Re: [trill] FW: New Version Notification for draft-tissa-trill-mt-encode-01.txt
Donald Eastlake <d3e3e3@gmail.com> Thu, 12 July 2012 15:26 UTC
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From: Donald Eastlake <d3e3e3@gmail.com>
Date: Thu, 12 Jul 2012 11:26:25 -0400
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To: Naveen Nimmu <naveen@broadcom.com>
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Subject: Re: [trill] FW: New Version Notification for draft-tissa-trill-mt-encode-01.txt
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A few comments: It seems to me that the top level difficulty with this draft is that it assumes that TRILL is an Ethernet protocol. But it isn't. Where do these tags go in the TRILL Data frame on a PPP link [RFC6361] or in the possible IPv4/6 link format in draft-mrw-trill-over-ip or in the possible MPLS TRILL Data format in draft-ietf-l2vpn-trill-evpn? You could put new tags after the Inner.VLAN or you could expand the TRILL Header but trying to put new tags in front of the TRILL Header seems problematic and also guarantees that only new hardware can process the frame at all. Ignoring the above problem and commenting on the multi-topology and nickname expansion aspects of the draft: I'm not sure why the topology ID tag has 16 bits of topology when all the other IS-IS related topology things I know about have 12 bits of topology ID and, in the real world, I understand it is very rare to use more than around 8 topologies. Also, the interesting alternative of encoding the topology in the Outer.VLAN tag, which only works on Ethernet links, would tend to use the 12-bit VLAN ID for topology although I suppose, depending on how big a change you are making in the port silicon, you could repurpose the priority and DEI bits... Anyway, having a few reserved flag bits sometimes turns out to be extremely useful so I'm thinking that sticking with 12 bits would be better. And, in any case, redefining the content of the VLAN tag while continuing to use the C-VLAN Ethertype would be viewed as a problem by some. I'm not sure why there has to be an MT Capability bit. Wouldn't just not including the MT TLV be a good enough indication if you required even an MT capable RBridge only participating in base topology zero to include the MT TLV? If you are going to expand the nickname space, I don't quite see why you only add 8 bits and why, it appears, you are going for a larger flat nickname space. There is power in hierarchy. Perhaps you mean for the 8 bits to be used somewhat hierarchically for naming areas in multi-level or the like but it doesn't sound like that. Going to a flat 24-bit nickname seems like it, in general, requires new silicon and biases the design towards high end switches with bigger tables, etc. If you need new silicon anyway, I think that adding 16-bits with a fixed hierarchy split of the upper and lower 16-bit parts and using something like the "swap nickname" logic suggest in draft-perlman-trill-rbridge-mulilevel-04.txt would enable forwarding tables to remain small and better support a wider range of switches. Thanks, Donald ============================= Donald E. Eastlake 3rd +1-508-333-2270 (cell) 155 Beaver Street, Milford, MA 01757 USA d3e3e3@gmail.com On Mon, Jun 18, 2012 at 3:12 PM, Naveen Nimmu <naveen@broadcom.com> wrote: > A new version of this draft is posted. This version adds proposed extensions to support TRILL nickname space from 16bits to 24 bits. > Please review and provide feedback. > Thanks > \naveen > > -----Original Message----- > From: internet-drafts@ietf.org [mailto:internet-drafts@ietf.org] > Sent: Monday, June 18, 2012 8:13 AM > To: tsenevir@cisco.com > Cc: aldrin.ietf@gmail.com; ginsberg@cisco.com; Naveen Nimmu; ayabaner@gmail.com > Subject: New Version Notification for draft-tissa-trill-mt-encode-01.txt > > > A new version of I-D, draft-tissa-trill-mt-encode-01.txt > has been successfully submitted by Tissa Senevirathne and posted to the > IETF repository. > > Filename: draft-tissa-trill-mt-encode > Revision: 01 > Title: Multi Topology Encoding within TRILL data frames > Creation date: 2012-06-17 > WG ID: Individual Submission > Number of pages: 12 > URL: http://www.ietf.org/internet-drafts/draft-tissa-trill-mt-encode-01.txt > Status: http://datatracker.ietf.org/doc/draft-tissa-trill-mt-encode > Htmlized: http://tools.ietf.org/html/draft-tissa-trill-mt-encode-01 > Diff: http://tools.ietf.org/rfcdiff?url2=draft-tissa-trill-mt-encode-01 > > Abstract: > Two alternate methods of encoding Multi Topology Identifier within > the TRILL data frames are presented. Methods proposed herein do not > require overloading TRILL RBridge nickname to encode Multi Topology > Identifier. A method that expands TRILL nickname space from 16bits > to 24 bits is also presented in this draft. > > > > > The IETF Secretariat > > _______________________________________________ > trill mailing list > trill@ietf.org > https://www.ietf.org/mailman/listinfo/trill
- [trill] FW: New Version Notification for draft-ti… Naveen Nimmu
- Re: [trill] FW: New Version Notification for draf… Donald Eastlake
- Re: [trill] FW: New Version Notification for draf… Tissa Senevirathne (tsenevir)
- Re: [trill] FW: New Version Notification for draf… Donald Eastlake