Frame Relay Notes – LMI, Headers, and Encapsulation

Local Management Interface
  • Manages link between the router and frame relay switch
  • Routers send Status Enquiry to the switch
  • The switch responds with a Status message informing the router of the DLCIs available
  • Serves as a keepalive
  • Default keepalive is 10 seconds, 3 misses is failed
  • Three types
    • cisco <- default
    • ansi (Annex D)
    • q933a

Headers and Encapsulation
  • Link Access Procedure for Frame-mode Bearer Services (LAPF) is the first header
    • Includes DLCI, DE, FECN, BECN
    • To be read by the frame relay switch
  • Frame relay encapsulation header is next
    • To be read by the router on the other end of the VC
  • Two types
    • cisco : proprietary <- default
    • ietf : IETF RFC 2427

Aaron Conaway

I shake my head around sometimes and see what falls out. That's what lands on these pages.

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