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JunosE 11.3.x IP, IPv6, and IGP Configuration Guide
Defining TCP Maximum Segment Size
ip tcp adjust-mss
Setting MSS for TCP Connections
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host1(config)#ip sa-validate trap-enable
Use the no version to disable the generation of source address validation failure traps
on the router.
See ip sa-validate trap-enable
The ip tcp adjust-mss command enables you to modify the TCP maximum segment
size (MSS) for TCP sessions.
When defined, the router modifies the maximum segment size (MSS) for TCP SYN
packets traveling through the interface. The modification occurs only for packets that
contain values smaller than the adjusted MSS value. When the packet does not contain
an MSS field value, the router assumes an MSS value of 536 and makes any modifications
accordingly.
NOTE: Implementation of the MSS value is identical for both ingress and
egress interface traffic. That is, the router uses the same MSS value when
adjusting inbound or outbound TCP traffic.
Use to modify the maximum segment size (MSS) for TCP SYN packets traveling through
the interface. The router compares the MSS value of incoming or outgoing packets
against the adjusted MSS setting and replaces smaller values that it detects in any
packets with the larger setting. If the packet does not contain an MSS value, the router
assumes a value of 536 for the packet MSS on which to base the comparison.
NOTE: The purpose behind using MSS is to alleviate problems with Path
Discovery (PMTUD) and resulting " black hole" detection issues. (See RFC
2923, " TCP Problems with Path MTU Discovery," for additional information
about the " black hole" scenario.)
Example
host1(config-if)#ip tcp adjust-mss 1000
Use the no version to remove the MSS assignment from the profile.
See ip tcp adjust-mss
MSS is used by TCP to define the maximum amount of data that a TCP interface can
accept in any single packet (or segment size). The MSS value is typically negotiated
during connection establishment and is not renegotiated.
Copyright © 2010, Juniper Networks, Inc.
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