[MMUSIC] Re: STUN/ICE: Username length inconstency

[Jonathan Rosenberg <jdrosen at cisco.com>]

This is a good catch. I recently introduced the limit in STUN based on 
last call comments, forgetting that we had ICE use cases that could 
result in values longer than 127. I had picked 127 thinking about human 
readable usernames. My bad. I think the limit in STUN should be 
increased to match ICE, not the other way around.

-Jonathan R.

Rémi Denis-Courmont wrote:
> 	Hello,
>
> It seems there is a minor error in the maximum username length between ICE-17 
> and RFC3489bis-09.
>
> STUN says USERNAME are at most 127 Unicode code points. There is no way a ICE 
> user fragment of 1024 bytes could fit in there. I would assume the ICE ufrag 
> should be limited to (127-1)/2 = 63 characters, so that the resulting STUN 
> username is always within the 127 code points limits, including one code 
> point for the semi-colon.
>
> In any case, an ICE implemention that fails to obey this limit would fail to 
> interoperate with another instance of itself, which is pretty lame :)
> Also, it ensures the ICE connectivity check packets size remain within the 
> minimum IPv4 MTU.
>
> I hope, that I either misunderstood something, or that this is a minor enough 
> change that it can still be done this late in the process.

--
Jonathan D. Rosenberg, Ph.D.                   600 Lanidex Plaza
Cisco Fellow                                   Parsippany, NJ 07054-2711
Cisco Systems
jdrosen at cisco.com                              FAX:   (973) 952-5050
http://www.jdrosen.net                         PHONE: (973) 952-5000
http://www.cisco.com

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