Label Distribution Protocol (LDP) to distribute labels via peer-to-peer negotiation from network edge to network edge, thus creating an end-to-end Label Switched Path (LSP) through the core network. Chapter 8 - Next-Generation OSS Label Packet ========= Site B Packet Label Switched Paths (LSPs) with Site A Network Different QoS Site C LER: Label Edge Router LSR: Label Switched Router Figure 33. MPLS Network MPLS technology is being used to support a number of applications. MPLS-enabled traffic engineering (TE) routes traffic flows across the network by analysing resources required by the traffic flow and resources available in the network. Using MPLS TE, pre-engineered explicit paths can be created through the network, without configuring each network device manually along the path. These pre-engineered paths can be used for services such as DSL aggregated traffic or VoIP tandem bypass traffic. Perhaps the most significant benefit of MPLS is in the area of VPNs. Businesses have typically used Layer 2 VPNs - based on FR and ATM - to establish connectivity between multiple sites. For each pair of sites that needs to be connected, a separate virtual circuit is required. For example, to connect "n" sites in a mesh using ATM VPNs, n(n-1)/2 number of virtual circuits need to be created and managed within the provider's WAN. Because Layer 2 VPNs do not scale, it becomes more difficult to add large volumes of sites quickly. Layer 3 tunneling architectures (e.g., using IP-Sec or GRE) operate across routed core networks, and since they are not scalable either, they also depend on creating and administering connections, not networks. Since MPLS is a network-based, not connection or tunnel based, it scales significantly better The Ultimate Guide to Building and Delivering OSS/BSS than ATM, FR or IP-Sec based VPNs. MPLS eliminates the need to create a full mesh of tunnels or VCs between all sites in the VPN. Softswitch Earlier in the chapter we talked about how the next generation networks are being built using packet based t