HP 600 Series, Services And Applications

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Table 7. DLCI Status bits returned in “Status” message
Bit Value Description
New 0 PVC is already present
New 1 PVC is new
Active 0 PVC is inactive (PVC is deleted)
Acitve 1 PVC is active
Figure 5 shows four routers attached to a Frame Relay network. Each router
has a PVC to each of the other routers on the network. Assume that R1 is the
first to initialize (power on) and become active on the network. The first
message that R1 sends to the Frame Relay network is a full status poll. This
indicates to the network that the router and the link to the router are now
functioning. The network returns a full status reply. This status reply,
however, contains an empty list of DLCIs (no DLCIs and accompanying
status information). This is because none of the other routers are yet active.
Figure 5. PVCs Connecting Routers
Now, let’s suppose that R2 powers on, and its Frame Relay interface is
initialized and enabled. Like R1, the first message it sends to the network is a
full status poll. As before, the network responds with a full status reply. This
time, however, the list of DLCIs is not empty. The full status reply contains
DLCI 133 and indicates that it is both new and active (see table 7). This
indicates to R2 that it may now communicate using DLCI 133 (to R1). At this
instant, however, R1 still has no active DLCIs and is not able to communi-
cate with R2. This situation is resolved after R1 sends its next full status poll
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Linking Up with Frame Relay
Local Management Interface
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