Path: utzoo!mnetor!uunet!husc6!bbn!uwmcsd1!ig!jade!ucbvax!PESCADERO.STANFORD.EDU!deering
From: deering@PESCADERO.STANFORD.EDU (Steve Deering)
Newsgroups: comp.protocols.tcp-ip
Subject: Re: Pseudo-Headers & Checksumming
Message-ID: <88.01.13.1239.060@pescadero.stanford.edu>
Date: 13 Jan 88 20:39:00 GMT
Sender: daemon@ucbvax.BERKELEY.EDU
Organization: The ARPA Internet
Lines: 20


	From: Thomas Narten <narten@purdue.edu>:

	     ...According the packet format given in the 86 SIGCOMM
	paper, entity identifiers are 32 bits long, hence the
	source/destination identifiers would use up all 64 bits of data. This
	leaves no room for other possibly important information like the
	forwarded entity identifier.  Without the forwarded entity identifier
	field, ICMP error processing would appear to be much more difficult if
	not impossible in some cases.

The VMTP header format has changed significantly since the SIGCOMM paper
was written.  Entity identifiers are now 64 bits long, and the client
entity id is the first field of the header, which means it (and it alone)
is returned in ICMP messages.  That works out well, because the client
entity id is all that is needed to identify the appropriate protocol
control block, both at the client end and the server end, as well as
in any intermediate forwarders.

Steve Deering