Figure 53. Three Steps For Scheduling - Alcatel 1850 TSS-320 Technical Handbook

The exchange of information for scheduling management can be divided into three precise steps: request,
credit and transmission phases.
During the "Request "phase the status of all the input queues is sent to the egress boards. In Figure 53.
on page 98 represented with red arrows.
In a second phase, the egress board determines how many cells will be sent by each of the ingress boards,
and sends information (the so called "credits") to the ingress boards. During this phase, the central
scheduler collects the credits from the egress boards in order to coordinate the requests towards the input
boards, thus avoiding collisions. In Figure 53. on page 98 represented with green arrows.
As a final step, each ingress board sends to the matrix the amount of traffic that has been granted in the
previous phase. In Figure 53. on page 98 represented with yellow arrows.
PIM
Input scheduler
PKT
PIM processor
manager
DATA BOARD
PIM
Input scheduler
PKT
PIM
processor
manager
DATA BOARD
Request phase
Credit phase
Transmission phase
Alcatel 1850 TSS-320 Rel. 1.1
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Traffic
UNIVERSAL
MATRIX
Traffic
CENTRAL
SCHEDULER
MATRIX
BOARD

Figure 53. Three steps for scheduling

Output scheduler
PKT
processor
Traffic
manager
DATA BOARD
Output scheduler
PKT
processor
Traffic
manager
DATA BOARD
Technical Handbook Common
PIM
PIM
Functional Description