RE: [Sip] Outbound issues: slides 9 and 10 - Why does every proxy need to support outbound?

["Christer Holmberg \(JO/LMF\)" <christer.holmberg at ericsson.com>]

Hi Rohan,

>Christer, please read the slides.  The issue we are trying to detect is
described in slide 9.  The UA sends through an 
>outbound-proxy that adds a Path, but does not support outbound.  The
registrar needs to detect that.

I am not arguing against that. I am simply commenting on the proposed
mechanisms that YOU wrote.

YOU said that ALL Path headers (not only the one inserted by the
outbound proxy) must contain the ob parameter, and I question that.

YOU said that the registrar must start comparing Vias with Paths, and I
propose a way to avoid that.

Regards,

Christer



On Aug 9, 2006, at 9:46, Christer Holmberg ((JO/LMF)) wrote:
>
> Hi,
>
> A couple of questions:
>
>> The issues on slide 9 (how does a registrar verify that an edge proxy
> supports outbound) and slide 10 (what does >"Supported: outbound" 
> mean) deal with detecting that all the required hops support outbound.

> Slide
>> 9 specifically uncovered a problem with outbound proxies that add a
> Path URI but don't include a flow token.
>>
>> The proposed solution is as follows.  If a proxy inserts a Path 
>> header
> with a flow token consistent with the rules d
>> escribed in outbound, it MUST add the ;ob parameter to the proxy URI
> that has the flow token.
>>
>> The registrar verifies that any Path header URIs contain the ;ob
> parameter.  If there are any Path URIs without the ob
>> parameter, the registrar does not return Supported: outbound.
>
> [CHH] Why would every Path header need to contain the ;ob parameter? 
> The
> REGISTER request may traverse, in addition to the outbound proxy, 
> multiple proxies which insert a Path header. Do all these proxies 
> really need to support outbound?
>
>> Furthermore, the registrar needs to check that the first hop after 
>> the
> UAC is represented in the Path list (unless the
>> registrar recognizes that the first hop after the UAC is in the same
> domain and doesn't need to include Path URIs with a
>> flow token).  Note that this implies that whatever the proxy puts in
> the Via (IP address or FQDN), it must put the same
>> hostname in the Path header (but there is no need for a complete URI
> comparison).  If the first hop is not correctly
>> represented, the registrar ignores the reg-id parameter and does not
> return Supported: outbound.
>
> [CHH] Isn't it much easier to mandate the outbound proxy to always 
> insert a Path header?
>
> OR, another possibility is that the outbound proxy, if it detects that

> the UAC supports outbound, insert some option-tag of itself in the 
> Supported header, to indicate to the registrar that it supports 
> outbound. Then the registrar does not need start looking at the Path 
> headers.
>
> Regards,
>
> Christer
>
>
>
>
>
>
>
>
> The implication of this is that an outbound-proxy that supports 
> outbound needs to support Path and flow tokens for registrations to 
> all foreign domains.  Inside the same domain, the first-hop proxy and 
> the registrar can still use Path to communicate with each other, but 
> they can use some other private mechanism to disaggregate this 
> functionality.
>
> thanks,
> -rohan
>
>
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