Setting Mss For Tcp Connections; Configuring Path Mtu Discovery; Enabling Pmtu Discovery - Juniper JUNOSE SOFTWARE FOR E SERIES 11.3.X - IP-IPV6-IGP CONFIGURATION GUIDE 2010-10-31 Configuration Manual

Setting MSS for TCP Connections

tcp mss

Configuring Path MTU Discovery

tcp path-mtu-discovery
Copyright © 2010, Juniper Networks, Inc.
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.
By default, the router uses an MSS value of 1280 bytes and the advertised MSS is derived
from the MTU of the transmitting interface. However, you can use the tcp mss command
to set the MSS for TCP use.
Use to specify the MSS value for TCP to use.
NOTE: The MSS value is equal to the MTU value minus the IPv6 and TCP
headers, so the MSS value is generally 60 bytes less than the MTU.
Use the vrfName variable to specify a VRF to which you want to assign the TCP MSS
value.
Example
host1(config)#tcp mss 1000
Use the no version to remove the MSS value so that the router uses the advertised
MSS derived from the MTU of the output interface.
See tcp mss
IPv6 hosts transmit large amounts of data to other hosts using a series of IPv6 datagrams.
To best use resources, increase performance, and avoid difficult reassembly, hosts try
to send datagrams that are as large as possible without requiring fragmentation anywhere
along the path from the source to the destination. This datagram size is referred to as
the path MTU (PMTU), and it is equal to the smallest MTU for each hop in the path.
Path MTU discovery is the process of discovering the PMTU value and using that value
when transmitting IP datagrams.

Enabling PMTU Discovery

Use the tcp path-mtu-discovery command to enable PMTU discovery on the active
virtual router.
Use to enable and configure path MTU discovery on the virtual router.
Issue the command without any keywords to enable path MTU discovery.
Issue the age-timer keyword to set the time (minutes) that TCP waits before attempting
to increase the path MTU after receiving an ICMP Too Big message or after previously
Chapter 2: Configuring IPv6
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