OECG – Chapter 18

444 Words. Plan about 1 minute(s) to read this.

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.

Ethan Banks writes & podcasts about IT, new media, and personal tech.
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