional voice and fax service. Voice over packet transfer can significantly reduce the per-minute cost, resulting in reduced long-distance bills.


Chapter 1

• VoIP-based services revolutionized communications with new innovative applications such as web-enabled call centers, electronic whiteboarding, remote teleworking, and personal productivity applications such as “follow-me” services, unified message handling, interactive shopping (web pages incorporating a “click to talk” button), streaming audio, white-boarding, and CD-quality conference calls in stereo.

IP Telephony Components

The heart of the IP telephony system is a Media Gateway. The Media Gateway is a VoIP system that acts as an IP PBX and messaging server and a VoIP gateway. In addition, it performs the function of a gatekeeper and an IP media management resource for tone detection and generation, conferencing, and call classification. IP telephones connect to a Media Gateway using IP network connections.

Media Gateway components are controlled through a Media Gateway Processor (MGP). The MGP detects when a media module is inserted or removed and transfers information from the VoIP engine to the other components.

Avaya’s implementation of IP telephony converges the power of Avaya Call Processing (ACP) software with the power of distributed switching. It provides IP PBX functionality using open standards and an open operating system.


2


VLANs

A VLAN is made up of a group of devices on one or more LANs that are configured (using management software) to operate as if they form an independent LAN, when in fact they may be located on a number of different LAN segments. VLANs can be used to group together departments and other logical groups, to reduce network traffic flow and increase security within the VLAN.

The figure below illustrates how a simple VLAN can connect several endpoints from different locations that are attached to different hubs. In this example, the Management VLAN consists of stations on numerous floors of the building which are connected to both Device A and Device B.

Figure 2-1. VLAN

Why Are They Called VLANs

Until recently, only real topological networks existed. A topological network is called real when the devices reside on the same physical network segment.

LAN 2 LAN 3Bridge 2

Device B

Device A

Management LAN

R&D LAN

R&D LAN

ManagementVLAN


Chapter 2

In virtual topological networks, the network devices may be located in diverse places around the LAN, such as in different departments, on different floors, or in different buildings. Connection is achieved through software. Each network device is connected to a hub, and the network manager uses management software to assign each device to a virtual topological network. Elements can be combined into a VLAN even if they are connected to different devices.

When to Use VLANs

Use VLANs whenever you want to separate one or more groups of network users from the rest of the network. Separating groups of users has several benefits:

• Increased security. For example, organizing the finance department into a VLAN prevents users in other departments from accessing the finance files.

• Division of traffic among network resources. For example, consider a network with three application servers and thirty users. By assigning ten users and one application server to each of three VLANs, network traffic is more evenly distributed, decreasing the chances of overload.

Benefits of VLANs

The following are some benefits of using VLANs:

• Increased security

• More bandwidth

• Easier configuration and maintenance

• Use of VIDP

Security

VLAN switching provides absolute security between the various VLANs. It is impossible for an element connected to one VLAN to directly access an element connected to another VLAN.


VLANs

Bandwidth

Packets that are broadcast on a VLAN, instead of being directed via switching, are sent only to destinations on that VLAN, minimizing the negative bandwidth effects of general broadcasting.

Configuration and Maintenance

VLANs offer independence from the physical limitations that plague conventional networks. This independence leads to an ease of network configuration and maintenance. A network manager can quickly and easily create, delete, and edit VLANs from Avaya's management software.

The use of VLANs completely changes network maintenance, and is the only practical way of handling dynamic and growing networks.

VIDP (VLAN Information Distribution Protocol)

VIDP is Avaya Inc.'s proprietary protocol to distribute VLAN information between Avaya P110 and Avaya M770 Devices. It allows stations in the same VLAN on different switches to communicate as if they were on the same bridged LAN. VIDP allows any Avaya P110 or Avaya M770 Device port to be used as an inter-switch connection that supports VLANs.

For proper operation of VIDP:

• No Cajun M400 Device may exist in the network, only Avaya P110 and Avaya M770 Devices.

• VIDP should be supported and enabled on all devices. (This is done in the Agent Configuration dialog box.)

• VLAN 0 should not be configured on switch ports. VLAN 0 should be removed from the VLAN list before enabling VIDP.

• If there is an Avaya P110 Device in the network, VIDP will only be supported if a Avaya P110 agent exists.

* Note: Other tagging schemes, such as 802.1Q, proprietary ISL, and ELAN to VLAN association, do not interfere with the proper functioning of VIDP.


Chapter 2

VLAN Tagging

VLAN Tagging controls the distribution of information on the network. The ports on devices supporting VLAN Tagging are configured with the following parameters:

• Port VLAN ID

• Tagging Mode

Port VLAN ID is the number of the VLAN to which the port is assigned. Untagged frames (and frames tagged with VLAN 0) that enter the port are assigned the port's VLAN ID. Tagged frames are unaffected by the port's VLAN ID.

The Tagging Mode determines the behavior of the port that processes outgoing frames. If Tagging Mode is set to Clear, the port only transmits frames that belong to the port's VLAN. These frames leave the device untagged. This mode is also known as Bind to Port VLAN ID.

If Tagging Mode is set to IEEE-802.1Q, all frames tagged with a VLAN ID between 1 and 3071 are transmitted. The frames keep their tags when they leave the device. This mode is also known as Bind to All.


3


ATM - Asynchronous Transfer Mode

ATM is an international standard for cell relay in which multiple service types (such as voice, video, and data) are conveyed in fixed-length (53-byte) cells. The constant and relatively small cell size allows ATM equipment to transmit video, audio, and computer data over the same network with an efficient allocation of network resources. Constant cell size also allows cell processing to occur in hardware. This reduces transit delays.

ATM is largely used today in high speed backbones for existing Ethernet and Token Ring LANs (refer to the figure below). The key to adding ATM to an existing network is LAN Emulation (LANE), an ATM Forum standard that makes an ATM backbone look like a high speed extension of the existing network.

Figure 3-1. ATM Backbone Network

ATM Backbone

MarketingLAN

AccountingLAN

EngineeringLAN

Sales LAN


Chapter 3

Call Setup and Termination

To initiate an ATM connection, the sending station sends a signalling packet to a switch. This signalling packet establishes a Virtual Channel between the two points. The switch then forwards the packet to another switch, establishing another Virtual Channel. This process repeats itself until the packet reaches the endpoint. The Virtual Channels together constitute a Virtual Path (also known as a Virtual Connection, Virtual Circuit, and Switched Virtual Circuit (SVC)). Data transfer takes place only after a Virtual Path is established.

Alternatively, a Permanent Virtual Connection (PVC) can be set up between two endpoints. A PVC uses a Virtual Path that is established with the help of an external mechanism, usually a network management system. Since PVCs require some manual configuration, they can be cumbersome. Therefore, they are not frequently used.

Once data transfer is complete, the sender sends a signalling packet to tell the network that the connection is no longer needed. The signalling packet travels along that Virtual Path, closing all the Virtual Channels.

Data Transfer

Once a Virtual Path is established, the data to be sent is put into fixed-size cells which are sent over the Virtual Path to the endpoint.

The ATM Cell

ATM data transfer uses fixed-sized cells consisting of 53 bytes. Of these, 48 bytes are the Cell Payload into which the user data to be transferred is placed, and 5 bytes are the Cell Header. The Cell Header carries the information required for the network to switch it along the appropriate Virtual Path.

LAN Emulation

The purpose of LAN Emulation (LANE) is to allow existing LAN clients to send data over ATM backbones and to communicate with ATM-based resources without requiring any change in the LAN-based clients.



An emulated LAN provides communication of user data frames among all its users, similar to a physical LAN. The LAN Emulation service essentially hides the ATM network from the LAN clients by emulating LAN behavior, so that LAN-based devices can continue to use LAN-based protocols. It does this by specifying the interfaces and protocols needed for providing LAN-supported functionality and connectivity in an ATM environment.

An emulated LAN enables legacy LANs to communicate across a high-speed ATM backbone without having to modify existing applications or infrastructure. It also enables legacy end-stations to access ATM-attached servers, routers, and other devices. Emulated LANs also enable end-to-end ATM applications to run legacy LAN protocols and applications.

Emulated LANs do not mix media. For example, an Ethernet client cannot communicate with a Token Ring server. This level of connectivity must be provided by a router. Multiple Emulated LANs can exist on the same physical LAN, but routers are required to provide connectivity between Emulated LANs.

LAN Emulation Components

The following are the basic LAN Emulation components:

• LEC - LAN Emulation Client

• LES - LAN Emulation Server

• BUS - Broadcast and Unknown Server

• LECS - LAN Emulation Configuration Server


Chapter 3

The figure below illustrates the interaction between the various LAN Emulation components.

Figure 3-2. Emulated LAN

LEC

The LEC resides in end systems and performs data forwarding, address resolution, and other control functions. The LEC provides the station with an interface to the ATM network and performs most of the work of LAN Emulation; it provides 802.3 or 802.5 emulation for higher level protocols, and performs Segmentation and Reassembly (SAR), which converts between the 1.5KB Ethernet and 16KB Token Ring frames, and 53-bytes ATM cells.

The LEC communicates with other LANE services to register itself on the network, find out about the services on the network, convert MAC addresses into ATM addresses, and support broadcasts and multicasts.

Every server and workstation on an ELAN has a LEC software component running it, and every LEC has a LAN address and an ATM address associated with it. When the network operating system passes a frame to a LEC for transmission, the LEC verifies that it already has a connection set up to that frame's LAN destination address.

