Subject: Re: [MMUSIC] RFC 5245: ice-ufrags of length 256 vs stun maximum username length of 512 bytes

From: Ari Keränen <[email-masked]>
Date: Sun, 3 Nov 2013 15:21:17 -0800

On 8/16/13 9:13 AM, Martin Thomson wrote:
> On 16 August 2013 00:48, Philipp Hancke <[email-masked]> wrote:
>> It's probably a good idea to mention this explicitly in 5245bis or
>> draft-ietf-mmusic-ice-sip-sdp though.
>
> Mention, or just fix.
>
> I'm guessing that this has never really been tested in practice, so
> fixing is probably quite feasible.

Apparently a simple fix would be to make offered ice-ufrag max length in 
ICE-bis 255 (instead of 256).

This would even be nicely backward-compatible since the other (legacy) 
endpoint can still offer 256 chars long ufrag and we would not end up 
exceeding the max length for STUN username.

Cheers,
Ari

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From: Philipp Hancke <[email-masked]>
Date: Mon, 04 Nov 2013 06:44:18 +0100

> exceeding the max length for STUN username.

And on the other side, if an ice-bis endpoint receives a ice-ufrag of 
length 256 from a "legacy" endpoint, it can still restrict it's reply to 
255 chars.
This might be easier to describe as "accept 256 chars, but do not send 
more than 255 chars".

That seems better than trying to figure out what should happen when we 
end up with 513 bytes, thanks.

philipp

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From: Ari Keränen <[email-masked]>
Date: Sun, 3 Nov 2013 21:47:31 -0800

> This might be easier to describe as "accept 256 chars, but do not send

Exactly.

Cheers,
Ari