What is QOS?

QoS refers to the capability of a network to provide better service to selected network traffic over various technologies, including Frame Relay, Asynchronous Transfer Mode (ATM), Ethernet and 802.1 networks, SONET, and IP-routed networks that may use any or all of these underlying technologies. Primary goals of QoS include dedicated bandwidth, controlled jitter and latency (required by some real-time and interactive traffic), and improved loss characteristics. QoS technologies provide the elemental building blocks that will be used for future business applications in campus, WAN, and service provider networks. This chapter outlines the features and benefits of the QoS provided by the Cisco IOS QoS.

The Cisco IOS QoS software enables complex networks to control and predictably service a variety of networked applications and traffic types. Almost any network can take advantage of QoS for optimum efficiency, whether it is a small corporate network, an Internet service provider, or an enterprise network. The Cisco IOS QoS software provides these benefits:

 

• Control over resources---You have control over which resources (bandwidth, equipment, wide-area facilities, and so on) are being used. For example, you can limit the bandwidth consumed over a backbone link by FTP transfers or give priority to an important database access.
• More efficient use of network resources---Using Cisco's network analysis management and accounting tools, you will know what your network is being used for and that you are servicing the most important traffic to your business.
• Tailored services---The control and visibility provided by QoS enables Internet service providers to offer carefully tailored grades of service differentiation to their customers.
• Coexistence of mission-critical applications---Cisco's QoS technologies make certain that your WAN is used efficiently by mission-critical applications that are most important to your business; that bandwidth and minimum delays required by time-sensitive multimedia and voice applications are available; and that other applications using the link get their fair service without interfering with mission-critical traffic.
• Foundation for a fully integrated network in the future---Implementing Cisco QoS technologies in your network now is a good first step toward the fully integrated multimedia network needed in the near future.

Basic QoS Architecture

The basic architecture introduces the three fundamental pieces for QoS implementation (see Figure 1):

 

• QoS within a single network element (for example, queuing, scheduling, and traffic shaping tools)
• QoS signaling techniques for coordinating QoS from end to end between network elements
• QoS policy, management, and accounting functions to control and administer end-to-end traffic across a network

Figure 1: A basic QoS implementation has three main components.