ATM Network

LEC

LEC

LESLECS

BUSLEC

LEC

LEC



LES

The LES maintains a list of all the active LECs on the ELAN, together with their MAC addresses and ATM addresses. There should only be one active LES/BUS, which may be part of a distributed LES, per ELAN.

When a new LEC attaches to the network, it registers with the LES and provides its MAC and ATM addresses. The LES provides address resolution by acting as a look-up table, enabling LECs to find out the ATM address of another LEC with a specified MAC address.

BUS

The BUS is generally part of the same software module as the LES. The BUS creates a connection to every LEC on the network. It handles data sent by a LEC to the broadcast MAC address and all multicast traffic. Broadcasts are sent out to every LEC on the network, whereas multicasts are only sent to clients that are registered to receive that multicast. The BUS also receives all packets for which the LES is unable to look up the ATM address of the recipient.

LECS

The primary function of the LECS is to provide configuration information to LECs, such as the addresses of LESs and the ELANs they should join. There should be one active LECS on an ATM network.

When a LEC joins the network, it sends a request to the LECS to find the ATM address of the LES. The LEC then registers itself with the LES, and uses the LES to look up the ATM address of other LECs.

The LEC obtains the ATM address of the LECS by using an Interim Local Management Interface (ILMI) request. Alternatively, the LECS can have a Well-Known Address (WKA), or the network manager can set up a Permanent Virtual Circuit (PVC) between every client and the LECS to enable the clients to find it.

Connections

The LEC establishes point-to-point bi-directional connections to the LECS, LES, and BUS. It receives point-to-multipoint connections from the LES and BUS. The LEC then establishes direct connections to the LECs identified by the LES.


Chapter 3

Proprietary Redundant Services

Some of Avaya Inc.'s devices, for example, the Avaya M770 ATM Device, support proprietary redundant LAN Emulation services, including Redundant and Distributed LES/BUS and Resilient LECS.

Redundant LES/BUS

A redundant LES and BUS requires an Avaya M770 LECS and two or more Avaya M770 LES/BUS implementations. The idea is that the LECS knows about all of the LESs that can support a particular ELAN. One of these LESs will be “active” and the remainder “standby”. In the event that the active LES/BUS fails, all LECs are directed to the next available standby LES.

Distributed LES/BUS

This is a proprietary system for a distributed LES/BUS in advance of implementing LAN Emulation version two. A single ELAN can be distributed over multiple LES/BUS pairs. Each LEC connects to a single LES/BUS, but these could be any of the LES/BUS pairs supporting the ELAN. In the Avaya M770 ATM Device, each module can support up to 16 LES/BUS pairs. Therefore, in each Avaya M770 ATM Device, there can be multiple LES/BUS pairs for the same ELAN on the same switch.

The distributed LES/BUS supports:

• Up to 2,500 LECs per ELAN.

• Up to 10 LES/BUS pairs per ELAN.

• Any ATM Forum-compliant LEC.

Distributed LES/BUS requires an Avaya M770 LECS, LES, and BUS.



Resilient LECS

Resilient LECS discover each other using a proprietary advertisement mechanism. A generic element protocol is then used to choose one LECS to be active, the remainder being standby. The LECS with the highest priority (configurable parameter) becomes active. If two or more LECS have the highest priority, the election is resolved by ATM address (host address). However, when recovering from a failure, or when bringing up a LECS in an Avaya M770 ATM Device in an already functioning network, the election process uses LECS uptime to determine the active LECS. The purpose of this is to minimize network disruption. If there is already a functioning LECS, there is no need to disable it and move functionality to another LECS. This helps keep the network stable.

* Note: It is possible to have one resilient LECS advertising its services at the WKA should it be elected, and another at a normal switch address.

Each LECS must have its ELAN information configured separately, and they must be consistent. There is no automatic checking of database consistency between LECS. The database information is located in the LECS ELANs Table.

LEC to LES Assignment

With a distributed LES, the LECS may have several different possible LESs for a particular ELAN, so it must decide which one to give to the LEC. There are three methods by which the LECS can assign a LEC to a LES:

• Equal Distribution (round robin) - Each LES address is used in turn.

• Shortest Path (longest address match) - The LES address supplied is the one which best matches the ATM address of the LEC (and it should also be the “nearest” LES in many cases, especially if a hierarchical addressing scheme is used).

• Group LES Address - Every LES uses the same address. When a LEC requests that ELAN, it is given the “common” address of the LESs. The LEC connects with the “nearest” switch via routing.

Equal Distribution is the default because it will normally guarantee an even spread of clients among all possible LESs. However, it is preferable in some cases to use Shortest Path or Group LES Address.


Chapter 3

Group LES Address usually gives the fastest recovery time. If a LES fails, it normally takes the LECS at least 90 seconds to time out on the address of this LES. If the scheme used is Shortest Path, any clients applying to join the ELAN during this period will be directed to the failed LES address. However, if the scheme is Group LES Address, then the address is still valid, and an active LES will be found as soon as PNNI reconfigures the routing tables. If the ELAN is configured for Equal Distribution, then the recovery time is unpredictable, and may be faster or slower.


4


Routing, Bridging, and Switching

This chapter discusses three common methods for transmitting data between and within networks:

• Routing - Routing uses a device called a router to transmit data by determining optimal routing paths and transmitting data packets through an internetwork.

• Bridging - Bridging uses a device called a bridge to transmit data by relaying frames from port to port, filtering out duplicate frames.

• Switching - Switching routes data packets directly to destination ports, allowing for simultaneous active communication. Switching technology is the cornerstone of Avaya Inc.'s high speed connectivity solutions.

Routing

Routing moves a packet of data from source to destination using a device called a router. Routing involves two basic activities: determination of optimal routing paths and transmission of information packets through an internetwork.

Routers use routing tables to determine the routes to particular network destinations and, in some cases, metrics associated with those routes. Routers communicate with one another and maintain their routing tables through the transmission of a variety of messages.

The Routing Update Message is one such message. Routing Updates generally consist of all or a portion of a routing table. By analyzing Routing Updates from all routers, a router can build a detailed picture of network topology.


Chapter 4

A Link-State Advertisement is another example of a message sent between routers. Link-State Advertisements inform other routers of the state of the sender's links. Link information can also be used to build a complete picture of the network's topology. Once the network topology is understood, routers can determine optimal routes to network destinations.

When a router receives a packet, it examines the packet's destination protocol address. The router then determines whether it knows how to forward the packet to the next hop. If the router does not know how to forward the packet, it typically drops the packet. If the router knows how to forward the packet, it changes the packet destination’s physical address to that of the next hop and transmits the packet.

The next hop may or may not be the ultimate destination host. If not, the next hop is usually another router, which executes the same switching decision process. As the packet moves through the internetwork, its physical address changes but its protocol address remains constant. This process is illustrated in the figure below.

Figure 4-1. Routing

Table 4-1. Routing Table

Network ID Next Hop

41 Node A

36 Node B

20 Node C

15 Node B

Destination

First HopProtocol Address: DestinationPhysical Address: Router 1

Router 1 Second HopProtocol Address: DestinationPhysical Address: Router 2

Router 2

Third HopProtocol Address: DestinationPhysical Address: Destination

Source



Routing is often confused with bridging, which performs a similar function. The principal difference between the two is that bridging occurs at a lower level and is therefore more of a hardware function, whereas routing occurs at a higher level where the software component is more important. Because routing occurs at a higher level, it can perform more complex analysis to determine the optimal path for the packet.

Bridging

Bridging moves data packets from source to destination. It is performed by a device called a bridge.

Bridges forward data from one station to another with no alteration of the original LAN frame. End-stations, such as workstations, file servers, and printers, communicate directly and transparently across bridges, as if they are on a single LAN. The LAN frame that is generated by the originating station is automatically passed to the destination station regardless of whether there are bridges in between. The bridges dynamically learn the addresses of the end stations so that, unlike repeaters, they forward only those frames that are not addressed to a station on the same network segment.


Chapter 4

Relaying and Filtering Frames

A bridge relays individual user data frames between the separate MAC addresses of the bridged LANs connected to its ports. The order of frames of a given user priority received on one port and transmitted on another is preserved.

Figure 4-2. Relaying Frames

Transmitting Station Receiving Station

Address Table

Bridge The source anddestination portsare different.



A bridge filters frames. This means that it does not relay frames received by a bridge port to other ports on that bridge in order to prevent the duplication of frames. Frames transmitted between a pair of end stations can be confined to LANs that form a path between those end stations.

Figure 4-3. Filtering Frames

Advantages an\\d Disadvantages of Bridging

The primary advantage of Bridging is that since it operates at the Data Link Layer (Layer 2) of the OSI reference model, it is transparent to the upper layers. Thus, bridges do not have to examine upper-layer information and they can rapidly forward traffic representing any network-layer protocol. It is not uncommon for a bridge to transmit AppleTalk, DECnet, TCP/IP, XNS, and other traffic between two or more networks.

On the other hand, because bridging takes place at a lower level, it cannot always determine the optimal path for the packet. In contrast, routing, which takes place at a higher level than bridging, can perform more complex analysis to determine optimal paths.

Spanning Tree Algorithm (STA)

The Spanning Tree Algorithm ensures the existence of a loop-free topology in networks that contain parallel bridges. A loop occurs when there are alternate routes between hosts. If there is a loop in an extended network, bridges may forward traffic indefinitely, which can result in increased traffic and degradation of network performance.

Transmitting Station Receiving Station

Packet is sent directly to the receiving station.

Address Table

Bridge

Destination port isthe same as sourceport. Bridge discardsthe packet.


