H3C Technologies H3C SecPath F1000-E - Manual (Page 25)

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• finwait timer: When a TCP connection is changed into FIN_WAIT_2 state, the finwait timer is
started. If no FIN packet is received within the timer interval, the TCP connection will be terminated.
If a FIN packet is received, the TCP connection state changes to TIME_WAIT. If a non-FIN packet is
received, the system restarts the timer upon receiving the last non-FIN packet. The connection is
broken after the timer expires.
Follow these steps to configure TCP timers:
To do… Use the command… Remarks
Enter system view system-view —
Configure the TCP synwait timer tcp timer syn-timeout time-value
Optional
75 seconds by default.
Configure the TCP finwait timer tcp timer fin-timeout time-value
Optional
675 seconds by default.
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 ICMP to Send Error Packets
Introduction
Sending error packets is a major function of ICMP. In case of network abnormalities, ICMP packets are
usually sent by the network or transport layer protocols to notify corresponding devices so as to facilitate
control and management.
Advantages 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 a default route to the default gateway in its routing table after startup. The default
gateway will send ICMP redirect packets to the source host, telling it to reselect a correct next hop to send
the subsequent packets, if the following conditions are satisfied:
• The receiving and forwarding interfaces are the same.
• The selected route has not been created or modified by ICMP redirect packet.
• The selected route is not the default route of the device.
• There is no source route option in the packet.
ICMP redirect packets function simplifies host administration and enables a host to gradually establish a
sound routing table to find out the best route.
2. Sending ICMP timeout packets