Avaya Configuring Frame Relay Services Bedienungsanleitung PDF herunterladen (Seite 31)

Frame Relay Overview

308624-14.10 Rev 01

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LAPF defines the following categories of management frames to support reliable

transfer of multiple numbered frames over SVCs:

• Unnumbered control -- Provides connection and disconnection services and

includes set asynchronous balanced mode extended (SABME), disconnect

(DISC), frame reject (FRMR), disconnected mode (DM), and unnumbered

acknowledgment (UA) frames.

• Numbered supervisory -- Provides flow control and retransmission

information and includes receiver not ready (RNR), receiver reader (RR), and

reject (REJ) frames.

• Numbered information (I) -- A numbered command/response that passes data

across the link using a sliding window protocol. The frames are numbered

sequentially and carry an acknowledgment of the highest numbered frame

received by the sending peer. The maximum number of frames outstanding is

configurable. These frames can only be sent after setup of multiple frame

communications on the link. A flag within the frame differentiates a

command from its response.

• Exchange identification (XID) -- An unnumbered command/response used to

allow peers to exchange identification information.

LAPF Operational States

LAPF has three main operational states:

• TEI-assigned -- The terminal endpoint identifier (TEI)-assigned state is the

base interface state. When the LAPF circuit is first established, this is its state.

No timers are running and only unnumbered frames are supported across the

link.

• Active -- This state indicates that multiple frame support is up and running on

the interface. Numbered information frames can travel across the link.

• Timer recovery -- This state indicates that a timer has expired and the peer is

attempting to recover either through retransmission (T200 timeout) or by

initiating an idle time handshake (T203 timeout).

Once multiple frame support is operating on the channel, numbered information

frames are exchanged to transfer data and acknowledge earlier transfers.

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Avaya Configuring Frame Relay Services Bedienungsanleitung Seite 31