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Carriers answer our 20 questions on frame relay.

In the April column, we offered 20 questions to ask frame relay (FR) carriers and equipment vendors. The questions were designed to help you determine if FR will be useful in your networks.

We asked members of the Frame Relay Forum to answer our questions. Results from the carrier members are summarized here. We'll look at vendors next month.

Direct responses came from AT&T, CompuServe, MCI and WilTel. Bell-South says it has not announced FR service, but is evaluating a FR trial. Reference to Sprint is periodically made by WilTel, although we did not receive a direct response from Sprint.

WilTel offered an interesting analogy for how its WilPak network will handle congestion. Consider a traffic circle into which vehicles enter, usually at different speeds and volumes. The cars are analogous to frames entering a network.

WilTel uses proactive congestion management, incorporating frame delays rather than frame discards. At each entry point into the circle a traffic light is placed. Each light permits a certain amount of traffic to pass; other streams attempting to enter the circle must wait (momentary burst capacity). Add to this the committed info rate (CIR) and WilTel has fashioned a technique which minimizes frame congestion and collision.

WilTel compared its congestion strategy to Sprint's.

According to WilTel, Sprint does not have a "traffic light" arrangement at each network entry point. Rather than regulating traffic, Sprint's network marks frames exceeding the CIR as eligible for discard.

If congestion and/or collisions occur, the problem is immediately cleared by automatically removing all frames marked as eligible or discard. Alarm indications are also rendered when congestion thresholds are exceeded. Sprint also uses FECN/BECN (forward/backward explicit congestion indicator) bits for congestion control.

MCI's FR service currently has no node-to-node protocol for congestion notification. A frame discard strategy will handle congestion at network boundaries, although MCI notes that their network will have sufficient capacity to carry FR traffic.

Both CompuServe's Frame-Net and AT&T InterSpan services offer proactive congestion management through the use of momentary bursts. Data is not marked as eligible for discard.

All carriers support a wide range of protocols for both wide area and local area networks. However, only WilTel stated that it has demonstrated interoperability with FR offerings from Nynex and Southwestern Bell.

All carriers comply with ANSI standards for end-to-end error checking. Error correction is handled by premises equipment.

Lost frames

Minimizing frame congestion will directly impact the potential number of lost frames. Each carrier has well-defined programs in place to handle congestion; higher-level network protocols will have lost frames transmitted if necessary.

While FR networks are essentially transparent to network management activities (use of the SNMP protocol), each carrier provides NM services in addition to those a user can provide. For WilTel, the service is called WilView; CompuServe uses StrataCom's StrataView; MCI offers NetExpert; AT&T will use NCR's StarSentry NM system, plus a dedicated FR Network Operations Center now under construction.

Since the concept of FR service is still relatively new to prospective customers, the initial activities include analyzing business applications, followed by tracking and analyzing data traffic before any FR network configuration can be attempted. Each company has trained staff available to work closely with prospective customers to assess traffic characteristics, provide detailed reports and assist in the definition of network parameters.

Pricing FR

WilTel and CompuServe both use flatrate pricing based on the aggregate CIR required by each permanent virtual circuit (PVC) in a node; the port connection speed is factored into pricing. Although MCI's rates have not been formally announced, the company expects to use a combination of fixed and usage-sensitive pricing.

Sprint uses two approaches. Standard Service is usage-sensitive and distance-insensitive, CIRs are not used, and all data is marked discard eligible. Reserved Service has a fixed monthly charge based on several factors. AT&T's FR service is expected to be priced on an individual case basis. The company does not plan to tariff the service.

No firm described its pricing as "confusing." After analyzing the schedules provided by WilTel and CompuServe, we don't think you'll need a degree in nuclear physics to figure out the rates (but it might help!).

FR is an important product growth area for each carrier. WilTel is proud it was the first U.S. carrier to officially offer FR service, underscoring its commitment to successful FR deployment. MCI sees strategic and competitive aspects of FR, particularly as the company moves further into "bandwidth on demand" services.

CIR is critical in normal operation: Each port accessing a FR network will not exceed committed information rate, so long as the port is not subscribed by more than 100%. However, WilTel encourages customers to exploit FR's ability to support bursty data transmission by using over-subscription to increase cost-effectiveness.

Both MCI and WilTel provide network performance reports to analyze how frequently CIRs are exceeded.

Based on the limited response received, we expect each carrier will support LMI transport, although that support may not be immediately available.

Each carrier has disaster recovery programs in place to support their overall network infrastructure, including FR.

Only WilTel and MCI responded to security concerns. WilTel stated security would be handled by customer-provided equipment. MCI would not discuss security measures prior to formal FR service introduction.

Similar long-term customer support facilities were mentioned by WilTel and MCI. They include regular updates of the service, introduction of new features, and a single point of contact for FR and CPE. WilTel has a special get-acquainted program in which customers can engineer a free trial of FR service and CPE.

Next month we'll review the responses of FR vendors. Stay tuned.
COPYRIGHT 1992 Nelson Publishing
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 1992 Gale, Cengage Learning. All rights reserved.

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Title Annotation:Communications Management
Author:Kirvan, Paul
Publication:Communications News
Article Type:Column
Date:Jun 1, 1992
Words:939
Previous Article:Is compressed video ready for school?
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