[rbridge] two minor issues with the isis-02 draft

[James Carlson]

Donald Eastlake writes:
> > (I was unable to find anything in protocol-11 that supported the need
> > for this particular restriction, though it's possible I missed
> > something.)
> 
> I don't think the Extended IS Reachability TLV is particularly
> wasteful. In the common case, both the TLV #2 and #22 data for an
> adjacency is 11 bytes long so 23 will fit into a TLV for either.

OK; maybe "wasteful" is too strong.  "Needless" is better.

> I think the primary motivation for the 24 bit metric per adjacency in
> the Extended IS Reachability TLV is that you have only 6 bits of
> default metric per adjacency in the original IS Reachability TLV (it's
> an octet but one bit is used up to indicate internal/external and one
> bit is now the up/down bit [RFC 2966]). A 6 bit integer metric (1 to
> 63) is very coarse and is insufficient to express the relative costs
> of a 10 megabit versus a 1 gigabit link, let alone the existing 10
> gigabit links and the 40 and 100 gigabit links under development. [RFC
> 3784] Given this problem, mandating the Extended IS Reachability TLV
> seems reasonable to me do you can have a globally consistent link
> speed derived metric.

That's a great argument for why one *should* use the newer metric
scheme.  What's the argument for an effective "must"?

> > The protocol draft doesn't seem to indicate how large this counter
> > needs to be (is 8 bits enough or would more be better?), but I think
> > this should be added into the existing "2.d VLANs and Bridge Roots"
> > sub-TLV.
> 
> Yes, draft-eastlake-trill-rbridge-isis is no longer being updated. The
> plan is for all the TRILL IS-IS TLV and sub-TLVs to be added to the
> draft-ward-l2isis draft. I'll check that this is being included in
> that transfer.

OK; thanks.  That sounds good.

-- 
James Carlson, Solaris Networking              <james.d.carlson at sun.com>
Sun Microsystems / 35 Network Drive        71.232W   Vox +1 781 442 2084
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