QoS Architectures for the IP Network

QoS Architectures for the IP Network

Harry G. Perros (North Carolina State University, USA)
DOI: 10.4018/978-1-5225-7598-6.ch095
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When we call someone over the internet using a service such as Skype or Google talk, we may experience certain undesirable problems. For instance, we may not be able to hear the other person very well, or even worse, the call may be dropped. In order to eliminate these problems, the underlying IP network has to be able to provide quality of service guarantees. Several schemes have been developed that enable the IP network to provide such guarantees. Of these schemes, the multi-protocol label switching (MPLS) and the differentiated services (DiffServ) are the most widely used. In this chapter, some of the salient features of MPLS and DiffServ are reviewed.
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QoS is a well-understood and studied topic within the networking community. It is typically expressed in term of the following three metrics: the end-to-end delay, the jitter, and the packet loss rate. The end-to-end delay is the amount of time it takes to transfer a packet from the transmitter to the receiver, and it consists of a) the end-to-end propagation delay, b) delays induced by transmission systems and processing times inside the routers, and c) delays a packet encounters due to queueing in the buffers of the routers. Jitter refers to the variability of the inter-arrival times of the packets at the destination, and the packet loss rate is the percent of packets that are lost.

Table 1.
QoS metrics for common networking services
Tolerance for packet lossTolerantConversational voice and videoVoicemailStreaming audio and videoFax
IntolerantRemote app., command and control gamese-commerce
web browsing
Texting, file transfer (foreground)File transfer (background), email
delay<<1 s
delay ~1 s
delay ~ 10 s
delay >> 10 s
Tolerance for delay

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