Re: p1: Via and gateways

David Morris <dwm@xpasc.com> Sat, 20 April 2013 15:19 UTC

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Date: Sat, 20 Apr 2013 08:17:31 -0700 (PDT)
From: David Morris <dwm@xpasc.com>
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Subject: Re: p1: Via and gateways
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On Sat, 20 Apr 2013, Mark Nottingham wrote:

> 
> On 20/04/2013, at 5:21 PM, David Morris <dwm@xpasc.com> wrote:
> > 
> > I don't care about MUST, but I think the Via header can be useful for
> > problem determination. A smart content server could also adjust for
> > a detected accelerator and/or transcoder ... perhaps by avoiding
> > optimizations dependant on a direct connection and byte/byte transfer
> > between the client and the server.
> > 
> > So I'm very much in favor of keeping the Via: header.
> 
> Definitely not talking about getting rid of it. The (only, specific)
> point here is whether a gateway that doesn't add Via to responses should
> be called non-conformant.

I didn't think you were making that suggestion, but I see comments about
lack of use turning into suggestions for removal.

> Personally, I think it should be a MUST for proxies, in both directions.
> However, for a gateway, it either shouldn't be a requirement at all (for
> responses), or it should be a SHOULD with a get-out clause for reasons
> of security (along with a note that they'll need to accept
> responsibility for any issues caused by omitting Via). Still should
> probable be a MUST for requests from gateways.

I'm not sure how to express it, but the requirement probably should be
based on whether the traffic leaves the control of the organization that
owns the gateway (or even proxy). I think Willy Tarreau noted a
performance concern for some types of gateways if the requirement is
added to modify the message.

Dave Morris