The mandate for SIP to be interoperable

Insightful analysis by consultants Steve Taylor and Jim Metzler, plus links to the latest WAN news headlines

This is the sixth and last in a series of newsletters devoted to the standards process. We will use this newsletter to wrap up the discussion of standards by looking at Session Initiation Protocol. We look at SIP as being a good example of a technology that is very slowly being standardized. According to Wikipedia, SIP was originally designed by Henning Schulzrinne (Columbia University) and Mark Handley (University College of London) starting in 1996. The latest version of the specification is RFC 3261 from the IETF SIP Working Group.

SIP is a signaling protocol, widely used for setting up and tearing down multimedia communication sessions such as voice and video calls over the Internet. Other feasible application examples include video conferencing, streaming multimedia distribution, instant messaging, presence information and online games. The protocol can be used for creating, modifying and terminating two-party (unicast) or multiparty (multicast) sessions consisting of one or several media streams. We believe strongly that in order for SIP to have an impact, it has to be interoperable so that IT organizations use it to set up multimedia communication sessions and not worry about which vendor created which end point device.

However, to date, most IP implementations have not provided the necessary interoperability.

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This is the sixth and last in a series of newsletters devoted to the standards process. We will use this newsletter to wrap up the discussion of standards by looking at Session Initiation Protocol. We look at SIP as being a good example of a technology that is very slowly being standardized. According to Wikipedia, SIP was originally designed by Henning Schulzrinne (Columbia University) and Mark Handley (University College of London) starting in 1996. The latest version of the specification is RFC 3261 from the IETF SIP Working Group.

SIP is a signaling protocol, widely used for setting up and tearing down multimedia communication sessions such as voice and video calls over the Internet. Other feasible application examples include video conferencing, streaming multimedia distribution, instant messaging, presence information and online games. The protocol can be used for creating, modifying and terminating two-party (unicast) or multiparty (multicast) sessions consisting of one or several media streams. We believe strongly that in order for SIP to have an impact, it has to be interoperable so that IT organizations use it to set up multimedia communication sessions and not worry about which vendor created which end point device.

However, to date, most IP implementations have not provided the necessary interoperability.

For example, at the Spring VoiceCon conference the results of a SIP survey was presented. This was the fourth year that the survey was given and as before, it was given only to vendors who are supporting or implementing SIP in new or re-engineered products.

The vendors were asked to rate the state of current SIP specifications from all sources on a scale of 1 to 5 with 5 meaning 'complete, clear, stable and unambiguous' and 1 meaning 'minimal to no standardization yet; or incomplete or ambiguous; needs a lot of work.' Our interpretation of this scale is that if a vendor rated a given SIP specification a 3, that the vendor believes that there is a moderate amount of standardization associated with that particular SIP specification.

The good news is that 'Basic dozen telephony features' was rated 4.7, up from last year’s rating of 4.4. The bad news is that relatively few other SIP specs rated a 4 or higher. SIP specifications that rated between 3 and 4 included SIP trunking, NAT/firewall traversal, audio-conference scheduling, unified messaging and find-me`/follow me. In addition, a handful of specifications rated below 3.

Given that work on SIP began over a decade ago, we feel justified in saying that SIP is a good example of a technology that is very slowly being standardized. The impact on the market is rather stark. Some of the IT organizations that we talked to suggested that vendors are just paying lip service to SIP and that they are not really serious about implementing a truly interoperable SIP standard. Others have stated that while what they really want is a standards-based interoperable SIP solution, they are forced to deploy proprietary solutions.

Steve Taylor is president of Distributed Networking Associates and publisher/editor-in-chief of Webtorials. Jim Metzler is vice president of Ashton, Metzler & Associates.