March 1, 2006

Q&A with John Leddy

By Jonathan Tombes

John Leddy
Innovation, OTI and Standards

Comcast VP of Network and Transport Engineering John Leddy is no stranger to cable's IP transport networks. At the SCTE Conference on Emerging Technologies in Tampa in January, Leddy received the IP Innovator of the Year Award. Sponsored by Cisco Systems, the award recognizes an SCTE member "who has achieved innovative achievement and creativity in the advancement and development of IP networking."

Congrats on the award. Could you tell us more about your background?

Thank you. I started working on the ARPANET quite a few years ago and began working in the cable space when I joined Continental Cablevision, where I first worked for Dave Fellows. After Continental was acquired by US West in 1996 and subsequently split to MediaOne, I left and went to work for Road Runner. In 2002, when AT&T Broadband was acquired by Comcast, I joined the company and once again began working for (Fellows).

Your colleagues at Comcast include Kevin McElearney and Vik Saxena, correct?

Yes. Kevin is the VP in charge of backbone deployment and engineering. Vik is a director, and works with me in multiple areas, but his expertise lies in the optics area. He has been responsible for driving much of the OTI (Open Transport Initiative), our RAN (regional area networks) rollouts, and our backbone itself.

Could you tell us more about the OTI?

The goal is to build a scalable, manageable and interoperable platform with our key vendors. A major driver for the backbone side of the OTI is the IP (Internet protocol) optical integration and convergence that has been taking place. In order to be able to effectively run and manage a large national network, along with all of our regional networks—we are in 35 states plus D.C.—we have to make sure we have interoperable standards between our vendors' equipment.

For example, although encoding schemes are based on standards, they don't always specify everything to the appropriate degree. Or it may be the case that they are implemented based on a certain specification, but the implementations may not interoperate, or interoperate only partially, but not to the level where they can be deployed and managed. We are looking to leverage the standards that exist, define what interfaces we expect to be there, and then work toward true interoperability.

There are standard form factors, such as GBIC, right?

Yes, GBIC and SMP on the 1-Gig level and then XENPAK and XMP on the 10. However, the types of FEC (forward error correction) and encapsulation currently in place are not as standardized as they could be.

What about other standards, such as generalized multi-protocol label switching (GMPLS)?

Let me take a step back. One of our objectives is to deploy our platform meet our cost-effectives in the RAN and then utilizing the same technology at the national level. We're deploying 10GigE technologies in the base, which is not as standardized as some of the SONET (synchronous optical network) technologies because it's still pretty new.

As far as GMPLS, much of the work provisioning circuit trunks dynamically with GMPLS has already been done. We're looking to extend that to the photonic domain to determine what characteristics and attributes need to be communicated. It's a great way to provide visibility to the optical infrastructure, so we can start to leverage applications like tunability and wavelength-selectable paths within the infrastructure.

So that plays into the reconfigurable add/drop multiplexers (ROADMs) category?

ROADMs and, as we move forward, there will be micro electromechanical systems (MEMs). One exciting aspect of the optics space is that there is a lot of technology that has yet to be taken advantage of and exploited for these new services.

Do you expect to take OTI to other MSOs or to CableLabs?

We're focused on meeting objectives that Comcast has. We're thrilled to have our two strategic vendors, Nortel and Cisco. It's really crucial to the success of our backbone project. If there's interest from other cable companies, I'm sure we can look into working with them, and if anything that gets developed out of the initiative, then they would certainly be able to take advantage of that.

These are the first two vendors. Do you expect others?

We'd certainly like to see other strategic vendors participate if that makes sense. And, if there are other vendors that bring unique technology, we're definitely interested in speaking with them, as well.

This was adapted from an interview that first appeared in CT's Pipeline.