TEL104: Telecommunications 4

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Packet-Switching

This week we look at packet switching. Two basic implementations of packet switching are datagram networks (also called "best-effort" or "connectionless" networks) and virtual circuit packet switched networks (also called "connection-oriented" networks).

In datagram networks, each packet has a destination address and commonly a packet sequence number. This eliminates the dedicated path requirement from source to destination which means that each packet placed on the medium may take a different route.

In virtual circuit packet switching, an initial setup phase is used to set up a fixed route between the intermediate nodes for every packet exchanged during a transmission between end points.

Below are three links to on-line resources for use during this module. The first link is to Cisco's On-line Internetworking Technology Handbook while the other two hyperlink to the about.com web portal.

1. Go to the Cisco Internetworking Technology Handbook and read the pages on:
   • Introduction to WAN Technologies
   • Frame Relay
   • Switched Multimegabit Data Service
   Note: concentrate on the portions that discuss Packet Switching.
2. Go to the About.com Switching Types page and read the info on switching.
3. Go to the About.com VoIP Basics page and read the info on VoIP basics.
   Note: as time permits, read a few of the related articles.

• Cisco Internetworking Technology Handbook
• About.com Switching Types
• About.com VoIP Basics

Be ready to :

1. Discuss the two types of packet switching networks.
2. Provide examples of packet switching technologies at the LAN and WAN levels.
3. Discuss VoIP.