The complete resource for understanding and deploying IP quality of service for Cisco networks

Learn to deliver and deploy IP QoS and MPLS-based traffic engineering by understanding:

• QoS fundamentals and the need for IP QoS
• The Differentiated Services QoS architecture and its enabling QoS functionality
• The Integrated Services QoS model and its enabling QoS functions
• ATM, Frame Relay, and IEEE 802.1p/802.1Q QoS technologies and how they work with IP QoS
• MPLS and MPLS VPN QoS and how they work with IP QoS
• MPLS traffic engineering
• Routing policies, general IP QoS functions, and other miscellaneous QoS information

Quality-of-service (QoS) technologies provide networks with greater reliability in delivering applications, as well as control over access, delay, loss, content quality, and bandwidth. IP QoS functions are crucial in today's scalable IP networks. These networks are designed to deliver reliable and differentiated Internet services by enabling network operators to control network resources and use. Network planners, designers, and engineers need a thorough understanding of QoS concepts and features to enable their networks to run at maximum efficiency and to deliver the new generation of time-critical multimedia and voice applications.

IP Quality of Service serves as an essential resource and design guide for anyone planning to deploy QoS services in Cisco networks. Author Srinivas Vegesna provides complete coverage of Cisco IP QoS features and functions, including case studies and configuration examples. The emphasis is on real-world application-going beyond conceptual explanations to teach actual deployment.

IP Quality of Service is written for internetworking professionals who are responsible for designing and maintaining IP services for corporate intranets and for service provider network infrastructures. If you are a network engineer, architect, manager, planner, or operator who has a rudimentary knowledge of QoS technologies, this book will provide you with practical insights on what you need to consider when designing and implementing various degrees of QoS in the network. Because incorporating some measure of QoS is an integral part of any network design process, IP Quality of Service applies to all IP networks-corporate intranets, service provider networks, and the Internet.

Remembering that the Internet is a best-effort service only, the author introduces the IP QoS functions in chapter 1. The advent of voice and video traffic over IP for example, requires the need for QoS in modern networks. QoS services are divided into levels: best-effort, which does not guarantee traffic delivery; differentiated service, which groups traffic into classes but does not guarantee its delivery; and guaranteed service, which allocates network resources to ensure specific service requirements. Bandwidth, packet latency, and packet loss are measures used to characterize connection performance.

Chapter 2 gives a more detailed overview of the differentiated services architecture for delivering QoS on the Internet. Called `diffserv' by the IETF, the author discusses the historical origins of it, and how it provides traffic differentiation by breaking traffic up into a small number of classes, with relative service priority existing among these classes. The presentation is straightforward to follow, once one gets used to remembering all of the many acronyms that are employed, such as PHB (per-hop behavior), DSCP (Differentiated Services Code Point), etc. The traffic conditioners, which are QoS functions that set the DSCP field and monitor traffic for profile compliance, and discussed in detail. Network provisioning, signaled QoS, and QoS policy manager are all discussed as resource provisioning policies.

In chapter 3, the author overviews the use of traffic conditioning functions at the network boundary as a tool for providing differentiated services. In one, called `packet classification', the packets are identified using one or more fields in a packet. This could be the MAC address, URL, IP Precedence, etc. Then `packet marking' is used to mark classified packets according to their traffic class. Traffic rate management, another conditioning function, is discussed via the token bucket scheme, along with the CAR traffic policing function. The strategy of borrowing of tokens for token buckets with extended burst capability is very interesting and is a good candidate for improvement using techniques and concepts from financial engineering and artificial intelligence. The token bucket scheme is also discussed in the context of traffic shaping.

In the next chapter on resource allocation, the author discusses how weighted fair queuing can be employed as a scheduling discipline in which flow differentiation occurs. The author makes some interesting and somewhat controversial remarks in this chapter, one being that after stating that some flows are delayed to offer a particular bandwidth to other flows, he concludes to the effect that a preferential treatment will result in another suffering. This is not really true as one can show using techniques from game theory. In fact, the max-min fair-share allocation scheme that he discusses next is a step in this direction. This is true also for the weighted max-min fair share allocation, in which each user is assigned a weight, with the fair-share being proportional to this weight. Generalized processing sharing (GPS) is discussed as an ideal scheduling mechanism that services an infinitesimally small amount of data from each nonempty queue via round-robin. This unrealistic requirement is then ameliorated by using fair queuing, a strategy that takes all flows to have the same weight, and simulates GPS by computing a sequence number for each arriving packet. Flow-based weighted fair queuing is also discussed in detail in this chapter. For those readers worrying about QoS for interactive voice traffic, the author is careful to point out that WFQ maybe unable to achieve the low-jitter requirements. Therefore, he includes a discussion of WFQ with priority queue in this chapter. A short overview of flow-based distributed WFQ is also included. The latter does not make use of the CPU, unlike ordinary WFQ. The author then outlines the class-based WFQ, which can be implemented in both distributed and nondistributed modes. Priority queuing, which divides queues into subqueues of decreasing order of priority, is also treated. The author also gives an overview of custom queuing, which is a strategy for guaranteeing a minimum bandwidth for each traffic classification.

Chapter 5 is an overview of the scheduling algorithms on routers that employ a switching architecture that is not bus-based. In this regard, the author gives a very detailed discussion of the use of Modified Weighted Round Robin and Modified Deficit Round Robin algorithms.