Abstract:
Historically, private WANs were provisioned using dedicated leased line connections, each line providing a point-to-point connection between two customer sites. Such networks are expensive to put in place, especially if the connections between sites need to supp011 some level of redundancy. There is also no scope in such a system to share under-uti! ized bandwidth across several customers or, conversely, to increase the bandwidth available between particular sites dynamically in order to meet short-term peaks in demand. Virtual Private Networks (VPNs) are a method of interconnecting multiple sites belonging to a customer using a Service Provider (SP) backbone network in place of dedicated leased lines. Each customer site is directly connected to the SP backbone. The SP can offer a VPN service more economically than if dedicated private W ANs are built by each individual customer because the SP can share the same backbone network resources (bandwidth, redundant links) between many customers. The customer also gains by outsourcing the complex task of planning, provisioning and managing a geographically distributed network to the SP. Unfortunately, existing VPN solutions are not all interoperable and may be tied to one equipment vendor or a single SP. This has created strong interest in IP-based VPNs running over the public Internet using standards-based interoperable implementations that work across multiple SPs. Many of these IP-based solutions require IP address-mapping or double encapsulation using two IP headers. This can require complex configuration management and requires additional processing at the entry to and exit from the SP's networks. The new Internet technology, Multi-Protocol Label Switching (MPLS) forwards data using labels that are attached to each data packet. Intermediate MPLS nodes do not need to look at the content of the data in each packet. In particular the destination IP addresses in the packets are not examined, which enables MPLS to offer an efficient encapsulation mechanism for private data traffic traversing the SP backbone. MPLS can, therefore, provide an excellent base technology for standards-based VPNs. This THESIS reviews the requirements placed on a base technology for VPNs, how MPLS meets these requirements, and the state of future of MPLS based VPNs in PTCL.
