3Com 3C780 User Guide - Page 95

The Link Error Monitor LEM examines the Link Error Rate LER per active

Get 3Com 3C780 - LinkBuilder FDDI Base Unit PDF manuals and user guides
UPC - 662705029917
View all 3Com 3C780 manuals
Add to My Manuals
Save this manual to your list of manuals

Page 95 highlights

4-8 Setting Up the Hub Target Token Rotation Time (T-Req) The FDDI ring is initialized every time a station joins or leaves the ring. During the initialization process, all stations on the ring agree on a "token rotation time." This is the maximum amount of time that any station has to wait for a token to arrive, and it establishes the minimum level of service on the ring. (Level of service relates to how often a station requires access to the token.) The Target Token Rotation Time (TTRT) is the service level required by an individual station. During the initialization process, each station makes a request for a level of service that is identical to its local TTRT. This service level request is called T-Req. T-Req is stored in nonvolatile RAM and can be set using the set treq command. The factory-set default is 165 milliseconds. Changes to T-Req take effect only when the system is reset. To display the current value of the Target Token Rotation Time parameter, enter the show treq command. This display appears: Current T-Req = 165000 microseconds Initialize T-Req as = 160000 microseconds Link Error Rate (LER) The Link Error Monitor (LEM) examines the Link Error Rate (LER) per active port as part of its responsibility for keeping link quality at an acceptable level. The LEM uses a threshold test to compare the current LER cutoff threshold to the LER alarm threshold. NOTE: You must always keep the LER_Alarm parameter larger than the value entered for the LER_Cutoff parameter. These two thresholds are explained below: LER_Alarm. This threshold is the LER at which a link connection exceeds the present threshold and will generate an alarm. The factory-set default is 10.E-08 (10-8). This error rate is equivalent to about one error per second.

  • 1
  • 2
  • 3
  • 4
  • 5
  • 6
  • 7
  • 8
  • 9
  • 10
  • 11
  • 12
  • 13
  • 14
  • 15
  • 16
  • 17
  • 18
  • 19
  • 20
  • 21
  • 22
  • 23
  • 24
  • 25
  • 26
  • 27
  • 28
  • 29
  • 30
  • 31
  • 32
  • 33
  • 34
  • 35
  • 36
  • 37
  • 38
  • 39
  • 40
  • 41
  • 42
  • 43
  • 44
  • 45
  • 46
  • 47
  • 48
  • 49
  • 50
  • 51
  • 52
  • 53
  • 54
  • 55
  • 56
  • 57
  • 58
  • 59
  • 60
  • 61
  • 62
  • 63
  • 64
  • 65
  • 66
  • 67
  • 68
  • 69
  • 70
  • 71
  • 72
  • 73
  • 74
  • 75
  • 76
  • 77
  • 78
  • 79
  • 80
  • 81
  • 82
  • 83
  • 84
  • 85
  • 86
  • 87
  • 88
  • 89
  • 90
  • 91
  • 92
  • 93
  • 94
  • 95
  • 96
  • 97
  • 98
  • 99
  • 100
  • 101
  • 102
  • 103
  • 104
  • 105
  • 106
  • 107
  • 108
  • 109
  • 110
  • 111
  • 112
  • 113
  • 114
  • 115
  • 116
  • 117
  • 118
  • 119
  • 120
  • 121
  • 122
  • 123
  • 124
  • 125
  • 126
  • 127
  • 128
  • 129
  • 130
  • 131
  • 132
  • 133
  • 134
  • 135
  • 136
  • 137
  • 138
  • 139
  • 140
  • 141
  • 142
  • 143
  • 144
  • 145
  • 146
  • 147
  • 148
  • 149
  • 150
  • 151
  • 152
  • 153
  • 154
  • 155
  • 156
  • 157
  • 158
  • 159
  • 160
  • 161
  • 162
  • 163
  • 164
  • 165
  • 166
  • 167
  • 168
  • 169
  • 170
  • 171
  • 172
  • 173
  • 174
  • 175
  • 176
4-8
Setting Up the Hub
Target Token Rotation Time (T-Req)
The FDDI ring is initialized every time a station joins or leaves the ring.
During
the initialization process, all stations on the ring agree on a “token rotation
time.”
This is the maximum amount of time that any station has to wait for a
token to arrive, and it establishes the minimum level of service on the ring.
(Level of service relates to how often a station requires access to the token.)
The Target Token Rotation Time (TTRT) is the service level required by an
individual station.
During the initialization process, each station makes a
request for a level of service that is identical to its local TTRT.
This service
level request is called T-Req.
T-Req is stored in nonvolatile RAM and can be set using the
set treq
command.
The factory-set default is 165 milliseconds.
Changes to T-Req take effect only
when the system is reset.
To display the current value of the Target Token Rotation Time parameter, enter
the
show treq
command.
This display appears:
Current T-Req = 165000 microseconds
Initialize T-Req as = 160000 microseconds
Link Error Rate (LER)
The Link Error Monitor (LEM) examines the Link Error Rate (LER) per active
port as part of its responsibility for keeping link quality at an acceptable level.
The LEM uses a threshold test to compare the current LER cutoff threshold to
the LER alarm threshold.
NOTE:
You must always keep the LER_Alarm parameter larger than the value
entered for the LER_Cutoff parameter.
These two thresholds are explained below:
LER_Alarm
.
This threshold is the LER at which a link connection exceeds the
present threshold and will generate an alarm.
The factory-set default is 10.E-08
(10
-8
).
This error rate
is equivalent to about one error per second.