[MMUSIC] On RFC2326-biz
Julius Friedman <juliusfriedman@gmail.com> Thu, 08 January 2015 18:36 UTC
Return-Path: <juliusfriedman@gmail.com>
X-Original-To: mmusic@ietfa.amsl.com
Delivered-To: mmusic@ietfa.amsl.com
Received: from localhost (ietfa.amsl.com [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id B40651A006C; Thu, 8 Jan 2015 10:36:45 -0800 (PST)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: 0.301
X-Spam-Level:
X-Spam-Status: No, score=0.301 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, FREEMAIL_FROM=0.001, HTML_MESSAGE=0.001, MANGLED_LOAN=2.3, SPF_PASS=-0.001] autolearn=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 ihnLS_-dnpyc; Thu, 8 Jan 2015 10:36:43 -0800 (PST)
Received: from mail-pd0-x236.google.com (mail-pd0-x236.google.com [IPv6:2607:f8b0:400e:c02::236]) (using TLSv1 with cipher ECDHE-RSA-RC4-SHA (128/128 bits)) (No client certificate requested) by ietfa.amsl.com (Postfix) with ESMTPS id D48C31A0039; Thu, 8 Jan 2015 10:36:42 -0800 (PST)
Received: by mail-pd0-f182.google.com with SMTP id p10so12629804pdj.13; Thu, 08 Jan 2015 10:36:42 -0800 (PST)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20120113; h=mime-version:date:message-id:subject:from:to:content-type; bh=+AnNrztbGDYi0WqSJrIoZYAtO3lO8jtuMu0skpqLttQ=; b=O0V+t2xBdDtj898itmpu2smnmHUi5cxhVdvJdf3FV6BH5QEtrdFMcyIrqDJRHONusF uNhix6kge2AgSvmHI+9iVvqwFaAoZvGl+2G/Gt9ufQRxs4NyFJ6zeLCdIeUaagpVBjLs jp6VYP0ozK4AFFpw56SSz6Mzn7zYyZ2RlQ6AtxukJjxDZPz0d6QaMH56kSh9MJRuBojM j4GUbrO4C86M9P8jdxf1pz/4lt5I5rvIQNjqo7JZqHo15CTuFGxlxaFiNw/WFywQLRgG jjNCaBJhZ/jA+j81ZorItfjXcT5kS7B028uXliSkJAzZM0yehLLtaO0mjTqQy+FszPrb 2FVg==
MIME-Version: 1.0
X-Received: by 10.70.140.130 with SMTP id rg2mr17199384pdb.49.1420742202045; Thu, 08 Jan 2015 10:36:42 -0800 (PST)
Received: by 10.70.117.99 with HTTP; Thu, 8 Jan 2015 10:36:42 -0800 (PST)
Date: Thu, 08 Jan 2015 13:36:42 -0500
Message-ID: <CACFvNHUfQyY9OrAx7iCCR5XLQM7LHKS28WfcJG=FsmWfJ8_BvA@mail.gmail.com>
From: Julius Friedman <juliusfriedman@gmail.com>
To: avt@ietf.org, mmusic@ietf.org
Content-Type: multipart/alternative; boundary="001a1134c7c8455ccf050c2852a8"
Archived-At: <http://mailarchive.ietf.org/arch/msg/mmusic/wMo-9b_POAv_olgnxQ4vik3dVyE>
Subject: [MMUSIC] On RFC2326-biz
X-BeenThere: mmusic@ietf.org
X-Mailman-Version: 2.1.15
Precedence: list
List-Id: Multiparty Multimedia Session Control Working Group <mmusic.ietf.org>
List-Unsubscribe: <https://www.ietf.org/mailman/options/mmusic>, <mailto:mmusic-request@ietf.org?subject=unsubscribe>
List-Archive: <http://www.ietf.org/mail-archive/web/mmusic/>
List-Post: <mailto:mmusic@ietf.org>
List-Help: <mailto:mmusic-request@ietf.org?subject=help>
List-Subscribe: <https://www.ietf.org/mailman/listinfo/mmusic>, <mailto:mmusic-request@ietf.org?subject=subscribe>
X-List-Received-Date: Thu, 08 Jan 2015 18:36:45 -0000
Reading further into the new draft I had some more feedback and questions which I feel should be addressed. I see that the re-transmission text has been moved elsewhere and that various nomenclature regarding 're-transmission' has been either removed or it's location and context has changed to totally oppose the previous concepts put forth... It seems that re-transmission is now only acceptable under UDP which the standard goes to remove support for? What about TCP? How should a RTSP 2 system deal with legacy RTSP 1 connection with that regard? I think there are several other places this mistake was made also. Appendix G <http://tools.ietf.org/html/draft-ietf-mmusic-rfc2326bis-40#appendix-G>. Requirements for Unreliable Transport of RTSP This appendix provides guidance for those who want to implement RTSP messages over unreliable transports as has been defined in RTSP 1.0 [RFC2326 <http://tools.ietf.org/html/rfc2326>]. RFC 2326 <http://tools.ietf.org/html/rfc2326> defined the "rtspu" URI scheme and provided some basic information for the transport of RTSP messages over UDP. The information is being provided here as there has been