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Configuring QoS Configuring Global QoS Parameters
OmniSwitch 6600 Family Network Configuration Guide April 2006 page 24-17
To change the flow timeout, enter the qos flow timeout comimand with the desired number of seconds.
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 “Applying the Configuration” on page 24-46.
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 “Applying the Configuration” on page 24-46.
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 “Applying the Configuration” on page 24-46.) The timeout does
not take effect if the qos classify fragments command has not been entered.