Re: [MMUSIC] Finding a max length of "a=mid" attribute

Nils Ohlmeier <nohlmeier@mozilla.com> Wed, 03 March 2021 15:07 UTC

Return-Path: <nohlmeier@mozilla.com>
X-Original-To: mmusic@ietfa.amsl.com
Delivered-To: mmusic@ietfa.amsl.com
Received: from localhost (localhost [127.0.0.1]) by ietfa.amsl.com (Postfix) with ESMTP id E843B3A1477 for <mmusic@ietfa.amsl.com>; Wed, 3 Mar 2021 07:07:02 -0800 (PST)
X-Virus-Scanned: amavisd-new at amsl.com
X-Spam-Flag: NO
X-Spam-Score: -2.099
X-Spam-Level:
X-Spam-Status: No, score=-2.099 tagged_above=-999 required=5 tests=[BAYES_00=-1.9, DKIM_SIGNED=0.1, DKIM_VALID=-0.1, DKIM_VALID_AU=-0.1, DKIM_VALID_EF=-0.1, SPF_HELO_NONE=0.001, SPF_PASS=-0.001, UNPARSEABLE_RELAY=0.001] autolearn=ham autolearn_force=no
Authentication-Results: ietfa.amsl.com (amavisd-new); dkim=pass (1024-bit key) header.d=mozilla.com
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 mNjgnj9Ys9Lw for <mmusic@ietfa.amsl.com>; Wed, 3 Mar 2021 07:07:01 -0800 (PST)
Received: from mail-qk1-x730.google.com (mail-qk1-x730.google.com [IPv6:2607:f8b0:4864:20::730]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by ietfa.amsl.com (Postfix) with ESMTPS id 261F73A1474 for <mmusic@ietf.org>; Wed, 3 Mar 2021 07:07:01 -0800 (PST)
Received: by mail-qk1-x730.google.com with SMTP id s7so14125680qkg.4 for <mmusic@ietf.org>; Wed, 03 Mar 2021 07:07:01 -0800 (PST)
DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=mozilla.com; s=google; h=from:mime-version:references:in-reply-to:date:message-id:subject:to :cc:content-transfer-encoding; bh=zeaO9Mh23ZVtb2hEl0VbwS0mZVOoZBtM0+QFCrzq5cc=; b=djol3kOLl5oCx5doW4xNdhEOkEygjRVCExd4Ku2mQ21s/E4KqlkXvZrQ0pzGkgEsVH tGeKQv4zs8OGedWZOsRZkfSh4yRubetdZmo8+6sDwG3SrprKOEcbLdENPH7Nv81ooi4j gzjnsJvEPdof2OX874rtT+Kfv1dkVGIqoq1xs=
X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:from:mime-version:references:in-reply-to:date :message-id:subject:to:cc:content-transfer-encoding; bh=zeaO9Mh23ZVtb2hEl0VbwS0mZVOoZBtM0+QFCrzq5cc=; b=aUqLLEpFtCCDaLsrrs8L8yEJ6CByOD6Mud8Cty2lQU0erpYDiQatpsu40zH5oN1gSd rTN1KynJBBprgWStuHGbYLQMjYmbJi3WLOs+4eFJ+iezqKN5AfvAy3kwuaBDQLHmi203 uyVmjVEKblZaWcba996Li1xa22D9wMyVQfo8MXylHBCgBcjWHBmvhyS9R3qO0e+zH50x eSzDc+ji1511MPBY56v5Ewz17fY5pq3NcCy1y8egQGoQgiNPDG1hVfwpaTzmOWXj1y6w KtU+tpDQvbEh0+onqro2apWvt2k/HqQ3Xon3BZuW1DdR03dzbWVPwLPuDmT05R0EHnCJ nf9A==
X-Gm-Message-State: AOAM530xx+hFBa/kHCfCiTbIRoR0qpdFo7cfQ/BASQbMEzOQjVD0lBqa cZtG/xjdJIKUILJ8jxAO7IO7dpPi7ZmeCQPLf9RAWA==
X-Google-Smtp-Source: ABdhPJyeY127Cr8lRQaKjKchWZ9LUTDjAzEpkJPkydBoFKdK4lgbpMRQI24n3QHgyj6TGfd/oFw6nqubefThgXNrlZY=
X-Received: by 2002:a37:bf04:: with SMTP id p4mr26394298qkf.459.1614784020077; Wed, 03 Mar 2021 07:07:00 -0800 (PST)
Received: from unknown named unknown by gmailapi.google.com with HTTPREST; Wed, 3 Mar 2021 07:06:59 -0800
From: Nils Ohlmeier <nohlmeier@mozilla.com>
Mime-Version: 1.0 (1.0)
References: <463c848c-d171-7184-d65b-9ea95438d442@alum.mit.edu>
In-Reply-To: <463c848c-d171-7184-d65b-9ea95438d442@alum.mit.edu>
Date: Wed, 03 Mar 2021 07:06:59 -0800
Message-ID: <CANKS34fmzw3TNJVJhkUQvWv+EM2SCuEZcp7JgyZbN-p7iqMxfg@mail.gmail.com>
To: Paul Kyzivat <pkyzivat@alum.mit.edu>
Cc: mmusic@ietf.org
Content-Type: text/plain; charset="UTF-8"
Content-Transfer-Encoding: quoted-printable
Archived-At: <https://mailarchive.ietf.org/arch/msg/mmusic/lSLpiwW7zFchnSo25cvOaSEh6IU>
Subject: Re: [MMUSIC] Finding a max length of "a=mid" attribute
X-BeenThere: mmusic@ietf.org
X-Mailman-Version: 2.1.29
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: <https://mailarchive.ietf.org/arch/browse/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: Wed, 03 Mar 2021 15:07:03 -0000

> Am 3/3/21 um 06:31 schrieb Paul Kyzivat <pkyzivat@alum.mit.edu>:
>
> On 3/3/21 3:51 AM, Harald Alvestrand wrote:
>> I'm searching for the source of a max length limit on the "a=mid" attribute.
>> I couldn't find it in RFC 5888 (grouping framework) or RFC 8843 (BUNDLE).
>> Does anyone remember where it's supposed to be?
>> (I have code that will insist that it should be 16 bytes or less, but I'm trying to verify that this is the correct limit.)
>
> Its defined as a token (from RFC4566/8866). And that is:
>
>  token = 1*(token-char)
>
> There is no upper limit on the length. You can't impose a limit for implementation convenience. But practically speaking it is limited by the length of the message body that contains it, so you could code using an offset+length into the message buffer.

While the SDP side might be able to handle really long MID values I
doubt the RTP header extension allow or support that. Maybe your 16
byte length limitation comes from the RTP side?

Best
  Nils