p for MPLS service, they give their provider a list of the IP addresses associated with each site that they want included in their MPLS service. Each IP address identifies a specific location on a network. The carrier uses this list to define a closed group of sites that are allowed to communicate with one another over the MPLS network. The list can be amended by notifying carriers of IP addresses to be added or deleted. In addition to an IP address, each location connected to the MPLS network requires an access line from the customer to the carrier's network. However, a single link from each location can transmit messages to all sites. Each location does not need a separate physical connection to every other site on the MPLS network. This is referred to as an any-to-any network. MPLS Networks Traffic intended for the organization's other sites is forwarded to the provider's edge router. Edge routers are routers at the edge of a carrier's network that link customer traffic to the carrier's high-speed backbone networks. In contrast to edge routers, which are connected to customers, core routers are located in a network's high-speed backbone and are connected only to other routers. Figure 5-3 presents a depiction of where each router is deployed in the network. High-speed Edge routers connected directly to customers core routers Core routers connected only to other routers MPLS network Edge routers attach labels to customers' packets Figure 5-3 Core and edge routers in a Multi-Protocol Label Switching (MPLS) network. Broadband and Wide Area Network Services The edge router examines the first packet's header and looks up addressing infor- mation in the router's tables for only this packet. It attaches a label with this address data to each subsequent packet of the transmission. The elimination of router table lookups for each packet is a major factor underpinning the high speeds of MPLS. Examining a label is faster than examining headers and looking up router tables. MPLS minimizes traffic jams by selecting the shor