Re: [rbridge] two minor issues with the isis-02 draft
Donald Eastlake <d3e3e3@gmail.com> Wed, 25 February 2009 05:14 UTC
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Date: Wed, 25 Feb 2009 00:09:45 -0500
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From: Donald Eastlake <d3e3e3@gmail.com>
To: James Carlson <james.d.carlson@sun.com>
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Cc: TRILL/RBridge Working Group <rbridge@postel.org>
Subject: Re: [rbridge] two minor issues with the isis-02 draft
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Jim, Thanks for review this. See below... On Thu, Feb 19, 2009 at 3:11 PM, James Carlson <james.d.carlson@sun.com> wrote: > > The good news is that I'm done with this pass over our source code and > the relevant TRILL documents, so you likely won't hear many more > issues out of me for a while. There's light at the end of the > tunneling protocol. > > > First issue: why does isis-02 specify the following? > > 1. Information on reachable RBridge neighbors and the cost of the hop > via the Extended IS Reachability TLV (Type #22) [RFC5305] (wide > metric). TRILL IS-IS does not use the IS Reachability TLV (Type > #2) (narrow metric). > > This restriction doesn't appear to be necessary, and for bridges that > don't need the extended metrics, it seems slightly wasteful. If > there's a purpose behind this (I have a bug filed against our code, as > we're still using #2), it'd be helpful to spell that purpose out > here. > > (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. 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. > Second issue: the following mechanism from protocol-11 seems to be > missing: > > 6.6 Per VLAN appointed forwarder status lost counter (see Section > 4.6.2). > > 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. > -- > James Carlson, Solaris Networking <james.d.carlson@sun.com> > Sun Microsystems / 35 Network Drive 71.232W Vox +1 781 442 2084 > MS UBUR02-212 / Burlington MA 01803-2757 42.496N Fax +1 781 442 1677 Thanks, Donald -- ============================= Donald E. Eastlake 3rd +1-508-634-2066 (home) 155 Beaver Street Milford, MA 01757 USA d3e3e3@gmail.com _______________________________________________ rbridge mailing list rbridge@postel.org http://mailman.postel.org/mailman/listinfo/rbridge
- [rbridge] two minor issues with the isis-02 draft James Carlson
- Re: [rbridge] two minor issues with the isis-02 d… Donald Eastlake
- Re: [rbridge] two minor issues with the isis-02 d… Donald Eastlake
- Re: [rbridge] two minor issues with the isis-02 d… James Carlson
- Re: [rbridge] two minor issues with the isis-02 d… mike shand
- Re: [rbridge] two minor issues with the isis-02 d… James Carlson
- Re: [rbridge] two minor issues with the isis-02 d… Radia Perlman
- Re: [rbridge] two minor issues with the isis-02 d… James Carlson
- Re: [rbridge] two minor issues with the isis-02 d… Donald Eastlake
- Re: [rbridge] two minor issues with the isis-02 d… James Carlson