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result is enhanced signal integrity and extended maximum lobe cable
distances. For length specifications for UTP and STP lobe cables, see
Section 2.2.2, UTP Cable Lengths to Stations and Section 2.3.2, STP Cable
Lengths to Stations.
Ring Speed Fault Protection
TDRMIMs provide Ring Speed Fault Protection on each lobe port to
protect against beaconing conditions caused by stations inserting at the
wrong ring speed. If there is a mismatch between the ring speeds of the
incoming signal and the destination ring, the TDRMIM keeps the lobe port
looped back on itself to keep the misconfigured station from disrupting
the ring. When the mismatch condition is eliminated, the port comes out
of loopback mode.
1.2.3
Cluster Switching
The ports of the TDRMIM are permanently grouped into two Clusters:
Cluster 1 comprises lobe ports 1-6 and Ring Ports 1, Cluster 2 comprises
lobe ports 7-12 and Ring Ports 2 (see Figure 1-3). These Clusters switch as
collective units; rather than taking port assignments on a port-by-port
basis, TDRMIMs take assignments on a per-Cluster basis and switch their
corresponding ports collectively. The TDRMIM is therefore called a
cluster-switching MIM.
Cluster 1
Cluster 2
2
3
4
5
6
1
X
2
X
3
X
4
X
5
X
6
X
7
X
8
X
9
X
1 0
X
1 1
X
1 2
X
Figure 1-3. Port Clusters of the TDRMIM
8
9
1 0
1 1
1 2
L N K
P E N
TX
Lobe Ports 1-6
R I
RX
Ring Ports 1
L N K
P E N
L N K
P E N
Lobe Ports 7-12
Ring Ports 2
L N K
P E N
About the TDRMIM
and
and
Page 1-5
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