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From: mitton@enet.dec.com (Dave Mitton)
Newsgroups: comp.protocols.iso
Subject: Re: ES-IS Resolved (Token Ring!)
Message-ID: <22963@shlump.lkg.dec.com>
Date: 29 May 91 00:28:15 GMT
References: <14934@encore.Encore.COM>
Sender: newsdaemon@shlump.lkg.dec.com
Reply-To: mitton@enet.dec.com (Dave Mitton)
Organization: Digital Equipment Corporation, Littleton MA
Lines: 49

>From: mckellar@pinocchio.encore.com (Steve McKellar)
>Newsgroups: comp.protocols.iso,comp.protocols.iso.dev-environ
>Subject: Re: ES-IS Resolved (Token Ring!)
>Date: 28 May 91 14:34:30 GMT
>Reply-To: mckellar@pinocchio.encore.com (Steve McKellar)

>
>In article <1991May24.031145.948@netcom.COM> cmilono@netcom.COM (Carlo Milono)
>writes:
>
>> Ah, I have found several references that back-up these standards - ahem, 
>> however...I failed to mention (because I didn't think it was an issue)
>> that I was attempting to route over Token Ring, which uses FUNCTIONAL
>> Addresses rather than multicast.
>
>um, could someone explain - or point to an explanation - of FUNCTIONAL
>addresses? what they are, how they're used, etc. thanks.
>
>
>steve mckellar

Sure!
	A Functional Address is an 802.5/Token Ring unique concept.
It is a set of Locally Administered space Group (aka Multicast) addresses
of the form:  (using IBM big-endian format)

	11000000:00000000:0uuuuuuu:uuuuurrr:iiiiiiia:iiiaaiaa
        GL-----mbz--------F

where each of the lettered bits are intended to be used as a bit mask value
instead of a unique binary value.

The IEEE 802.5 std. does not further divide them, but the IBM Arch Specs
call out the lower bits as "Reserved to IBM" and the upper bits as "User
assignable".   I have indicated with "i" known IBM uses of FAs.  The
"a" bits are assigned by the standard to ring functions and bridging.


WRT to the cisco topic that started this discussion: 

	Current implementations of Token Ring data link chips are incapable of
receiving the assigned multicast addresses for ISO ES-IS,  therefore NIST
in cooperation with IBM has assigned Functional Address bits for use by ES-IS 
routers and end stations.
	This of course, creates another Token Ring to Ethernet interoperability
issue for bridges.

	Dave Mitton.
	Digital Equipment Corp.