Chapter 14Wide Area Networks

Introduction►The main difference between LAN and WAN is distance

►Generally WAN services are leased from service providers

►The idea of using WAN protocols is to change networks with large distances between them into LAN-like connected network

Defining WAN Terms

☼Customer premises equipment: (CPE) Customer premises equipment (CPE) is equipment that’s owned by the subscriber and located on the subscriber’s premises.

☼Demarcation point: The demarcation point is the precise spot where the service provider’s responsibility ends and the CPE begins. It’s generally a device in a telecommunications closet owned and installed by the telecommunications company (telco). It’s your responsibility to cable (extended demarc) from this box to the CPE, which is usually a connection to a CSU/DSU or ISDN interface.

☼Local loop: The local loop connects the demarc to the closest switching office, which is called a central office.

☼Central office (CO): This point connects the customer’s network to the provider’s switching network. Good to know is that a central office (CO) is sometimes referred to as a point of presence (POP).

☼Toll network: The toll network is a trunk line inside a WAN provider’s network. This network is a collection of switches and facilities owned by the ISP.

Data Terminal Equipment (DTE) & Data Communicational Equipment (DCE)

►All CISCO serial interfaces are DTE and they need a DCE to provide clock rate to them

►The Channel Service Unit/ Data Service Unit (CSU/ DSU) provides clock rate and makes connection between Digital LAN network & Digital WAN network

►The modem provides clock rate and makes connection between Digital LAN network & Analogue WAN network

CablesMajor cables are Serial cables: DB-60 pin from router side and

EIA/TIA-232EIA/TIA-449

V.35X.21

EIA-530(DTE only) at CSU/DSU side

WAN Services focus on:

Layer 2

Layer 1

EncapsulationWAN encapsulation protocols

HDLC, PPP, Frame Relay,X.25, ATM, LAPB, LAPD,PPPoE, Cable, DSL, MPLS

WAN Connection Types

•All these encapsulation protocols make error detection since they all use CRC in the FCS of the frame•LAPD is the only protocol who by default make Error Correction, PPP also support error correction but it’s not enabled by default

Leased lines

►referred to as a point-to-point or dedicated connection

►pre-established WAN communications

►no hard setup procedures are required

►expensive

►synchronous serial lines

►up to 45Mbps

►frequently use HDLC and PPP

High Level Data Link Control (HDLC)

•Protocol at Data Link layer.•Encapsulate only one Network Layer protocol (IP, IPX, or Apple Talk) at the same link.•Work only on Synchronous Interfaces (Serial, BRI) and is the default encapsulation on all CISCO Serial Interfaces.•Does not have Authentication, Callback, or Dynamic addressing capability.•Work only on similar vendors.

Point-To-Point Protocol (PPP)

•Protocol at Data Link layer.•Can Encapsulate several Network Layer protocol (IP, IPX, or Apple Talk) at the same link.•Work on Synchronous Interfaces (Serial, BRI) and Asynchronous Interfaces (Aux).

•Support Authentication, Callback, and Dynamic addressing capability.•Can Work on different vendors.

PPP uses

1- LCP Line Control Protocol -It is a method for Establishing, configuring maintaining and

terminating PPP connection

-LCP offers different PPP encapsulation options:-authentication-compression-error detection-multilink-PPP callback

2- NCP Network Control Protocol allow PPP to simultaneous use of multiple network layer protocols, for example IPCP ( Internet Protocol Control Protocol)

PPP Session Establishment

1. Link establishment phaseeach router sends LCP packet to configure and test the link, the LCP packetcontains the option field to negotiate about authentication, compression, data size2. Authentication phaseusing PAP or CHAP3. Network layer protocol phasethe PPP will use NCP to choose the network layer like IP

Password Authentication Protocol (PAP)

Two-way Handshake

•Remote Router sends his user name and password and continue until authentication is acknowledged or connection is terminated•Password is sent in clear text•Remote Router is in control of the frequency and timing of the login attempts

Challenge Handshake Authentication Protocol (CHAP)

Three-Way Handshake

•Local Router sends “Challenge”, the remote router. Response with a value calculated using one-way hash function MD5 based on Password and Challenge message•The local router checks the response by his own expected hash if the value match authentication is acknowledged or connection is terminated•The hash value is unique and random (actual password is not sent across the link)•Local Router controls the frequency and timing of challenges

PPP Authentication Methods

Configuring PPP

Router(config)#hostname RouterARouterA(config)#enable secret ciscoRouterA(config)#username RouterB password ciscoRouterA(config)#int s0RouterA(config-if)#encapsulation pppRouterA(config-if)#ppp authentication chap papRouterA(config-if)#ppp pap sent-username RouterA password cisco

