Switches in Networking

B. Konkoth

Network Traffic Scalability

Ability to handle growing amount of work Capability of a system to increase performance

Latency Amount of time it takes for a packet of data to get

from one designated point to another Network failure

Failure of a component of a network because of malfunction or natural or human-caused error

Collisions Two devices on the same Ethernet network

attempting to transmit data at exactly the same time.

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Switches A switch is a combination of a hub and a bridge.

It can interconnect two or more workstations, but like a bridge, it observes traffic flow and learns.

When a frame arrives at a switch, the switch examines the destination address and forwards the frame to the necessary connection.

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Switches:

Isolating traffic patterns and providing multiple access.

Switches are easy to install and have components that are hot-swappable.

The backplane of a switch is fast enough to support multiple data transfers at one time.

Major role

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Workstations connected to a shared segment of a LAN

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Workstations connected to a dedicated segment of a LAN

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A Switch with Two Servers Allowing Simultaneous Access to Each Server

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A server with two NICs and two connections to a switch

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A pair of remote bridges and switch combinationdesigned to isolate network traffic

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Switch providing multiple access to an e-mail server

Switches vs Routers

Switches Routers Switches are

considered layer-two devices

Uses MAC address Faster Switches are used

within networks to forward local traffic intelligently

Routers are layer-three devices

Uses IP address Because of the

additional processing required have high latency

Routers are used between networks to route packets in the most efficient manner

Fully switched network

Switches replace all the hubs of an Ethernet network with a dedicated segment for every node

Since any segment contains only a single node, the frame only reaches the intended recipient

This allows many conversations to occur simultaneously

Full Duplex vs Half Duplex

Full Duplex Half Duplex

A data communications term that refers to the ability to send and receive data at the same time

Information can move in only one direction at a time

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Full duplex connection of workstations to a LAN switch

Network Segment

A network segment is a single span of physical connectivity between two computer devices

Also used to describe a group of computer equipment organized as a network using the same range of addresses

Network Segment

Cut-through switch

A packet switch where the switch starts forwarding that frame (or packet) before the whole frame has been received, normally as soon as the destination address is processed.

This technique reduces latency through the switch, but decreases reliability

Store and forward switch

Switch will save the entire packet to the buffer and check it for errors or other problems before sending

If the packet has an error, it is discarded.

Fragment-free switch

It works like cut-through except that it stores the first 64 bytes of the packet before sending it on.

The reason for this is that most errors, and all collisions, occur during the initial 64 bytes of a packet.