Configuring The Tcp Send/Receive Buffer Size - HP 10500 Series Configuration Manual

A router that fails to forward the packet because it exceeds the MTU on the outgoing interface
2.
discards the packet and returns an ICMP error message, which contains the MTU of the outgoing
interface.
Upon receiving the ICMP message, the TCP source device calculates the current path MTU of the
3.
TCP connection.
The TCP source device sends subsequent TCP segments that each are smaller than the MSS (MSS
4.
=path MTU–IP header length–TCP header length).
NOTE:
If the TCP source device still receives ICMP error messages when the MSS is smaller than 32 bytes, the
•
TCP source device fragments packets.
• An ICMP error message received from a router that does not support RFC 1 191 has the MTU of the
outgoing interface set to 0. Upon receiving the ICMP message, the TCP source device selects the path
MTU smaller than the current path MTU from the MTU table as described in RFC 1 191 to calculate the
TCP MSS. The MTU table contains MTUs of 68, 296, 508, 1006, 1280, 1492, 2002, 4352, 8166, 17914,
32000, and 65535 bytes. Because the minimum TCP MSS specified by the system is 32 bytes, the actual
minimum MTU is 72 bytes.
After you enable TCP path MTU discovery, all new TCP connections detects the path MTU. The device
uses the path MTU to calculate the MSS to avoid IP fragmentation.
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 1 191.
• If no ICMP error message is received within two 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
1. Enter system view.
2. Enable TCP path MTU
discovery.

Configuring the TCP send/receive buffer size

To configure the TCP send/receive buffer size:
Step
1. Enter system view.
2. Configure the size of TCP
receive/send buffer.
Command
system-view
tcp path-mtu-discovery [ aging
minutes | no-aging ]
Command
system-view
tcp window window-size
96
Remarks
N/A
Optional.
Disabled by default.
Remarks
N/A
Optional.
The default is 8 KB.