Cisco Systems 8600 Series manual Traffic and Congestion Management, FairShare

Traffic and Congestion Management

Traffic and Congestion Management

The BPX switch provides ATM standard traffic and congestion management per ATM Forum TM 4.0 using BXM cards.

The Traffic Control functions include:

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Usage Parameter Control (UPC)

Traffic Shaping

Connection Management Control:

Selective Cell Discarding

Explicit Forward Congestion Indication (EFCI)

In addition to these standard functions, the BPX switch provides advanced traffic and congestion management features including:

•Support for the full range of ATM service types per ATM Forum TM 4.0 by the BXM-T3/E3, BXM-155, and BXM-622 cards on the BPX Service Node.

•FairShare, dedicated queue, and rate controlled servers for each VPC/VCC at the network ingress.

•OptiClass, guarantees QoS for individual connections by providing up to 16 queues with independent service algorithms for each trunk in the network.

•AutoRoute, end-to-end connection management that automatically selects the optimum connection path based upon the state of the network and assures fast automatic alternate routing in the event of intermediate trunk or node failures.

•PNNI, a standards based routing protocol for ATM and Frame Relay SVCs.

•Frame Based Traffic Control (FBTC) for AAL5 connections, including early and partial frame discard.

•ForeSight, an end-to-end closed loop rate based congestion control algorithm that dynamically adjusts the service rate of VC queues based on network congestion feedback.

•ABR Standard with VSVD congestion control using RM cells and supported by BXM cards on the BPX Switch.

FairShare

Fairshare provides per-VC queueing and per-VC scheduling. Fairshare provides fairness between connections and firewalls between connections. Firewalls prevent a single non-compliant connection from affecting the QoS of compliant connections. The non-compliant connection simply overflows its own buffer.

The cells received by a port are not automatically transmitted by that port out to the network trunks at the port access rate. Each VC is assigned its own ingress queue that buffers the connection at the entry to the network. With ABR with VSVD or with ForeSight, the service rate can be adjusted up and down depending on network congestion.

Network queues buffer the data at the trunk interfaces throughout the network according to the connections class of service. Service classes are defined by standards-based QoS. Classes can consist of the four broad service classes defined in the ATM standards as well as multiple sub-classes to each of the four general classes. Classes can range from constant bit rate services with minimal cell delay variation to variable bit rates with less stringent cell delay.

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