3Com CoreBuilder 7000, Operation Manual, Page: 55 / 264

Hierarchy in an E-IISP Network 55
Hierarchy in an
E-IISP Network
E-IISP also introduced the concept of hierarchy in a network design.
Using E-IISP, most 3Com ATM networks are based in the ATM address of
47.0.0.0.0.0.3c.0.0.a* i.e., utilizing the last four bytes of the switch
portion of the ATM address. In the ATM address space, hierarchy
translates into a tree structure as shown in Figure 10. The network core is
designated as the roots of the network and the other switches
subordinate to them are attached as branches. In Figure 10, A, B and C
are the switches that comprise the network core. Each subordinate
switch can also have switches attached to it. As you progress down the
hierarchy, the node name (or ID) is lengthened to include the parent
node. Finally, all of the roots (A, B, and C) are connected together to
ensure that every node can reach every other node.
Figure 10 Connecting Switches in a Hierarchical Topology
This type of topology is well-suited for installation in a group of buildings.
Each of the trees A, B, C would be installed in a separate building where
the root node would be located in the basement and the branches
distributed throughout the floors.
Hierarchical ATM
Addressing
Figure 11 shows the components of the ATM address of a switch.
A12 A15
A1
A2
B8 B7
B71
B
B84
C9 C4
C
A
Network Core (Root of Hierarchy)
Edge Devices
(Branches)