Viewing PPP StatusRouterA#sh int s0

1. Authenticated but without checking IPsUP UPLCP OpenOpen: IPCP

Check validity of IPs using command: Router#sh cdp neighbors detail

2. Wrong password or user nameUP DownLCP ClosedClosed: IPCP, CDPCP

3. Mismatched encapsulationUP DownLCP REQsentClosed: IPCP, CDPCP

RouterA#debug ppp authentication

Packet Switching

►always connected (like leased line)

►bandwidth sharing

►synchronous serial

►56Kbps to 45Mbps

►use virtual circuit

►to send data constantly DO NOT USE PACKET SWITCHING

►frame relay and X.25 are packet switching technologies

Frame Relay

►saves money

►high performance

►successor of X.25 but does not use error correction

►Non Broadcast Multi Access NBMA (i.e. by default no broadcast is passing through it)

►dynamic bandwidth allocator

►connection oriented data-link technology

►deals with data-link layer and physical layer

►in data-link layer frame-relay encapsulates information from the upper OSI layers, as example IP traffic would be encapsulated into a frame format that can be transmitted over frame-relay link

►in physical layer the same serial cables that support ppp support frame-relay, they are: EIA/TIA-232, EIA/TIA-449, V.35, X.21 EIA/TIA-530

Why we use Frame Relay

Frame-relay reserves the leased B.W to you, this B.W is a part of a shared B.W (let’s say 256 Kbps of 1.544 Mbps)

When the rest of the B.W is not used you can use it, this is offered by packet-switch nets

Frame-relay sites will share telecommunication company backbone net Telecommunication company switches are responsible of mapping the connections

between the sites

Frame Relay Structure

Frame Relay Terminology

AccessRate

CIR

Access Rate: the maximum speed that frame relay interface can transmit

CIR (Committed Information Rate): the maximum B.W that your service provider guarantee to be delivered

T1

Lin

k1.5

44

Mbps

256

K

bps

128 Kbps

256 Kbps

64 Kbps

T1: 1.544 Mbpsa

b

c

Supposing link a and link b are not transmitting right now then link c can extend beyond the 64 Kbps and use all available B.W that may reach to 1.544 Mbps

Any sent data more than CIR is flagged with the Discard Eligibility (DE)= 1 When congestion happens in frame-relay switch, it sends Backward Explicit

Congestion Notification (BECN) to the source, sends Forward Explicit Congestion Notification (FECN) to the destination, and starts deleting any packet with DE= 1

When notifications reach source and destination they both start using flow control

DLCI Data Link Connection IdentifierDLCI is a number that identify the logical circuit between router and frame-relay switch (16 - 1007), it is supplied by provider.Router(config-if)#frame-relay interface-dlci 400 <16 - 1007>

Local DLCI

Global DLCI

LMI Local Management InterfaceSignaling standard between router and frame relay switchLMI is responsible for managing the connection and maintaining the status between devicesIt will provides messages about

Keepalive: verify that data is flowing Multicasting: allow efficient distribution of routing information and ARP requests over

frame relay network. Multicasts use DLCI 1019 – 1022 Global addressing: allow global significant making frame relay cloud to work exactly

like LAN Status of virtual circuit:

Active: every thing is up and routers can exchange informationInactive: remote router is not workingDeleted: no LMI is being received from switch could be line failure

LMI Types: Cisco (also called gang of four) ANSI Q.933A

Router(config-if)#frame-relay lmi-type cisco ansi q933a

Auto sensed in 11.2 or newer

DLCI MappingDynamic Mapping x Static Mapping

In order For each router to get to the remote router ,it will built Mapping Table inone of two way :1. Dynamic Mapping using Inverse ARP .2. Static Mapping.Both map Local DLCI no. with Remote Router IP address.

Router(config)#frame-relay inverse-arp protocol DLCIProtocol: IP, IPX, Apple TalkDLCI: DLCI of the interface we want to exchange IARPIARP is ON by default

Frame Relay switch builds mapping table by doing the following:

1. Reads source DLCI2. Searches the opposite DLCI3. Sends the slot port that is connected to the destination

Static Mapping

Static mapping is used to spread broadcast (for example to publish RIP)Router(config-if)#frame-relay map protocol destination_address local_DLCI broadcast

Frame Relay Encapsulation Types

• Cisco (default)• IETF Internet Engineering Task Force

Router(config-if)#encapsulation frame-relayRouter(config-if)#encapsulation frame-relay ietf

Frame Relay Topologies

Star (Hub and Spoke)• Least expensive Topology• Most Poplar• Use single interface• Must use subinterfaces to connect to multiple PVCs

