Network Broadband IP/ATM Wireless Aggregator Cable Figure 32. Broadband Aggregator The Ultimate Guide to Building and Delivering OSS/BSS 2.3 MPLS IP is rapidly becoming the platform of choice for delivering integrated services. Service providers are looking to create new differentiated IP services quickly and scale them to a large number of users handling large traffic volumes. However, IP has some inherent limitations, namely scalability, security and quality of service. In order to use IP for business services on a mass scale, these shortcomings must be overcome. The design objective of the Internet Engineering Task Force (IETF)'s MPLS effort was to address some of these shortcomings. MPLS combines the intelligence of routing with the performance of switching by overlaying the hop-by-hop mechanism of IP networks with a label-based switching approach to packet forwarding. MPLS technology is the key to delivering scalable services such as VPNs and end-to-end quality of service. MPLS uses a technique called label switching to forward data through the network. When an IP packet enters the MPLS network, a Label Eagle Router (LER) inserts a fixed-format label at the front of the packet. The labels are assigned to packets based on groupings or Forward Equivalence Classes (FECs). Packets belonging to the same FEC get the same treatment through the network. Label Switched Routers (LSRs) are core routers responsible for processing the packet according to the label attached to the IP header. Thus the core network simply reads labels, applies appropriate services, swaps the label and forwards the packet based on the label. The labels only have local significance at each core router. At the egress LSR at the destination site, the MPLS label is removed and normal IP routing is performed to forward the packet to the final destination. Since core routers don't need to look at the IP header of each packet, packet-processing overhead is reduced resulting in faster transition through the core. Each LSR in the MPLS network runs a 