2-20
Cisco MGX 8230 Edge Concentrator Installation and Configuration
Release 1.1.31, Part Number 78-11215-03 Rev. B0, May 2001
Chapter2 Module and Service Descriptions
Frame Relay Service Modules
Frame Relay Service Modules
The primary function of the Frame Relay Service Modules (FRSM) is to convert between the Frame
Relay formatted data and ATM/AAL5 cell-formatted data. For an individual connection, you can
configure network interworking (NI W), servic e interw orking (SIW), ATM-to-Frame Relay UNI (FUNI),
or frame forwarding. An FRSM co nverts th e h ead er f o rm at an d tr an s lates t he ad d re ss f or:
•Frame Relay port number and DLCI
•ATM-Frame UNI (FUNI) port number and frame ad d re ss o r fram e forwarding port
•ATM virtual connection identifier (V P I/ V CI )
See Configuring Frame Relay Service, page 6-27 for instructions to configure the FRSMs.
This section contains the following information:
•Features Common to Al l FRSMs, page 2-20.
•Redundancy for Frame Service Modules, page 2-22.
•Connection Types on the FRSM, page 2-22.
•Types of Frame Service Modules, page 2-27.
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FRSMs for T1 and E1 Lines, page 2-27.
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FRSMs for T3 and E3 lines, page 2-32.
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FRSMs for Serial Connections, page 2-38.

Features Common to All FRSMs

This section describes features common to all FRSMs. For features specific to the individual module
types, see Types of Frame Service Modules, page 2-27. For information to configure the FRSMs, see
Configuring Frame Relay Service, page 6-27.

Data-Link Layer features

•Each logical port on an FRSM independently configurable to run Frame Relay UNI, Frame Relay
NNI, ATM FUNI, or frame forwarding.
•7E flags used to delineate fram es (with bit stuffing to prevent false flag s) an d f or i nterframe gaps.
•One flag between frames is cons id er ed valid u po n r ecei p t.
•Supports configuration of one- or two-flag minimum interframe gap for transmission.
•Valid frame sizes from 5 up to 4510 octets.

Frame Relay features

•Each logical port independentl y co nfigu r ab le as Fr am e R ela y UNI or Frame Relay NNI.
•Meets ANSI T1.618, using two-octet headers.
•Interpreted CCITT-16 CRC at end of the frame (frame discard if in error).
•Supports ITU-T Q.933 Annex A, ANSI T1.617 Annex D, and LMI local management for
semipermanent virtual circuits (both UNI and NNI portions); enhanced LMI provides
autoconfiguration of traffic management parameters for attached Cisco routers.