[ISN] What are critical issues with VoIP service?

http://www.networkworld.com/news/2008/073108-burning-voip.html

By Brad Reed
Network World
07/31/2008

VoIP services are rapidly becoming the bread and butter of enterprise 
voice networks, as roughly 72% of all enterprise voice lines shipped by 
vendors in 2007 were IP-capable. Now that companies are definitively 
moving away from the traditional Time-Division Multiplexing (TDM) voice 
networks and into Session Initiation Protocol-based (SIP) VoIP networks, 
we examine the VoIP industry's most pressing issues, including SIP 
interoperability, TDM-to-SIP transition services and VoIP security 
issues.


Is SIP interoperability still a major concern?

As Nemertes Research analyst Irwin Lazar puts it, "it's more a hindrance 
than major flaw at this point. Three years ago, a team of iLab engineers 
found that while different VoIP vendors could ensure basic connectivity 
between their SIP-based phones and devices, there were also "significant 
failure rates" for enterprise VoIP features and standard security 
parameters. Lazar says that today key basic VoIP features such as caller 
ID, message waiting lights, hold and three-way calling are "pretty well 
standardized," but that more advanced features such as multiple line 
appearances, call bridging and intercom still face significant SIP 
interoperability issues between vendors.

Jeff Brandt, the general manager of IT infrastructure design and 
engineering for business processing firm Sutherland Global Services, 
expresses a similar viewpoint and says that he has concerns about a lack 
of SIP interoperability for advanced carrier-level features for his 
company's call centers, noting in particular that there are limits to 
advanced enterprise options that have strong SIP interoperability. 
Brandt says that his main concerns are features such as interfacing with 
percent allocation capabilities, as well as general bandwidth capacity 
concerns for SIP-based systems.

"In a contact-center space, it's difficult to predict spikes in the 
network that are unforeseen," he says. "After AT&T launches the 3G 
iPhone, for instance, who knows what that will bring to our call 
centers? The SIP world has not fully matured yet to handle that kind of 
flux in traffic."

Brandt also says that some companies might experience SIP 
interoperability problems simply because SIP is a relatively new 
technology for a lot of enterprises and that IT departments don't yet 
have the same familiarity with SIP-based systems as with TDM systems.

"Everyone understands how TDM works, but in the SIP environment there 
has to be some more effort to get people to understand how it operates," 
he says.

But Marc Tolbert, the volunteer IT coordinator for Bullitt County Adult 
& Community Education in Shepherdsville, Ky., says that the big SIP 
interoperability problems are largely experienced by large enterprises, 
and that small and midsize businesses with more basic VoIP needs will 
have very trouble-free experiences with their SIP systems.

"Previously, a lot of people would experience problems because of a lack 
of standards, but that was a few years back," he says. "When it comes 
down to it, unless you're doing something really bizarre and funky with 
your implementation, you won't have many problems."

[...]


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