TMC1254 Communication and Computer Network Semester 2 2013/2014

Switching

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Learning Unit Objectives
• Understand the concept of switching. • Understand and able to differentiate between different types of switching.

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• How many connection per device?

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Introduction
• A network is a set of connected devices • How to connect them for communication?
– Using mesh topology but wasteful – Used switching

• Switched network consists of a series of interlinked nodes, called switches (temporary connection btw 2 or > devices)

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Switched network

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Simple Switching Network

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Taxonomy of switched networks

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Circuit Switched Networks
Three Phases Efficiency Delay

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CIRCUIT-SWITCHED NETWORKS
• consists of a set of switches connected by physical links. • Connection between two stations is a dedicated path made of one or more links. – However, each connection uses only one dedicated channel on each link. – Each link is normally divided into n channels by using FDM or TDM.

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How circuit-switched network works?
• Consist of three phases: 1. Setup phase:
– When end system A needs to communicate with end system M, system A need to request a connection to M that must accepted by all switches as well as by M – Allocation of resources as needed

2. Data transfer: data is transferred from node to node. 3. Teardown: After all data have been transferred, the circuits are torn down.
– Circuit is terminated, de-allocation of resources
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Several points need to be emphasized
• Circuit switching takes place at physical layer • Before starting communication, the stations must make a reservation for the resources to be used during the communication • Data transferred btw the two stations are not packetized • There is no addressing involved during data transfer. The switches route the data based on their