- What is Frame Relay?
Frame Relay is a communications service that permits multiple communications
protocols to share a connection, and is in some cases a cost effective way to
interconnect a business home office with its branch offices.
- What does Frame Relay do?
Frame Relay is a shared service offered by telecommunications companies. Frame relay has been widely available
since the early 1990s. It shares some similarities with X.25, but offers increased speed and less functionality - as X.25 was meant to
operate mostly with slow, "character at a time" asynchronous terminals (VT100s, Decwriters, early PCs, etc).
Frame Relay is normally used to operate a Wide Area Network (WAN) without your company having to do the network management
functions. Frame Relay is -not-
an Internet protocol, although it is possible to route Frame Relay traffic to a TCP/IP internet gateway.
Like X.25, there are two basic types of connections, Switched Virtual Circuits (SVCs) and Permanent Virtual Circuits (PVC).
An SVC is a connection made on demand between a terminal, PC or computer to another resource on the network. A PVC is
always active between two computers, similar to a leased line - but without a need for a
dedicated leased circuit to each end-point on the WAN. Unlike X.25, a Switched Virtual Circuit is defined when the service
is ordered and configured by the network provider - Frame Relay is not a wide open network where anyone can connect to anyone else's computers.
For those who understand telecom jargon, Frame Relay is a Level 2 implementation of the OSI 7 layer model providing HDLC
capabilities. It provides very basic call setup and variable length packet routing and delivery. Frame Relay does not
provide end to end error recovery and correction - that functionality must be present in the applications which use the
Frame relay connection for transport.
Because Frame Relay is level 2 OSI compliant,
any OSI Compliant protocol (IBM SNA, TCP/IP, Novell IPX, Appletalk, Microsoft NetBIOS) can all share the same physical link.
- Who can sell Frame Relay to me?
Primarily Frame Relay is sold by the local incumbent phone company (ILEC) - the one that has been around forever, although perhaps a few name changes -
SBC, Qwest, Verizon, BellSouth, Frontier/Citizens, Alltel, Sprint, etc...
AT&T, Sprint, and MCI also operate Frame Relay networks, however you will still need a local circuit to connect to their network,
probably rented from your ILEC. If your WAN needs to operate in more than one phone company's service area, or internationally,
you're more likely to go with one of these networks, since the ILEC has regulatory issues when they operate
outside of their local service area, and end up partnering with one of the non-ILEC frame relay networks anyhow.
Access to a Frame Relay network is done usually via digital access lines - ISDN for low speeds, standard DS1 (1.4 Mb/sec) up
through DS3 (45 Mb/sec) are typically offered. It also is possible to connect to a Frame Relay network over DSL,
although that is less common.
At each location,
the lines are connected to a Frame Relay Router, which understands how to manage Frame Relay connections to the phone company
switch, and provide the interfaces necessary to connect to your LAN or other local networks.
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What does it cost?
What Frame Relay costs is primarily determined by two factors: CIR and network management.
CIR is the "Committed Information Rate" - it is the bit rate the vendor is guaranteeing to be available to you
at the endpoints all the time. In most situations, you can "burst" for short periods at a rate higher than the
CIR, but that ability is not guaranteed. As your usage goes up, you may want to increase the CIR in order to
get improved performance from the network. In many cases, that requires no new equipment - just the phone company
bumping up your CIR on their network interfaces and sending a bigger bill each month.
How little or much of the work your company wants to do to setup the Frame Relay network is the other major cost
factor. If you want the phone company to buy the equipment, do all of the installation and setup, and provide
24x7 monitoring of the routers on your premises, than plan on paying more. If you have in-house staff to do
that work, and you intend to do your own monitoring and maintenance of equipment and configuration, then the
phone company costs will be less.
Since Frame Relay networks tend to be highly customized for each company, typically pricing is done by asking
for the phone company to provide quotes. You should contact some of the non-ILEC telecom companies to see
if they can provide service in your areas in order to negotiate the best price and service levels.
What's next?
Frame Relay is still a useful technology, but it has competition. The technologies which are competing with Frame Relay or
may evolve to displace Frame relay include:
- ATM - Asynchronous Transfer Mode is designed to support extremely fast connections.. Instead of
using variable length packets, ATM uses simple fixed length packets. Since the packets are a fixed size, a router can start sending
the packet out before it has finished receiving it - reducing latency (delay) in the router.
- VPN - Virtual Private Network. If you do not have a need to run a number of dissimilar protocols
(old IBM 3270 terminals, RJE, Appletalk, etc..) but just need the ability for your branches to connect back to the home office,
a VPN may be all that you need. Traffic is routed over a normal Internet TCP/IP connection, and the VPN provides the security
and encryption necessary to protect your data on a public network
- MPLS - MultiProtocol Label Switching - MPLS is a different way of routing traffic through a
high speed network. It runs on top of ATM, SONET or Frame Relay (or a mix of the above) and simplifies overall network management
and provides the foundation for different levels of service for different types of traffic. VPNs are much simpler to implement
with MPLS. MPLS finds much of its use on extremely fast fiber optic circuits, or hybrid networks where voice traffic is commingled
with data traffic, and the voice traffic needs priority in order to keep a solid signal and not introduce latency in a
congested routing point.
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