Re: What's 16 bits between friends?
Brian Dickson <briand@ca.afilias.info> Tue, 18 September 2007 20:09 UTC
Return-path: <ipv6-bounces@ietf.org>
Received: from [127.0.0.1] (helo=stiedprmman1.va.neustar.com) by megatron.ietf.org with esmtp (Exim 4.43) id 1IXjNq-0001OV-3A; Tue, 18 Sep 2007 16:09:22 -0400
Received: from [10.90.34.44] (helo=chiedprmail1.ietf.org) by megatron.ietf.org with esmtp (Exim 4.43) id 1IXjNo-0001K8-1u for ipv6@ietf.org; Tue, 18 Sep 2007 16:09:20 -0400
Received: from vgateway.libertyrms.info ([207.219.45.62] helo=mail.libertyrms.com) by chiedprmail1.ietf.org with esmtp (Exim 4.43) id 1IXjNj-0006IA-EP for ipv6@ietf.org; Tue, 18 Sep 2007 16:09:15 -0400
Received: from briand-vpn.int.libertyrms.com ([10.1.7.90]) by mail.libertyrms.com with esmtp (Exim 4.22) id 1IXjNi-00007R-R4; Tue, 18 Sep 2007 16:09:14 -0400
Message-ID: <46F03060.6010504@ca.afilias.info>
Date: Tue, 18 Sep 2007 16:09:04 -0400
From: Brian Dickson <briand@ca.afilias.info>
User-Agent: Thunderbird 2.0.0.6 (Windows/20070728)
MIME-Version: 1.0
To: michael.dillon@bt.com
References: <20070918120411.GF2363@cs.uni-bonn.de> <46EFD636.7040008@ca.afilias.info> <D03E4899F2FB3D4C8464E8C76B3B68B0010D6F7E@E03MVC4-UKBR.domain1.systemhost.net>
In-Reply-To: <D03E4899F2FB3D4C8464E8C76B3B68B0010D6F7E@E03MVC4-UKBR.domain1.systemhost.net>
Content-Type: text/plain; charset="ISO-8859-1"; format="flowed"
Content-Transfer-Encoding: 7bit
X-SA-Exim-Mail-From: briand@ca.afilias.info
X-SA-Exim-Scanned: No; SAEximRunCond expanded to false
X-Spam-Score: 0.0 (/)
X-Scan-Signature: a2c12dacc0736f14d6b540e805505a86
Cc: ipv6@ietf.org
Subject: Re: What's 16 bits between friends?
X-BeenThere: ipv6@ietf.org
X-Mailman-Version: 2.1.5
Precedence: list
List-Id: "IP Version 6 Working Group \(ipv6\)" <ipv6.ietf.org>
List-Unsubscribe: <https://www1.ietf.org/mailman/listinfo/ipv6>, <mailto:ipv6-request@ietf.org?subject=unsubscribe>
List-Post: <mailto:ipv6@ietf.org>
List-Help: <mailto:ipv6-request@ietf.org?subject=help>
List-Subscribe: <https://www1.ietf.org/mailman/listinfo/ipv6>, <mailto:ipv6-request@ietf.org?subject=subscribe>
Errors-To: ipv6-bounces@ietf.org
michael.dillon@bt.com wrote: >> From what I have seen so far as responses, the counter arguments are: >> - there are these wonky things that maybe a few dozen >> research sites are playing with that use 64-bits for MAC >> - changing the spec would require, like, actual work. Let's >> just leave it alone >> >> IMHO, those arguments don't hold water. >> > > If your goal is to enable IPv6 to be deployed in the global Internet, > then any changes which reserve FEWER bits for interface addresses would > be counterproductive. Since IPv6 does reserve a full 64 bits for > interface addresses, that means that there are only 64 bits that can be > used in network prefixes, i.e. routing table entries. This allows router > vendors the possibility to optimize their code or their route table > storage by only allowing 64 bits of data per entry if there are no known > prefixes longer than 64 bits. Your proposal to reduce the interface bits > makes it less possible to apply such an optimization which reduces the > ability of network operators to scale up the IPv6 Internet. > First of all, not all routes are /64. There are of course aggregates, shorter prefixes. But, there can be, and are, longer prefixes than /64. They just don't work with autoconf. Many infrastructure routes on large IPv6 transit networks make use of the full range, all the way down to /126's for point-to-point links. Those are often aggregated internally, by router, by site, and by region, e.g. as /120's, /112's, and /104's. And loopbacks with /128's. It isn't IPv6 that