Ethernet rate control services

Overview

Rate-controlled services offer a statistical multiplexing model that makes efficient use of shared bandwidth. Alcatel-Lucent 1665 DMX currently supports two of the primary forms of rate control. The two primary forms of rate control are rate limiting and guaranteed rate services (plus various combinations of both).

Rate limiting is achieved using Peak Information Rate (PIR) provisioning. Guaranteed rate service is achieved using Committed Information Rate (CIR) provisioning. PIR institutes a limit, or "ceiling", of maximum bandwidth to be allocated to a particular customer at any time. CIR, on the other hand, provides a guaranteed minimum, or "floor" throughput even during periods of high congestion. Alcatel-Lucent 1665 DMX provides support of CIR.

Description

The figure above demonstrates the relationship between CIR and PIR services for a single customer's “bursty” data stream. Again, PIR represents the maximum bandwidth a particular customer will be allocated at any time, while CIR is guaranteed minimum bandwidth that insures a constant level of service even during periods of high congestion.

As the figure above suggests, if the maximum bandwidth for a customer (PIR) is exceeded, surplus packets may be dropped. Rate guarantees can be changed in-service and are provisionable at sub-rate levels (1 Mbps).

Policing takes place first in order to ensure that a customer meets the CIR/PIR stipulations of their contract. The priority queuing relative to other customer's traffic then occurs providing another QoS capability.

Figure 3-8: Bandwidth allocation within Ethernet circuit packs

Application advantage

Rate control provides the capability to offer a maximum "ceiling" throughput at all times (PIR). It also supports commitments to minimum bandwidth availability (CIR). This combination of CIR and PIR rate control enables Alcatel-Lucent 1665 DMX to both help service providers meet detailed service level agreements (SLAs) and to ensure adequate capacity for end-users at all times. SLAs also can be offered with sub-rate guarantees. Rate control can enable oversubscription with increased revenue potential. Finally, all Private Line traffic is protected by time-tested SONET layer protection (1+1, UPSR, and BLSR).