Chapter 4

The Spanning Tree Algorithm:

• Produces a logical tree topology out of any arrangement of bridges. The result is a single path between any two end-stations on an extended network.

• Provides a high degree of fault tolerance. It allows the network to automatically reconfigure the spanning tree topology if there is a bridge or data-path failure.

The figure below illustrates the function of the Spanning Tree Algorithm. Without STA, a frame from the Source station to the Destination station would be forwarded from LAN 1 to LAN 2 over Bridge 1. From LAN 2 to LAN 3, the frame could be forwarded over either Bridge 2 or Bridge 3. If the frame is forwarded over Bridge 2, LAN 3 could then forward the frame over Bridge 4 to LAN 4. However, LAN 3 could also forward the frame over Bridge 3 back to LAN 3, which would then forward the frame back over Bridge 2 to LAN 3, and back again creating an indefinite loop.

STA ensures that there is a fixed path from the Source to the Destination, thereby ensuring that the frame will travel over Bridge 2 or Bridge 3, but not both. STA is also flexible enough to deal with topology changes in the network. For example, if the fixed path from the Source to the Destination includes Bridge 2, and Bridge 2 goes out of service, the STA will adopt a new path that includes Bridge 3.

Figure 4-4. Bridged Network with Parallel Bridges

The Spanning Tree Algorithm requires five values to derive the spanning tree topology. These are:

• A multicast address specifying all bridges on the extended network. This address is media-dependent and is automatically determined by the software.

• A network-unique identifier for each bridge on the extended network.

• A unique identifier for each bridge/LAN interface (port).

Bridge 1

LAN 1 LAN 2 LAN 3

Bridge 2 Bridge 4

LAN 4

Source Destination

Bridge 3

LAN 5



• The relative priority of each port.

• The cost of each port.

After these values are assigned, bridges multicast and process the formatted frames (called Bridge Protocol Data Units, or BPDUs) to derive a single, loop-free topology throughout the extended network. The bridges exchange BPDU frames quickly, minimizing the time that service is unavailable between hosts.

Switching Technology

Switching technology - used to solve bandwidth limitations introduced by other LAN technologies - is the cornerstone of Avaya Inc.'s high speed connectivity solutions.

Switching vs. Routing and Bridging

In the past, problems with bottlenecks and limited bandwidth in LANs were solved by dividing LANs into separate LAN segments using bridges and routers. But this increases cost and complicates networks, making them more difficult to manage.

Switching technology can now be used to overcome bandwidth problems simply, easily, and at low cost.

How Switching Works

Traditional Ethernet LANs use broadcasting to transmit information packets. In broadcasting, every port on the network receives the packet being sent, though only the port with the proper address passes it on to the user. Because of this, when any one port is transmitting, no other ports can transmit.

Switching technology routes packets directly to destination ports, allowing simultaneous active communication.


Chapter 4

The figure below shows a simple example of a switched network architecture in which each device contains four switch modules. The switches route packets from one switch to another and from one device to another. In this way, a packet can be routed directly from any module to any other module in the network. Failure of a module does not effect any other module.

Figure 4-5. Switched Network Topology

Benefits of Switching Technology

Switching increases the LAN speed and efficiency by providing dedicated lines between endpoints. By establishing these direct lines and being able to change them instantly, switches manage traffic, increase network flexibility, enhance performance and ease network moves, additions and changes.

Aggregate bandwidth and productivity increase as a result of the multiple simultaneous connections that are capable through the switch fabric. With their inherent flexibility, switches enable a scalable, dedicated network and promise a migration path to ATM-cell switching.

Segment Switching

Dynamic Segment Switching is a highly cost effective solution to multisegment LANs with differing bandwidth requirements.

BackboneLink

Device 2Device 1



Avaya Inc.'s switching modules allow high bandwidth data transfer within and between LANs. However, not all the devices connected to the switch require the full bandwidth of up to 100 Mbps. By using segment switching, each switch port is able to connect to an entire network segment to support the full range of bandwidth requirements.

Compatibility

• ATM - Avaya Inc.'s switch architecture is based on ATMcompatible cell-relay technology. This will allow for the integration of ATM technology when it matures as the standard.

• Existing LANs - Switching technology integrates smoothly with existing LANs.


5


Network Management Applications

This chapter describes several of the network management applications supplied or supported by Avaya Inc. These include:

• Network Agents - Agents are Avaya modules that send detailed system information to designated management stations and enable comprehensive system management.

• Switch Monitoring - The RMON monitoring standard, as expanded by Avaya's SMON technology, enables network managers to view comprehensive network data in a simple, topdown display.

• Port Mirroring - Port Mirroring copies all packets received and transmitted by a port to a predefined destination port.

• Port Classification - Port Classification allows the network manager to specify a level of importance for each port. This lets the system adjust alarm degrees to the port's defined level of importance.

• Severity Degrees (UNIX and NT-OV Only) - Severity Degrees enable the network manager to assign individual severity levels to each type of system port, on a per-hub basis.

• Link Aggregation Groups (LAGs) - Link Aggregation Groups enable you to link a group of ports so that they act like a single port.

• Policy Based Management - Policy based management enables you to prioritize network traffic by creating policies with rules on how to forward traffic based on packet source, destination, and QoS tags.

Network Agents

Network Agents are responsible for managing devices. Network Agents enable such management features as statistical reporting, configuration information, trap reporting, and multi-protocol support.

Network Agents send messages and alarms to Managers, workstations that are on the Agent's Manager list. Any SNMP management console can be a Manager. Alarms are not sent to any other workstations.



Network Agents can communicate with their Managers in the following ways:

• In-Band Transmission

• Side-Band Transmission

• Out-of-Band Transmission

A Network Agent can use more than one transmission method simultaneously. Refer to the appropriate Agent Installation Guide for details on installing and configuring that Agent.

In-Band Transmission

In-band transmission uses the same frequencies or channels normally used for information transmission on the network. You can configure several alternative routes for transmission of management data, depending on the particular Agent. The Agent then selects the route it will use when it is ready to transfer data. The figure below illustrates an example of in-band transmission.

Figure 5-1. In-Band Transmission

SB

NM

A-R

S

Ethernet Bus 3

Ethernet Bus 2

Ethernet Bus 1


Chapter 5

Side-Band Transmission

Side-band transmission uses a direct connection that bypasses the frequencies and channels normally used for information transmission. The side-band connection for Avaya Network Agents lets the Agent transmit information to an external Ethernet segment, and then on to the Managers. A typical application would be to dedicate a separate external network to management, while freeing up the internal segments for data only. The figure below illustrates an example of side-band transmission.

Figure 5-2. Side-Band Transmission

SB

NM

A-R

S



Out-of-Band Transmission

Out-of-band transmission uses SLIP (Serial Line Internet Protocol), thereby bypassing the frequencies and channels normally used for information transfer. Unlike side-band transmission, out-of-band transmission requires a modem. The figure below illustrates an example of out-of-band transmission.

Figure 5-3. Out-of-Band Transmission

Switch Monitoring

Switches are often used in networks with complex topology. Switches are typically deployed either at the center of a network between clients and servers, or in backbones to provide high bandwidth and to secure connectivity.

Effective switch management requires a comprehensive monitoring mechanism. This section discusses the RMON and SMON monitoring standards.

RMON, the internationally recognized network monitoring standard, is a network management protocol that allows network information to be gathered at a single workstation. RMON probes can only be used to monitor and analyze a single segment. When you deploy a switch in the network, there are additional components in the network that cannot be monitored using RMON, such as switch fabric, VLANs, and statistics for all ports.

SB

NM

A-R

S

Modem


Chapter 5

SMON is Avaya Inc.'s proprietary switch monitoring technology. SMON extends the RMON standard to provide the additional switch monitoring tools and features that the network administrator needs to analyze the switched network and all of its components.

SMON provides the basis for top-down network monitoring. Top-down monitoring begins when the network manager notices particular traffic flow patterns in a global view of the network. The network manager can progressively focus in and find the specific source or sources of the traffic. Using this method, the amount of information the network manager must assess is kept to a minimum. Top-down monitoring is robust enough to enable control of even the most complex and sophisticated networks.

RMON

RMON is the internationally recognized and approved standard for detailed analysis of shared Ethernet and Token Ring media. It ensures consistency in the monitoring and display of statistics between different vendors.

RMON's advanced remote networking capabilities provide the tools needed to monitor and analyze the behavior of segments on a network. In conjunction with an RMON agent, RMON gathers details and logical information about network status, performance, and users running applications on the network.

RMON has two levels:

• RMON I analyzes the MAC layer (Layer 2 in the OSI seven-layer model).

• RMON II analyzes the upper layers (Layers 3 and above).

An RMON agent is a probe that collects information about segments, hosts, and traffic, and sends it to a management station. The network administrator uses specific software tools to view the information collected by the RMON agent on the management station.

SMON

SMON is an extension of the RMON standard. SMON adds to the monitoring capabilities of RMON in the following ways:

• It provides additional tools and features for monitoring in the switch environment.



• It allows monitoring of ATM networks that are based on cells rather than packets.

• It provides a global view of traffic flow in a network with multiple switches.

SMON monitoring provides a global view of traffic for all switches on the network, an overall view of traffic passing through a specific switch, detailed data of the hosts transmitting packets or cells through a switch, an analysis of traffic passing through each port connected to a switch, and a view of traffic between various hosts connected to a switch.

SMON extends both RMON I for the MAC layer, and RMON II for the network layer and above. SMON monitoring collects and displays data in real-time.

