[OpenSER-Users] record_route() for responses

[Aymeric Moizard]

On Sun, 18 Nov 2007, Iñaki Baz Castillo wrote:

> El Domingo, 18 de Noviembre de 2007, Juha Heinanen escribió:
>> Iñaki Baz Castillo writes:
>> >> defining an outbound
>> >> proxy should imply that the ua refuses to talk with anybody else.
>> >>
>> > > Sure of that? does this behaviour appear in any RFC and so?
>>
>> it is a common sense implementation issue of a sip ua, not
>> a protocol (rfc) issue.
>
> Anyway I think most SIP UA use "outbound proxy" (if configured) just for
> initial requests, not for incoming initial or sequential requests.

I think this is one of the topmost wrong behavior implemented in UAs:
today, most UAs contains several "checkbox" for defining such behavior:

  * send all message to an IP whatever its content.
  * send to an IP first message, for others, follow "normal routing rules".
  * always follow normal rules.

Other possible "checkbox" (about building content of messages):
  * always add an optionnal "pre-route" set.
  * add an optionnal "pre-route" set only if calling an "external address"
    (just to get the SIP trapezoid)
  * never add an optionnal "pre-route" even if the call is for a remote
    domain.

All those checkbox are just "workarounds" for proxy that are not correctly
configured for example.
  * The Route header is often NOT removed in initial INVITEs and that leads
    to 483 Too many hops...
  * Some admin don't know about "record-routing"...

> Is there any SIP UA with the behaviour you mean?

I've never seen any SIP UA in the market that don't have those "checkbox":
except when they cannot be configured to use "any" network.

Even if I'm personnaly pushing my customers to use pre-route set and
follow the "transport layer" routing rules: they require me to offer
configuration alternative because they must be able to interoperate
with any mis-configured/broken proxy. In 90% case, they just remove
the pre-route set and makes it the default behavior. I cannot blame
them....

Another well-know example is xlite. you have 3 checkbox:
  * outbound proxy
  * domain
  * target domain

-> Those are just variant of the SIP "transport layer".

-> In fact, among those checkbox, there is only 1 compliant way: but
those options needs to exist to interoperate with mis-configured proxy.
(Note that in most case, any of those algo leads to the same behavior
if the proxy is correctly configured...)

My own opinions...
Aymeric

> Regards.
>
>
> -- 
> Iñaki Baz Castillo
>
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