VoIP, Led by SIP, Forges Ahead

Carl Weinschenk

It's interesting to see technological innovations lead to real changes in how people get their services.


Last week, ABI Research released research concluding that the burgeoning popularity of powerful mobile devices and the increasing dominance of Internet Protocol (IP) networks is leading to an explosion in the deployment of Session Initiation Protocol (SIP)-based applications.The research suggests that SIP will become the normal way in which services are deployed. By 2012, just under half of all subscribers will use at least one SIP service, with many using more. Such services -- instant messaging, video sharing, conferencing and scores of others -- will generate more than $150 billion in revenue. Cumulative capital expenditures on SIP by 2012 will exceed $10 billion.


The folks at the Lippis Group do their usual comprehensive job in this report on SIP. Indeed, the piece has a double benefit. On one hand, it breaks overall SIP technology into three easier-to-understand elements: SIP connections, SIP endpoints and the SIP platform. The piece defines each of these elements and, perhaps most importantly, lists the main players in each. For instance, the key vendors in the SIP connections category are Avaya, Cisco, Siemens, Nortel, Alcatel, ShoreTel and Mitel. The piece says that many service providers have entered the trunking segment during the past two years. In the U. S., new service providers include AGN Networks, AT&T, BandTel, Global Crossing, Onvoy, Paetec, Verizon Business, McLeodUSA, Qwest and TelePacific.


This is a fairly technical description of SIP at Train Signal Training. The most valuable elements of the piece are a description of the benefits of "the new version of SIP" (no more information on what this means is provided) and a glossary of SIP terms. The new version of SIP, the writer says, is adaptable to network changes; scalable; text-based for easier programming; focuses intelligence in the end device; and easily adopts new services.


The way in which networks provision services and manage connections is monstrously complex. This is the role of SIP in VoIP and Signal System 7 (SS7) in the legacy public switched telephone network (PSTN). These two systems must communicate. This, according to this feature at Engineer Live, is done in two ways. The first is a group of standards that enable the encapsulation of ISDN User Part (ISUP) messages in SIP networks. These include SIP for Telephones (SIP-T) and SIP with encapsulated ISUP (SIP-I).


The second approach involves "custom interworking functions," which appear to be proprietary specifications. The explanation is complex. The takeaway, however, is that organizations planning large internal SIP-based VoIP networks must be aware of the need for the new system to communicate with the legacy SS7 network.


The world of VoIP, this story says, is still in its early days. That means a lot of things, including the reality that security vulnerabilities must be confronted. This PC World piece doesn't say exactly how SIPtap, a proof-of-concept program written by BorderWare co-founder Peter Cox, uses SIP to eavesdrop on VoIP calls. But the ramifications are scary: A hacker would only need to insert a Trojan into one machine to monitor multiple streams of calls on a network. The criminal would be able to listen, create WAV file recordings and index them using SIP identity information.


There are many SIP-related resources available, including a wealth of information at the SIP Forum. The bottom line is that IT departments must be familiar with these complex SIP-related issues as they plan their network transitions.

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