Figure 5-4. SMON Monitoring


Chapter 5

Port Mirroring

Port Mirroring copies all received and transmitted packets (including local traffic) from a source port to a predefined destination port, in addition to the normal destination port of the packets. Port Mirroring, also known as “sniffing”, is useful in debugging network problems.

Port Mirroring enables the network manager to define a source port and a destination port, regardless of port type. For example, a 10Mbps and a 100Mbps port can form a valid source/destination pair. In addition, it allows a single pair of ports in the switch to be defined as a port duplicate pair. The network manager cannot, however, define the Port Mirroring source and destination ports as the same port.

Port Classification

Avaya Inc.’s network management applications allow the network manager to specify each port's level of importance. In most applications, the network manager specifies the port's level of importance in the Port Classification field of the Port Configuration dialog box. Ports are classified as follows:

• Backbone - hub or switch connections (most important)

• Valuable - servers or critical users (less important)

• Regular - normal users (least important)

The importance of a port is reflected in its status change in response to a fault. For example, if a port is classified as Backbone and is missing a physical link, the port's icon appears red. When the same port is classified as Regular, the port's icon appears yellow.

Severity Degrees

Severity degrees can only be assigned in a UNIX environment or when running NT-OV in a Windows NT environment.

The network manager can assign an individual severity level to each type of system fault. The network manager can also assign specific security levels to fault types on specific hubs.



Every object on the network (e.g., ports, modules, etc.) is represented in Chassis View by a symbol. When a fault occurs, the color of the symbol that represents the object in which the fault occurred changes to indicate that a fault exists. The color depends upon the fault's severity setting. The following table shows the relationship between the severity degree, object status, and symbol colors in Chassis View.

Avaya network management applications, using Avaya's Event Configuration application, let network managers set fault severity degrees system-wide (for all hubs on the network simultaneously) or for one hub at a time (per IP). If the system-wide setting and an individual hub's setting conflict, the individual hub's setting takes precedence.

Some faults include the port's classification in their definition. For example, there are different faults defined for “Connection Lost”: one for a regular port, one for a valuable port, and one for a backbone port. This lets the network manager define the fault severity according to the type of port. This can be used to define more significant warnings for more important ports. For example, a fault occurring on a port connected to a server is more important than a port connected to a general user. The network manager can define the server as a valuable port and the general user as a regular port. Then, the network manager can define the severity of a particular fault for a regular port as “Warning” and for a valuable port as “Critical”.

Table 5-1. Severity Degrees, Object Status, and Colors

Severity Degree Object Status Symbol Color

Normal OK

Info

Green

Warning

Minor

Warning

Error

Yellow

Major

Critical

Fatal Red


Chapter 5

Link Aggregation Groups (LAGs)

A LAG uses multiple ports to create a high bandwidth connection with another device. For example, assigning four 100BaseT ports to a LAG on each of two Avaya P130 switches allows the switches to communicate at an effective rate of 400 Mbps. LAGs provide a cost-effective method for creating a high bandwidth connection. LAGs also provide built-in redundancy for the ports that belong to a LAG. If a port in a LAG fails, its traffic is handled by another port in the LAG.

To create a LAG, a base port must be selected. The behavior of the LAG is derived from the base port. The attributes of the base port, such as port speed, VLAN number, etc., must be applied to the other ports in the LAG.

Policy Based Management

Policy-Based Management is one of the newest and fastest growing trends in network management. Network managers can control network traffic by applying rules to packets, based on the packets' classification, application, source, and destination.

Policy Management allows network managers to implement forwarding and routing based on policies and rules, and focus on Quality of Service (QoS). For example, you can define a set of rules that states, “packets from the R&D department to the marketing department are forwarded with a lower priority than packets from the R&D department to the development team”.

Policies determine the actions taken on network traffic entering a module. A policy is a set of rules governing the forwarding of information packets on a module.



Rules

Rules are the building blocks of policies. Rules provide the information about how the module forwards a defined data packet. A module can forward packets with a priority of 0 to 7, permit the packets to pass as is, or block the passage of the packet, optionally sending a message to the module's manager.

A rule includes the following information:

• A description of the packets to which the rule applies.

• The action to perform on the described packets.

• Whether or not the rule is mandatory.

For example, you can define a rule as “FTP packets from IP address 143.32.1.2 to subnet 145.7.0.0 must be forwarded with a priority 4”.

• Packet Description - “FTP packets from IP address 143.32.1.2 to subnet 145.7.0.0”.

• Mandatory - “Must be”.

• Action - “Forwarded with Priority Level 4”.

QoS

Packets tagged using either DSCP (Differential Service Code Point) or CoS (Class of Service) tags, can be given QoS (Quality of Service) levels based on their tags. This ensures proper handling of real time, mission critical, and high-priority network traffic.

DSCP Differential Service Code Point (DSCP) provides a method of tagging IP packets with priority information.

A DSCP value between 0 and 63 is added to the IP header of data packets. The DSCP Mapping table allows you to configure the correlation of DSCP priorities to QoS levels. DSCP values 0-63 are assigned a QoS level between 0 and 7, where zero is the lowest priority and seven is the highest.


Chapter 5

Class of Service

Class of Service (CoS) is the 802.1p priority scheme used to provide a method of tagging packets with priority information.

A CoS value between 0-7 is added to the Layer II header of the data packets. Zero is the lowest priority and seven is the highest.

CoS tags can be used in rules to determine the priority with which to forward packets.

Trust A data packet can contain conflicting priority information. A DSCP tag may give a packet a very high priority, while the CoS tag may give the same packet a very low priority.

Trust determines the QoS scheme used for packets entering a module. Each module has its own Trust settings. There are four possible Trust settings:

• DSCP Value - Only the packet’s DSCP tag. If a packet entering a module matches no rules, or matches a rule with a permit operation, the packet will be forwarded with a priority based on the DSCP Mapping of the packet’s DSCP tag.

• CoS Priority - Only the packet’s CoS tag. If a packet entering a module matches no rules, or matches a rule with a permit operation, the packet will be forwarded with the priority in the packet’s CoS tag.

• Untrust - Both DSCP tags and CoS priority tags are ignored. If a packet entering a module matches no rules, or matches a rule with a permit operation, the packet will be forwarded with the default priority.

• Both - Both DSCP tag and CoS priority tags are used. If a packet entering a module matches no rules, or matches a rule with a permit operation, the packet’s DSCP priority (based on the DSCP Mapping table) and the packet’s CoS are compared. The packet is forwarded with the higher of the two priorities.


6


Network Features

This section describes the following topics:

• Redundancy - An overview of the concepts and types of Redundancy.

• Security - A description of the means used to ensure confidentiality in a network.

• Load Balancing - A description of various load balancing elements and applications.

Redundancy

Redundancy means a duplication of devices, services, or connections, so that, in the event of a failure, the redundant device, service, or connection can take over for the one that failed.

Since computer networks are critical for business operations, it is vital to ensure that the network continues to function even if a piece of equipment fails. Even the most reliable equipment may fail on occasion, but a redundant component can ensure that the network continues to operate despite such failure.

Switching Redundancy

Not all switch designs treat redundancy in the same way. Switches designed with a central switching fabric have a central component that performs all switching functions. In contrast, switches designed with a distributed switching architecture separate and distribute the switching functions among different hardware components of the switch so that there is no single point through which all frames or cells must travel. This gives distributed switching an important advantage in that there is no single point of failure. Each switching engine performs its own switching functions and is unaffected by the failure of any other switching engine.


Chapter 6

Port Redundancy

To achieve port redundancy, the network manager can define a redundancy relationship between any two ports in a hub. One port is defined as the primary port and the other as the secondary port. If the primary port fails, the secondary port takes over. Once a port has been designated in a redundancy scheme, either as a primary or a secondary port, it can not be designated in any other redundancy scheme.

Security

The prime goal of network security is confidentiality in the network. This is accomplished by identifying authorized devices and limiting network access to those devices.

Another aspect of network security is how to handle attempts to access the network by unauthorized users.

Security Methods

In Ethernet networks, security is managed per port. In Token Ring networks, security can be managed either per port or per ring (but not both simultaneously).

For each port or ring, the network manager can define a list of devices that are authorized to access the network via the port or ring. This is called the Security Address List. Also, for each port or ring, the network manager can determine how the network handles unauthorized access attempts. This is called the Security Policy.

When managing security per ring, the network manager creates a list of specific users with authorization to enter the Token Ring. When managing security per port, the network manager creates a list of specific users with authorization to access each individual port.

Security Nullification

The network manager can nullify the security option manually. This is necessary, for example, if the Security Address list of the management console port is set without including the address of the management station, thus cutting off the management console from the network.


Network Features

The network manager can nullify the security option in the following ways:

• Using another management station on the network to turn off the security of the console port.

• Attaching the console to a different port and nullifying the security from there.

• Physically removing and replacing the module in the device. This resets the module and automatically nullifies security for the module ports.

Load Balancing

Load balancing is a means of routing network requests to various servers, instead of overloading them all onto one server. In essence, load balancing takes the “load” of network traffic off of one server and “balances” it among several servers that contain identical applications and data. System administrators balance the load by replacing single firewalls and servers with multiple firewall and server farms. This achieves the following:

• Improving resilience by removing single points of failure.

• Improving performance by utilizing multiple units instead of a single one.

This improves the scalability and maintainability of the firewalls and servers in the network.

