Foreword
Historically, telecommunications networks have been based on circuit-switched technologies. In these networks a physical path, or dedicated time slot, is allocated to each connection. The allocation of dedicated resources to each connection meant that delays were small and fixed, and that congestion-related loss could not occur. To prevent congestion, this type of network blocked new connection attempts when there were insufficient resources available for all potential users. The inherent quality of service (QOS) associated with a circuit-switched network (CSN) is very high because these networks were designed to support loss-sensitive and delay-sensitive applications such as voice.
Internet Protocol (IP) based networks became ubiquitous with the advent of the World Wide Web (WWW) and the Internet. The networks were predominantly best effort and required very little QOS differentiation among various types of traffic. However, with the exponential growth of Internet traffic, and high availability demanded by users, the resiliency and efficiency of IP-based networks were enhanced greatly – chief among them being the use of Multiprotocol Label Switching (MPLS) and Traffic Engineering (TE).
With the availability of MPLS and TE, the continued acceptance of IP has been no surprise, given its ease of use, its well-known operational characteristics, and most importantly its ability to adapt to ever-changing networking requirements. Some of these include the need for virtual networking, ...
