Packet Switching

Packet Switching

•          Data transmitted in small packets

–        Typically 1000 octets

–        Longer messages split into series of packets

–        Each packet contains a portion of user data plus some control information

–        Control information

–        Routing (addressing) information

–        Packets are received, stored briefly (buffered) and passed on to the next node

Store and forward

 

Switching Technique

•          Station breaks long message into packets

•          Packets sent one at a time to the network

•          The two types of packet switching are:

–        Datagram packet switching

Virtual circuit packet switching

Features of Datagram Packet Switching

•          Each packet is treated independently

•          Packets can take any practical route

•          Packets may arrive out of order

•          Faster delivery to destination

•          Alternate rooting on node failure

Suitable for short messages

Virtual Circuit Packet Switching

•          Preplanned route established before any packets sent

•          Call request and call accept packets establish connection (handshake)

•          Each packet contains a virtual circuit identifier instead of destination address

•          No routing decisions required for each packet

•          No dedicated path

Virtual circuit packet switching