Ready to bundle? - university merges voice and data on T3 - Internet/Web/Online Service Information

Communications News, Oct, 1999

Combine Internet data with voice on a T3 to really compete.

For an increasing number of enterprises, the combination of voice and data traffic is sufficient to warrant a T3 access line. For some, voice traffic may already have exceeded the crossover point at which T3 becomes more economical than multiple T1s, and that traffic may already be on a T3. In such a case, spare bandwidth is often available for the taking. All that is required is to implement the right combination of equipment and services to make the convergence of voice and data a success. An Eastern U.S. university worked with its service and equipment partners to successfully merge a growing Internet data application onto a T3 voice connection.

At the beginning of the project, the university's voice and Internet data networks were completely separate, with different access equipment and different service providers (Figure 1). Voice requirements had grown over the years to eight T1s, economically justifying a T3 access line. (Since a T3 consists of 28T1s, using 8T1s for voice left the university with 20 spare T1s on its T3.) In the few years since residence halls had been networked, Internet requirements had grown to three individual T1s. While a growth path for voice was well provided for, the more critical growth path for Internet data consisted of adding individual T1 lines.

[Figure 1 ILLUSTRATION OMITTED]

CONVERGING VOICE AND DATA

Network managers at the university saw an opportunity to cut operating costs by moving current and future Internet connections to the spare T1s. They determined that there were no compelling reasons to keep the two important communication networks separate. In cooperation with their vendor partners, they determined that the technology involved in the convergence of voice and Internet data would not be burdensome, and that annual savings would be significant.

The university's partners in the project were AT&T and Larscom, a vendor of wide area network access equipment. The university served as a beta test site for AT&T WorldNet Services, which would become the university's Internet service provider. Larscom provided inverse multiplexing equipment on a 60-day free evaluation. The inverse multiplexing equipment would play a key role in the WorldNet access architecture.

HOW'D THEY DO THAT?

How were the university's voice and Internet data merged? In the university's switchroom (Figure 2), three T1 ports on the Cisco 7000 router used for Internet access were replaced by a single serial port, which connected to a Larscom Orion 4000 T1 inverse multiplexer. The Orion 4000 mapped the router traffic across four T1s, which were combined onto the same T3 as the voice traffic by the voice network's original T3 multiplexer. Specifically, channels 1 through 8 of the T3 were assigned to voice, channels 25 through 28 were assigned to Internet access, and channels 9 through 24 were available as spare capacity for voice and/or data.

[Figure 2 ILLUSTRATION OMITTED]

The T3 from the university's switchroom was terminated at the nearest AT&T POP, in Lanark, Pa. At the Lanark POP, the T1s carrying voice connected to the public telephone network. The T1s carrying Internet data were sent to another Larscom Orion 4000T1 inverse multiplexer at the WorldNet POP in Philadelphia, which connected to the Internet backbone.

An important aspect of the Internet connection was that the T1s were "inverse multiplexed" into a single data channel. Although the Internet data was physically transported by parallel T1s between the two Orion 4000s, the connection functioned as a 6-Mbps "fat pipe." This 6-Mbps channel was more efficient than four separate 1.5-Mbps T1 connections and provided notable improvements in response over the three separate T1 connects used previously.

Another advantage of inverse-multiplexed Internet access for the university was that it provided a smoother growth path than separate T1 connections. Network managers at the university were well aware that Internet access requirements would grow relatively rapidly (the current expectation is to add one T1 per semester), so future expansion had to be taken into account from the beginning. The Orion 4000 supports multiple data channels of up to 12 Mbps (8 T1s) each, so it has the capacity to allow the university eventually to use all 20 of its spare T1s for Internet access. For the university, the only hardware expense of expansion would be additional modules for the Orion 4000 if the Internet connection grew beyond 12 Mbps; the only new operating cost would be the WorldNet service charge for the added T1s. There would also be some reconfiguration required at the POP, which would be the responsibility of AT&T.

BENEFITS WORTH CONSIDERING

Installing the equipment, switching over to the WorldNet service, and completing the trial took about one month. With the successful completion of the trial, the university's network managers had simultaneously increased performance and reduced cost, pleasing both the provost and budget offices--not an insignificant achievement.