Packet Fragmentation And Reassembly - D-Link DES-3326 User Manual

24-port NWay Ethernet Switch User's Guide
the Internet. This default gateway is also used whenever no
specific route is found for a packet, or when there are several
gateways on a network.
Local computers can use default gateways, but the gateways
themselves need a more complete routing table to be able to
forward packets correctly. A protocol is required for the
gateways to be able to communicate between themselves and to
keep their routing tables updated.

Packet Fragmentation and Reassembly

TCP/IP can be used with many different types of networks, but
not all network types can handle the same length packets.
When IP is transmitting large files, large packets are much more
efficient than small ones. It is preferable to use the largest
possible packet size, but still be able to cross networks that
require smaller packets.
To do this, IP can ' negotiate' packet size between the local and
remote ends of a connection. When an IP connection is first
made, the IPs at both ends of the connection state the largest
packet they can handle. The smaller of the two is selected.
When a IP connection crosses multiple networks, it is possible
that one of the intermediate networks has a smaller packet size
limit than the local or remote network. IP is not able to
determine the maximum packet size across all of the networks
that may make up the route for a connection. IP has, therefore,
a method to divide packets into multiple, smaller packets to
cross such networks. This division of large packets into smaller
packets is referred to as fragmentation.
Switch Management and Operating Concepts
101