Finally: Frame relay SVCs

MCI this week due to become first major carrier to offer them.

By David Rohde
Network World Fusion, 6/9/98

After years of hearing that it's "just around the corner," users are finally going to get a crack at the dial-up equivalent of frame relay connections.

Pricing details

Speed of circuit in bit/sec Maximum monthly charge for PVCs* Maximum monthly charge for SVCs*

16K $16 $48

56/64K $47 $141

512K $472 $1,180

1,024K $1,050 $2,363

* These are monthly caps; actual charges for both PVCs and SVCs are 5.5 cents per megabyte up to the subscribed speed of the circuit, or 4.5 cents per megabyte for bursts up to the carrier port speed. NOTE: SVCs have no minimum as opposed to PVCs, which have a $5 minimum charge each month.
SOURCE: MCI, Washington, D.C.
MCI Communications Corp. on Friday is expected to file its long-awaited tariff for frame relay switched virtual circuits, becoming the first major U.S. carrier to enter the SVC market.

SVCs are temporary paths through a frame relay network, with a call set-up and tear-down routine similar to telephone calls. Unlike frame relay permanent virtual circuits (PVC), SVCs do not have to be provisioned in advance between two user sites in the network.

An advance copy of MCI's SVC pricing provided to Network World shows that MCI will offer the service for the same basic price as its PVC offering: 5.5 cents per megabyte up to the subscribed speed, or committed information rate (CIR), or 4.5 cents per megabyte for data bursts up to the carrier's port speed.

However, MCI will set a much higher pricing cap on SVCs than for PVCs. At lower speeds, the maximum monthly charge for SVCs - the level at which all further usage is free - is triple that of PVCs. For example, charges on a 32K bit/sec PVC top out at $31 a month, while a 32K bit/sec SVC can rack up charges as high as $93 a month.

At speeds from 112K to 768K bit/sec, the maximum SVC charge is two and a half times as high as the PVC charge. Above that level, the cap is two and one fourth times as high. MCI officials said they had to set the levels that way to make certain they did not cannibalize their own existing frame relay traffic.

"This was the best way to make sure that customers don't dump all their PVCs," said Melanie Hanssen, MCI's executive manager for frame relay services. Despite all that, SVCs can still save money over PVCs. Reason: Users don't have to mesh their circuits among multiple sites. Once an SVC is established for a given customer site, that single SVC can reach all of the other SVC sites without establishing any additional circuits with the carrier. As a result, Hanssen explained, the maximum number of SVCs cannot exceed the number of user sites.

Under traditional frame relay networking, the number of PVCs can rapidly multiply to several times the number of user sites just to make sure they can all communicate with one another.

For these reasons, Hanssen said, SVCs are well-suited to any application that potentially requires broadcast messages from any site, such as many intranet and extranet applications. Another possibility for SVCs: voice over frame relay, where any site may wish to talk to any other. They are not as well suited to star-configured remote-to-host applications, where all data flows back and forth between a single central site.

MCI's initial pricing comes with a few asterisks. The carrier is not ready to do call-by-call accounting to tote up the SVC usage charges, so it will initially charge a flat rate based on the usage maximum. A temporary promotion to be filed at the Federal Communications Commission with the SVC tariff will bring that flat rate down to the PVC price cap. MCI will change the SVC tariff to the full usage-based pricing scheme when the testing of call-by-call bill accounting with its Bay Networks, Inc. switches is complete. That will probably be in August, Hanssen said.

Another customer incentive: The SVCs will come with no monthly minimum. Any site can let the feature go unused for a month without penalty. All PVCs in the MCI network come with a $5 a month minimum charge.

Though SVCs open up new vistas for frame relay applications, they are not quite as simple as traditional dial-up voice or data connections.

Each SVC site - even an extranet location such as a car manufacturer's parts supplier or an insurance company's independent agent - must have a router or FRAD that supports the Frame Relay Forum's SVC implementation agreement. For example, Cisco routers that support Release 11.2 of Cisco's Internetwork Operating System (IOS) will work.

In addition, MCI will offer a free option called "closed user-group screening." This feature gives certain sites and individual employees the right - or denies them the right - to reach certain other locations. Along with an optional limitation on SVC bursting called Peak Information Rate - a rate above the CIR but below the port speed on the carrier's switch - these features help network managers to make sure SVC usage charges don't run out of control or block mission-critical PVC traffic from getting through.