Classification and mapping

Service classes define a standard architecture to provide end-to-end QoS on a broad range of Ethernet switching and voice products. They function as default QoS policies built into the product. They incorporate the various QoS technologies to provide a complete end-to-end QoS behavioral treatment. The switch includes a built-in QoS implementation for service classes.

The switch includes eight preconfigured queues (corresponding to the eight service classes) on each port of an interface module.

A service class domain classifies traffic as one of the following:

• Network control traffic (Critical/Network)

• Subscriber traffic (Premium, Metal, or Standard)

Queue 7 — Critical/Network Service Class (PHB of CS6/CS7)

The switch uses the Critical/Network Service Class for traffic within a single administrative network domain. If such traffic does not get through, the network cannot function.

Queue 6 — Premium Service Class (PHB of CS5/EF)

The switch uses the Premium Service Class for IP telephony services, and provides the low latency and low jitter required to support such services. IP telephony services include Voice over IP (VoIP), voice signaling, Fax over IP (FoIP), and voice-band data services over IP (for example, analog modem). The switch can also use the Premium Service Class for Circuit Emulation Services over IP (CESoIP).

Metal Service Classes

The Platinum, Gold, Silver, and Bronze Service Classes are collectively referred to as the metal classes. The metal Service Classes provide a minimum bandwidth guarantee and are for variable bit rate or bursty types of traffic. Applications that use the metal Service Class support mechanisms that dynamically adjust their transmit rate and burst size based on congestion (packet loss) detected in the network. The following list describes the individual metal classes:

• Queue 5 — Platinum Service Class (PHB of CS4/AF41)

  The switch uses the Platinum Service Class for applications that require low latency, for example, real-time services such as video conferencing and interactive gaming. Platinum Service Class traffic provides the low latency required for interhuman (interactive) communications. The Platinum Service Class provides a minimum bandwidth assurance for Assured Forwarding (AF) 41 and Class Selector (CS) 4-marked flows.

• Queue 4 — Gold Service Class (PHB of CS3/AF31)

  The switch uses the Gold Service Class for applications that require near-real-time service and are not as delay-sensitive as applications that use the Platinum service. Such applications include streaming audio and video, video on demand, and surveillance video.

  The Gold Service Class assumes that traffic buffers at the source and destination and, therefore, the traffic is less sensitive to delay and jitter. By default, the Gold Service Class provides a minimum bandwidth assurance for AF31, AF32, AF33 and CS3-marked flows.

• Queue 3— Silver Service Class (PHB of CS2/AF21)

  The switch uses the Silver Service Class for responsive (typically client- and server-based) applications. Such applications include Systems Network Architecture (SNA) terminals (for example, a PC or Automatic Teller Machine) to mainframe (host) transactions that use Data Link Switching (SNA over IP), Telnet sessions, web-based ordering and credit card processing, financial wire transfers, and Enterprise Resource Planning applications.

  Silver Service Class applications require a fast response and have asymmetrical bandwidth needs. The client sends a short message to the server and the server responds with a much larger data flow back to the client. For example, after a user clicks a hyperlink (that sends a few dozen bytes) on a webpage, a new webpage appears (that downloads kilobytes of data). The Silver Service Class provides a minimum bandwidth assurance for AF21 and CS2-marked flows.

  The Silver Service Class favors short-lived, low-bandwidth TCP-based flows.

• Queue 2 — Bronze Service Class (PHB of CS1/AF11)

  The switch uses the Bronze Service Class for longer-lived TCP-based flows, such as file transfers, e-mail, or noncritical Operation, Administration, and Maintenance (OAM) traffic. The Bronze Service Class provides a minimum bandwidth assurance for AF11 and CS1-marked flows. As a best practice, use the Bronze Service Class for noncritical OAM traffic with the CS1 DSCP marking.

Queue 1 and 0 — Standard (PHB of CS0/DF) and Custom Service Classes

The switch uses the Standard and Custom Service Classes for best-effort services. Delays, loss, or jitter guarantees for these service classes are not specified. However, the Standard Service Class has more forwarding resources than the custom service classes.