[Sip] Review of draft-ietf-sip-hop-limit-diagnostics-03
"Vijay K. Gurbani" <vkg@lucent.com> Wed, 19 July 2006 19:12 UTC
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Date: Wed, 19 Jul 2006 14:12:14 -0500
From: "Vijay K. Gurbani" <vkg@lucent.com>
Organization: Bell Labs Security Technology Research Group
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To: Scott Lawrence <slawrence@pingtel.com>
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Cc: SIP LIST <sip@ietf.org>
Subject: [Sip] Review of draft-ietf-sip-hop-limit-diagnostics-03
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Scott: I went through draft-ietf-sip-hop-limit-diagnostics-03; here are my comments on the draft. I went through the existing WG list discussions regarding this draft to make sure that I was not duplicating any items that have already been discussed. To the best of my knowledge, the following have not yet been discussed. 1) In Montreal, I had mentioned to you that the ICMP sends back more than 64 bits of original datagram, and that maybe 64 "bits" was transcribed in error. As it turns out, rfc792 does indeed say 64 bits of orgininal datagram. However, in practice, we have observed far more data is returned from the original datagram than 64-bits. RFC1122 allows implementations to send more than 8 octets (see Section 3.2.2 of rfc1122). So... what we have observed is that Linux returns 520 bytes of the original datagram, and Solaris returns 64 bytes; but for Solaris, this is configurable in the kernel. And ICMPv6 (rfc2463) tries to fit as much of the original datagram without exceeding the minimum IPv6 MTU in the ICMP message. So, what does this all mean to hop-limit-diagnostics-03? Probably no changes, but interesting and relevant background information if you will like to maintain it in the text. 2) Section 3.1, third paragraph talks about removal of "Via and Route headers". I think you meant Record-Route headers instead of (or in addition to?) Route headers. In a dialog-establishing INVITE, there'll be greater chances of Record-Route headers being present than Route headers (which, if they are present consists of a pre-loaded Route set). Moreover, the Route headers would be consumed at every hop thereby reducing the size of the message, whereas the R-R headers are inserted, thus increasing the size. It seems that we ought to preserve the Via headers as much as possible, at the expense of R-R or Route headers. The Vias give diagnostic information on which intermediaries have handled the request, which is of interest. The Route header, on the other hand, portends which intermediary will handle the request beyond the element that generated a 483. 3) Nit: Section 3.1, third paragraph, first sentence is incomplete. It states, "...acceptable; the only exception to this rule is when ." 4) In the SIP messages, headers that continue should be indented (LWS). The Via headers, for instance, contain a branch parameter that begins on a new line without the continuation LWS. 5) Section 5 appears to lay the legal groundwork for why a UAC should accept a response that contains a body for which the UAC did not express an interest in receiving. I think this is good to have. I would change the first sentence of the second paragraph to read as follows: Note that a UAC MUST be prepared to receive message bodies that it does not understand and did not request in a response; this is ... That is, move the object of what the UAC must be prepared to do closer to the UAC. 6) In Section 6, it appears that the 483 response has been pruned, although the text does not indicate so. By my count, if the UAC started with a M-F of 9, then it should have 9 Via headers, whereas the example shows the number of Via headers to be 7. You may just want to simply mention that the request has been pruned in the response. Other than that, I am glad that the draft is out -- need this stuff. Thanks, - vijay -- Vijay K. Gurbani vkg@{lucent.com,research.bell-labs.com,acm.org} Bell Laboratories, Lucent Technologies, Inc. 2701 Lucent Lane, Rm. 9F-546, Lisle, Illinois 60532 (USA) _______________________________________________ Sip mailing list https://www1.ietf.org/mailman/listinfo/sip This list is for NEW development of the core SIP Protocol Use sip-implementors@cs.columbia.edu for questions on current sip Use sipping@ietf.org for new developments on the application of sip
- [Sip] Review of draft-ietf-sip-hop-limit-diagnost… Vijay K. Gurbani