Overview Of Fragmentation; Reassembly Parameters; Fragmentation Commands - Avaya G350 Administration

Configuring the router
Configuring fragmentation

Overview of fragmentation

The G350 supports IP fragmentation and reassembly. The G350 router can fragment and reassemble IP
packets according to RFC 791. This feature allows the router to send and receive large IP packets where
the underlying data link protocol constrains the Maximum Transport Unit (MTU).
IP fragmentation involves breaking a datagram into a number of pieces that can be reassembled later. The
IP source, destination, identification, total length, and fragment offset fields, along with the more
fragment and don't fragment flags in the IP header, are used for IP fragmentation and reassembly.
IP fragmentation works as follows:
•
Each IP packet is divided into fragments.
•
Each fragment becomes its own IP packet.
•
Each packet has same identifier, source, and destination address.
Fragments are usually not reassembled until final destination. The G350 supports fragmentation of IP
packets according to RFC 791, and reassembly of IP packets destined only to its interfaces.

Reassembly parameters

Reassembly is associated with the following user-configurable parameters:
•
Fragment Size — The maximum number of concurrently reassembled packets:
Range: 0 to 200. Default: 100.
•
Fragment Timeout — The maximum time, in seconds, to wait for a packet to be reassembled:
Range: 5 to 120. Default: 10.
•
Fragment Chain — The maximum number of fragments allowed per packet:
Range: 2 to 2048. Default: 64.

Fragmentation commands

Use the following commands to configure fragmentation and reassembly. For more information about
these commands, see Avaya G350 Media Gateway CLI Reference, 555-245-202.
•
Use the
•
Use the
single IP packet destined to the router. Use the
to its default value.
•
Use the
to the router to reassemble at any given time. Use the
fragment size to its default value.
•
Use the
fragmented IP packet destined to the router. Use the
timeout to its default value.
•
Use the
interface.
•
Use the
are destined to a router.
158
command to clear the fragment database and restore its default values.
clear fragment
command to set the maximum number of fragments that can comprise a
fragment chain
command to set the maximum number of fragmented IP packets destined
fragment size
command to set the maximum number of seconds to reassemble a
fragment timeout
command to set the treatment for IP fragmentation packets entering on an
fragments
command to display information regarding fragmented IP packets that
show fragment
no form of this command to set the fragment chain
form of this command to set the
no
form of this command to set the fragment
no
Administration of the Avaya G350 Media Gateway
June 2004