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Talk is cheap with frame relay

More frame relay access devices are carrying IP voice traffic, as vendors vie for a piece of the VPN market.

January 20, 1999
Web posted at: 2:38 p.m. EST (1938 GMT)

by Tim Greene

(IDG) -- The latest word in frame relay access devices (FRAD) is voice.

With all the talk about service providers migrating to IP networks to carry voice and data, FRAD vendors seem to be responding with IP voice of their own. Nine of 20 FRAD makers included in our online Buyer's Guide chart now support voice over IP and voice over frame relay. The combination gives FRAD users the option of carrying voice over IP among sites or buying a frame relay link into a service provider's IP network.

IP voice support is a way for frame relay to sell itself as the access link to IP virtual private networks (VPN) that connect corporate sites to each other or to the sites of business partners. With IP voice, workers at those same sites can talk to each other as well as share data, making a VPN more cost effective.

FRAD makers' interest in VPNs is also made clear by the inclusion of encryption capabilities in their boxes. Encryption is a standard requirement for corporations using public IP networks to link sites that share sensitive corporate data. Five products in our chart include encryption: 3Com's OC NETBuilder 120 KF; Cisco's 2600 series; Hypercom Network Systems' IEN 4000; Motorola's Vanguard 6450/30 series; and TimePlex Group's Synchrony IAN-150.

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For years, vendors shied away from adding voice capabilities to their FRADs. The advent of a standard for voice over frame relay in 1997 seems to have turned the tide strongly in favor of voice. Part of the appeal of voice over frame relay links is that they can reduce the amount of voice traffic among corporate sites that must travel over traditional public voice networks or dedicated voice trunks. That feature can save money.

Frame relay voice, which in demonstrations is of high enough quality to carry conversations easily, is suitable to VPNs because users realize they are using a packet network and have lower expectations than they would for a circuit-switched telephone network.

All the FRAD vendors in our chart that include voice capabilities build them right into the FRAD, eliminating the need for separate voice gateways to packetize voice calls coming from the local PBX.

Advances in voice compression technology squeeze that traffic down to less than 5K bit/sec in the case of ACT Networks' SDM-9350 and SDM-9400, Develcon Electronics' Athena Access, Hypercom's IEN 4000 and Netrix's Network Exchange 2210.

The effect of compression is twofold. First, compression reduces the total traffic traveling over the frame relay link. That means the link doesn't need to be as large, saving the customer money. Second, compression reduces the demand on the link for guaranteed bandwidth, which is known as committed information rate (CIR). Voice requires low and predictable latency. If the voice traffic is compressed, it requires less bandwidth and, therefore, a smaller, less expensive CIR.

FRAD vendors are making an attempt to pinch bandwidth being used by data over the network by including data compression. While the numbers are not as impressive as they are for compressing voice, data compression can cut the size of WAN data transmissions by roughly 75%. That assumes, of course, that the data is not already compressed. Also, the compression achievable may depend on the type of data involved.

All the FRAD vendors surveyed also prioritize traffic over single permanent virtual circuits (PVC). That prioritization means specific types of traffic can get onto the network faster than others without having to pay for extra PVCs.

Another new twist in FRADs is support for ATM. So far, though, just one of the 21 FRADs included in our survey supports ATM -- Cisco's 2600 series.

That feature enables the box to fit into hybrid frame relay/ATM networks. It also allows users to buy the FRAD to fit into a frame relay network knowing that the FRAD will still be useful if that site is later served by an ATM link instead.

The latest FRADs seem to be designed for busier sites, with five vendors offering support for 10/100M bit/sec Ethernet LANs: Cisco, Memotec Communications, Netrix, Nuera Communications and TimePlex. All the other FRADs (with the exception of HT Communications' AsyncFramer, which doesn't support Fast Ethernet) still support just 10M bit/sec Ethernet for sites that put less demand on their LANs.

As frame relay has become more popular, FRADs have become more sophisticated to keep pace with user needs. Most of the FRADs surveyed include some form of dial backup to keep a site connected if the frame relay link fails; only HT's AsyncFramer, Newbridge Networks' 3609 MainStreet product and Nuera's F200ip don't. The devices also offer some form of data collection to keep track of traffic in and out of sites. Reports based on that data help users track whether service providers are living up to the levels of service they promise.

With the addition of more new features to the simple frame relay assembler/disassembler, expect FRADs to become sophisticated edge devices that may deserve to be called more than just a FRAD.

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