[SIPForum-discussion] What should proxies respond to OPTIONS ?

nitin kapoor nitinkapoorr at gmail.com
Mon Apr 20 16:21:16 UTC 2009


OPTIONS method is used to query a user agent or server about its
capabilities and discover its current availability. The response to the
request lists the capabilities of the user agent or server. A proxy never
generates an OPTIONS request. A UA or server responds to the request as it
would to an INVITE (i.e., if it is not accepting calls, it would respond
with a 4xx or 6xx response). A success class (2xx) response can contain
Allow, Accept, Accept-Encoding, Accept-Language, and Supported headers
indicating its capabilities. An OPTIONS request may not contain a message
body. A proxy etermines if an OPTIONS request is for itself by examining the
Request-URI. If the Request-URI contains the address of the proxy, the
request is for the proxy.Otherwise, the OPTIONS is for another proxy or user
agent and the request is forwarded.

Nitin Kapoor

2009/4/15 Yevgen Krapiva <ykrapiva at gmail.com>

> Hi again.
> The quotation from RFC about OPTIONS request:
> >   Allow, Accept, Accept-Encoding, Accept-Language, and Supported header
> >   fields SHOULD be present in a 200 (OK) response to an OPTIONS
> >   request.  If the response is generated by a proxy, the Allow header
> >   field SHOULD be omitted as it is ambiguous since a proxy is method
> >   agnostic.
> If Allow header should not be present in proxy's response, then what
> should I reply in Accept* headers ? And how to say that this proxy
> understands SUBSCRIBE and REGISTER methods, for example ?
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