Bradner's column: Convergence from the other side

At some random network conference over the last year, I signed up to get one of the magazines designed for the traditional telephone companies. I've now started getting the publication and am surprised about the amount of familiar information in it.

America's Network bills itself as covering "technology for the public network since 1909." It is definitely a magazine for telephone carriers and their suppliers. It has articles about telephone carrier topics, such as reusing the old digital loop carrier cabinets, 100,000 of which are scattered around the landscape, and telephone billing systems.

But each of the issues I've received also has contained a number of Internet-related articles. For example, the November 15 issue included articles on the IETF's Multi-protocol Label Switching (MPLS) technology, alongside a research report on the future of wireless telephones.

MPLS is in the final stage of being approved by the IETF as a proposed standard. The technology's origins lie in Cisco's Tag Switching, and MPLS was initially targeted at giving ISPs the ability to do traffic engineering. This ability involves directing IP traffic through paths in the ISP backbone that normal IP routing would not have chosen. For example, ISP traffic from Boston to San Francisco might normally be routed through Chicago. If the ISP links through Chicago get overloaded and the ISP has excess capacity in a fiber link through Cincinnati, the service provider can use MPLS to direct the Boston-to-San Francisco traffic through the Cincinnati link.

This function is just what some ISPs with underlying ATM networks have been doing via ATM virtual circuits. MPLS allows non-ATM-based ISPs to do traffic engineering.

Later it became clear that this same traffic engineering could be used to help provide better-quality IP service for specific applications. Determining what MPLS path to use was based on what application was being run, rather than what city the traffic was coming from.

Most ISPs in the U.S. are focusing on the use of MPLS for non-QoS traffic engineering.

The articles in America's Network, on the other hand, focus on the QoS aspects. The same technology is being looked at from a different vantage point. Most of the magazine's IP-related articles are from this different vantage point - telephone companies' vantage point. More and more telephone representatives are participating in the IETF, so some of these other views are now being incorporated into IETF work. But at times this can be a very different viewpoint indeed because the architectural and management assumptions that underlie the phone networks and the Internet are so very different. It will be interesting to see if we can keep true to the Internet model while learning from the phone input.

Disclaimer: Harvard has made a science of having different management assumptions for each of its schools, but the above observation is mine.

(Bradner is a consultant with Harvard University's University Information Systems. He can be reached at sob@harvard.edu.).com.)

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