3Com CoreBuilder 7000, Operation Manual

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92 C
HAPTER
4: P
RIVATE
N
ETWORK
-
TO
-N
ETWORK
I
NTERFACE
(PNNI) V
ERSION
1.0
Figure 31 Signaling in a Hierarchical Network
There are many paths that the signal can take. Based on reachability, QoS
metrics and current information available about the links, the path from
A.1.1 to A.2.6 is chosen. A DTL is created as shown in Figure 31. Each
Line of the DTL represents a level in hierarchy. A pointer is also used with
the DTL to mark where in the address list the transmission is. A signal
with PVPC (Permanent Virtual Path Connection) and PVCC (Permanent
Virtual Channel Connection) is created and a set of DTLs are generated.
The connection is established and the data is sent. These connections are
permanent because they are established administratively, rather than on a
demand basis. If the signal is to be established by demand, it is known as
a soft PVC or soft PVCC.
C.1.1
C.1.2
A.3.2
A.3.1
A.1.3
A.1.1
A.1.2
A.2.2
A.2.1
A.2.3
B.1.1
B.1.3
B.1.4
B.1.2
B.2.2
B.2.1
B.2.3
Peer Group Leader
Source
Destination
Chosen Path to Take
Physical Link
DTL List for this Transmission:
DTL: [A.1.1, A.1.2, A.1.3]
DTL: [A.1, A.3, A.2]
DTL: [A, B, C]