Full Mesh• Costly• Needs direct connection to each site (many physical interfaces)• Redundancy

Partial Mesh• Not all sites have direct access to all other sites

Configuring Frame Relay

RouterA(config)#int s0RouterA(config-if)#ip add 172.16.5.5 255.255.255.0RouterA(config-if)#no shutRouterA(config-if)#encapsulation frame-relayRouterA(config-if)#frame-relay interface-dlci 100

No static mapping is required because IARP is on but if you turn it off then static mapping will be like this:

RouterA(config-if)#frame-relay map ip 172.16.5.7 100 broacast

RouterB(config)#int s0RouterB(config-if)#ip add 172.16.5.7 255.255.255.0RouterB(config-if)#no shutRouterB(config-if)#encapsulation frame-relayRouterB(config-if)#frame-relay interface-dlci 400

RouterB(config-if)#frame-relay lmi-type ansi

No static mapping is required because IARP is on but if you turn it off then static mapping will be like this:

RouterB(config-if)#frame-relay map ip 172.16.5.5 400 broacast

Configuring Subinterfaces

Point-to-Point

• Each point-to-point subinterface requires it’s own subnet•Subinterfaces act like leased lines

Multipoint

• Use single subnet so it saves address space• Subinterfaces act like NBMA so they do not solve split-horizon problem

Configuring Point-to-Point

RouterA(config)#int s0/0RouterA(config-if)#no ip addRouterA(config-if)#no shutRouterA(config-if)#encapsulation frame-relayRouterA(config-if)#int s0/0.110 point-to-ponitRouterA(config-subif)#ip add 172.17.0.1 255.255.255.0RouterA(config-subif)#frame-relay interface-dlci 110RouterA(config-subif)#bandwidth 64RouterA(config-subif)#int s0/0.120 point-to-ponitRouterA(config-subif)#ip add 172.18.0.1 255.255.255.0RouterA(config-subif)#frame-relay interface-dlci 120RouterA(config-subif)#bandwidth 64

S0/0.110 172.17.0.1 DLCI 110

S0/0.120 172.18.0.1 DLCI 120

RouterA

RouterB

RouterC

172.17.0.2

172.18.0.2

Configuring MultiPoint

RouterA(config)#int s0/0RouterA(config-if)#no ip addRouterA(config-if)#no shutRouterA(config-if)#encapsulation frame-relayRouterA(config-if)#int s0/0.2 multiponitRouterA(config-subif)#ip add 172.17.0.1 255.255.255.0RouterA(config-subif)#bandwidth 64RouterA(config-subif)#frame-relay map ip 172.17.0.2 120 broadcastRouterA(config-subif)#frame-relay map ip 172.17.0.3 130 broadcastRouterA(config-subif)#frame-relay map ip 172.17.0.4 140 broadcast

S0/0.210 172.17.0.1 DLCI 120

DLCI 130

DLCI 140

172.17.0.2

172.17.0.3

172.17.0.4

Configuring 2500 Router to act like Frame Relay Switch

2500(config)#frame-relay switching2500(config)#int s02500(config-if)#no ip add2500(config-if)#no shut2500(config-if)#clock rate 560002500(config-if)#encapsulation frame-relay2500(config-if)#frame-relay intf-type dce2500(config-if)#frame-relay route 110 interface s1 2202500(config-if)#int s12500(config-if)#no ip add2500(config-if)#no shut2500(config-if)#clock rate 560002500(config-if)#encapsulation frame-relay2500(config-if)#frame-relay intf-type dce2500(config-if)#frame-relay route 220 interface s0 110

2600A 2600B

2500

S0/1DLCI 110IP 172.17.0.1 /30

S0/0DLCI 220

IP 172.17.0.2 /30

S0 S1Frame Relay

Switch

Router#sh int s0/0To view encapsulation, LMI DLCI (default 1023, ansi or q.933a 0), B.W, MTU, Keepalive, MAC, Status of interface

Router#sh frame-relay mapTo view value of DLCI, IP of next hop, MAPPING TYPE [dynamic (IARP), static (broadcast)]

Router#sh frame-relay pvcTo view PVC status, no. of each type of PVC, value of DLCI, presence of congestion, presence of packets with DE= 1, BECN and FECN

Show Frame-relay CMDs

Circuit Switched

►like phone call

►low cost

►no data can transfer before an end-to-end connection is established

►uses dial-up modems or ISDN

►low-bandwidth

►asynchronous serial

ISDN (Integrated Service Digital Network)

►a replacement to the traditional analogue modem

►features:

