To SIP Or Not To SIP?

SIP, or Session Initiation Protocol, in a nutshell, is a means of initiating and terminating VoIP calls, to offer functionality similar to regular telephony and more (e.g., video calls). That includes things like ringtones and notification of incoming calls. In regular telephony, “trunk lines” are segmented and carry the calls. PBXes, or Private Branch eXchanges, are essentially switches that route the calls. In IP communications, the IP equivalents function in pretty much the same way.

One component of some IP telephony systems is the SIP protocol. (Not all of them follow it.) But this is a new problem that is arising amongst SIP-based IP PBXes: different implementations by different manufacturers, which will lead to incompatibility. Brian Riggs of VoIP Loop notes that this happened early on in the history of WLANs (Wireless LANs), until a standards body formed. When manufacturers of WLAN equipment started being certified, WLANs became interoperable. He suggests that SIP trunks and IP PBXes need a standards body as well. (Garrett Smith has a piece entitled 9 benefits of SIP trunking, if you want some more insight.)

IP telephony has enough going against it, from the perception of enterprise, universities and governments (depending on the flavour of VoIP). It’s a threat to the status quo of regular telephony. At least to those blind to the idea that they are welcome to participate as well. But for participation from all, IP telephony has to be interoperable. There are already enough VoIP and VoIM clients that cannot talk to each other, though developers are trying to rectify that with various bridging applications. But when it comes to the guts of IP communications, all the hard and soft switches, etc., not all SIP trunks are compatible with all IP PBXes.

The IP industry is old enough now to have a standards body, but maybe young enough that it only has forums, like the SIP Forum, for example (who have something called the SIPconnect Interface). My guess is that a body will form, and it’ll have to be spearheaded by a company such as IBM or Cisco, who have the wherewithal to promote. Let’s hope this happens sooner rather than later.