Cisco GSR12/60 - 12012 Router -AnyLAN, SONET/SDH Installation And Configuration Manual page 55

Each clock and scheduler card or switch fabric card provides OC-12/STM-4 (622 Mbps)
switching bandwidth for the system. By adding three more cards in the lower card cage, the
bandwidth is increased to OC-48/STM-16 (2.4 Gbps). Table 1-5 lists the switch fabric
bandwidth and the card configurations needed to support the bandwidth.
Table 1-5 Switch Fabric Configurations
Switch Fabric Bandwidth
OC-12/STM-4
OC-12/STM-4 redundant
OC-48/STM-16
OC-48/STM-16 redundant
1. One clock and scheduler card must be installed in a system.
A minimally configured system has one clock and scheduler card installed. This
configuration provides an OC-12/STM-4 bandwidth, but no switch fabric, clock, or
scheduler redundancy. Adding a second clock and scheduler card provides fabric, clock,
and scheduler redundancy, but no increase in bandwidth. Adding three switch fabric cards
to a system with a single clock and scheduler card increases the system bandwidth to
OC-48/STM-16, but no clock or scheduler redundancy. Adding a second clock and
scheduler card to the system gives you OC-48/STM-16 bandwidth plus fabric, clock, and
scheduler redundancy.
The clock and scheduler card contains the following functionality:
•
System clock—Sent to all line cards, RP, and switch fabric cards. The system clock
synchronizes data transfers between line cards or line cards and the RP through the
switch fabric. In systems with redundant clock and scheduler cards, the two system
clocks are synchronized so that if one system clock fails, the other clock takes over.
•
Scheduler—Handles requests from the line cards for access to the switch fabric. When
the scheduler receives a request from a line card for switch fabric access, the scheduler
determines when to allow the line card access to the switch fabric.
Physical and Functional Overviews
Clock and
Scheduler Switch Fabric
Card Card
1
1 0
2 0
1 3
2 3
Product Overview 1-27