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Re: [Ice] STUN attribute 0xC057 - What is this?

Taylor Brandstetter <deadbeef@google.com> Fri, 10 June 2016 17:19 UTC

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From: Taylor Brandstetter <deadbeef@google.com>
Date: Fri, 10 Jun 2016 10:19:14 -0700
Message-ID: <CAK35n0a6dNJng3=Ex5393fK7zn73u+oeNNwLPuW+Ven8C+Wu+w@mail.gmail.com>
To: Ross Finlayson <finlayson@live555.com>
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Cc: ice@ietf.org
Subject: Re: [Ice] STUN attribute 0xC057 - What is this?
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Not off-topic at all, actually. We're using 0xC057 for an experimental
"network cost" attribute, which is described in this draft:
https://tools.ietf.org/html/draft-thatcher-ice-network-cost-00

This is used in order to communicate an endpoint's preference for different
networks (if the endpoint is using multiple network interfaces), so that
the controlling ICE endpoint can select the preferred one based on certain
criteria. We can't just use the ICE candidate priority, because the "type
preference" part of the priority (local, stun, relay) takes precedence over
the "local preference". There are other reasons as well, which are
discussed in the draft.

On Thu, Jun 9, 2016 at 6:15 PM, Ross Finlayson <finlayson@live555.com>
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?
>
>
> Ross Finlayson
> Live Networks, Inc.
> http://www.live555.com/
>
> _______________________________________________
> Ice mailing list
> Ice@ietf.org
> https://www.ietf.org/mailman/listinfo/ice
>

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