[prev in list] [next in list] [prev in thread] [next in thread] 

List:       sip-implementors
Subject:    RE: [Sip-implementors] When and how to forward an end-to-end ACK in a proxy
From:       Jonathan Lennox <lennox () cs ! columbia ! edu>
Date:       2003-02-24 18:35:33
Message-ID: 15962.26101.705928.670612 () grandcentral ! cs ! columbia ! edu
[Download RAW message or body]

On Monday, February 24 2003, "Jiri Kuthan" wrote to "hisham.khartabil@nokia.com, lennox@cs.columbia.edu, sip-implementors@cs.columbia.edu" saying:

> On Fri, 21 Feb 2003 hisham.khartabil@nokia.com wrote:
> 
> > I have always assumed that even if a proxy is used as an outbound 
> > proxy, an ACK (or any request within a dialog for that matter) does not
> > get sent to that outbound proxy unless the outbound proxy has
> > record-routed.
> 
> That's not the case always. Many phones keep sending ACK to outbound 
> proxy.
> 
> > Having said that, I would expect that a stray ACK arriving at a proxy
> > would just be dropped since it arrived there by accident. I also think
> > that this might be implementation specific. 
> 
> That would cause the INVITE transaction to never complete in the case 
> I mention.

So what do you recommend for the stray-ACK problem?

I was wrong to say that ACK proxying is non-amplifying -- forwarding an ACK
can cause a single UDP packet to trigger a DNS lookup and a TCP or TLS
connection attempt.

-- 
Jonathan Lennox
lennox@cs.columbia.edu

[prev in list] [next in list] [prev in thread] [next in thread]