3Com CoreBuilder 9000, User Manual

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Hierarchy in an E-IISP Network 335
Features of E-IISP E-IISP includes the following features:
Minimal manual configuration of the switch
Registers addresses of neighboring switches either automatically or
manually
Nodes learn addresses automatically in case of link or node failure
Hierarchic Routing protocol based on hop-by-hop routing, utilizing a
best match scheme
Works with hierarchic network topologies of any size
Prevents network loops
Finds a path to a node if one exists
Crankback mechanism when destination is not found
Allows redundancy and load sharing among nodes
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* that is, 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 11. The network core is
designated as the roots of the network and the other switches
subordinate to them are attached as branches. In Figure 11, 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.