3Com CoreBuilder 7000, Operation Manual, Page: 77 / 264

PNNI Routing 77
Information
Exchange in PNNI
Each node exchanges hello packets with its immediate neighbors and
uses this information to determine its local state information.
Hello Messages
In Figure 17 there are 3 peer groups. A, B and C. Each group has different
switches and workstations connected to it. Each group has a unique
address that identifies itself in the group and the peer group to which it
belongs. The individual switches broadcast a
hello protocol which
identifies itself. They send this message only to the nodes to which they
are directly connected. They receive hello messages from their neighbors
and begin to build a list of local state information. This information
includes the identity and peer group membership of each node’s
immediate neighbors, and the status of the links to its neighbors. This
hello protocol runs as long as the RCC is operational. The hello protocol
can therefore act as a link detector when other mechanisms fail.
Figure 19 shows the hello packet transmission between node A.1.2 and
its neighbors.
Figure 19
Hello Packet Transmission
"HELLO"
"HELLO"
"HELLO"
A.3.2
A.3.1
A.1.3
A.1.1
A.1.2
A.2.2
A.2.1
A.2.3
Peer Group A.2
Peer Group A.3
Peer Group A.1
Peer Group Leader