Frame relay was long the most popular WAN technology, and is still widely installed in many enterprise WANs. This chapter explains the details of how frame relay delivers data to multiple WAN-connected sites. Frame relay most closely compares to the OSI data link layer (Layer 2). If you remember that the word "frame" describes the data link layer protocol data unit (PDU), it will be easy to remember that frame relay relates to OSI Layer 2. Like other data-link protocols, frame relay can be used to deliver packets (Layer 3 PDUs) between routers.
Frame relay protocol headers and trailers are simply used to let a packet traverse the frame relay network, just like Ethernet headers and trailers are used to help a packet traverse an Ethernet segment. This chapter describes the frame relay protocol details, along with the associated configuration. It includes details on:
- The difference between frame relay protocols and standards
- Virtual circuits
- LMI and encapsulation types
- DLCI addressing details
- How network layer and addressing works with frame relay
- Frame relay service interworking
- Configuration examples and diagrams
- A pre-test and post-test
Excerpted from CCNA ICND Exam Certification Guide by Wendell Odom (ISBN: 158720083X). Copyright 2004, Cisco Systems, Inc. Reproduced by permission of Pearson Education, Inc., 800 East 96th Street, Indianapolis, IN 46240. Written permission from Pearson Education, Inc. is required for all other uses.
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