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SIP INVITE

Good morning,

Please, could you kindly help me with the following matter?

I have some questions regarding how CUCM builds some fields in a SIP INVITE message. Last week I was reviewing logs and I found the below R-URI when an extension calls another extension:

A number--> 7100 ---(1 SIP invite) ----> CUCM ---- (2 SIP invite) ----> B number 7101

1 SIP invite R-URI: sip:0@192.168.1.3; user=phone

2 SIP invite R-URI: sip:5ea27f5e-033b-880c-e304-0729574bfb1@192.168.1.2:51544;transport=tcp where

5ea27f5e-033b-880c-e304-0729574bfb1 is the user part.

I thought the first invite should be sip:7101@192.168.1.3; user=phone. Concerning the invite from CUCM to B number, how does CUCM build the user part from the B number?

Moreover, what are Contact ang tag fields  used for in a sip message? how does CUCM build them?

Thanks in advance.

Juan.

20 Replies 20

Ayodeji Okanlawon
VIP Alumni
VIP Alumni

Delgado,

Some of your question will be answered in this document titled understanding sip traces..Please have a read.

https://supportforums.cisco.com/docs/DOC-27105

The request uri ideally will be to a valid extension but in cases where conferencing is involved, the r-uri is usally to some hexadecimal numbers similar to what you have posted.

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"opportunity is a haughty goddess who waste no time with those who are unprepared"

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Hi Aokanlawon,

Thanks for your quick response.

I had already read this thread but i didn't find any info regarding the topics i have explained.

In the case i'm facing, conference is not involved, just a basic call between 2 extensions. I have analyzed the complete SIP message and there is no field in the first INVITE (from IP phone to CUCM) where the B number is considered (R-URI sip:0@CUCM IP), so, how CUCM knows where the call has to be progressed? Concerning the 2nd INVITE (from CUCM to IP phone), what does the number indicated (hexadecimal) in the R-URI mean?

Wrt Contact field, why sometimes shows "From" field (A number) and others the hex number?

Thanks,

Juan

Can you please attach the full trace

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"opportunity is a haughty goddess who waste no time with those who are unprepared"

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        Hi,

I cannot include the complete trace but a short piece. I hope this help to understand my question.

Thanks¡¡¡

Juan

since I didnt see the full INVITE sent by CUCM to IP Phone2, I can only assume that the INVITE was sent using the contact header rather than the AOR (address of record)

The Contact header says where you are (or rather, where your User Agent is), while the From header says who you are.

You might have several SIP devices all registered to the same Address of Record (the URI you put in the From header).

Further, REGISTER requests use Contact headers to maintain SIP's location service: they let a user agent update a registrar's location information..

Can you check if the contact header for IP Phone 2 matches what you have in the request uri..

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"opportunity is a haughty goddess who waste no time with those who are unprepared"

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Hi Aokanlawon,

I have not understood your answer.

I have noticed 2 unexpected behaviours:

- SIP INVITE between IP phone1 and CUCM. R-URI is sent in a strange format (0@CUCM-IP) instead of using B number to complete the R-URI. Why?

- SIP INVITE between CUCM and IP phone2. R-URI is built by adding a large string without sense for me. Why?

In both cases, Contact Header shows A number details. My question regarding Contact Header is why sometimes is complete with a large string as well instead of A number/extension.

BR,

Juan

What version of CUCM is this?

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"opportunity is a haughty goddess who waste no time with those who are unprepared"

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CUCM version 8.6.2

I dont know whats going on there..My CUCM 8.6.2 shows the logs in the proper format

INVITE sip:907666930701@10.10.10.32:5060 SIP/2.0

Via: SIP/2.0/UDP 10.10.0.11:5060;branch=z9hG4bK2342979336fbf

From: "Strand" <02065543200>;tag=144360~ffa80926-5fac-4dd6-b405-2dbbc56ae9a2-392166051

To: <907666930701>

Date: Mon, 20 May 2013 15:20:16 GMT

--

--

--

User-Agent: Cisco-CUCM8.6

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"opportunity is a haughty goddess who waste no time with those who are unprepared"

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Hi Juan,

     I can answer the second question for you now:

> When a SIP Phone registered with the CUCM makes a calls, the Contact URI is the PKID; the hex value which the CCM application uses to store PID ( Process Identifiers ) in the database.

To answer your second questions, I need you to let me know if when dialing phone B, were you making an enbloc call or digit by digit?

Regards,

Jagpreet

Hi Jagpreet,

I dial the number digit by digit.

Br,

Juan

+5 Jagpreet..I missed the point that these are sip phones

Juan,

If you look down into the trace you will see the remainder of the dialled digits. This is expected with sip phones. Just as with SCCP phones you will see the digits dialled one by one and cucm performing digit analysis. It is very similar. I am sure down in the remainder of the logs you will see the remaining digits dialled..I missed the fact that it was a sip phone

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"opportunity is a haughty goddess who waste no time with those who are unprepared"

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Sorry Aokanlawon, I cannot find the dialed digits in the trace. This is what puzzles me. In the original SIP I only find the A number (82052015) and the R-URI and To header completed with a "0". I supposed that perhaps the caller had pressed Recall button, but no. I have dialed B number digit by digit getting the same result.

Jagpreet & Aokanlawon, your help is much appreciate.

Juan

Juan,

     A complete set of CCM SDI and SDL traces would be helpful here if you can upload it for a test call.

I shall look into this otherwise as well.

Regards,

Jagpreet

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