at at least one commercial implementation and compatibility with that should be maintained. The following points should be considered for an interoperable implementation: o Requests shall be acknowledged by the receiver. If there is no acknowledgement, the sender may resend the same message after a timeout of one round-trip time (RTT). Any retransmissions due to lack of acknowledgement must carry the same sequence number as the original request. o The round-trip time can be estimated as in TCP (RFC 6298 <http://tools.ietf.org/html/rfc6298>) [RFC6298 <http://tools.ietf.org/html/rfc6298>], with an initial round-trip value of 500 ms. An implementation may cache the last RTT measurement as the initial value for future connections. o The Timestamp header (Section 18.53 <http://tools.ietf.org/html/draft-ietf-mmusic-rfc2326bis-40#section-18.53>) is used to avoid the retransmission ambiguity problem [Stevens98 <http://tools.ietf.org/html/draft-ietf-mmusic-rfc2326bis-40#ref-Stevens98>]. o The registered default port for RTSP over UDP for the server is 554. o RTSP messages can be carried over any lower-layer transport protocol that is 8-bit clean. o RTSP messages are vulnerable to bit errors and should not be subjected to them. o Source authentication, or at least validation that RTSP messages comes from the same entity becomes extremely important, as session hijacking may be substantially easier for RTSP message transport using an unreliable protocol like UDP than for TCP. Bullet 5 - *TCP is too, what does this statement add?* *This information in the header seems to contradict what information is given later on in Appendix I.* *Additionally the information related to re-transmission and Timestamp is still ambiguous IMHO as the Timestamp header plays no role TCP re-transmissions, furthermore since it's syntax [The Timestamp header] only has meaning to a Client the Server has no way of measuring or comparing the previous Timestamp unless they attempt parsing of various ways of conveying the information. * *There needs to be more definite syntax related to Timestamp and it needs to further be indicated that TCP re-transmissions can cause partial data to appear to a receiver and that when using TCP and how to handle this as I previously indicated. * *Some text about minimum packet size with respect to Blocksize utilized would also be beneficial so there is no reason for clients to attempt to verify data which cannot be verified by a packet with no Timestamp header (Rtsp or Rtp or otherwise e.g. a Rtcp packet)* *The contradicting text from Appendix I is listed below.* " * The description on how rtspu works is not part of the core specification and will require external description. Only that it exists is defined here and some requirements for the transport is provided. " *Additionally this section seems to further contradict the above paragraphs.* 4.2 <http://tools.ietf.org/html/draft-ietf-mmusic-rfc2326bis-40#section-4.2>. RTSP IRI and URI RTSP 2.0 defines and registers or updates three URI schemes "rtsp", "rtsps" and "rtspu". The usage of the last, "rtspu", is unspecified in RTSP 2.0, and is defined here to register the URI scheme that was defined in RTSP 1.0. The "rtspu" scheme indicates unspecified transport of the RTSP messages over unreliable transport (UDP in RTSP 1.0). An RTSP server MUST respond with an error code indicating the "rtspu" scheme is not implemented (501) to a request that carries a "rtspu" URI scheme. Lastly wouldn't that also mean that a client can still use UDP but their requests simply can't have a 'rtspu' scheme? I am not sure if that wan intended or not but it seems silly to indicate that the scheme of the location means anything when in fact the protocol of the connection is what really matters. Why would anyone care if a client used a different scheme in their request? Sincerely, Julius Friedman
- [MMUSIC] On RFC2326-biz Julius Friedman
- Re: [MMUSIC] On RFC2326-biz Magnus Westerlund