Switching Technologies-1

7/29/2019 Switching Technologies-1

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Course plan

Basics of switching

Virtual Local Area Networks (VLAN)

Function of reliability and performance increase

Quality of service (QoS)

Security and network access functions

Multicast

Switch management functions Review of D-Link switches


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PRACTICAL WORKS

1. Basic switch commands2. Commands of switch firmware updating and switch configuration loading/backup

3. Commands of MAC and IP addresses forwarding tables, ARP tables management

4. Configuration of VLAN on the basis of IEEE 802.1Q

5. GVRP protocol configuration

6. Self-work to create LAN on the basis of IEEE 802.1Q standard

7. Configuration of asymmetric VLAN8. Configuration of Traffic Segmentation

9. Configuration of Q-in-Q (Double VLAN) function

10. Configuration of STP, RSTP, MSTP protocols

11. Configuration of LoopBack Detection function

12. Link Aggregation

13. Access Control Lists14. Management of nodes connection to switch ports. Port Security function

15. Switch ports connection management. IP-MAC-Port Binding function

16. QoS configuration. Traffic prioritization. Bandwidth management

17. Port Mirroring


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Basics of switching

switch


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Switch is

operated on OSI data link layer.

could simultaneously establish several connections (microsegmentation).

allowed each workstation to transfer and to accept data simultaneously,

using the whole bandwidth in both directions (full duplex).


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Switch operation in a local network

In local networks, switches process frames on the basis of transparent bridge algorithm,

according to the IEEE 802.1D standard. Its operation begins with creation of the forwardingtable (Forwarding DataBase, FDB).


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When a switch receives a frame sent by computer A to computer B, itreads MAC address of receiver and looks for this MAC address in its

forwarding table. As soon as the record associating MAC address of

receiver (computer) with one of the switch ports (except for source

port) is found, the frame is transferred through appropriate egressport. This process is called frame forwarding.

If egress port is appeared to coincide with the source port, a frame

will be discarded by a switch. This process is called filtering.

If MAC address of a receiver in an arrived frame is unknown (there is

no appropriate record in a forwarding table), switch creates multiple

copies of this frame and transfers these copies through all ports, except

that it arrived to. This process is called flooding.


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Switching methods

The first step made by switch before making the decision on frame transmission, is framereceiving and content analysis. One of three operation modes can be implemented in a

switch to define its behavior when receiving a frame:

Store-and-forward switching;

Cut-through switching;

Fragment-free switching.


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Switch form factor

Desktop switch

Rack mounted switch Chassis switch


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Switch physical stacking

A ring stack is built as follows: each device is connected to overlying and underlying,

thus the lowermost and uppermost switches in a stack are also interconnected. During data

transmission a packet is transferred from one device of a stack to another sequentially until

it reaches the port of destination. The system automatically defines an optimal way of

transmission for traffic that allows gaining full usage of bandwidth. Advantage of ringtopology is that if an output of one device is out of operation or there is a communication

breakaway, then remaining devices will continue to operate in a normal mode.

In chain stack (linear topology) each device is connected with overlying and underlying.

The uppermost and lowermost switches are not interconnected.


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Switches interfaces


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For easy connection possibility many switches are equipped with special slots for

compact replaceable:

GBIC

(Gigabit Interface Converter); SFP (Small Form Factor Pluggable);

SFP+ (Enhanced Small Form Factor Pluggable);

XFP (10 Gigabit Small Form Factor Pluggable).


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GBIC SFP

XFPSFP+


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Architecture of switches

One of the main components of all switching equipment is a switch

fabric. A switch fabric is a chipset connecting inputs with outputs on

the basis of fundamental technologies and principles of switching. A

switch fabric has three functions: to switch traffic from one port of a fabric to another, providing

their equivalence;

to provide quality of service (QoS);

to provide fault tolerance.


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Shared bus architecture

Shared bus architecture, as appears from its name, uses a bus which provides communication ofinput/output devices (ports) connected to it as to the shared environment. A bus is used in time

sharing mode, and that is at each point in time only a single source is allowed to send traffic on

the bus. Bus access management is performed by a centralized arbiter that grants a source to

send data on the bus.


