Swirling flow

What is Frame Relay?

Frame Relay is a Wide Area Network topology that utilises packet-switched technology. Packet-switched networks enable end stations to dynamically share the network medium and available bandwidth across a WAN. Frame Relay was originally designed for use across ISDN (Integrated Services Digital Network) interfaces but today its used across a wide range of access technologies from dial all the way through to Megastream leased lines.

Frame relay is more commonly used in the United States where it is seen as a cost effective way of connecting multiple sites, however Frame Relay is now being replaced especially in the UK by MPLS (Multi Protocol Label Switching) networks. The main Frame Relay providers in the UK are BT and Energis (now Cable & Wireless) with both providers aiming to close down their Frame Networks over the next 5 years. BT is concentrating on their 21CN network connecting fibre to the home. BT are currently utilising their Frame Relay network as a wholesale flat rate leased line product to UK ISP’s enabling ISP’s to offer fixed cost Internet Facing pipes anywhere in the UK utilising BT’s local points of presence. The typical offering for this product is a 2Mbs pipe with 1.5Mbs guaranteed throughput burstable up to 2Mbs with pricing around £2500 installation and £9000 per annum.

How does Frame Relay work?

Frame Relay connects a Customer’s Sites to a Frame Relay Network by means of an access tail(s) with bandwidth options available from 64Kbs to 155Mbs. The Customer presents data at the Service Termination Point at each Site and the Frame Relay provider will carry the data in the form of frames across the Frame Relay Network to another Site to which the data is addressed, by means of Permanent Virtual Circuits (“PVCs”).

PVCs are software-configured paths through a Frame Relay Network between customer’s sites. A committed Information Rate or “CIR” is then applied to the PVC committing to a certain amount of bandwidth between sites. For example a customer could have a 3-site Frame Relay network, one HQ with two remote sites, with a 2Mbs access point at the head end and 1Mbs access points at the two remote sites. Frame Relay can be used as a meshed networks so sites A & B could have a CIR of 512Kbs to each other and 512Kbs to the head end.

With all Wide Area Networks the Head End site will always require an access tail equal to the sum of all the remote sites access points. If you had 4 remote sites with 512Kbs access points then you will need a minimum of 2Mbs at the Head End.