The load balancer also serves as a ‘smart redirector’, allowing traffic redirection, commonly known as Application Redirection. This allows for:

• Intercepting web traffic and forwarding it to deployed web caches.

• Redirecting specific application traffic to content inspection engines.

• Policy based routing, providing routing based on application or data source.


Chapter 6

Load Balancing Elements

There are several abstract load balancing elements:

• Real Server (RS) - An RS is a physical server that is associated with a Real IP address. One or more RSs may belong to a Real Server Group.

• Real Server Group (RSG) - An RSG is a logical grouping of RSs used for load balancing. For example, for Server Load Balancing, the load balancer distributes packets to RSs belonging to a specific RSG.

• Virtual Service - Virtual Services are abstract links to the RSGs provided by a Virtual Server. For example, load-balanced forwarding of HTTP or FTP packets is a Virtual Service.

• Virtual Server - A Virtual Server represents the server to the outside world. It is associated with a Virtual IP address and provides Virtual Services. For example, a load balancer that intercepts traffic from the WAN acts as a Virtual Server.

Traffic from the WAN is directed to the Virtual Server. The Virtual Server provides Virtual Services when transferring packets to the RSG, which is comprised of RSs.

The following figure illustrates the conceptual load balancing model:

Figure 6-1. The Conceptual Load Balancing Model


Network Features

Load Balancing Applications

There are several different load balancing applications:

• Firewall Load Balancing

• Server Load Balancing

• Application Redirection

Firewall Load Balancing

Firewall Load Balancing (FWLB) intercepts all traffic between the LAN and the WAN, and dynamically distributes the traffic among the available firewalls. Using FWLB, all of the firewalls are utilized concurrently, providing overall improved firewall performance, scalability, and availability.

The firewalls are the RSs, and the group of firewalls is the RSG. The firewall group is associated with a Virtual Service, which is a routing or bridging firewall.

The load balancer does the following:

• Balances traffic across two or more firewalls (up to 1024) in your network, allowing the firewalls to work in parallel. Preventing one firewall from becoming overloaded by all of the network traffic maximizes firewall productivity.

• Ensures that all traffic between specific IP address source and destination pairs flows through the same firewall by maintaining state information about the traffic flowing through the load balancer.

• Performs health checks on all paths through the firewalls. If any path is not operational, the load balancer diverts traffic away from that path, maintaining connectivity across the firewalls.

Often, two load balancers are needed to support FWLB. One device is deployed on the LAN side (internal) of the firewalls and another on the WAN side (external). If a Demilitarized Zone (DMZ) is implemented to allow remote access, a third load balancer must be deployed on the DMZ side of the network. Additional devices can be added to provide redundancy, eliminating any device or path as a single point of failure.


Chapter 6

The following figure illustrates FWLB:

Figure 6-2. Firewall Load Balancing

Server Load Balancing

Server Load Balancing (SLB) intercepts all traffic between clients and servers, and dynamically distributes the load among the available servers, based on the SLB configuration.

In a non-balanced network, each server provides access to specific applications or data. Some of these applications may be in higher demand than others. Servers that provide applications with higher demand are over-utilized while other servers are under-utilized. This causes the network to perform below its optimal level.

SLB provides a solution by balancing the traffic among several servers which all have access to identical applications and data. This involves intercepting all traffic between clients and load-balancing servers and dynamically distributing the load according to configured schemes (metrics).

The server load balancer changes one of the source and destination IP addresses. When a packet arrives from a client to a server, the load balancer changes the destination IP from the Virtual IP address to the Real IP address. When a packet is sent from a server to a client, the load balancer changes the source IP address from the Real IP dress to the Virtual IP address.

The following figure illustrates SLB:

Figure 6-3. Server Load Balancing


Network Features

Application Redirection

With the growing importance of the Internet as a source of information, an organization’s LAN may suffer from performance degradation due to congestion of the router connecting the network to the Internet.

Since much information retrieved from the Web is either repeatedly requested by a user or requested by multiple users, many organizations implement a local caching mechanism to prevent unnecessary Internet traffic. The local caches must be on the traffic path between the client and the Internet router. As a result, all traffic, even traffic not intended for the cache, passes through the cache.

Load balancing solves this problem by redirecting packets from their original destination to an alternative server based on the Application Redirection (AR) configuration. By redirecting client requests to a local cache or application server, you can increase the speed at which clients access information and free up valuable network bandwidth.

AR improves network performance by:

• Providing faster client access to information.

• Increasing effective network bandwidth.

• Filtering traffic.

• Directing only suitable traffic to the local cache.

• Connecting and load balancing multiple caches.

• Performing the redirection process in a way that is transparent to the client.

• Allowing redundant caches to be configured.

Cache Redirection is the most common implementation of AR. For Cache Redirection, the load balancer is positioned on the traffic route and redirects traffic from the original destination to an alternative cache server. The redirection process involves the following steps:

1. The load balancer checks whether the packet characteristics comply with one of the defined filter rules. The user configures rules to define which clients or destinations are to be redirected to the cache.

2. The load balancer checks whether the application port is suitable for redirection.

3. The load balancer routes the packet to the cache server instead of to the original destination on the Internet.


Chapter 6

4. The cache checks if it has the relevant information. If it does, it forwards the cached information to the client. If it does not have the information, it retrieves the information from the Internet, saves it to the cache, and then forwards the information to the client.

The following figure illustrates Cache Redirection:

Figure 6-4. Cache Redirection

Persistency

Persistency is the maintenance of the connection between the server and the client over multiple sessions. Persistency ensures that all traffic from the client is directed to the same RS.

Persistency is achieved by using naturally persistent load balancing metrics (such as Hash or MinMiss Hash) or by forcing persistent load balancing decisions on non-persistent load balancing metrics (such as Round Robin). Persistency is forced by storing the history of the latest decisions in a cache for a limited time, and then sending the packets to the appropriate RS according to the previous load balancing decisions.

Persistency is achieved by opening a new session for a server group based on the following:

• New session on source IP address - All sessions from a specific source are directed to the same RS. This is useful for applications where client information must be retained on the RS between sessions.

• New session on destination IP address - All sessions to a specific destination are directed to the same RS. This is useful for caching applications to maximize successful cache hits when information is not duplicated between RSs.


Network Features

• New session on source IP and destination IP addresses - All sessions from a given source to a given destination are directed to the same RS. This is useful for FWLB, since it ensures that the two unidirectional flows of a given session are directed through the same firewall.

Load Balancing Metrics

There are several methods, or metrics, that a load balancer can use to distribute traffic among multiple servers, firewalls or caches. These metrics tell the load balancer which RS should receive each session.

Some commonly used metrics are:

• Round Robin

• Hash

• MinMiss Hash

Round Robin Using Round Robin, the load balancer issues sessions to each RS in turn. The first RS in the group receives the first session, the second RS receives the next session, and so on. When all the RSs receive a session, the issuing process starts over with the first RS. Round Robin ensures that each RS receives an equal number of sessions.

Round Robin is a non-persistent load balancing metric. Nevertheless, persistency can be forced by storing the history of the latest decisions in a cache for a limited time, and then sending the packet to the appropriate RS according to the previous load balancing decisions.

Hash Using the Hash, sessions are distributed to RSs using a predefined mathematical hash function. The hash function is performed on a specified parameter. The source IP address, destination IP address, or both can be used as the hash function input.

The load balancer creates a list of all the currently available RSs. The result of the hash function is used to select an RS from the list. Any given parameter always gives the same hash result, providing natural persistency.


Chapter 6

If an RS is removed or added to the group, persistency is broken. This occurs since the order of the RSs in the list changes, but the hash still points to the same list entries. The following figure illustrates how a loss of persistency occurs when an RS becomes non-operational:

Figure 6-5. Hash Metric - Loss of Persistency

In the above figure, when Firewall 2 becomes non-operational, the list of available firewalls is readjusted, causing a lack of persistency. However, if Firewall 2 becomes operational again, the list of available firewalls is restored to its original order, and persistency is recovered.

MinMiss Hash

MinMiss Hash distributes sessions to RSs in the same way as the Hash metric. However, MinMiss Hash retains persistency even when an RS is removed from the group. When an RS fails or is removed, the load balancer does not change the position of all the RSs in the list. Instead, it redistributes the remaining RSs to the list entries freed by the failing RS. The following figure illustrates how persistency is retained when an RS becomes non-operational.

Figure 6-6. MinMiss Metric - Persistency Retained

In the above figure, when Firewall 2 becomes non-operational, the list of available firewalls is not readjusted. Only the list entries that are now empty are replaced with other available firewalls. Therefore, persistency is retained for all available firewalls. However, if Firewall 2 becomes operational again, the list of available firewalls is recalculated so that the smallest number of firewalls is affected. The list is not restored to its original configuration. As a result, persistency is only partially recovered.


7


Glossary

100BaseTX 100-Mbps baseband Fast Ethernet specification based on the IEEE 802.3 standard. 100BaseTX uses two pairs of either UTP (Unshielded Twisted Pair) or STP (Single Twisted Pair) wiring. One pair is used to receive data; the other is used to transmit data.

10BaseT 10-Mbps baseband Ethernet specification based on the IEEE 802.3 standard. 10BaseT uses two pairs of UTP (Unshielded Twisted Pair) wiring. One pair is used to receive data; the other is used to transmit data.

AAL ATM Adaptation Layer. The AAL is a collection of standardized protocols that adapt different classes of applications to the ATM layer. This is necessary for ATM to support various types of services with different traffic characteristics and system requirements. The AAL is divided into the Convergence Sublayer (CS) and the Segmentation and Reassembly Sublayer (SAR).

