Fri, 23 Oct 87 10:59:08 PDT
Yes, I see what you mean. It does appear (from the IBM
documentation) that the LLC-layer hides source routing in
type 2 service. This is, I suppose, one of the big reasons for
complaints about source routing.
You mention that if one of the bridges goes down, everything
goes crazy. However, this is the case with MAC-level bridges (eg: TransLan),
and with "proxy ARP routing". So, this doesn't put source routing
in any worse company than those (although none of those are what I
would pick for a network - mainly for this reason).
Now, I have previously asked the question "what's the politics
of source routing in the IEEE 802 committees?". I then reported on
a conversation with an IBMer on 802.5. From that conversation, it
seemed that source routing was, probably, only a matter of time (though
the IBMer, to his credit, was very cautious about anyone's ability to
predict the outcome of any given standardization process).
I have talked to one final 802 person. This person is
Mick Seaman, of DEC, who is on the 802.1 committee. He prefaced
his comments, and reiterated throughout, that his comments were
HIS PERSONAL comments; that they DID NOT necessarily represent DEC
or IEEE 802 views.
Mick Seaman's introductory remarks were that source routing
was something IBM was interested in in order to support existing IBM
products. However, he said, there was a general 802 interest in
supporting multiple paths. He expressed a bit of worry, though,
that some schemes might conflict with (to-be-developed) ISO schemes.
He also expressed his view that source routing MIGHT not make it
through the standardization effort (though he attributed this view to
his lack of cynicism about standardization processes). He felt much
surer that ISO would be very unlikely to standardize source routing,
even in an 802.5 environment.
He said there were some improvements to source routing that
could be made, but wasn't sure that the 802.5 committee was consistent
in looking at the overall picture (as opposed to spending time on
bits and other low-level issues).
When I mentioned there was some interest within the internet
to standardize on 802 encapsulation, including source routing for
802.5 networks, he said he was worried that the source routing (802.5)
document was not yet technically stable (from the specification point
End of report.
ps - Someone, in a private note, mentioned that maybe 802.1 (the
internetworking portion) had been quashed by ISO. From what Mick
Seaman said (though I didn't ask him about this), it appears that
the original 802.1 charter had been "to solve all the world's networking
problems, in the context of 802", but that the current charter seems
to be "solve those problems in networking which are peculiar to LAN's,
and which no one else [ISO, I suppose] is actively working on". He
seemed quite happy with the current charter, and they are apparently
quite close to releasing a draft standard.
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