Nortel Networks OPTera Metro 3500 - Manual (Page 97)

Operation, administration, and maintenance (OAM) features 2-59
Planning and Ordering Guide—Part 1 of 2 NTRN10AN Rel 12.1 Standard Iss 1 Apr 2004
Telemetry byte-oriented serial (TBOS)
The OPTera Metro 3500 network element is equipped with a telemetry
byte-oriented serial (TBOS) subsystem that facilitates display of alarms at
remote network elements. The TBOS subsystem determines the location of the
network element that triggered the alarm.
When a remote alarm is detected by the TBOS system, the remote LED
illuminates at the network element defined as the TBOS head-end.
When the network element that has raised the alarm is identified, you can log
in to that network element and identify the fault details.
The OPTera Metro 3500 network element supports TBOS monitoring through
a dedicated TBOS port and a subset of TBOS information through the Site
Manager. OPTera Metro 3500 supports TBOS through a four-wire, half
duplex, 2400 baud, RS-422 port on the Left OAM (LOAM). Remote telemetry
can be performed using the TBOS port and an E2A monitor. A TBOS status
matrix can also be displayed using the Site Manager interface.
TBOS data is transmitted using 8 bytes containing 4 bits of data each. These
32-bit displays represent alarm conditions on a network element.
The TBOS standard states the following:
• There must be 64 bits assigned to represent alarm conditions on a network
element.
• There must be a total of eight such displays.
Single-ended TBOS
The OPTera Metro 3500 allows a single TBOS link to monitor several
interconnected network elements such as those in a UPSR or in a linear system.
(A linear system has no limit on chain size. However, the head-end only
monitors 16 network elements from the head-end.) The monitored network
elements are in what is called a monitored span. Network elements in the
monitored span communicate their alarm status to each other. This
communication allows TBOS to obtain alarm information about all the other
network elements in the monitored span.
TBOS mapping assignments are set up at one network element in each
monitored span. This network element is called the TBOS head end. Any node
can be selected as the head-end network element.
Protocol problems occur if more than one network element is configured as a
TBOS head end. If a second head end is set up, the TBOS remote flag becomes
erroneous.