3 Apr
2009
3 Apr
'09
1:18 p.m.
Hello,
I am trying to setup a redirecting proxy server with Ser, but I find that
my GXP-2020 phone gets into an endless loop. Is this common?
The phone is configured to use my ser service which is set as a proxy.
If it tries to dial things that this proxy shouldn't handle, it sends
back a "305 Use Proxy" response. The phone seems to ignore the proxy
and tries again.
1) Is it common for the proxy redirection not to work? I've seen it being
ill-advised on iptel.org because the RFC isn't too clear how it works.
2) What would be the proper formula to get Ser to send back a proxy
redirect? I may be approaching it wrongly, but I cannot find much
documentation about it online.
Thanks,
Rick van Rein
OpenFortress
3 Apr
3 Apr
2 p.m.
Hi Rick,
I am trying to setup a redirecting proxy server with
Ser, but I find that
my GXP-2020 phone gets into an endless loop. Is this common?
The phone is configured to use my ser service which is set as a proxy.
If it tries to dial things that this proxy shouldn't handle, it sends
back a "305 Use Proxy" response. The phone seems to ignore the proxy
and tries again.
unfortunately the usage of 305 is totally under specified. And I haven't
it being used in the field ever. Anybody else maybe?
On a first look this seems to be the perfect response if you want to make
the sender of a request to retry this request on a different proxy, BUT:
- is a proxy on the path back allowed to consume the 305 and retry it by
himself on behalf of the originator?
- or is only the originator (UAC) allowed to follow the URI from the reply?
- if it is only the originator: how can the originator assure that the
request will traverse exactly the same path except for the last hop? Use a
Route header? But when it receives the 305 response it does not know which
path the original request took.
- in case of the the originator trying to follow this reply: what should
the UAC do in case it uses an fixed outbound proxy? Use a pre-loaded Route
header with two entries?
- and the biggest question: how should the URI look like which you send
back in the 305 response? Just the URI of the proxy without usernames? Or
should it be the complete URI which should be retried at that proxy?
1) Is it common for the proxy redirection not to work?
I've seen it being
ill-advised on iptel.org because the RFC isn't too clear how it works.
2) What would be the proper formula to get Ser to send back a proxy
redirect? I may be approaching it wrongly, but I cannot find much
documentation about it online.
I would recommend you to avoid the 305. Which also means there is nothing
like a proxy redirect.
You could either try to use a 301 response instead. Or you just configure
the proxy to froward the request to the correct proxy instead of replying
with a 305.
Best regards
Nils Ohlmeier
VoIP Freelancer
3:01 p.m.
Hello,
(Nils: Thanks for your helpful reply.)
unfortunately the usage of 305 is totally under
specified. And I haven't
it being used in the field ever. Anybody else maybe?
There are good reasons for using it though. For me, these are:
1. I want to pass off any POTS calls to upstream SIP providers without
having to worry about RTP proxies (setting them up, or wondering if
they would be needed at all). If traffic goes through an outside-NAT
proxy, the sip2pots provider would probably decide no RTP proxy is
needed.
2. I want to avoid being responsible for the traffic that I pass on.
This means that I can be a proxy to unregistered users, if they like.
It makes it very easy for them to try out a service if they only have
to set the "proxy" field in their phone.
I understand that all this reasoning won't help to improve the RFC, as this
is not the task of the people on this list. I just wanted to clear up why
this is useful (to me at least).
Thanks,
-Rick
3:44 p.m.
Hi Rick,
(Nils: Thanks for your helpful reply.)
sure, I totally agree that there are good use-cases for this response. But
the problem seems to me that you will have to teach every SIP element in
your setup how to treat this response correctly (like you expearienced
already with your Grandstream phone). Good luck with that. And I would be
really interested if you make progress on that front.
BTW there were some discussion about this response on the IETF mailing
list several years ago. But they somehow died.
Regards
Nils Ohlmeier
VoIP Freelancer
unfortunately the usage of 305 is totally under
specified. And I haven't
it being used in the field ever. Anybody else maybe?
There are good reasons for using it though. For me, these are:
1. I want to pass off any POTS calls to upstream SIP providers without
having to worry about RTP proxies (setting them up, or wondering if
they would be needed at all). If traffic goes through an outside-NAT
proxy, the sip2pots provider would probably decide no RTP proxy is
needed.
2. I want to avoid being responsible for the traffic that I pass on.
This means that I can be a proxy to unregistered users, if they like.
It makes it very easy for them to try out a service if they only have
to set the "proxy" field in their phone.
I understand that all this reasoning won't help to improve the RFC, as
this
is not the task of the people on this list. I just wanted to clear up why
this is useful (to me at least).
5718
days inactive
5718
days old
3 comments
2 participants
participants (2)
-
Nils Ohlmeier -
Rick van Rein