Lisa's SIP Trunking Session at InteropLisa's SIP Trunking Session at Interop

Why you should pay attention to off-net traffic, and why price isn't the most important thing to worry about if you're starting a migration to SIP trunks.

Lisa Pierce's session on SIP Trunking drew a really strong crowd this Friday morning at Interop NY, testimony both to Lisa's reputation and to the topic's growing importance to enterprises. I blogged a preview of the session that highlighted Lisa's estimates of how the providers were doing in various aspects of SIP trunk offerings, and how she expected them to progress by 2012--so here I just want to follow up with a couple of discrete points that Lisa made during the session. (You can also check out this Ask the Analyst feature by Lisa for some more on the current state of SIP trunking.

The thing that I picked up on as most interesting from Lisa's talk was the context that she helped bring to the whole issue of migrating to SIP trunks. One point she reminded the audience members about was the statistic that, however much time you may spend thinking about on-net traffic, the fact is that in the typical enterprise, 75% of traffic is off-net, versus just 25% intra-company. That means when you're pricing SIP trunk offers, you want to pay close attention to the pricing of off-net traffic.

"We can all talk about on-net, but from a price perspective, it doesn't matter," Lisa said. "Off-net matters."

However, Lisa made another point: We all focus on the savings--you hear anywhere from 20% to 80%--but she strongly suggested that enterprises focus on the benefits of end-to-end IP that SIP trunking brings; and the risks that the transition could also potentially pose.

"You want to learn a lot about what this is for you, and then ask the question about price," she said.

It's also important to think about the provider's broader picture--evolution plans, other services they may try to get you into. That's because, Lisa pointed, we've seen with MPLS that as providers get you into new services, they're likely to draw you into various new managed elements that tie you closer to them.

Finally, Lisa showed a chart explaining why the carriers, as much as they may be trying to incent migration to SIP trunking, aren't rushing into things--IP data services remain significantly less than 50% of their revenues for data services, while legacy services will continue to dominate for several years into the future.