Verizon’s network suffered another of those large-scale outages, and there’s no official word on just what created the problem. One story I’ve heard is that it’s the same last time, which is an IMS-based signaling system overload. If true, the problem illustrates one of the major challenges for both vendors and operators.
IMS has been seen by telephony purists as the natural utopian goal to which all mobile networks aspire. To web guys, it’s kind of like innovation with both arms and legs tied up. Underneath the religious war is a simple truth, which is that modern broadband services based on the web model are provably scalable and that’s not yet true with IMS. Many believe they can’t be, some (myself included) believe we shouldn’t be trying to find out in the first place.
IMS is based on a session-managed notion of communication where connectivity is authorized. I remember seeing a diagram of the signaling to be proposed to access a website via IMS, and it made ISDN call setup look like blowing a kiss to a passing car. The issue with IMS is less with IMS for how it works, then, than IMS for how it’s applied. For broadband web-like apps, we need a web model. However, web guys have been just as intransigent as IMS guys. The latter refuse to come up with a logical web-service model, and the former refuse to come up with anything that’s useful for pay-for services. Operators don’t want to give mobile broadband away, and they don’t want to kiss off their current mobile voice revenues, so they need a transition strategy.
Vendors have implicitly divided themselves on this issue, with traditional players like Alcatel-Lucent, Ericsson, and NSN taking a pro-IMS stance and IP players like Cisco and Juniper taking a pro-web stance. Note that I didn’t say “anti-IMS”; it’s risky to put yourself in the path of a carrier cash cow heading for the monetization barn. Both camps seem frozen into functional immobility. My view is that the future will be a kind of “IMS-plus” world, where IMS manages voice and registration and data services are handled another way. What way? That’s what vendors and operators need to hammer out. Verizon’s problem may stem from trying to accommodate a transition nobody really wants to face.