AAL5 One of several types of AAL. AAL5 is used for LAN Emulation (LANE).

ABR Available Bit Rate. An ATM service in which the network guarantees a minimum data transfer rate and allows data to be transferred at a higher rate when the network is free.

Address Resolution

Conversion of an IP address into a corresponding physical address. This is usually done using ARP (Address Resolution Protocol). For more information, refer to ARP.

Agent (Network Agent)

A special control module that interfaces between the network manager and the managed devices, using the MIB as a management terms dictionary. Network Agents relay device events and execute instructions via embedded software.

Alarm An audible or visible warning signal alerting designated management stations that a significant event has occurred on the network.

ARP Address Resolution Protocol. A TCP/IP protocol used to convert an IP address into a physical address, such as an Ethernet address. The sender broadcasts an ARP request onto the TCP/IP network. The host whose IP address matches the requested address then replies with its physical hardware address.


Chapter 7

ATM Asynchronous Transfer Mode. ATM is an international standard for cell relay in which multiple service types, such as voice, video, or data are conveyed in fixed-length (53-byte) cells. The constant and relatively small cell size allows ATM equipment to transmit video, audio, and computer data over the same network with an efficient allocation of network resources. Constant cell size also allows cell processing to occur in hardware. This reduces transit delays.

For more information refer to ATM - Asynchronous Transfer Mode in The Reference Guide.

Backbone A high-bandwidth connection between switches. A backbone link normally operates in Full Duplex Mode, sending packets in both directions simultaneously.

Beacon Frame Refer to Beaconing.

Beaconing An error detection mechanism in Token Ring networks. When a station detects a serious network problem, it sends a Beacon Frame. The Beacon Frame defines a failure domain that includes the station reporting the failure, its nearest active upstream neighbor, and everything in between. Beaconing initiates a process in which the nodes in the failure domain perform diagnostics and attempt to reconfigure the network around the failed areas.

BGP Border Gateway Protocol. An Internet protocol that enables groups of routers to share routing information so that efficient, loop-free routes can be established.

BOOTP Bootstrap Protocol. An Internet protocol that enables a diskless workstation to discover its own IP address, the IP address of a BOOTP server on the network, and a file to be loaded into memory to boot the machine. This enables the workstation to boot without a hard or floppy disk drive.

BPDU Bridge Protocol Data Unit. A packet that is transmitted at configurable intervals to exchange information among bridges in the network. Among other things, BPDUs inform the bridges of the topology of the network and detect loops and topology changes.

Broadcasting A common method of information transmission in which a packet is sent to every port on the network.

Bridge A device connecting two networks using similar protocols. A bridge filters and forwards data between the networks according to their destination addresses.


Glossary

Burst A transmission of data at a faster rate than normal. Data bursts can be carried out in several ways. A burst is always limited in time and can take place only under special conditions.

Bus A transmission path or channel. A bus is typically an electrical connection with one or more conductors, where all attached devices receive all transmissions at the same time.

BUS Broadcast and Unknown Server. A multicast server used in ELANs that is used to forward multicast and broadcast traffic to the appropriate clients.

For more information refer to BUS in The Reference Guide.

CAM Content Address Memory. A list kept by each port containing the addresses of all network elements connected to the port. CAM is accessed according to its contents, not its memory address.

CBR Constant (or Continuous) Bit Rate. An ATM class of service that supports the transmission of a continuous bit-stream of information. CBR is used for connections that depend on precise timing to ensure undistorted delivery, such as voice and video.

Cell The basic ATM transmission unit, consisting of a 53-byte packet (5-byte header and 48-byte payload). User traffic is segmented into cells at the source and reassembled at the destination.

For more information refer to ATM - Asynchronous Transfer Mode in The Reference Guide.

Cell Header The 5-byte ATM cell header contains control information regarding the destination path and flow control.

Chassis View Avaya Inc.’s Network Management System’s graphic depiction of a network device.

Client A computer system or process that requests a service from another computer system or process (a "server"). Typically, a client is an application that runs on a personal computer or workstation and relies on a server to perform some operations.

Collision In Ethernet, a collision occurs as the result of two nodes transmitting simultaneously. The frames from each device impact and are damaged from the impact.


Chapter 7

CRC Cyclic Redundancy Check. A data transmission error-checking technique in which the frame recipient calculates a remainder by dividing frame contents by a prime binary divisor and compares the calculated remainder to a value stored in the frame by the sending node.

CSMA/CD Carrier Sense Multiple Access with Collision Detection. A multi-user network allocation procedure in which every station can receive the transmissions of all others. Each station waits for the network to be idle before transmitting and each station can detect collisions by other stations.

Data Link Layer

Layer 2 of the OSI reference model. The Data Link Layer is responsible for physical addressing, network topology, line discipline, error notification, ordered delivery of frames, and flow control.

DHCP Dynamic Host Configuration Protocol. A protocol for assigning dynamic IP addresses to network devices. With dynamic addressing, a device can have a different IP address every time it connects to the network. In some systems, the device's IP address can even change while it is still connected. DHCP also supports a mix of static and dynamic IP addresses.

Domain A group of computers and devices on a network that are administered as a unit with common rules and procedures.

Dot1Q Standard for VLAN tagging under the IEEE 802.1Q VLAN standard.

DRU Domain Resource Unit. The unit of measure of resources available in a Avaya M770 Device DomainX.

Duplex Mode The state of the device with regard to simultaneous transmission and reception of information. In Full Duplex Mode, the device or circuit permits simultaneous transmission and reception. This is also known as bisynchronous communication. In Half Duplex Mode, the device or circuit does not permit simultaneous transmission and reception. This is also known as asynchronous communication.

Edge Device A device used to take frames from LANs and send them over an ATM network as cells. An edge device normally provides LAN emulation.

ELAN Emulated LAN. A technique that specifies the interfaces and protocols needed for providing LAN-supported functionality and connectivity in an ATM environment. This enables legacy protocols to be interoperable with ATM protocols, interfaces, and devices.

For more information refer to LAN Emulation in The Reference Guide.


Glossary

Emulated LAN A technique that specifies the interfaces and protocols needed for providing LAN-supported functionality and connectivity in an ATM environment. This enables legacy protocols to be interoperable with ATM protocols, interfaces, and devices.


End System An end-user device on a network. Also used to denote a non-routing host or node in an OSI network.

ESI End System Identifier. A portion of a network address that identifies the end system.

Ethernet One of the most widely implemented LAN standards, Ethernet is standardized as IEEE 802.3. Ethernet uses the CSMA/CD access method to handle simultaneous demands and supports data transfer rates of 10 Mbps. A newer version of Ethernet, called 100Base-T (or Fast Ethernet), supports data transfer rates of 100 Mbps. The newest version, Gigabit Ethernet, supports data rates of 1 gigabit per second.

For more information refer to Ethernet Standards in The Reference Guide.

FCS Frame Check Sequence. A field added to a frame for error-control purposes.

FDDI Fiber Distributed Data Interface. A set of ANSI protocols for sending digital data over fiber optic cable. FDDI networks are token-passing networks, and support data rates of up to 100 Mbps. FDDI networks are typically used as backbones for wide-area networks.

FDX Full Duplex. A circuit or device permitting simultaneous data transmission between sending and receiving stations. For more information, refer to “Duplex Mode” on page 52.

Flow Control Avaya’s devices use a proprietary form of flow control that enables one endpoint to inform another endpoint that it should refrain from sending additional packets. The flow control mechanism avoids packet loss. Flow control is used in Full Duplex Mode.

Fragment Ethernet packet shorter than 576 bits (usually the result of a collision).

Frame A logical grouping of information sent as a Data Link Layer unit over a transmission medium. The word Frame often refers to the header and trailer, used for synchronization and error control, that surround the user data contained in the unit.


Chapter 7

FTP File Transfer Protocol. An application protocol, part of the TCP/IP protocol stack, used for transferring files between network nodes.

Full Duplex (FDX)

A circuit or device permitting simultaneous data transmission between sending and receiving stations. “Duplex Mode” on page 52.

Half Duplex (HDX)

A circuit or device permitting data transmission in only one direction at a time between sending and receiving stations. For more information, refer to “Duplex Mode” on page 52.

HDX Half Duplex. A circuit or device permitting data transmission in only one direction at a time between sending and receiving stations. For more information, refer to “Duplex Mode” on page 52.

HEC Header Error Check. Also called Header Error Control or Header Error Correction. A 1-byte field in the ATM cell header used for detecting single bit and certain multiple bit errors.

Hop Passage of a data packet between two network nodes (for example, between two routers).

Host A computer, attached to a network, that provides services to another computer beyond simply storing and forwarding information.

HTTP Hyper Text Transmission Protocol. The protocol used between clients and servers on the World Wide Web for transmission of HTML documents.

Hub A common connection point for devices in a network. Hubs are commonly used to connect segments of a LAN.

IANA Internet Assigned Numbers Authority. The organization responsible for assigning new Internet-wide IP addresses.

ICMP Internet Control Message Protocol. An extension to the Internet Protocol (IP). ICMP supports packets containing error, control, and informational messages.

IEEE Institute of Electrical and Electronics Engineers. Among other things, the IEEE develops standards for the computer and electronics industry. In particular, the IEEE 802 LAN standards are widely followed.

IEEE 802.3 IEEE standard for Ethernet LANs.

IEEE 802.5 IEEE standard for Token Ring LANs.


