Frame relay NNIs in the cross-fire

By David Rohde, Network World |  Networking

AT&T officials are candid that they will present users with alternatives if they try to force frame nets together. One alternative is AT&T's Local Frame Relay service, introduced last year, which puts multiple sites in a metro area on AT&T's switches for much less than the cost of AT&T's national frame relay. Another is an AT&T service called IP-Enabled Frame Relay, which sends one permanent virtual circuit from each site into an IP cloud that can terminate the connection at any other site. A third alternative is AT&T's Transparent LAN Service, which provides native LAN-speed connections, again generally in metropolitan areas.

Steve Taylor, president of Distributed Networking Associates in Greensboro, N.C., has aa different idea. He suggests that if users find themselves with frame nets from two carriers that won't agree to an NNI, the user can install a frame relay switch at a central site and set up the NNI there.

Sprint has a different approach. Although Sprint doesn't have regular public NNIs with local carriers that can be shared among multiple users, for a single user it will sometimes provision a private link, such as a T-1, between its frame relay net and another carrier's.

Not all carriers balk

But there are several second-tier, long-distance carriers that will happily link together local frame relay clouds across LATAs for multiple users who prefer to employ the regional Bell operating companies for frame relay. According to a recent survey by Distributed Network Architects, these include Frontier, IXC Communications and even GTE -- a non-Bell local carrier with no long-distance restrictions.

Another carrier that has specialized in working NNIs with RBOCs is Intermedia, a Tampa, Fla.-based company that began as a competitive local exchange carrier and has branched into long-distance data services. "Traditionally Intermedia has been very willing to do NNIs and is very aggressive in that market," Taylor says. Intermedia even offers network-availability guarantees across its NNIs that are only slightly less robust than those entirely on its network.

One of the old knocks on NNIs was that each carrier couldn't see across the connection to view the other carrier's network, leaving users in the dark as to who to call in case of an outage. NNI proponents claim that scenario is outdated. To address this question, the Frame Relay Forum approved a variation on NNIs in 1997 - Implementation Agreement FRF.10 - which allows two carriers to pass switched virtual circuits between each other to gain more flexibility.

To further alleviate finger-pointing problems, Sprint and local carriers sharing an NNI for a particular user will attempt to create a common addressing database. "You want to be sure that they have some common mechanism for referring to a particular circuit," says Tom Mennona, director of Sprint's packet data services center.

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