3Com Switch 8800 Advanced Software V5 Configuration Guide

238 CHAPTER 24: IP PERFORMANCE CONFIGURATION
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CAUTION: The actual length of the finwait timer is determined by the following
formula:
Actual length of the finwait timer = (Configured length of the finwait timer - 75) +
configured length of the synwait timer
Configuring TCP MSS
for the Interface
The TCP maximum segment size (MSS) on an interface determines whether TCP
packets need to be fragmented when forwarded. If the size of a packet is smaller
than the TCP MSS, the packet is unnecessarily to be fragmented; otherwise, it will
be fragmented according to the TCP MSS.
Follow these steps to configure TCP MSS for the interface:
Configuring ICMP
Error Packet Sending
Sending error packets is a major function of Internet control message protocol
(ICMP). In case of network abnormalities, ICMP packets are usually sent by the
network or transport layer protocols to notify corresponding devices, thus
facilitating control and management.
Advantage of sending ICMP error packets
There are three kinds of ICMP error packets: redirect packets, timeout packets and
destination unreachable packets. Their sending conditions and functions are as
follows.
1 Sending ICMP redirect packets
A host may have only one default route to the default gateway in its routing table
after startup. If certain conditions are satisfied, the default gateway will send ICMP
redirect packets to the source host and notify it to reselect a correct next hop
router to send the subsequent packets.
Configure TCP synwait timer’s
timeout value
tcp timer syn-timeout
time-value
Optional
By default, the timeout value
is 75 seconds.
Configure TCP finwait timer’s
timeout value
tcp timer fin-timeout
time-value
Optional
By default, the timeout value
is 675 seconds.
Configure the size of TCP
receive/send buffer
tcp window window-size Optional
By default, the buffer is 8
kilobytes.
To do... Use the command... Remarks
To do... Use the command... Remarks
Enter system view system-view -
Enter interface view interface interface-type
interface-number
-
Configure TCP MSS for the
interface
tcp mss value Required
1,460 bytes by default.