Glossary

ILMI Interim Local Management Interface. Specification developed by the ATM Forum for incorporating network management capabilities into the ATM UNI.

IMAP Internet Message Access Protocol. A protocol for retrieving E-mail messages. IMAP uses SMTP for communication between the E-mail client and server.

In-Band Transmission of auxiliary information, such as management messages, using the same frequencies or channels normally used for information transfer.

Internet Protocol

Refer to “IP” on page 55 and “TCP/IP” on page 62.

Internet A collection of networks and gateways that use the TCP/IP suite of protocols. An internet is two or more networks connected by an internal or external router. The word “internet” is a generic term. “The Internet” is the world’s largest internet.

Interswitch Link (ISL)

Interswitch Link. An Avaya proprietary mechanism to tag packets with VLAN and priority information across the backbone. This allows two Avaya devices to act as a single logical entity.

IP The protocol that governs packet forwarding within the TCP/IP standards developed and used on the Internet. Refer to “TCP/IP” on page 62.

IP Address A 32-bit address assigned to hosts using TCP/IP. An IP address is written as 4 octets separated by periods (dotted decimal format). Each address consists of a network number, an optional subnetwork number, and a host number. The network and subnetwork numbers together are used for routing, while the host number is used to address an individual host within the network or subnetwork. A subnet mask is used to extract network and subnetwork information from the IP address.

IPX Internetwork Packet Exchange. A network layer protocol used for transferring data from servers to workstations. IPX is primarily used in Novell NetWare operating systems.

ISL Interswitch Link. An Avaya proprietary mechanism to tag packets with VLAN and priority information across the backbone. This allows two Avaya devices to act as a single logical entity.

ISO International Standards Organization. A voluntary organization founded in 1946, responsible for creating international standards in many areas, including computers and communications.


Chapter 7

Jabber An error condition in which a network device continually transmits random, meaningless data onto the network. In IEEE 802.3, Jabber refers to a data packet, the length of which exceeds the maximum length prescribed in the standard.

LAG Link Aggregation Groups (LAGs) provide a method of creating a high-bandwidth link. A LAG consists of a group of ports acting as a single logical port. All ports participating must have the same configuration.

LAN Local Area Network. A high-speed, low-error data network that spans a limited area. LANs connect workstations, peripherals, terminals, and other devices in a single building or other geographically limited area.

LANE Refer to LAN Emulation.

LAN Emulation A technique that specifies the interfaces and protocols needed for providing LAN-supported functionality and connectivity in an ATM environment. This enables legacy protocols to be interoperable with ATM protocols, interfaces, and devices.


LEC LAN Emulation Client. A LEC is an entity in an end system that performs data forwarding, address resolution, and other control functions for a single end system within a single ELAN. A LEC also provides a standard LAN service interface to any higher-layer entity that interfaces with the LEC. Each LEC is identified by a unique ATM address, and is associated with one or more MAC addresses reachable through that ATM address.

For more information refer to LEC in The Reference Guide.

LECS LAN Emulation Configuration Server. A LECS is an entity that assigns individual clients to particular ELANs by directing them to the LES that corresponds to the ELAN. There is logically one LECS per administrative domain that serves all ELANs within that domain.

For more information refer to LECS in The Reference Guide.

LES LAN Emulation Server. An entity that implements the control function for a particular ELAN. There is only one logical LES per ELAN, and it is identified by a unique ATM address.

For more information refer to LES in The Reference Guide.


Glossary

Link-State Protocols

A series of routing protocols, such as OSPF, which permit routers to exchange information about the accessibility of other networks and the cost or metric to reach the other networks.

Lobe In a Token Ring network, a lobe is a section of cable that attaches a device to an access unit.

LSA Link-State Advertisement. A broadcast packet, used by Link-State Protocols, that contains information about neighbors and path costs. LSAs are used by receiving routers to maintain their routing tables.

MAC Address Media Access Control Address. The MAC Address is a hardware address that uniquely identifies each node of a network.

MAC Layer In IEEE 802 networks, the MAC layer is a sublayer of the Data Link Control (DLC) layer. The MAC layer interfaces directly with the network media. Each different type of network media therefore requires a different MAC layer.

MAC List A list of MAC Addresses of devices that are allowed to access the network through the selected port. Each port can have a MAC List. If the port's security option is enabled, no device can access the port unless the device's address is on the port's MAC List.

MAN Metropolitan Area Network. A data communications network designed for a town or city. Usually characterized by high-speed connections using fiber optical cable or other digital media.

MIB Management Information Base. A database of network management information that can be monitored by a Network Management System. Both SNMP and RMON use standardized MIB formats that enable any SNMP and RMON tool to monitor any device defined by a MIB.

Module A self-contained communications unit that may be used in combination with other units. Examples include individual Avaya P330 units and cards that slot into the Avaya P580/P882 Device.

Multicasting A method of information transmission in which copies of the packet are delivered to multiple ports, but only a subset of all possible destinations.

Netmask A portion of an IP address that identifies the bits that denote the network number.

Network A collection of computers, printers, routers, switches, and other devices that can communicate with each other over some transmission medium. A network can consist all or in part of subnetworks.


Chapter 7

Network Agent

A special control module that interfaces between the network manager and the managed devices, using the MIB as a management terms dictionary. Network Agents relay device events and execute instructions via embedded software.

Network Mask A portion of an IP address that identifies the bits that denote the network number.

NMS Network Management Station. A station that is responsible for managing all or part of a network. An NMS communicates with Network Agents to help keep track of network statistics and resources.

NNI Network Node Interface. Also known as Network-to-Network Interface. A standard that defines the interface between two ATM switches that are both located in a private network (P-NNI) or that are both located in a public network (public NNI).

Node A point of interconnection to a network or a junction of two or more lines in a network. A node can be a computer or some other device, such as a printer. Every node has a unique network address.

NSAP Network Service Access Point. An ISO-specified network address.

OID Object Identifier. Used in SNMP to identify managed objects. In the SNMP Manager/Agent Network Management Paradigm, each managed object must be identified by a unique OID.

OSI Open Systems Interconnection reference model. A model for network communications consisting of seven layers that describe what happens when computers communicate with one another.

OSPF Open Shortest Path First. A routing protocol featuring least-cost routing, multipath routing, and load balancing.

Out-of-Band Transmission of auxiliary information, such as management messages, using frequencies or channels outside the frequencies or channels normally used for information transfer. Out-of-band signaling is often used for error reporting in situations in which in-band signaling can be affected by whatever problems the network might be experiencing.

Packet Logical grouping of information that includes a header containing control information and usually user data. Packets are most often used to refer to application layer data units.

PING Packet Internet Groper. Determines whether a specific IP address is accessible by sending a packet to the specified address and waiting for a reply.


Glossary

Plus Tagging A proprietary Avaya tagging mechanism that enables extended VLAN capabilities.

PNNI Private Network to Network Interface. The interswitch interface within a private ATM domain. The PNNI trunking protocol for hierarchical ATM-layer routing and QoS support.

POP Post Office Protocol. Used to retrieve E-mail from a mail server. Most E-mail applications use the POP protocol, although some can use the newer IMAP (Internet Message Access Protocol). POP3, unlike earlier versions, can be used with or without SMTP.

Port A physical port is a connecting component that allows a microprocessor to communicate with a compatible peripheral. A port is identified by a port number.

Protocol A set of rules and conventions that governs how devices exchange data, especially across a network. Low level protocols define the electrical and physical standards to be observed, bit- and byte-ordering, the transmission, error detection, and correction of the bit stream. High level protocols deal with data formatting, including message syntax, terminal to computer dialogue, character sets, message sequencing, etc.

Protocol Stack A layered set of protocols which work together to provide a set of network functions. Each intermediate layer uses the layer below it to provide a service to the layer above.

PSTN Public Switched Telephone Network. The collection of interconnected systems operated by the various telephone companies and administrations around the world.

PVC Permanent Virtual Circuit. A permanent, virtual connection established by the network management between an origin and a destination.

QoS Quality of Service. A measure of performance for a transmission system that reflects the system’s transmission quality and service availability.

Query The process of extracting information from a database and presenting it for use.

Redundancy A duplication of devices, services, or connections, so that, in the event of a failure, the redundant device, service, or connection can take over for the one that failed.

For more information refer to Redundancy in The Reference Guide.


Chapter 7

Repeater A device that automatically amplifies, restores, or reshapes signals distorted by transmission loss.

RIP Routing Information Protocol. Specifies how routers exchange routing table information. RIP is gradually being replaced by a newer protocol called OSPF (Open Shortest Path First).

RMON Remote Monitoring. A network management standard that allows network information to be gathered at a single workstation. In contrast to the Standard MIB which gathers network data from a single type of Management Information Base (MIB), RMON defines nine additional MIBs that provide a much richer set of data about network usage. For RMON to work, network devices, such as hubs and switches, must be designed to support it.

For more information refer to Switch Monitoring in The Reference Guide.

Router A software and hardware connection between two or more networks, usually of similar design, that permits traffic to be routed from one network to another on the basis of the intended destinations of that traffic. A router located in a server is called an internal router; a router located in a workstation is called an external router.

Routing Table A table stored in a router or other internetworking device that keeps track of routes to particular network destinations and, in some cases, metrics associated with those routes.

SAP Service Advertising Protocol. A protocol used to identify the services and addresses of servers attached to the network. The responses are used to update a table in the router known as the Server Information Table. SAP is primarily used in Novell NetWare operating systems in conjunction with IPX.

