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APPENDIX A: BASIC FDDI NETWORKS
Page A-8 BRIM-F6 User’s Guide
Connection Management (CMT) controls physical layer insertion and
removal of stations. CMT has three main components:
• Entity Coordination Management (ECM) controls bypass
switches and coordinates trace (recovery) functions.
• Configuration Management (CFM) controls PHY and MAC entity
configuration within a node. Attaching or removing a station from
the ring changes the logical structure of the ring.
• Physical Connection Management (PCM) controls the physical
connection between adjacent PHYs. It tests the quality of the link
and enforces connection rules, screens marginal connections, and
supports maintenance activities.
A.5 FDDI Connection Rules
One of the primary functions of SMT Connection Management is to
control physical connections among A, B, M, and S type ports. The
following table summarizes the FDDI connection rules.
V - valid connection
X - illegal connection
U - undesirable connection
P - valid, but when both A and B connect to M ports, only the B
connection is active. Connecting A and B to M ports creates a dual
homing configuration. Dual homing provides a redundant
topology for concentrators. Figure A-6 illustrates how to configure
three concentrators into dual homing configuration.
A B S M
A V,U V V,U V,P
B V V,U V,U V,P
S V,U V,U V V
M V V V X
BRIM-F Book Page 8 Monday, January 29, 1996 9:26 AM