Protocols, 2nd ed. (Reading, Massachusetts: Addison-Wesley, 1999). 56. Jayant Kadambi, Ian Crawford, and Mohan Kalkunte, Gigabit Ethernet: Migrating to High-Bandwidth LANs (Upper-Saddle River, New Jersey: Prentice-Hall, 1998). 57. Marina Smith, Virtual LANs: Construction, Operation, and Utilization (New York: McGraw-Hill, 1998). Downloaded from Digital Engineering Library @ McGraw-Hill (www.digitalengineeringlibrary.com) Copyright © 2004 The McGraw-Hill Companies. All rights reserved. Any use is subject to the Terms of Use as given at the website. THE EVOLUTION OF NETWORK TECHNOLOGY: DISTRIBUTED COMPUTING AND THE CONVERGENCE OF NETWORKS THE EVOLUTION OF NETWORK TECHNOLOGY 25 that all the core routers of the ISP network must possess and maintain the entire Internet routing table, which requires an enormous amount of memory and leads to a very high degree of CPU utilization. The MPLS standard introduced a fundamentally new approach in the deployment of IP networks. The control mechanism was supposed to be separate from the forwarding mechanism and the concept of label was supposed to be introduced for packet forwarding. MPLS can be deployed on router-only networks or in ATM environments that integrate the layer 2 and layer 3 infrastructures into one sin- gle consolidated ATM network. 58,59,60 An MPLS network has label-switched routers (LSRs) in the core of the provider's network and edge label-switched routers (Edge-LSRs) at the periphery of the provider's network. Within the MPLS network, traffic is forwarded using labels. The Edge-LSRs at the ingress side of the MPLS cloud (the MPLS network point from where an incoming packet is entering) assign the appropriate label to each packet and forward the packets onto their next-hop LSR along the path that the traffic has to follow in order to go through the MPLS cloud. The label's value is actually a pointer used by all LSRs on a table that points to the next hop and a new label. At each LSR, the old label is exchanged with a new one and the packet is forwarded onto the