Frame Relay Applications: TCP/IP Suite

Traditionally, four networking suites are deployed using Frame Relay as the Layer 2 transport mechanism. We will cover them all in-depth, starting with the TCP/IP suite.

By Cisco Press | Posted Jan 30, 2002
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Network Consultants Handbook - Frame Relay
by Matthew Castelli

Network Consultants Handbook -- Click here to go to publisher's site

Traditionally, four networking suites are deployed using Frame Relay as the Layer 2 transport mechanism:

  • TCP/IP Suite
  • Novell IPX Suite
  • IBM Systems Network Architecture (SNA) Suite
  • VoFr
The following sections will discuss the application of these protocol suites across Frame Relay WANs and some of the special issues, challenges, and solutions that have been developed.

Frame Relay and the TCP/IP Suite
The TCP/IP Suite comprises two components: the IP operating at Layer 3 (Network) and the Transmission Control Protocol (TCP) operating at Layer 4. IP is a best-effort delivery protocol, relying on the transmission control mechanisms (that is, packet acknowledgement, sequencing) supported by TCP. IP datagrams, or packets, are routed from source to destination based on the address information found in the packet header. IP traffic is typically bursty in nature, making it an ideal network-layer protocol for Frame Relay WANs.

Figure 15-16 illustrates the correlation between the OSI model and an IP-over-Frame Relay implementation.

Figure 15-16: OSI Reference Model with IP/Frame Relay
Click image for larger view in a new window
(Click image for larger view in a new window)

Virtual LANs (VLANs) and IP Subnets
Multiple IP FRADs or routers can be interconnected via a Frame Relay WAN in a configuration behaving like a Virtual LAN (VLAN), or an IP subnet.


NOTE:   An IP subnet is a set of systems, or nodes/hosts, that share certain characteristics, such as the following:
  • Their IP addressing starts with the same network and subnet numbers.
  • Any system, or node/host, can communicate directly with any other system in the subnet. Data traffic in the same subnet will not flow through an intermediate router.

Figure 15-17 illustrates three routers that are interconnected by Frame Relay PVCs in a fully meshed configuration.

Figure 15-17: Frame Relay with IP Subnet
Click image for larger view in a new window
(Click image for larger view in a new window)


NOTE:   Fully meshed configurations enable every device in the system to directly communicate with every other device in the same system. Partially meshed configurations, generally known as hub-and-spoke, enable communication between devices with a central hub point providing the interconnection between end nodes.

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