Frame Relay Concepts
Frame Relay remains the most commonly deployed WAN technology used by routers. A slow
migration away from Frame Relay has already begun with the advent and rapid growth of IP-based
VPNs and MPLS. However, Frame Relay will likely be a mainstay of enterprise networks for the
fore-seeable future.
Frame Relay standards have been developed by many groups. Early on, Cisco and some other
companies (called the gang of four) developed vendor standards to aid Frame Relay adoption and
product development. Later, a vendor consortium called the Frame Relay Forum (FRF) formed for
the purpose of furthering Frame Relay standards; the IETF concurrently defined several RFCs
related to using Frame Relay as a Layer 2 protocol in IP networks. (Cisco IOS documentation
frequently refers to FR standards via FRF Implementation Agreements [IAs]—for instance, the
FRF.12 fragmentation specification.) Finally, ANSI and ITU built on those standards to finalize
U.S. national and international standards for Frame Relay.
This section briefly covers some of the more commonly known features of Frame Relay, as well
as specific examples of some of the less commonly known features. This section does not attempt
to cover all of Frame Relay’s core concepts or terms, mainly because most engineers already
understand Frame Relay well. So, make sure to review the definitions listed at the end of this
chapter to fill in any gaps in your Frame Relay knowledge.