reserves 64 bits, it is only those subsets of IPv6 functionality that use Interface Identifiers, such as autoconf. My goal is to keep the *number* of prefixes in the *DFZ* as small as possible. /64's or /80's, whichever is used for LAN networks doing autoconf, should *never* appear in the DFZ. Only the top level PI blocks or fully aggregated PA blocks, with no longer-prefixes, should appear in the DFZ. So, the size of the autoconf prefix is actually irrelevant for what you're thinking of. The only places where deaggregated prefixes should be seen, is where they are an ISPs infrastructure prefixes, or an ISP's PA assignments, both of which need to be carried internally. > Of course, there is a similar negative factor here at a higher level. By > making fundamental changes to IPv6 at this late date, we would force > vendors to change their code, and network operators to update all their > routers. These things all take time, therefore your proposed changes > would delay the deployment of IPv6 on the global Internet. Actually, if you paid attention to what I was saying - this ONLY affects HOSTS doing AUTOCONF. IT DOES NOT REQUIRE ANY ROUTER CODE CHANGES. It *does* support the notion of those *using* routers changing the assignments they use on subnets that are doing autoconf, from /64 to /80. Those don't even need to change for deployed subnets; this primarily addresses long-term need for new deployments. And, it isn't a one-size-fits-all alternative. There are side cases where special IPv6 stuff uses, and needs, and expects to be given, a /64. That's fine. /64's and /80's can live together happily. The number of end user assignments, be they /80 or /64, for autoconf subnets, remains the same. The only difference is, how much space gets chewed up by a bazillion such assignments. That's why I originally discussed the importance of understanding the value of an *extra* 16 bits. You can fit 64k networks of size /80, in one /64, which means you can give loads of room for growth to each customer, without impacting the overall capacity within, say, a /48, which is the smallest current assignment. A /48, broken down to /80, is 4.3 BILLION networks. Even giving 8 bits of growth room to each end assignment, that is still 16 MILLION networks. That's a lot. On the other hand, if you do the /64 thing, a /48 only has room for 64K networks, and no room to grow any of them. *THAT* is the squeeze play that can, and likely will, blow up the DFZ on IPv6 without changing the current /64-only world of autoconf. Brian -------------------------------------------------------------------- IETF IPv6 working group mailing list ipv6@ietf.org Administrative Requests: https://www1.ietf.org/mailman/listinfo/ipv6 --------------------------------------------------------------------
- Re: (no subject) Tim Osburn
- (no subject) FIGEN CETIN
- (no subject) B.Svante Eriksson
- (no subject) masuda yuko
- (no subject) masuda yuko
- (no subject) timbeck04
- RE: (no subject) Christian Huitema
- (no subject) timbeck04
- RE: Are privacy extensions, RFC 3041, defined for… John Spence
- RE: Are privacy extensions, RFC 3041,defined for … timothy enos
- (no subject) judith minkin
- (no subject) Anjali Gajendragadkar
- (no subject) Ignatios Souvatzis
- Re: What's 16 bits between friends? Brian Dickson
- Re: What's 16 bits between friends? Ignatios Souvatzis
- RE: What's 16 bits between friends? michael.dillon
- Re: What's 16 bits between friends? Brian Dickson
- Re: What's 16 bits between friends? Brian Dickson
- Re: What's 16 bits between friends? Mark Smith
- RE: What's 16 bits between friends? michael.dillon
- RE: What's 16 bits between friends? Templin, Fred L