R2511-HP MSR Router Series Layer 3 - IP Services Configuration Guide(V5)

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The path MTU uses an aging mechanism to make sure the source device can increase the path MTU
when the minimum link MTU on the path increases:
• When the TCP source device receives an ICMP error message, it reduces the path MTU and starts
an age timer for the path MTU.
• After the age timer expires, the source device uses a larger MSS in the MTU table as described in
RFC 1191.
• If no ICMP error message is received within 2 minutes, the source device increases the MSS again
until the MSS is as large as the MSS negotiated during TCP three-way handshake.
To enable TCP path MTU discovery:
Step Command Remarks
1. Enter system view.
system-view N/A
2. Enable TCP path MTU
discovery.
tcp path-mtu-discovery [ aging minutes |
no-aging ]
Disabled by default.
Configuring the TCP send/receive buffer size
Step Command Remarks
1. Enter system view.
system-view N/A
2. Configure the size of TCP
receive/send buffer.
tcp window window-size
Optional.
8 KB by default.
Configuring TCP timers
You can configure the following TCP timers:
• synwait timer—When sending a SYN packet, TCP starts the synwait timer. If no response packet is
received within the synwait timer interval, the TCP connection cannot be created.
• 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 is 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.
The actual finwait timer is determined by the following formula:
Actual finwait timer = (Configured finwait timer – 75) + configured synwait timer
To configure TCP timers:
Step Command Remarks
1. Enter system view.
system-view N/A