Verizon, SKT run risks of leading LTE pack

Verizon Wireless blotted its LTE copybook at the end of 2011, after a generally exemplary rollout of its 4G network, given the speed of progress and the risks of being such an aggressive frontrunner. But being at the cutting edge has pitfalls, especially for a carrier moving at break-neck speed, and the worst of these center on networks that are not fully tuned up for the levels of signalling and traffic imposed on them. After a major outage in April, it suffered a series of new ones late in December, all of which were traced back to deploying such a new breed of net-work so rapidly – in particular, to the IMS or service delivery core.

Verizon‘s IMS deployment, to support its LTE rollout with all-IP services, is just about the most advanced project of its kind in the world, and its “big bang” approach is closely watched by more cautious cellcos elsewhere. But the outages have raised questions over whether the carrier should be moving so quickly, and whether its technology is fully ready for the commercial big time.

While IMS is fairly well established, there are few comprehensive commercial deployments and none, apart from Verizon's, in an LTE network. In April, the first and most serious outage was traced back to a software bug in a network element of the IMS core, triggered by heavy signalling and rapidly spreading throughout the system. (Another early LTE deployer, Telenor of Norway, suffered an 18-hour outage which was also caused by a signalling overload earlier in the year). Meanwhile, a December 7 outage was caused by the failure of a back-up communications database. The two late December incidents were triggered by different IMS elements not responding or communicating properly.

In an interview with GigaOM, Verizon Wireless‘s VP of network engineering, Mike Haberman, said: “being the pioneers, we‘re going to experience some growing pains. These issues we‘ve been experiencing are certainly regrettable but they were unforeseeable.” In other words, Verizon is discovering many of the downsides of LTE on behalf of its more cautious peers – and taking the flak for them too.

Haberman said that once each IMS problem has been fixed, it has never recurred, but this points to a series of bugs, and to the complexity of a huge platform involving many elements from a range of vendors (notably Alcatel-Lucent, Nokia Siemens, Acme Packet and Tekelec). Haberman is putting various safeguards in place against further glitches, notably geographically segmenting the LTE network, so that a problem can be isolated to a particular region.

He is also upgrading the signalling infrastructure to handle the storms better, committing to the new Diameter signal routing platform, which replaces point-to-point communications between servers with multipath routing. Tekelec signed the most prominent Diameter contract to date in the 4G world in August, after Verizon's initial signalling-related outage.