Ethan Banks Not writing about IT.

OECG – Chapter 18


access link – the link between the router and the frame-relay switch

access rate – the actual clock rate of the line

BECN – backward explicit congestion notification – when this bit it set, it tells the router that there’s congestion upstream from the router

DCE – data communications equipment – not the router. A CSU/DSU or frame-relay switch. Opposite end is the DTE.

DE – discard eligible bit – when this bit is set, this frame is to be discarded before others without the DE bit set.

DLCI – data link connection identifier – in frame relay, this identifies the virtual circuit. Of local significance only.

DTE – data terminal equipment – usually the router. DCE is on the other end of the link.

Dual FIFO – used by router to implement interleaving in fragmented frame-relay networks. High priority packets end up in one FIFO queue, and regular packets in the other.

FECN – forward explicit congestion notification – when this bit is set, implies that the frame has experienced congestion.

FRF – frame relay forum – a group of vendors that worked on standardizing frame-relay implementations.

FRF.5 – a FRASI standard where the DTEs both use frame-relay, but ATM is in the middle.

FRF.8 – a FRASI standard where one DTE uses frame-relay, and the other ATM.

FRF.9 – a standard for payload compression on frame networks

FRF.11-c – a standard for LFI for VoFR, where voice frames are interleaved in front of data frames’ fragments
FRF.12 – a standard for LFI for data virtual circuits

LAPF – link access procedure for frame-mode bearer services – a standard for the frame-relay header, which includes DLCI, DE, FECN and BECN bits, plus a frame check in the LAPF trailer.

LMI – local management interface – used between a frame-relay DTE and DCE to manage the connection; messages for SVCs, PVC status and keepalive.

LZS – Lempel Ziv STAC compression algorithm. Uses a dictionary to map binary strings to shorts strings that will be sent across the wire.

NLPID – network layer protocol ID defined in RFC 2427. Tells the type of L3 packet in a frame-relay frame.

PVC – permanent virtual circuit – sort of like a leased line, in concept.

service internetworking – combining ATM and frame-relay in a single PVC
SVC – switched virtual circuit – a VC set up dynamically, sort of like a demand dial circuit.

VC – virtual circuit – the logical path traveled between 2 DTE endpoints of a link.

VoFR – voice over frame relay – defined in FRF.11. Uses a different header than FRF.3 data frames, allowing for voice payloads directly inside the LAPF header.

By Ethan Banks
Ethan Banks Not writing about IT.

You probably know Ethan Banks because he writes & podcasts about IT. This site is his, but covers other stuff.

Get the details on his about page.