Dial VCU from external network

Occasional Contributor

Dial VCU from external network



I'm a starter of using Polycom, please bear with me about asking general question.


Do you mind sharing the requirements of calling SIP from external network? The current environment as below:

1) VCU - Polycom RealPresence Group 500 with VBP (supported SIP/H.323)

2) VBP has public Internet access

3) SIP address for this VCU: SYDNEYVCU2@managedvideo.net


Please let me know if further clarification required. Many thanks.

Message 1 of 2
Polycom Employee

Re: Dial VCU from external network

The requirements for dialing SIP from outside your network to an internal device are pretty straight forward. In your case you have a VBP. When the call is received by the VBP it will forward the INVITE to the SIP registrar configured in the VBP for username/IP address resolution.


I tried calling the address in your post. What I found is that there is a problem with the Session Expiration timer. When I call I use a SE of 1800. The call is being rejected by a device calling itself TANDBERG/4132 (X8.7.3) with a SIP 422 - Session Interval Too Small error


SIP/2.0 422 Session Interval Too Small
Via: SIP/2.0/TCP;branch=z9hG4bK-3836-d84654616413ea008f103a104e8ad034;received=;ingress-zone=DefaultZone
Call-ID: 1327280c-d845-44c2-bc43-f7f3998fe7fc
From: "Michael Bromley" <sip:mbromley@polycomsupport.info>;tag=EDD13B86-23316633
To: <sip:SYDNEYVCU2@managedvideo.net;transport=tcp>;tag=4f799c50505b1231
Server: TANDBERG/4132 (X8.7.3)
Min-SE: 2000
Warning: 399 "Session Interval Too Small"
Content-Length: 0

The Tandberg VCS is declaring a minimum Session Expiration timer of 2000 where I am using an SE of 1800. 1800 is the usual default for Session Expiration so if you can find where to reconfigure that on the VCS to 1800 I believe your SIP calls may start working.



Michael K. Bromley, CVE, CCENT, WCNA, VCA-DCV
Technical Lead
Infrastructure Technical Support Center
Message 2 of 2