1. Ability to carry variety of user traffic, video, telex, and telephone, in the same time2. Faster call setup (less than a second) by using D-channel (Delta-channel) which is

responsible of call setup, alarm messages (signaling information)3. Faster data transfer rate using B-channel (Bearer-channel) (64Kbps), each B-

channel can carry one type of data

ISDN Standard Access Methods

BRI Basic Rate Interface2B + 1D2x64K + 1x16K (max B.W)= 144Kbps

PRI Primary Rate Interface

USA and Japan23B + 1D23x64K + 1x64K (max B.W)= T1

1.544MbpsEurope

30B + 1D30x64K + 1x64K (max B.W)= 2.048Mbps

~

~

BRI and PRI Call Process

1. The D-channel from the local router to the local switch comes up2. The ISDN switch uses Signaling System 7 SS7 to setup a path to remote switch3. The remote switch setup the D-channel link to the remote router4. The B-channels are then connected end to end

ISDN Components

BRI

U

TE1NT1

U

TE1

NT1S/T

U

NT1S/T

TAR

US/TTAR NT1NT2

S/T

‼Function (Devices)• Native ISDN (TE1): device with BRI interface• Non-native ISDN (TE2): device without BRI interface (serial only)

‼Reference Point (Interface cables)• R• S• T• U

ISD

N S

ervi

ce P

rovi

der

Router(config)#isdn switch-type basic-ni to define type of switch of provider

Router(config)#int bri0Router(config-if)#isdn spid1 123…12 5551111 a SPID is a number supplied by the provider to identify line configuration of BRI serviceRouter(config-if)#isdn spid2 123…12 5552222

ISDN Basic Configuration

1. The message reaches the router and be compared with R.T, the router determines the exit interface. If it is the BRI then

2. Check that is the message allowed to pass through DDR, if yes then establishment of call (D-channel is working)

3. The router determines the next hop and determines how to call it4. Wait 120 sec idle then disconnect if there is no traffic

Dial- on Demand Routing DDR

1. Define static routes2. Define the interest traffic (also known as dialer list)3. Dialer information (no. to call) + BRI interface (on which dialer list will applied)

Configuring DDR

ISDN NetworkBRI1

RouterA

10.10.0.15551000

BRI0

RouterB

10.10.0.25552000

10.30.0.0

10.40.0.0Step 1: Define static routesRouterA(config)#ip route 10.30.0.0 255.255.255.0 10.10.0.2RouterA(config)#ip route 10.40.0.0 255.255.255.0 10.10.0.2RouterA(config)#ip route 10.10.0.2 255.255.255.255 bri1

Step 2: Define the interest traffic (also known as dialer list)RouterA(config)#dialer list 1 protocol IP permitORRouterA(config)#dialer list 1 protocol IP list 110RouterA(config)#access-list 110 permit tcp any any eq telnet

Step 3: Dialer information (no. to call) + BRI interface (on which dialer list will applied)RouterA(config)#int bri1RouterA(config-if)#ip address 10.10.0.1 255.255.255.0RouterA(config-if)#no shutRouterA(config-if)#encapsulation pppRouterA(config-if)#ppp authentication chapRouterA(config-if)#dialer-group 1RouterA(config-if)#dialer string 5552000ORRouterA(config-if)#dialer map IP 10.10.0.2 name RouterB 5552000

RouterA(config-if)#dialer idle-timeout 120RouterA(config-if)#dialer load-threshold 125

To view current call, phone number, and time left to end callRouter#sh isdn active

To check for switch connectivity problemsRouter#sh isdn status

To view number of reached dialer string, idle time out of B-channel, and good information about dialerRouter#sh isdn dialer

To view layer 2 information onlyRouter#sh isdn q921

To view layer 3 information, including call setup and teardownRouter#sh isdn q931

To debug using call setup and teardown activityRouter#debug dialer

Router#isdn disconnect bri0 or Router(config-if)#shutdown

Show ISDN CMDs

Cable and DSL

How to select1. Speed2. Security3. Popularity4. Customer Satisfaction

Cable

1. Headend2. Distribution network: HFC Hybrid Fiber-Coaxial architecture with 100-

2000 customers3. DOCSIS (data over cable service interface specification)

Digital Subscriber Line (DSL)

Most popular types are:• Symmetrical DSL• Asymmetrical DSLBut The term xDSL covers a number of DSL variations, such as ADSL, high-bit-rate DSL(HDSL), Rate Adaptive DSL (RADSL), Synchronous DSL (SDSL), ISDN DSL (IDSL), andvery-high-data-rate DSL (VDSL) which is employed by cisco to build new technology called Cisco Long Range Ethernet (LRE) with speeds from 5 to 15Mbps (full duplex) at distances up to 5,000 feet traveling over existing twisted-pair wiring