Bottleneck blues

Communications News, April, 1998 by Alan Stewart

Figuring out what's slowing the Internet down is the first step to developing corrective measures.

It was a shock to many of us to read about the travails of America Online (AOL). Millions of users of the Internet realized suddenly that Internet service providers (ISPs) were experiencing significant growing pains that required a substantial investment to alleviate. A year later, it had become apparent that the problem did not lie only with the ISPs--it was a growing issue for the local exchange carriers (LECs) as well.

In its interim report to the Federal Communications Commission, the Network Reliability Steering Committee (NRSC) found that excessive Internet usage was leading to significant slowdowns in parts of the public switched telephone network (PSTN). "The principal point of congestion is at the ISP's local switch," notes Bell Atlantic's Ray Albers, who chairs the NRSC. "There have been reports of delayed dial tone and all circuits busy."

There is little doubt that the legacy telephone network is being stressed by a rapidly escalating number of Internet calls. The LECs spend millions of dollars a day on upgrades that bring them not a penny of extra revenue. This, in a nutshell, is the dilemma faced by U.S. telcos as they struggle to accommodate the ISPs and their subscribers.

"Long holding times tie up both switch resources and interoffice trunks and small increases in Internet traffic can increase the probability of call blocking," say Bellcore consultants A. H. Atai and J. J. Gordon.

Alan Pearce, who served as chief economist at the FCC at the time of divestiture, believes that the regional Bells should do more. "There are some people who say that congestion is a direct result of unbundling the local loop," he says. "They claim that this is potentially dangerous because it affects network reliability. The Commission's response to this was to tell the incumbent local exchange carriers (ILECs) to set up a proper organization to study the issue. I think that later this year we'll have some pricing and technical clarity."

The problem is not one of complete network failure, says Albers. Rather, it involves a creeping paralysis in certain portions of the network due to Internet traffic. Over the next few years, the PSTN will provide more and more residential users with access to the Internet and other data networks. Both network providers and equipment vendors are seeking ways of off-loading Internet traffic from the PSTN onto data networks.

Today's network economics encourage Internet users to stay online twice as long (on average) as with metered rate plans, say Atai and Gordon. "Understandably, given the number of online users, this doubling of call duration can result in significantly higher loads for the PSTN. Internet growth forecasts from several sources predict that in two years, 30% of U.S. households will be online compared with 15% in 1997."

This is what troubles the LECs, says Albers. Bell Atlantic filed a study with the FCC based on 10 telephone exchanges with ISP connections in the Washington, D.C., area. In one case, all Internet traffic from the District of Columbia, Northern Virginia, and Maryland was homing in on one exchange used by AOL in Hernden, Va. The LEC could not keep up with traffic surges, leading to subscriber complaints of slow dial tone and busy trunks.

APPROACHES

Atai and Gordon take a technical approach to the problem. The solutions most popular with the telcos lead to architectures that off-load Internet traffic and treat it differently from voice calls. This strategy involves Internet call administration, authorization, and authentification (AAA) procedures that are unpopular with the ISPs, as they claim it reduces their ability to manage their businesses.

Most off-load architectures move modem functionality away from the ISP and closer to end users, so that Internet calls can be converted to packet format as early as possible. This lets the telco take advantage of gains achieved through multiplexing Internet connections. But to do this without alienating the ISPs, the LECs must address their concerns regarding access to, and security of, ISP customer information.

"ISPs are extremely sensitive about relinquishing the administration of modems (or modem functionality) to third parties such as the LECs," note Atai and Gordon. "Retaining control of modems allows them to directly manage their own customer bases without having third parties intrude on this relationship. Sensitivities regarding customer access are heightened by the fact that some LECs have ISP subsidiaries."

OFF-LOADING

There is little disagreement that data circuits are a more efficient means of carrying Internet traffic than the PSTN. Thus it seems obvious that this traffic should be taken off the PSTN as quickly as possible. The contentious issue that faces both the LECs and the ISPs is how and where this should be done without disrupting current services.

The first approach involves the interception of Internet calls and their redirection to a packet network on the subscriber side of the local exchange. In this way all PSTN elements including the originating switch, trunks, and the egress switch are bypassed. The local switch still has responsibility for some call-related signaling.