Hierarchical CoS Shaping-Rate Adjustments Overview
This overview describes how MX Series 5G Universal Routing Platforms installed in a subscriber access network can adjust hierarchical class-of-service (CoS) parameters to prevent bandwidth contention at subscriber interfaces.
Hierarchical CoS is supported only for subscriber interfaces on Enhanced Queueing (EQ) DPCs or MPC interfaces operating in hierarchical scheduler mode.
The characteristics of voice, data, and video applications vary widely in their requirements for traffic throughput, bandwidth management, delay and jitter tolerance, and buffer depth. To prevent bandwidth contention at subscriber interfaces, you can configure applications such as ANCP and Multicast to perform real-time adjustments to the shaping rate configured for subscriber interfaces for residential gateways. Enabling shaping-rate adjustments on the router can prevent bandwidth contention at the interface from causing degradation of the subscriber’s voice, data, or video services.
Types of Shaping-Rate Adjustments
The ANCP application supports absolute adjustments to a specific shaping-rate value. You can configure ANCP to communicate the subscriber local loop speed to the MX Series router, which in turn throttles traffic destined to the associated subscriber interface so that it matches the subscriber local loop speed. ANCP acquires subscriber line rate information from DSLAMs and then communicates this data transmission rate for use with CoS.
The OIF mapping and reverse OIF mapping multicast applications support delta adjustments that increase or decrease the current shaping rate by a certain value. The system adjusts traffic destined to the subscriber using reverse OIF mapping enabled on a specified multicast interface. Reverse OIF mapping is used to determine the subscriber VLAN interface and the multicast traffic bandwidth on the interface.
Levels of Shaping-Rate Adjustments
Both absolute and delta adjustments are made to a subscriber’s aggregate shaping rate on a level 3 scheduler node.
Adjustments that occur on the scheduler node can also impact the shaping rates for all queues. This adjustment can be undesirable for service providers who want to provide a premium level of service on specific queues.
For delta-based adjustments by multicast applications, you can control the distribution of shaping rates among queues by assigning the percentage of adjustment allowed for each queue. In addition, you can set a minimum adjusted shaping rate for each queue.
Figure 1 shows a sample multicast network with shaping rates adjusted at the scheduler node level. The shaping rate is reduced by 4 Mbps (from 41 Mbps to 37 Mbps) at the scheduler node for subscriber interface 1, which reduces the rates of both the best effort and video on demand (VoD) service queues.
Figure 2 shows the same network with queue-based adjustments enabled for the best-effort queue on subscriber 1. The shaping rate of the best-effort queue is reduced by 4 Mbps (from 5 Mbps to 1 Mbps). The VoD service queue is not affected.
