[SIPForum-discussion] Route advance query

Wed Oct 29 22:06:46 UTC 2008

As I have observed, if the call "thinks" it got a signal establishment, then it won't attempt another route.  I have seen 180 ringing messages that go unanswered, and my alternate routing works because no signal has been established between the endpoints.

Once you receive the SDP, which indicates that a session has been signal terminated (just like in traditional telephone routing), the call is assumed to be established, and media will follow.

What we have done is to limit our invite per dialing pattern to 1 invite, and if that isn't responded to during the timer duration, then the next alternate route is sent out to establish another path.  If the first reply (180 or 183) comes back with a SDP before the next choice, then the first one will still establish the call path and set up media using those parameters.  However, if the first one doesn't come back, and your next choice does, then that path will be used.

In the testing that I've done, I've rarely seen a 503 after a 18x with SDP.    I've seen it as a call failure without the call setup, which invokes alternate routing.

Sandra.Cirlincione @boeing.com
SSG - IT, Enterprise Voice Engineering, VoIP/Convergence
MOC pilot 425.865.3214    (One number reach)
Home Office 425.373.8293
Desk  206.766.5888
Cell 425.417.3138
Wishing you happiness, hope, or health, take what you need.

From: Ankit [mailto:erankitkumar at gmail.com]
Sent: Wednesday, October 29, 2008 5:41 AM
To: Huseyin ALTUN; discussion at sipforum.org
Cc: Mishra2, Abhishek (NSN - IN/Bangalore); Cirlincione, Sandra; discussion at sipforum.com
Subject: Re: [SIPForum-discussion] Route advance query

Any thoughts please?

--
Thanks and Regards,
Ankit Kumar
2008/10/28 Ankit <erankitkumar at gmail.com<mailto:erankitkumar at gmail.com>>
Hi Huseyin,

Logic is known to me, but i am just trying to find the possibility of using route advance for those calls as well.

Just a thought:-

There are some Switches which doesn't go for SDP (may be with 180 or 183). If we consider 180 without SDP and disabling 183, then will that help me out?
As per SIP, 183 establishes one way media path between calling party's telephone switch to the called party's telephone switch in the PSTN prior to the call being answered. Secondly ring tone, busy tone, or a recorded announcement are all heard in the media path carried by SDP. So will removing SDP help me out from that if we use 180 instead of 183 as no media path will be there with 180.

Let me know your observations.

--
Thanks and Regards,
Ankit Kumar
2008/10/27 Huseyin ALTUN <huseyin.altun at verscom.com<mailto:huseyin.altun at verscom.com>>

Hi Ankit,

It is actually independent of the message, if there is SDP in message (180 with SDP or 183 with SDP) and if the media is relayed through SBC, then it will stop hunting.  If there is no SDP, in your example 180 and getting release code would enable hunting.  But concerning 18x messages itself contains call state information (Ringing, Buzzed, etc), it would still stop hunting.  I can't understand why your remote gateway sends 503 after sending 18x messages.  It should turn something like 480 or 486, etc.

Thinking logically here will help you why Nextone stops hunting.  If there is an indication of called party's status (like busy, temporarily unavailable, no answer, etc), hunting shouldn't be performed as Calling party has information on Called party's state.  Then, Calling party shouldn't get same information multiple times.

Let me know if you have questions.

Thanks,

Huseyin

From: Ankit [mailto:erankitkumar at gmail.com<mailto:erankitkumar at gmail.com>]
Sent: Monday, October 27, 2008 7:01 PM
To: Huseyin ALTUN
Cc: Mishra2, Abhishek (NSN - IN/Bangalore); Cirlincione, Sandra; discussion at sipforum.org<mailto:discussion at sipforum.org>; discussion at sipforum.com<mailto:discussion at sipforum.com>

Subject: Re: [SIPForum-discussion] Route advance query

Hi Huseyin,

Thanks for your explanation.

Then i think receiving 183 is the cause of the problem which is creating early media and disabling the route advance (Hunt). If we get simply 180, then after getting 180 and then the release code will make the route advance (hunt) still enable, but 183 will disable it.

What do you think?

--
Thanks and Regards,
Ankit Kumar

2008/10/26 Huseyin ALTUN <huseyin.altun at verscom.com<mailto:huseyin.altun at verscom.com>>

Hi Ankit,

If 18x has SDP and media is received (on SBC and source side), means caller receives an information about callee, like an Operator message, and then any response (4xx and 5xx) is received, re-routing should be stopped.  If no media is received, then as Abhishek and Sandra mentioned, alternate routes would be tried.

