Subject: FARP formats

From: "Black, David" <[email-masked]>
Date: Thu, 10 Dec 1998 09:54:26 -0500

I was asked to reflect my comments on this at the WG meeting in Orlando to
the mailing list.

Context:
	- There are two different FARP request payload formats,
		and a total of four operating modes (FARP Match
		Address Code Points) with one more reserved for IPv6.
	- MATCH_WW_PN is the only mandatory operating mode, all
		others are optional.
	- A responder may ignore FARP requests for optional operating
		modes.

Problem:
	There is no requirement for a requestor to eventually issue
	a MATCH_WW_PN FARP request, as a result a requestor may never issue
	a FARP request that the responder supports.  In this situation,
	the responder ignores all of the requestor's FARP requests,
	creating the possibility that two implementations that comply
	to the spec may fail to	communicate; this is a problem.

Suggestion:
	(Mostly implied by the problem statement).  If the only operating
	mode that must be supported by responders is MATCH_WW_PN, then
	initiators using FARP MUST eventually issue that mode of FARP
request,
	including timing out the lack of response to any other mode on the
assumption
	that the responder does not support it and therefore did not
respond.
	The failure of a node to respond to a FARP request of any mode other
than
	MATCH_WW_PN MUST not prevent a requestor from communicating with
that node.
	In particular, if a responder only supports MATCH_WW_PN, then the
initiator
	must eventually issue a MATCH_WW_PN FARP request, timing out the
lack of
	response to other modes of FARP request issued before that.  The
modes
	other than MATCH_WW_PN are best viewed as optimizations, as
requestors must
	interoperate with responders that don't support them.

--David

David L. Black, Senior Technologist
EMC Corporation, 35 Parkwood Drive, Hopkinton, MA  01748
+1 (508) 435-1000 x76140, FAX: +1 (508) 497-6909
[email-masked]