% of the band- width. Gold, Silver and Bronze could be mapped to AF classes AF1, AF2 and AF3 for example. Figure 12.18 illustrates the typical traffic conditioner at the edge of a DS domain. A DS internal node enforces the appropriate PHB by employing policing or shaping techniques, and sometimes remarking of profile packets, depending on the policy or the SLA. 12.10 MULTI PROTOCOL LABEL SWITCHING (MPLS) An introduction to MPLS is included in Chapter 7. MPLS is used at speeds up to 10 Gbit/s. In classical IP over ATM the IP packets need to be put together again (from cells) in each IP node, which is cumbersome. The need for a new switching technology with IP packets to replace IP over ATM was identified in 1996 and standardization of MPLS started in 1997. MPLS runs over many existing network hardware like Ethernet, frame relay and ATM and supports the forwarding of IP packets over virtual circuits. MPLS is implemented in IP routers. Essentially, MPLS improves IP scalability and quality of service by creating virtual label-switched paths (LSP) across a network of label switching routers (LSR). In MPLS, each packet carries a virtual circuit identifier, called a label, as a field of a shim header inserted between the IP header and the link layer header of a packet. A single packet can carry more than one shim header. An MPLS header is 32 bits long and labels take only 20 bits out of these 32 bits, therefore leaving room for further information inside the header. The 'label' is a number, which identifies a path across the network. The packets are routed more quickly based on a label, than when having to look up the destination address in the IP packet. MPLS handles labels just like all other virtual circuit identifiers are handled in other virtual circuit switching technologies. Consider an IP packet sent through the network in Figure 12.19. The packet is forwarded through an MPLS network or domain. When the packet arrives at the first MPLS router, also called the ingress label edge router (ingress LER) of the MPLS d