Skype Connect with Cisco CUCM 8.5.1

[ahassiotis1]

Hi,

I am trying to integrate CUCM 8.5.1 with Skype Connect either through Registration or IP Authentication.

No CUBE or other hardware/software is used.

Currently I have setup:

A SIP Realm (for 'Realm' I have used the internal IP of the Publisher CUCM server. User and Digest Credentials as provided from Skype Profile)

I have registered a CIPC using SIP on CUCM. It uses a Device Security profile with following characteristics: non secure profile with Digest Auth enabled. Also uses a standard SIP profile.

I have setup a SIP Trunk to sip.skype.com with a Caller ID DN being the User provided by Skype Profile: 99XXXXXXXXX. The Trunk is setup with 'Destination Address is an SRV'. Uses SIP Trunk Security profile with Digest Auth and X.509 Subject name the same 99XXXXXXXXX number. Security profile is Non Secure. 

During outbound call setup testing to Skype Test number 0017606604690, I am getting about 6 outbound SUBSCRIBE messages that get unanswered, see attached file subscribe.png.

Following to that I get an outbound INVITE (invite.png) to which Skype responds with a Status 100: Trying (trying.png) and a Status 404: Not Found (not found.png attached).

Does anyone have any idea what might be missing?

I am surprised I don't see any other posts on this CUCM to Skype Connect topic.

Thanks,

A.

[Vivek Batra]

Hi,

1. I doubt on To and From field in INVITE message which should be in form;

"sip:xxxx@3.sip.skype.com"

2. I assume you are using IP authenticated trunk as you have not mentioned anywhere that INVITE was challenged. Have you registered your NAT/Public IP with Skype service?

3. If doesn't work with point2 and 3, is it possible to share completed PCAP trace?

Thanks

Vivek 

[ahassiotis1]

Hi Vivek,

Not sure exactly what you mean on point 1. What do you reckon looks not right with the URI? The From has the form of 99XXXXXXXX@<CUCM_PUBLIC_IP> on the outside interface of the firewall. The To has the form: <DIALLEDNUMBER>@3.sip.skype.com I have tried replacing 3.sip.skype.com with plain sip.skype.com. What would you expect to see as URI instead?

I have setup a SIP Realm on CUCM to support Registration. I have also setup an Application User with UserID the 99XXXXXXX number and Digest Credentials as supplied from Skype Profile. I have associated the Application User to the CIPC Phone. I have also tried IP Authenticated. The INVITE is shown in the trace. Not sure how a Challenged Invite would look like but from the trace I suppose there is no Challenge.

I have registered the public IP that CUCM gets NATed to on Skype Profile.

The Skype profile though shows: 'SIP user is not yet registered at sip.skype.com'

[Vivek Batra]

Hi,

I meant from point1 that with most of the ITSP, they expect their server address in all of the three fieldt is viz Req-URI, To and From.

Req-URI and To seems ok in your INVITE message however set From field to <sip:DDI_Number@3.sip.skype.com>

If you have registered your IP in Skype profile, then it should IP authenticated trunk and digest authentication may not be required.

As Skype is returning 404 which means that server couldn't found the user. Just to diagnosis further, although you are not able to make an outgoing call, but you should get incoming call if someone from PSTN dials your DDI number. Are you getting incoming calls?

Thanks

Vivek

[ahassiotis1]

Hi again Vivek,

I thought that having registered my public IP in Skype Profile (Skype Manager), would allow outbound calls coming with a From: being 99XXXXXXXX@<CUCM_PUBLIC_IP>.

99XXXXXXX, is the Skype Profile user. In some of my tests I have seen the internal user DN show up instead of the Skype Profile user. Not sure what change causes this.

Anyway, to test what you are saying, do you have any idea on how I can instruct CUCM to alter the <CUCM_PUBLIC_IP> with 3. sip.skype.com in the From: field of the INVITE?

I have attached a trace that shows internal IPs. These get properly NATed, (including SIP Invite header) to public IPs.

I haven't set up an incoming number yet, so I can't test incoming.

A.

[Vivek Batra]

Hi,

I'm not sure how you can manipulate From field in CUCM even not sure it's supported or not.

I observed another point in captures that INVITE is being sent by CUCM without SDP offer. Most of the service providers expect INVITE with SDP offer.

IMO, best way is to use any standard SIP softphone like Zoiper, XLite etc and check if you can make an outgoing call successfully. This will let us know where the problem is. Don't forget to disable registration while configuring softphone.

Thanks

Vivek

[ahassiotis1]

Things have unexpectedly started to work. The last thing we changed was to untick the 'Destination Address is an SRV' under the SIP Trunk configuration and add the the generic sip.skype.com.

We will continue with further testing also to include inbound calls... thanks for your comments till now.

[k.scholtens]

Would you mind sharing your redacted configuration?  I've been struggling trying to get either method to work with Skype Connect.  It's quite frustrating.  Thank you.