rfc4941bis: trying to keep focus
Fernando Gont <fgont@si6networks.com> Thu, 30 January 2020 20:51 UTC
Return-Path: <fgont@si6networks.com>
X-Original-To: ipv6@ietfa.amsl.com
Delivered-To: ipv6@ietfa.amsl.com
Received: from localhost (localhost [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id F0BE612086F for <ipv6@ietfa.amsl.com>; Thu, 30 Jan 2020 12:51:09 -0800 (PST)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -1.9
X-Spam-Level:
X-Spam-Status: No, score=-1.9 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, RCVD_IN_DNSWL_NONE=-0.0001, SPF_HELO_NONE=0.001, SPF_PASS=-0.001] autolearn=ham autolearn_force=no
Received: from mail.ietf.org ([4.31.198.44]) by localhost (ietfa.amsl.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id SrP9hSeUXI4V for <ipv6@ietfa.amsl.com>; Thu, 30 Jan 2020 12:51:08 -0800 (PST)
Received: from fgont.go6lab.si (fgont.go6lab.si [91.239.96.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by ietfa.amsl.com (Postfix) with ESMTPS id E034D120872 for <6man@ietf.org>; Thu, 30 Jan 2020 12:51:07 -0800 (PST)
Received: from [192.168.100.103] (unknown [186.183.50.221]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by fgont.go6lab.si (Postfix) with ESMTPSA id B386586A1D; Thu, 30 Jan 2020 21:51:01 +0100 (CET)
From: Fernando Gont <fgont@si6networks.com>
Subject: rfc4941bis: trying to keep focus
To: "6man@ietf.org" <6man@ietf.org>
Message-ID: <4085840f-6c30-323a-b2e9-544f1a783103@si6networks.com>
Date: Thu, 30 Jan 2020 17:50:45 -0300
User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.9.1
MIME-Version: 1.0
Content-Type: text/plain; charset="utf-8"; format="flowed"
Content-Language: en-US
Content-Transfer-Encoding: 7bit
Archived-At: <https://mailarchive.ietf.org/arch/msg/ipv6/dddGvk-LxIdH2E8Rdj-FE87YQwA>
X-BeenThere: ipv6@ietf.org
X-Mailman-Version: 2.1.29
Precedence: list
List-Id: "IPv6 Maintenance Working Group \(6man\)" <ipv6.ietf.org>
List-Unsubscribe: <https://www.ietf.org/mailman/options/ipv6>, <mailto:ipv6-request@ietf.org?subject=unsubscribe>
List-Archive: <https://mailarchive.ietf.org/arch/browse/ipv6/>
List-Post: <mailto:ipv6@ietf.org>
List-Help: <mailto:ipv6-request@ietf.org?subject=help>
List-Subscribe: <https://www.ietf.org/mailman/listinfo/ipv6>, <mailto:ipv6-request@ietf.org?subject=subscribe>
X-List-Received-Date: Thu, 30 Jan 2020 20:51:12 -0000
Folks, I'm trying to summarize what I've seen as part of the recent discussion about (or at least triggered by) rfc4941bis. First, let me give the (obvious) context: rfc4941bis is meant, for the most part, to address flaws in RFC4941 -- RFC4941 is a Standards Track document, already. rfc4941bis is not proposing or introducing temporary addresses, but simply addressing flows in the scheme *we already have* (which is widely deployed). Now, let's move to the main topics of this discussion: 1) "temporary addresses results in too many addresses" This is not a problem araising from RFC4941, but a problem with SLAAC. In SLAAC, routers offer network configuration information, and hosts do... what they virtually please. Routers could also advertise many different prefixes on the same link, leading to many addresses. Hosts could also manually configure lots of addresses. An OS might also provide a proprietary interface for proprietary apps to request "one address per flow". Given a sufficient number of prefixes and hosts, this may get to a point where implementation limits such as the maximum number of NCE may be hit. If folks are concerned about the maximum number of addresses that may be employed in a network (a valid concern), then I guess energy should be spent on how to address this general issue of SLAAC, *in SLAAC*, as opposed to simply bother about one of the many possible ways in which a host may configure addresses. I'd note that we have a BCP (RFC7934) about the topic of "number of addresses". In the typical/default case, RFC4941 will lead to a maximum of 7 addresses per host. In the context of RFC7934, I guess being able to handle 7 addresses per host is the least one could expect. I do understand that some systems can't handle them (given a sufficient number of hosts). Maybe we need to send a signal to router vendors. Maybe a few thousand entries in the NC is way too IPv4ish? All these issues are worth discussing... but they are issues with SLAAC or ipv6 network configuration, and not with RFC4941. That said, and given recent feedback, it seems sensible to reduce the preferred lifetime and valid lifetime of temporary addresses to 1 day and 2 days, respectively. This would result in one preferred and one deprecated temporary addresses (as opposed to 1 preferred and 6 deprecated addresses resulting from RFC4941). 2) The value of temporary addresses As noted above, one would assume that since RFC4941 has not been deprecated, there is consensus that RFC4941 provides value in the area of privacy. Everytime you reuse an identifier, it leaks information. Temporary addresses reduce the address lifetime, and hence limit the amount of time you reuse an identifier. That's an improvement. And it is a middleground between not using temporary addresses (and hence resuse the same identifier forever) or doing "one address per flow" which, while interesting, would take the number of addresses employed in any network to another dimension. As such (a middle-ground), it can't be expected to be perfect. Temporary addresses are meant employed for outgoing connections. Maybe RFC4941 should provide stronger hints or even recommendations that this use mode is enforced. For connection-oriented transport protocols, the concept is straightforward. For stateless protocols, not so much. But even if this mode is enforced for connection-oriented transport protocols, this would make temporary addresses reduce host exposure quite a lot. This is another area where temporary addresses have value. That said, I'm not sure to what extent it makes sense to argue about the value of temporary addresses in the context of *this* document. If we take the to extreme possible outcomes: * we don't publish rfc4941bis, and we keep a flawed RFC4941 * we publish rfc4941bis, and have an improved version of rfc4941 Only one of these options will improve RFC4941, and none of them will obsolete rfc4941. 3) Should temporary addresses be enabled by default? One would assume that since RFC4941 has not been deprecated, there is consensus that RFC4941 provides value in the area of privacy. In that sense, and in the context of RFC7258, I believe it would be a hard case to make to have temporary addresses disabled by default. I do believe some network might want to disable them. That would require the network to be able to convey this policy to hosts. This was tried (draft-gont-6man-managing-slaac-policy) and rejected ten years ago. I believe that, at least in the absence of policy, and in the context of RFC7258, it is sensible for the default to be "on". Besides, in a post-Snowden era, I believe we'd nevertheless have a hard time recommending OS vendors to disable them by default. Thanks! Cheers, -- Fernando Gont SI6 Networks e-mail: fgont@si6networks.com PGP Fingerprint: 6666 31C6 D484 63B2 8FB1 E3C4 AE25 0D55 1D4E 7492
- rfc4941bis: trying to keep focus Fernando Gont
- Re: rfc4941bis: trying to keep focus Pascal Thubert (pthubert)
- Re: rfc4941bis: trying to keep focus Lorenzo Colitti
- Re: rfc4941bis: trying to keep focus Gyan Mishra
- Re: rfc4941bis: trying to keep focus Gyan Mishra
- Re: rfc4941bis: trying to keep focus Gyan Mishra