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The PVC status information element contains the following information: the local
DLCI number for the particular PVC; the state of the PVC (active or inactive); and
whether the PVC is new or an existing PVC that management already knows about.
Note: The number of PVCs supplied at the FR interface is restricted by the
network frame size and the amount of individual PVC information elements
that can fit into a full status report. For example, 202 is the maximum
number of PVCs for a network with a 1K frame size.
Link Integrity Verification Report
The link integrity verification report, sometimes referred to as
heartbeat polling
,
contains the link integrity verification element. This element is where the exchange
of the send and receive sequence numbers takes place. By exchanging sequence
numbers, management and the end station can evaluate the integrity of the
synchronous link. The send sequence number is the current send sequence
number of the message originator. The receiver looks at this number and compares
it to the last send sequence number to verify that this number is incrementally
correct. The receive sequence number is the last send sequence number that the
originator sent out over the interface. It is the receiver’s responsibility to place a
copy of the send sequence number into the receive sequence number field. This
way the originator can ensure that the receiver receives and interprets the frames
correctly.
When an end-station fails to participate in this polling process, all remote
end-stations with logically attached PVCs are notified through management’s full
status report mechanism that the PVC is inactive.
Consolidated Link Layer Management (CLLM)
CLLM is an optional FR management function that is not widely supported by the
industry but it has been adopted by some Frame Relay switch manufacturers.
CLLM provides some of the same management information provided by LMI, in
particular, outage notification. CLLM’s main use is to provide asynchronous
congestion notification of PVCsto attaching devices. A single CLLM message may
indicate outage or congestion for multiple PVCs. The Frame Relay protocol
supports the following standards for CLLM: ANSI T1.618, ITU-T (CCITT) Q.922
Annex A, and ITU-T (CCITT) X.36 Annex C.
Frame Relay Data Rates
This section introduces data rates for Frame Relay permanent virtual circuits
(PVCs).
Committed Information Rate (CIR)
The CIR is the data rate that the network commits to support for the VC under
normal, uncongested conditions. Any VC that is configured or is learned is provided
a CIR (by the FR service provider). The CIR is a portion of the total bandwidth of
the physical link of either 0 or between 300 bps and 2 Mbps reserved for the VC.
64 Kbps or a single DS0 channel is most common.
You define the CIR with the add permanent-virtual-circuit, change
permanent-virtual-circuit, add switched-virtual-circuit,orchange
Using Frame Relay
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MRS V3.2 Software User’s Guide
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