Specifications

A.15 Token Ordering of Trees or Dual Rings
FDDI Configuration Capabilities A–35
A.15 Token Ordering of Trees or Dual Rings
The DEChub 900 backplane uses a defined token order algorithm for FDDI dual
rings or trees that are created in the hub. This section describes how the algorithm
controls the token flow in the DEChub 900 backplane.
A.15.1 Description
The token flow is defined as the order in which the token flows to the MAC
addressed slots in the DEChub 900 backplane. The token flow is from slot 1 towards
slot 8, whether the backplane network is a dual ring or a tree. If there are multiple
FDDI networks, each of the networks independently orders the token flow, from the
lowest slot to highest slot, as closely as is allowed by the FDDI rules.
The token flow algorithm ensures that repaired modules return to the same token
order that had been assigned prior to the occurrence of a module fault.
NOTE
The token flow algorithm also matches the power shedding algorithm
(which sheds modules from slot 1 towards slot 8).
The following examples illustrate the concept of the token flow algorithm:
A.15.2 Example 1 — Token Flow Through Dual Ring Network Modules
Figure A–29 shows a hub that is configured as a dual ring with FDDI network mod-
ules in slots 1, 2, 3, 4, 6, and slot 8.