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Shared memory architecture

Shared memory architecture is based on large capacity fast RAM memory as a general

buffer of switching system intended to store incoming packets before their transmission.


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Crossbar architecture

Two types of switches with a crossbar switch fabric can be singled out: buffered crossbar;

arbitrated crossbar.


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In buffered crossbar switches buffers are installed at three main stages: at input,

output, and switch fabric directly. Due to the queues appearing at three stages, this

architecture allows to avoid the complexities caused by centralized arbiter. Queues

management implemented by one of the dispatching algorithms is used at output of

each stage.

Arbitrated crossbar switches architecture has buffer-less switching elements and an

arbiter that controls traffic transmission between fabric inputs and outputs.

Absence of buffers in switching elements is compensated by buffers at ingress and

egress ports. Usually developers use one of three buffering methods:

- output buffers,

- input buffers,- combined input and output buffers.


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Input-queued switch architecture

Memory of each ingress port is

organized as FIFO (First Input

First Output) queue which is used for

packets buffering before the process of

switching begins. One

of the problems of such switch fabric is

Head-Of-Line blocking (HOL). It

happens when switch tries to transfer

packets from several input queues to

one egress port simultaneously.


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Output-queued switch architecture

Packets are buffered only at egress

ports after the end of

switching process.


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Virtual output-queued switch architecture

Memory of each ingress

port is organized as N (N

quantity of egress

ports) FIFO logical

queues, one per egress

port. These queues are

used for buffering of

incoming packets which

are sent to

egress port j (j = 1, .N).


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Combined Input and Output Queued (CIOQ)

switch architecture

Buffers are connected both to ingress and egress ports. Memory of every ingress port is

organized as N virtual FIFO output queues, one per egress port.

The switching system is based on a pipeline principle when each stage is called a time

slot.


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Properties affecting switches performance

Switch performance can be characterized by following parameters:

frames filtering rate;

frames forwarding rate;

throughput;

forwarding delay.

Besides, there are several switch characteristics which strongly affect specified performance

characteristics. They are:

switching type;

size of frame buffer(s);

switching capacity;

processor(s) performance; size of forwarding table.


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Flow control in half duplex and in full duplex modes


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Switching technologies and OSI model

Layer 2 switches analyze incoming frames, make the decision on their further

transmission and transfer frames to their destinations using MAC addresses of OSIdata link layer. Primary benefit of L2 switches is transparency for top layer

protocols.

L2 switching is a hardware-based one. Frame transmission can be carried out by

specialized ASIC controller. As a rule L2 switches are used for network segmentation

and working groups consolidation.Along with advantages of L2 switching there are some restrictions. Presence of

switches does not prevent broadcast frames propagation in all segments of a

network.

L3 switches carry out switching and filtering using addresses of data link (layer 2)

and network (layer 3) layers. L3 switches perform switching within working group

and fulfill routing between various subnets or virtual local networks (VLAN).

L3 switches carry out packet routing like conventional routers. They support RIP

(Routing Information Protocol), OSPF (Open Shortest Path First), BGP (Border

Gateway Protocol) to communicate with other L3 switches or routers, to create

routing tables, to carry out routing using policies strategy, to control multicast

traffic.


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Three-layer network model


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Three-layer network model

Core layer is on the top of hierarchy and provides reliable and fast transmission of big

data pieces. Traffic transferred through a core is common for many users. User data areprocessed at distribution level which sends requests to core if necessary. Core layer should be

reliable as any failure at this layer can lead to disconnection between network distribution

layers.

Distribution/Aggregation layer, also known as layer of working groups, is a link between

the access layer and core layer. Depending on implementation, the distribution layer can fulfill

the following functions: Routing, quality of service and network security;

Link aggregation;

Transfer between technologies (for example, between 100Base-TX and 1000Base-T).

Access layer regulates the access of users and working groups to resources in incorporated

network. Its primary goal is creation of users log-in/log-out points. This layer has following

functions:

Users access and network policies management;

Creation of separate collisions domains (segmentation);

Working groups connection to distribution layer;

Using switched local networks technology.

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Switching Technologies-1

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