Chapter 6 Configuring Frame Relay; Dlci Sharing; Frame Relay Backup - Cabletron Systems SmartSwitch 6000 User Manual

DLCI Sharing

Frame Relay Backup

Frame relay ports in the Netlink FRX4000, FRX6000, and Frame Relay Module are
used to carry frame relay traffic, as well as other protocols encapsulated in frame relay
(per RFC 1490, via logical X.25 ports over frame relay). A frame relay port can act as
physical DCE, connecting to end-user devices, or DTE, connecting to a network or
frame relay PVC.
A frame relay port can contain multiple logical ports: up to 56 in an FRX4000 or FRM
and up to 56 per RLP in an FRX6000. In either case, all 56 logical ports can reside on
one physical port, or be spread over several physical ports.
Each logical connection on a physical frame relay port is assigned a Data Link Con-
nection Identifier (DLCI), which identifies a point-to-point connection, as shown in
the following example. (The numbers represent DLCIs.)
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Multiple protocols can be passed over a single physical frame relay port by sharing a
DLCI. Each node supports up to 976 user-configurable DLCIs. (Several more are sup-
ported, but are reserved for internal use.)
Frame relay virtual-circuit backup in the FRX/FRM provides frame relay DLCIs with
automatic backup protection in the event of LMI loss or port failure. (A DLCI is con-
sidered down/inactive if level 1 is down. If LMI is used, the DLCI is also considered
inactive if not reported as active in a Full Status Message from the DCE.)
A physical frame relay port can be dedicated to providing backup DLCIs, or backups
can co-exist with "regular" DLCIs on a port.
In a backup configuration, one end is considered the "initiating" node and the other the
"remote" node. The initiating end is the one that will establish the backup link if it dis-
covers that the primary link is down. (A node can be the initiating node for some
backup configurations and the remote node for others.)
Configuring Frame Relay
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Chapter 6
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