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Is ‘reading’ SIP a required skill?

Jan 16, 20062 mins

* How fluent should you be in Session Initiated Protocol?

Over the past couple of years, it has become evident that Session Initiated Protocol will eventually become the unifying “language” for the establishment of connections (sessions) for converged communications between both current- and next-generation devices, such as SIP phones and their follow-ons. As such, SIP is often said to be analogous with HTTP and current-generation Web construction.

But the unanswered question is how fluent the networking professional needs to be in “reading” SIP messages. Continuing the analogy to Web page construction, in the early days Web “authors” often had to write the coding for Web pages directly in HTTP. However, as Web-authoring tools like Microsoft’s FrontPage and Adobe/Macromedia’s ColdFusion have emerged, the nitty-gritty of Web-developers having to deal with “raw” HTTP has often been eliminated. Nevertheless, when something goes awry, one must sometimes dig back into the HTTP code to diagnose the problem.

We believe that the analogy of having to understand and to possess at least a minimal competency to “read” SIP will hold with converged communications. While many tools are available and/or are under development to manage and diagnose SIP-based communications, the fundamental ability to “read” these messages in their most basic form will be a requisite skill for advanced troubleshooting.

Steve recently ran across an excellent, vendor-independent paper that provides an example of breaking down a simple IP telephony call into a series of SIP messages. This paper, authored by Mark Miller of Diginet (albeit sponsored by Network General), demonstrates the exact message flow in setting up a call between a Cisco IP phone and an analog phone connected to a Cisco SIP gateway. The paper is available here.

Do you really need to know this much? Maybe not. The ability of automated systems has come a long way from when we were forced to diagnose problems by looking at a “datascope” reading and deciphering hex code. Nevertheless, we also fear that relying totally on advanced diagnostic tools without having the ability to dig deeper and to have a fundamental understanding of the underlying protocol could come back to haunt you.

But, then again, we also believe that people should know how to check the oil in their cars without having to wait for a diagnostic light to come on.


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