[rtcweb] ALPN question - other labels?

Paul Kyzivat <pkyzivat@alum.mit.edu> Thu, 07 August 2014 21:24 UTC

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Date: Thu, 07 Aug 2014 17:24:30 -0400
From: Paul Kyzivat <pkyzivat@alum.mit.edu>
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Subject: [rtcweb] ALPN question - other labels?
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Section 2 says:

    The following identifiers are defined for use in ALPN:
...
    Only one of these labels can be used for any given session.  A peer
    acting in the client role MUST NOT offer both identifiers.  A peer in
    the server role that receives a ClientHello containing both labels
    MUST reject the session, though it MAY accept the confidential option
    and protect content accordingly.

This does not quite say that a peer in a server role must reject a 
session that contains some *other* label. It doesn't even explicitly 
forbid a peer in a client role from offering some other label. Does it 
intend to do so?

This could be an issue in interoperation. For instance, if CLUE 
endpoints want to be capable of interoperating with WebRTC devices must 
they always use one of the webrtc ALPN values?

This could be handled saying that any other ALPN value is to be treated 
by browsers as equivalent to "webrtc".

(Note: we haven't worked out in detail how to interoperate CLUE and 
WebRTC, but we are trying to ensure we don't do anything to preclude it.)

	Thanks,
	Paul