Subject: I-D ACTION:draft-bvenkat-mtu-tcpmss-00.txt

From: [email-masked]
Date: Tue, 22 Dec 1998 16:55:26 -0500

A New Internet-Draft is available from the on-line Internet-Drafts directories.

	Title		: MTU discovery using TCP MSS and Discussion 
                          on MSS value in SYN acknowledgment
	Author(s)	: B. Venkat
	Filename	: draft-bvenkat-mtu-tcpmss-00.txt
	Pages		: 6
	Date		: 18-Dec-98
	
   Path MTU discovery as it exists now finds the least MTU of a given
   path. Traceroute through IP option [3] provides a method for finding
   the MTU on each hop using an ICMP message as a reply from the target
   host, with output link MTU in a portion of the message. The method
   proposed in this document intends to find the MTU on each hop on
   an internet path, without using the ICMP message for traceroute.
   This mechanism intends to acheive the same goal as the traceroute
   through IP option, but through a different mechanism.
 
   Discovery  of the MTU of each router on a internet path would serve
   as a valuable network debugging tool. The way in which it is
   proposed to be implemented, it has the advantage of being
   automatically supported by all of the routers that support the TCP
   layer. It has a couple of disadvantages that it generates quite a few
   TCP packets and the amount of time it takes to run to discover each
   MTU along the path is quite substantial.
 
   This document specifies the MTU discovery mechanism with the
   existing IP and TCP options and the ICMP message types that
   exist on all routers that support TCP layer in the internet. This
   method is suggested as an alternative to the Traceroute through
   IP option [3]. The intention is not to obsolete RFC 1393.
 
   This document also suggests that by default a reply SYN packet
   from a target host should include a MSS value that is derived from
   the MTU of a connected network.

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