SAR Segmentation and Reassembly. One of the two sublayers of the AAL. SAR inserts data from the information frames into the cell. It adds any necessary header or trailer bits to the data and passes the 48-octet data packet to the ATM layer. Each AAL type has its own SAR format.

Segmentation Segmentation is a common solution to LAN bandwidth limitations. The LAN is divided into separate LAN segments using bridges and routers. If segmented correctly, most network traffic will remain within a single segment, enjoying the full 10 Mbps bandwidth. Hubs and switches are used to connect each segment to the rest of the LAN.

SELector (SEL) The last byte in an NSAP address.The SELector is often used to identify particular ATM applications.


Glossary

Side-Band Transmission of auxiliary information, such as management messages, by means of a direct connection that bypasses the frequencies and channels normally used for information transfer. Unlike out-of-band transmission, side-band transmission does not require a modem.

SLIP Serial Line Internet Protocol. SLIP is the standard protocol for point-to-point serial connections, using a variation of TCP/IP.

SMON Switch Monitoring, Avaya’s proprietary switch monitoring technology. SMON extends the RMON standard to provide additional tools and features for monitoring in the switch environment. SMON enables a global view of traffic for all switches on the network, an overall view of traffic passing through a specific switch, detailed data of the hosts transmitting packets or cells through a switch, an analysis of traffic passing through each port connected to a switch, and a view of traffic between various hosts connected to a switch.

For more information refer to Switch Monitoring in The Reference Guide.

SMTP Simple Mail Transfer Protocol. Used to send E-mail messages between servers. Also used to send messages from a mail client to a mail server.

SNAP SubNetwork Access Protocol. Internet protocol that operates between a network entity in the subnetwork and a network entity in the end system. SNAP specifies a standard method of encapsulating IP datagrams and ARP messages on IEEE networks.

SNMP Simple Network Management Protocol. Protocol for communications between remote network management stations (like a management umbrella console) and managed network elements (such as Avaya Inc.’s devices). The management umbrella uses SNMP for network management and can manage all SNMP devices.

Socket An addressable entity within a node connected to an AppleTalk network. Sockets are owned by software processes known as socket clients. An AppleTalk socket is similar in concept to a TCP/IP port.

Spanning Tree Protocol

Refer to “STA” on page 61.

STA Spanning Tree Algorithm. The algorithm used by the Spanning Tree Protocol to create a spanning tree. The Spanning Tree Protocol (STP) is a bridge protocol that uses the STA to enable a learning bridge to dynamically work around loops in a network topology by creating a spanning tree. Bridges exchange BPDU messages with other bridges to detect loops, and then remove the loops by shutting down selected bridge interfaces.


Chapter 7

For more information refer to Spanning Tree Algorithm (STA) in The Reference Guide.

Stack A layered set of protocols which work together to provide a set of network functions. Each intermediate layer uses the layer below it to provide a service to the layer above.

Standalone Mode

An option to separate a module from the other modules in a device so that its bus is independent. This may be desirable, for example, if one module has exceptionally heavy traffic that might affect other modules.

Subnet Short for subnetwork. A subnet is a portion of a network that shares a common address component. On TCP/IP networks, a subnet includes all devices whose IP addresses have the same prefix. For example, all devices with IP addresses that start with 133.100.100 are part of the same subnet.

Subnet Mask A 32-bit address mask used in IP to indicate the bits of an IP address that are being used for the subnet address.

SVC Switched Virtual Circuit. A logical connection between two points that is dynamically established and only exists during transmission. In ATM networking, the SVC connection is established via signalling.

Switch A device that filters and forwards packets between LAN segments. Switches operate at the Data Link Layer of the OSI reference model and support any packet protocol.

Switch Monitoring

Refer to “SMON” on page 61.

TCP/IP Transmission Control Protocol/Internet Protocol. Common name for the suite of protocols used to connect hosts on the Internet. TCP/IP uses several protocols, of which TCP and IP are the main ones.

Telnet A terminal emulation protocol for TCP/IP networks. Telnet is used for remote terminal connection, enabling users to log in to remote systems and use these resources as if they were connected to a local system.

TFTP Trivial File Transfer Protocol. A simple form of File Transfer Protocol, using User Datagram Protocol (UDP) and providing no security features. TFTP is often used by servers to boot diskless workstations, X-terminals, and routers.


Glossary

Token Ring A type of LAN standardized as IEEE 802.5. In a Token Ring network, a supervisory frame, or token, is passed from station to adjacent station sequentially. Stations wishing to gain access to the network must wait for the token to arrive before transmitting data.

Transceiver A device that both transmits and receives analog or digital signals. Usually used to describe the LAN component that applies signals onto the network wire and detects signals passing through the wire.

Trap Message sent by an SNMP agent to an NMS, console, or terminal to indicate the occurrence of a significant event, such as a specifically defined condition or a threshold that was reached. Similar to an alarm.

Tree View A resizeable window containing a hierarchical representation of the modules and ports of the device.

UDP User Datagram Protocol. Connectionless transport layer protocol in the TCP/IP protocol stack. UDP is a simple protocol that exchanges datagrams without acknowledgments or guaranteed delivery, requiring that error processing and retransmission be handled by other protocols.

UNI User-Network Interface. The interface - defined as a set of protocols and traffic characteristics, such as cell structure - between the user and the ATM network.

Unicast A single packet sent to a single network destination.

VBR Variable Bit Rate. VBR is a QoS class for ATM networks. It is subdivided into a real time (RT) class and non-real time (NRT) class. VBR-RT is used for connections in which there is a fixed timing relationship between samples. VBR-NRT is used for connections in which there is no fixed timing relationship between samples, but that still need a guaranteed QoS.

VC Refer to “Virtual Channel” on page 64, “Virtual Circuit” on page 64, and “Virtual Connection” on page 64.

VCI Virtual Channel Identifier. A 16 bit value in the ATM cell header that provides a unique identifier for the Virtual Channel (VC) within a Virtual Path that carries a particular cell.

VIDP VLAN Information Distribution Protocol. VIDP is a proprietary Avaya protocol running between Avaya P110 Device and Avaya M770 Device agents. A station’s VLAN information is distributed to all agents in order to use this information throughout the network.


Chapter 7

For more information refer to VIDP (VLAN Information Distribution Protocol) in The Reference Guide.

Virtual Channel

Describes the unidirectional flow of ATM cells between connecting (switching or end-user) points that share a common identifier number.

Virtual Circuit A connection set up across an ATM network between a source and a destination where a fixed route is chosen for the entire session and bandwidth is dynamically allocated.

Virtual Connection

A connection established between end-users (source and destination), where packets are forwarded along the same path and bandwidth is not permanently allocated until it is used.

Virtual Path A group of virtual channels that can support multiple virtual circuits.


Index

AAdvantages of bridging 23Agents 28Asynchronous Transfer Mode (ATM) see

ATMATM

call setup 12call termination 12cell 12data transfer 12LAN Emulation 12

Auto-negotiation 3

BBenefits of switching 26Benefits of VLANs 8Bridging

advantages 23and routing vs. switching 25definition 21disadvantages 23filtering frames 22overview 19relaying frames 22Spanning Tree Algorithm (STA) 23

Broadcast and Unknown Server (BUS) 15

CCall setup and termination 12Cell, ATM 12Classifying ports 34Components of LAN Emulation 13Connections for LAN Emulation 15

DData transfer 12Disadvantages of bridging 23Distributed LES/BUS 16

EEthernet

definition 1

Ethernet, continuedfast 2gigabit 2

FFast Ethernet 2FDDI 3Filtering frames 22

GGigabit Ethernet 2Glossary 49

HHow switching works 25

IIn-band transmission 29Information Distribution Protocol (VIDP) 9Interim Local Management Interface (ILMI)

15IP Multicast 3IP Multicast filtering 4

LLAN Emulation

Broadcast and Unknown Server (BUS) 15Client (LEC) 14components 13Configuration Server (LECS) 15connections 15overview 12proprietary redundant services 16Server (LES) 15

LAN Emulation Client (LEC) 14LAN Emulation Configuration Server

(LECS) 15LAN Emulation Server (LES) 15LAN protocols 1

MMirroring ports 34


Index

Monitoring switches 31

NNetwork

agents 28features 39management applications 28

Nullification of security 40

OOut-of-band transmission 31Overview of Reference Guide vi

PPermanent Virtual Circuit (PVC) 15Port

classification 34mirroring 34redundancy 40

Port VLAN ID 10Proprietary redundant services 16Protocols

auto-negotiation 3Ethernet 1FDDI 3overview 1VIDP 9

RRedundancy

overview 39port 40switching 39

Redundant LES/BUS 16Reference Guide overview viRelaying frames 22Resilient LECS 17RMON standard 32Routing

and bridging vs. switching 25definition 19overview 19

SSecurity

methods 40nullification 40overview 40

Segment switching 26Severity degrees 34Side-band transmission 30SMON 32Spanning Tree Algorithm (STA) 23Switch monitoring 31Switching

benefits 26compatibility 27definition 25how it works 25overview 19redundancy 39segment 26vs. routing and bridging 25

TTagging mode 10Transmission

in-band 29out-of-band 31side-band 30

VVirtual LAN see VLANsVLAN Tagging 10VLANs

background 7bandwidth 9benefits 8configuration 9maintenance 9security 8VIDP 9

WWell-Known Address (WKA) 15Why are they called VLANs 7


Date post:	21-Jan-2021
Category:	Documents
Upload:	others
View:	8 times
Download:	0 times

Network Manager Reference Guide - Avaya...

Documents