Thanks,

Huseyin

From: discussion-bounces at sipforum.org<mailto:discussion-bounces at sipforum.org> [mailto:discussion-bounces at sipforum.org<mailto:discussion-bounces at sipforum.org>] On Behalf Of Mishra2, Abhishek (NSN - IN/Bangalore)
Sent: Saturday, October 25, 2008 8:15 PM
To: ext Ankit; Cirlincione, Sandra

Cc: discussion at sipforum.org<mailto:discussion at sipforum.org>; discussion at sipforum.com<mailto:discussion at sipforum.com>
Subject: Re: [SIPForum-discussion] Route advance query

Hi Ankit

 Till the call is successful (origin gets 200 OK) , the alternate route should not be discarded.  As Sandra mentioned,18x can happen due to hetrogeneous network. Tags are useful for such calls

Thanks & Regards

Abhishek

________________________________

From: discussion-bounces at sipforum.org<mailto:discussion-bounces at sipforum.org> [mailto:discussion-bounces at sipforum.org<mailto:discussion-bounces at sipforum.org>] On Behalf Of ext Ankit
Sent: Friday, October 24, 2008 11:45 PM
To: Cirlincione, Sandra
Cc: discussion at sipforum.org<mailto:discussion at sipforum.org>; discussion at sipforum.com<mailto:discussion at sipforum.com>
Subject: Re: [SIPForum-discussion] Route advance query

Sandra,

Its a problem of a Voice call

Call flow is like:-

Clients GW<------->Our SBC<------->Vendor GW

Our SBC legs are:-

Leg1-- clients GW<----Our SBC
Leg2-- Our SBC<----Vendor GW

Call flow between Our SBC and Vendor GW is:-

Our SBC                                           Vendor GW
                     Invite.....>
                    <100 trying..........
                    <180/183..............
                    < 503 service unavailable----------------

As, you can see above that vendor is sending us 180 and then 503. So my concern is that will my SBC do any route advance for my client for the same Call-id, if my running vendor sends me error code like above?

--
Thanks and Regards,
Ankit Kumar

2008/10/24 Cirlincione, Sandra <sandra.cirlincione at boeing.com<mailto:sandra.cirlincione at boeing.com>>

This sounds like you have an intermediate device that is providing the 18x response.  If that's the case, then the device that is providing the 18x response, should also be receiving the 503, and would then reroute on its alternate path, not return the 503 back to the vendor.  The other condition is that you may get one leg connectivity, with a one-way conversation, without the other side terminating.

What we saw, was that we only received the 503 if the 18x could not complete. If the 18x completed, but the call could still not be connected, then we saw a 200 Ok message, but the call was not connected, and we received a fast busy on the caller side.

Are you doing voice only, or a mix of other media?

Sandra.Cirlincione @boeing.com<http://boeing.com>
SSG - IT, Enterprise Voice Engineering, VoIP/Convergence
MOC pilot 425.865.3214    (One number reach)

Home Office 425.373.8293
Desk  206.766.5888
Cell 425.417.3138
Wishing you happiness, hope, or health, take what you need.

From: Ankit [mailto:erankitkumar at gmail.com<mailto:erankitkumar at gmail.com>]
Sent: Friday, October 24, 2008 10:01 AM
To: Cirlincione, Sandra
Cc: discussion at sipforum.org<mailto:discussion at sipforum.org>; discussion at sipforum.com<mailto:discussion at sipforum.com>

Subject: Re: [SIPForum-discussion] Route advance query

Sandra,

I appreciate your response.

As per the response code, it should definitely do route advance. But my concern is that will it do route advace, if my vendor sends me the release code after 18X......not after 100 trying message.

Concern is that once 18X is being sent from my vendor side, it indicates that OLC has been established / or Media path has been established. So will route advance works, if media path has already been established on the current vendor?

--
Thanks and Regards,
Ankit Kumar

2008/10/24 Cirlincione, Sandra <sandra.cirlincione at boeing.com<mailto:sandra.cirlincione at boeing.com>>

Ankit,

Experience over the last few days with this, would indicate that it will  advance if you have something in your configuration to force the next route.

A 503 error seems to indicate that the service is not reachable, unavailable, or cannot complete.  It basically looks like an "unsuccessful" call attempt which tells your system that the route you've chosen was not successful.  That reply allows the routing device to try the next preference route.

Sandra.Cirlincione @boeing.com<http://boeing.com>
SSG - IT, Enterprise Voice Engineering, VoIP/Convergence
MOC pilot 425.865.3214    (One number reach)

Home Office 425.373.8293
Desk  206.766.5888
Cell 425.417.3138
Wishing you happiness, hope, or health, take what you need.

From: discussion-bounces at sipforum.org<mailto:discussion-bounces at sipforum.org> [mailto:discussion-bounces at sipforum.org<mailto:discussion-bounces at sipforum.org>] On Behalf Of Ankit
Sent: Friday, October 24, 2008 2:49 AM
To: discussion at sipforum.com<mailto:discussion at sipforum.com>
Subject: Re: [SIPForum-discussion] Route advance query

Can somebody help me out?

--
Thanks and Regards,
Ankit Kumar

2008/10/24 Ankit <erankitkumar at gmail.com<mailto:erankitkumar at gmail.com>>

Hi Folks,

I need one suggestion on a query. Scenario is:-

Lets say we have 2 backup vendor on routing. Will the GW or Switch or SBC do route advance if he gets error (lets say 503 or 34 in ISDN) from his previous vendor after 18X message?

Ex:-

Invite.....>
<100 trying..........
<180/183..............
< 503 service unavailable----------------

If yes, then why so and if no, why no?

--
Thanks and Regards,
Ankit Kumar

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