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[Ice] draft-thatcher-ice-network-cost (was Re: STUN attribute 0xC057 - What is this?)

Adam Roach <adam@nostrum.com> Fri, 10 June 2016 02:10 UTC

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To: Ross Finlayson <finlayson@live555.com>, ice@ietf.org
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From: Adam Roach <adam@nostrum.com>
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Subject: [Ice] draft-thatcher-ice-network-cost (was Re: STUN attribute 0xC057 - What is this?)
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On 6/9/16 8:15 PM, Ross Finlayson wrote:
> (Apologies in advance for the slightly off-topic question)
>
> I’ve found that my STUN server (in my WebRTC server implementation) often receives STUN Binding Requests that contain an unknown attribute type 0xC057.  This attribute is always 4-bytes long, with each of the four bytes being zero.
>
> This unknown attribute is sent by Chrome (and Opera) browsers, but apparently never by Firefox.
>
> According to RFC 5389 (and IANA), STUN attribute 0xC057 is unassigned, but is in the 'Designated Expert’ Comprehension-Optional range.
>
> Does anyone know what this is?

Yep, it's part of the webrtc.org code:

https://chromium.googlesource.com/external/webrtc/+/6ab3db249b075e0e820a263d54804f521e7bc24b/webrtc/p2p/base/stun.h#611

It appears to have been introduced here:

https://codereview.webrtc.org/1815473002

And it seems to be described, at least at a high level, here:

https://tools.ietf.org/html/draft-thatcher-ice-network-cost-00

Maybe Peter will explain his draft further? I would suggest that the 
IANA section, at least, is incorrect.

/a

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