About Packet Fragmentation...

Packet fragmentation occurs when a packet too large for the subsequent link reaches a network interface and is broken up into a series of fragments the size of the MTU of the ensuing link. Packet fragmentation has a negative impact on network performance for several reasons. First, a router has to perform the fragmentation - an expensive operation. Second, all the routers in the path between the router performing the fragmentation and the destination have to carry additional packets with the requisite additional headers.

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Glossary

Packet:

A discrete unit consisting of data that needs to be transported across a network and information necessary to direct that data to its destination.

Payload:

The data that needs to be transported across a network.

IP header:

Information prepended to the payload that allows the payload to reach its destination, including the source and destination and a checksum for error detection.

MTU:

Maximum Transmission Unit -- the largest size of packet that can be transported across a given link.

Path MTU:

The smallest MTU of all the links in a path.

Fragment:

When a fragment is larger then the next link, it is broken up into pieces called 'fragments' that are no larger than the MTU of the next link.

Fragment Series:

The set of fragments that composed a single original packet.

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The following pages contain graphs and analysis of fragmented packet traffic on several links:

Analysis by Trace

UCSD-CERF

The Poster I presented at the SDSC Student Intern Poster Session. (contains data from several traces)

May 17-June2, 2000

Ames Internet Exchange

Coming Soon!

Analysis by Data Type

Fragments per Fragment Series

Sizes of Fragment Series

First Fragment Sizes

Last Fragment Sizes

Original Packet Transmission Time