Differences between version 3 and revision by previous author of MSS.
Other diffs: Previous Major Revision, Previous Revision, or view the Annotated Edit History
| Newer page: | version 3 | Last edited on Sunday, October 30, 2005 12:57:45 pm | by PerryLorier | Revert |
| Older page: | version 2 | Last edited on Saturday, October 29, 2005 9:45:07 pm | by LindsayDruett | Revert |
@@ -1,16 +1,21 @@
[Acronym] for __M__aximum __S__egment __S__ize
----
-__Cisco's
TCP MSS Adjustment Feature__
+!!Adjusting the
TCP MSS on an intermediate routej
+The [TCP]
MSS Adjustment feature enables the configuration of the maximum segment size (MSS) for transient packets that traverse a router, specifically TCP segments in the SYN bit set, when Point to Point Protocol over Ethernet (PPPoE) is being used in the network. PPPoE truncates the Ethernet maximum transmission unit (MTU) 1492, and if the effective MTU on the hosts (PCs) is not changed, the router in between the host and the server can terminate the TCP sessions.
-The
TCP MSS Adjustment feature enables the configuration of the maximum segment size (MSS) for transient packets that traverse a router, specifically TCP segments in the SYN bit set, when Point to Point Protocol over Ethernet (PPPoE) is being used in the network. PPPoE truncates the Ethernet maximum transmission unit (MTU) 1492, and if the effective MTU on the hosts (PCs) is not changed, the router in between the host and the server can terminate the TCP sessions. The __ip
tcp adjust
-mss__ command specifies
the MSS value on the intermediate router of the SYN packets to avoid truncation
.
-----
-__Usage Guidelines__
+!!Linux's
TCP MSS Adjustment Feature
+use <tt>iptables --insert OUTPUT --jump TCPMSS --protocol
tcp --set
-mss ''mss'' </tt> to modify
the MSS value.
-When a host (usually a PC) initiates a
TCP session with a server, it negotiates the IP segment size by using the
MSS option field in the TCP SYN packet.
The value of
the MSS field is determined by the maximum transmission unit (MTU) configuration
on the host. The default MSS value for a PC is 1500 bytes.
-
-The PPP over Ethernet (PPPoE) standard supports a MTU
of only 1492 bytes. The disparity between
the host and PPPoE MTU size can cause the router in between the host and the server to drop 1500-byte
packets and terminate TCP sessions over the PPPoE network. Even if the path MTU (which detects the correct MTU across the path) is enabled on the host, sessions may be dropped because system administrators sometimes disable the ICMP error messages that must be relayed from the host in order for path MTU
to work
.
+!!Cisco's
TCP MSS Adjustment Feature
+
The __ip tcp adjust-mss__ command specifies
the MSS value
on the intermediate router
of the SYN
packets to avoid truncation
.
*The __ip tcp adjust-mss__ command helps prevent TCP sessions from being dropped by adjusting the MSS value of the TCP SYN packets.
*The __ip tcp adjust-mss__ command is effective only for TCP connections passing through the router.
[More information here on Cisco Systems web site|http://www.cisco.com/en/US/products/sw/iosswrel/ps1839/products_feature_guide09186a00804247fc.html]
+----
+__Usage Guidelines__
+
+When a host (usually a PC) initiates a TCP session with a server, it negotiates the IP segment size by using the MSS option field in the TCP SYN packet. The value of the MSS field is determined by the maximum transmission unit (MTU) configuration on the host. The default MSS value for a PC is 1500 bytes.
+
+The PPP over Ethernet (PPPoE) standard supports a MTU of only 1492 bytes. The disparity between the host and PPPoE [MTU] size can cause the router in between the host and the server to drop 1500-byte packets and terminate TCP sessions over the PPPoE network. Even if the path MTU (which detects the correct MTU across the path) is enabled on the host, sessions may be dropped because system administrators sometimes disable the ICMP error messages that must be relayed from the host in order for path MTU to work.
