Switch

1

2

• It is a Physical layer device (Layer 1)

• It is Dummy Device

• It works with 0’s and 1’s (Bits)

• It works with broadcasting

• It works with shared bandwidth

• It is has 1 Broadcast Domain and 1 Collision Domain

• Collisions are identified using Access Methods called

CSMA/CD and CSMA/CA

Hub

3

Broadcast Domain & Collision Domain

• Broadcast Domain

Set of all devices that receive broadcast frames

originating from any device within the set.

• Collision domain

In Ethernet, the network area within which frames that

have collided are propagated is called a collision

domain.

• A collision domain is a network segment with two or

more devices sharing the same bandwidth.

• Repeaters and hubs propagate collisions, LAN switches,

bridges, and routers do not.

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• Active Hubs uses power supply and

regenerates the data (i.e.) strengthens the

signals in case of disturbances.

• Passive Hubs doesn’t use power supply and it will not

not regenerates the data (i.e.) strengthens the signals

in case of disturbances. It is used only to share the

physical media

• Intelligent Hubs are sometimes called as smart hubs.

These devices basically function as active hubs, but also

include a microprocessor chip and diagnostic

capabilities and are useful in troubleshooting situations.

Types of Hubs

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• It is Datalink layer device (Layer 2)

• Its is An Intelligent device

• It works with Physical addresses (i.e. MAC addresses)

• It works with fixed bandwidth

• It works with Flooding and Unicast

• It has 1 Broadcast domain and Number of Collision

domains depends upon the number of ports.

• It maintains a MAC address table

Switch

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Types of Switches

• Manageable switches

On a Manageable switch an IP address can be assigned

and configurations can be made. It has a console port .

• Unmanageable switches

On an Unmanageable switch configurations cannot be

made, an IP address cannot be assigned as there is no

console port.

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Bridge Vs Switch

• Bridges are software

based

• Bridges have lesser

no. of ports

• Generally used for

connecting two

different topology

(Segment)

• Switches are hardware

based

• Switches have higher

no. of ports

• Generally used for

connecting single

topology (Segment)

Bridge Switch

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• It is a Network layer device (Layer 3)

• Its is an Intelligent device

• It works with Logical Addressing (i.e. IP,IPX,AppleTalk)

• It works with Fixed bandwidth

• Number of Broadcast domains depends upon the

number of ports and Number of Collision domains

depends upon the number of ports.

Router

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How many Broadcast & Collision Domains

E0 E1

10

Broadcast Domains

E0 E1

11

Collision Domains

E0 E1

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Cisco divided the Switches into 3 Layers

• Access Layer Switches

Switches Series : 1900 & 2900

• Distribution Layer Switches

Switches Series : 3000 & 5000

• Core Layer Switches

Switches Series : 7000, 8000 & 10,000

Cisco’s Hierarchical Design Model

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Access Layer Switch

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Three types of Switching Mode :

• Store & Forward

• Fragment Free

• Cut through

Switching Mode

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• Store and forward switching pulls in the whole frame into

the port buffer, checks the CRC and then switches the frame

if its error free

• All switches support Store and Forward

• A Default switching method for distribution layer switches.

• Latency : High

– Latency is the period of time from when the beginning of a

frame enters to when the end of the frame exits the switch.

– Latency is directly related to the configured switching process

and volume of traffic.

Store & Forward

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Store & Forward

Whenever, a Frame is received by the SwitchWhenever, a Frame is received by the Switch

It will store the Complete FrameIt will store the Complete Frame

It will run CRC on Complete FrameIt will run CRC on Complete Frame

If, ErrorIf, Error If, No ErrorIf, No Error

Contact SourceTransport Layer

Contact SourceTransport Layer Check MATCheck MAT

If, Entry is there

If, Entry is there

If, Entry is notthere


UnicastUnicast FloodingFlooding

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• It is also referred to as Modified Cut-Through or

Runtless switching method.

• The switch checks the first 64 bytes of a frame before

forwarding it for fragmentation, thus guarding against runt

frames.

• 64 bytes is the minimum legal size of an Ethernet frame.

Frames smaller than 64 bytes are called Runt frames.

• Faster compared to Store and Forward but could switch corrupt

or bad frames.

• A Default Switching method for access layer switches.

• Latency : Medium

Fragment Free

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Fragment Free


It will store the FrameIt will store the Frame

It will run CRC on 64 byte of FrameIt will run CRC on 64 byte of Frame

If, ErrorIf, Error If, No ErrorIf, No Error

Contact SourceTransport Layer

Contact SourceTransport Layer Check MATCheck MAT

If, Entry is there

If, Entry is there




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• The switch reads only the first part of the frame

(i.e) the destination MAC address before forwarding

• It is faster compared to store and forward but the

biggest Problem is it may be switching bad frames.

• Although this occurs infrequently and the destination

network adapter will discard the faulty packet upon

receipt

• A Default switching method for the core layer switches

• Latency : Low

Cut Through

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Cut through


Check MATCheck MAT

If, Entry is there

If, Entry is there




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Catalyst 1900

12 A B1110987654321

10BaseT

External of Switch

Fast Ethernet 100 mbps Ports

10 mbps Ports

Education

Switch