Fragment Classification; Enabling/Disabling Fragment Classification; Setting The Fragment Timeout - Alcatel OmniSwitch 6624 Network Configuration Manual

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Configuring QoS
To change the flow timeout, enter the
For example:
-> qos flow timeout 100
The timeout will not be active on the switch until you enter the qos apply command. For more informa-
tion about the qos apply command, see

Fragment Classification

By default, fragments are not classified. The commands available for configuring fragment classification
are listed here:
qos classify fragments
qos fragment timeout
When an IP packet reaches a hop with an MTU smaller than the size of the packet, it may be fragmented.
If the IP packet contains a TCP or UDP packet, then the TCP/UDP header is copied to the first IP frag-
ment. The remaining fragments contain only user data.
Some policies require that a TCP or UDP packet be classified based on TCP/UDP port number.
The switch has a default policy for fragments, which is to accept all fragments; however, a packet with a
fragment offset of 1 will be dropped. IP packets with a fragment offset of 1 are typically used for security
attacks.

Enabling/Disabling Fragment Classification

To enable fragment classification, enter the qos classify fragments command:
-> qos classify fragments
The switch will now classify each fragment in the flow.
To disable fragment classification, enter the following command:
-> qos no classify fragments
The setting is not active until the qos apply command is entered. For more information about the qos
apply command, see

Setting the Fragment Timeout

If fragment classification is enabled, the switch waits for all fragments of a packet to arrive. By decreas-
ing the wait time, you can free some memory that the switch is using to keep track of packets; the default
value is 10 seconds.
To change the fragment timeout, enter the qos fragment timeout command with the desired number of
seconds. For example:
-> qos fragment timeout 5
The timeout will not be active on the switch until you enter the qos apply command. (For more informa-
tion about the qos apply command, see
not take effect if the qos classify fragments command has not been entered.
OmniSwitch 6624/6648 Network Configuration Guide
qos flow timeout
"Applying the Configuration" on page
"Applying the Configuration" on page
"Applying the Configuration" on page
Configuring Global QoS Parameters
comimand with the desired number of seconds.
21-46.
April 2004
21-46.
21-46.) The timeout does
page 21-17

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