Related Documentation
Scheduling and Shaping on SONET/SDH OC48/STM16 IQE PICs
The SONET/SDH OC48/STM16 IQE PIC supports the following scheduling and the shaping behavior:
- Per unit scheduling via data-link connection identifier
(DLCI) at egress, where each DLCI gets a dedicated set of queues and
a scheduler.
Note: Because the SONET/SDH OC48/STM16 IQE PIC is not an oversubscribed PIC, there is no ingress queuing. therefore, the ingress scheduling or shaping is not supported in SONET/SDH OC48/STM16 IQE PIC.
- When a per unit scheduling is configured , the shaping can be configured at the logical and the physical interface levels.
- In both guaranteed and excess regions, the traffic on queues at the same priority is scheduled in weighted-round-robin (WRR) discipline and there is no shaping at queue-level.
On SONET/SDH OC48/STM16 IQE interfaces, you can configure a CIR (guaranteed rate) and a PIR (shaping rate) per data-link connection identifier (DLCI). The configured rates are gathered into a traffic control profile. If you configure a traffic control profile with a CIR (guaranteed rate) only, the PIR (shaping rate) is set to the physical interface (port) rate.
The computation of CIR and PIR on logical interfaces is shown in Table 1. X and Y are values configured from the command-line interface.
Table 1: Computation of CIR and PIR on the Logical Interfaces
Port Mode | JUNOS OS CLI Configuration | SONET/SDH OC48/STM16 IQE PIC | ||
|---|---|---|---|---|
Configured CIR | Configured PIR | Computed CIR | Computed PIR | |
Default (no CIR or PIR configured on logical interface) | Not configured | Not configured | Port speed | Port speed |
Both CIR and PIR are configured on logical interface | X | Y | X | Y |
CIR Mode (CIR is configured on at least one logical interface) | X | Not configured | X | Port speed |
Not configured | Y | 50 Kbps | Y | |
Not configured | Not configured | 50 Kbps | Port speed | |
PIR Mode (PIR is configured on at least one logical interface) | Not configured | Y | Y | Y |
Not configured | Not configured | Remaining (port speed minus sum of PIRs of other logical interfaces) bandwidth is equally divided. | Port speed | |
The SONET/SDH OC48/STM16 IQE PIC supports rate limit on all queues. The computation of rate limit is shown in Table 2.
Table 2: Computation of Rate for the Rate Limit Configured on the Queue with Transmit Rate Percentage
Scenario | Configured CIR Value for the Logical Interface or DLCI | Configured PIR Value for the Logical Interface or DLCI | SONET/SDH OC48/STM16 IQE PIC |
|---|---|---|---|
1 | No | No | Port value |
2 | Yes | No | CIR value |
3 | No | Yes | PIR value |
4 | Yes | Yes | CIR value |
| Note: When the queue transmission rates are oversubscribed, the rate-limit option configured on any of the queues uses the configured rate limit values, although the transmission rates are oversubscribed. |
Transmit Rate Adding Up to More than 100 Percent
The SONET/SDH OC48/STM16 IQE PIC supports the maximum bandwidth optimization by overconfiguring the bandwidth up to 300 percent.
When the sum of transmission rates for all queues exceeds 100 percent, the interface is in an oversubscribed state. At the time of oversubscription, the queues are split into three priority groups. :
- Strict-High
- High, Medium-High, and Medium-Low
- Low
This computation is done after the internal mapping of the excess priority or the excess rate.
The sum of transmission rates for all queues in each of the priority groups is less than or equal to 100 percent, thereby allowing the SONET/SDH OC48/STM16 IQE PICs to support the maximum bandwidth optimization by overconfiguring the available bandwidth up to 300 percent.
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