Switching to VoIP

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Interoperability

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Don’t forget to reenable the codecs after doing this experiment, or

you’ll have a real problem to troubleshoot!

Call-signaling issues can be frustrating, especially when using a mixed bag of SIP

products from different vendors and vintages. Just as you can reveal SDP failures as

in Project 11.2 and authentication problems as in Project 11.1, packet capture is the

best tool for exposing any and all signaling problems.

Interoperability

Interoperability is a sore spot among some VoIP admins because of the multitude of

signaling standards, RFC revisions, and competing commercial standards. Interop

problems are the main reason lots of enterprise decision-makers used to talk down

VoIP technology and perhaps the key reason VoIP wasn’t a rising star of enterprise

telecom sooner.

Of course, talking about interoperability problems is easier than pinpointing them in

the field. During a signaling exchange, two participating endpoints may not be “on

the same page,” so to speak. Caller and receiver may be assuming a different

approach because, though they’re both using SIP, there’s enough leeway in the spec

to allow for app-specific “dialects.”

Mismatched capabilities is one example. A video phone might have a preference for

video calls, but it could also be configured to permit ...