A question for all the Voice people

burbankmarc

Does anyone know anything about qsig and sip? We're about to run this experiment involving Nortel PBX to Cisco SIP gateways. What we're curious about is qsig path replacement.

Here's a sweet ascii diagram:

[NortelPBX]

---

qsig

---

[3945]

---

sip

---

[3845]

---

qsig

---

[astratelecomPBX]

What our switch vendors are telling us is that the qsig D channel remains intact across the sip trunk, and back to the astratelecom PBX. If this is the case then theoretically path replacement should work fine.

However, if the D channel is not intact, then how do the SIP gateways translate the qsig messages into SIP messages?

Kelkin

To my understanding it doesnt translates but encapsulates it in a sip messages.. heres a white paper on cisco.

ISDN Q-Interface Signaling Protocol Q.931 Tunneling over the IP Network  [Empowered Branch Solution] - Cisco Systems

networker050184

My understanding as well Kelkin. Its been a while since I've messed with it, but my understanding is that the QSIG messages are put inside SIP messages to be "tunneled" through the SIP portion of the network.

drkat

encapsulation would be the deal.


Since you have the PRI hand off to the gateway it takes the q931 and encaps it into the SIP trunk and then de-encaps it at the other end when it hands it back off PRI

burbankmarc

Awesome, thanks everyone!

Also, if anyone stumbles upon this thread in the future I'll link to the doc that tells you exactly how to do it.

http://www.cisco.com/en/US/docs/voice_ip_comm/cucme/pbx/interop/notes/681800.pdf

Turns out this voice stuff isn't so bad after all.