QOS-Enabled Networks: Tools and Foundations (Wiley Series on Communications Networking & Distributed Systems)
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Written by two experts in the field who deal with QOS predicaments every day and now in this 2nd edition give special attention to the realm of Data Centers, QoS Enabled Networks:Tools and Foundations, 2nd Edition provides a lucid understanding of modern QOS theory mechanisms in packet networks and how to apply them in practice. This book is focuses on the tools and foundations of QoS providing the knowledge to understand what benefits QOS offers and what can be built on top of it.
packets in this particular queue, as well as all packets in other queues, must wait until it is their turn to be removed from the queue. Let us illustrate this behavior with the example in Figure 2.17, which shows two queues named A and B and a scheduler that services them in a round‐robin fashion, starting by servicing queue A. Packet X is the last packet inside queue B, and we are interested in calculating the delay introduced into its transmission. The clock starts ticking. The first action
create Ethernet lossless networks sounds perfect at first glance; however, it does create some challenges such as congestion propagation and HOL blocking. For example, at present the design of a DC network regarding the transport of FCoE is typically made using a simple logical topology with a small number of hops, and then special care is given to the oversubscription ratios. The major challenge created regarding virtualization is the increase and predictability of East–West traffic. To cope
However, if no voice traffic is present, the total amount of bandwidth that nonvoice traffic can use is nevertheless limited to 8 Mbps. The leftover bandwidth created by the absence of voice traffic is not accessible to nonvoice traffic, which can be good or bad depending on the desired behavior. This waste of bandwidth is the price Figure 6.11 Different types of traffic with different policing requirements 110 QOS-Enabled Networks Figure 6.12 Interconnection between the credit rates of
transmit. However, with oversubscription, transient situations can occur in which the bandwidth of the interface to the destination is insufficient to cope with the amount of bandwidth being transmitted to it, as illustrated in Figure 6.14. Oversubscription is a scenario commonly used with the shaping tool, because its application makes it possible to guarantee that the rate of traffic arriving at the logical interface to a destination complies with the shaper’s rate. So by setting the shaper
have reliable control of traffic paths, which means that the number of congestion points need to be minimal and the end‐to‐end delay, in milliseconds, needs to be predictable. For these applications, designers generally think that buffers should be small and paths should be well designed. Also, in the case of a network path outage, equivalent convergence backup paths should be included in the design. 148 QOS-Enabled Networks Figure 8.6 End‐to‐end QOS policy for certain traffic classes Here