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

If length is >16, shouldn't the 2 byte header extension be used instead?
that would allow mid values up to 256 bytes.

Best regards
Sergio

El mié., 3 mar. 2021 22:40, Harald Alvestrand <harald@alvestrand.no>
escribió:

>
> On 3/3/21 4:06 PM, Nils Ohlmeier wrote:
> >> 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?
>
> I found that it is impossible to encode an 1-byte RTP header extension
> longer than 16 bytes (the length is a 4-bit field with a bias value of
> 1). So in practice, it's an RTP restriction.
>
> I think Postel once advised that one should always have length limits -
> "if you don't have a length limit, you just have an implementation
> defined limit, and that's worse".
>
> So the next question (now that we've settled that the standards don't
> impose one) is: Should the standards specify a limit?
>
> And the third question: if asked to handle a BUNDLEd connection where
> the MID is > 16 bytes, is it reasonable to just ignore the over-long MID
> value?
>
>
>
>
> >
> > Best
> >    Nils
> >
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