Subject: Re: [MMUSIC] draft-ietf-mmusic-rfc2326bis-23, proxy + via

From: "Martin Stiemerling" <[email-masked]>
Date: Fri, 23 Apr 2010 14:14:22 +0200

Hi all,

> -----Original Message-----
> From: [email-masked] [mailto:[email-masked]] On
> Behalf Of Wolfgang
> Sent: Wednesday, March 24, 2010 4:36 AM
> To: [email-masked]
> Subject: [MMUSIC] draft-ietf-mmusic-rfc2326bis-23, proxy + via
> 
> I'm not sure if the usage of Via in RTSP is a good idea. Judging from
> the error codes, a proxy is expected to wait for responses and send a
> 504 Gateway Timeout if it doesn't receive one. This means it has to
> keep state anyway. If we keep Via, the Security Considerations section
> should mention the dangers associated with all source-routing schemes.

I'm also reasoning for myself why there is the Via header, given that we
have TCP as transport and stateful proxies...

The text from the via header (below) suggest that a record of the used
transport protocols could be of use to somebody. Anyhow, we have only
a single transport protocol and there is no sign that there will be more.

16.56. Via

   The Via general-header field MUST be used by proxies to indicate the
   intermediate protocols and recipients between the user agent and the
   server on requests, and between the origin server and the client on
   responses.  The field is intended to be used for tracking message
   forwards, avoiding request loops, and identifying the protocol
   capabilities of all senders along the request/response chain.

   Multiple Via field values represents each proxy that has forwarded
   the message.  Each recipient MUST append its information such that
   the end result is ordered according to the sequence of forwarding
   applications.

   Proxies (e.g., Access Proxy or Translator Proxy) SHOULD NOT, by
   default, forward the names and ports of hosts within the private/
   protected region.  This information SHOULD only be propagated if
   explicitly enabled.  If not enabled, the via-received of any host
   behind the firewall/NAT SHOULD be replaced by an appropriate
   pseudonym for that host.

   For organizations that have strong privacy requirements for hiding
   internal structures, a proxy MAY combine an ordered subsequence of
   Via header field entries with identical sent-protocol values into a
   single such entry.  Applications MUST NOT combine entries which have
   different received-protocol values.

> And the via-branch syntax should be removed as it is not described in
> the draft.

Added to the issue tracker and waiting for somebody to complain about
this. 

[email-masked]

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