MPLS-based VPNs is the latest technology for providing secure VPN connectivity to corporate clients, as they migrate to converged IP Services. MPLS technology delivers new services, also allowing migration from old to new networks and reducing the configuration and management requirements at the customer end. Solutions providers can derive great benefits for their customers, riding on this technology.

MPLS is the abbreviated form for Multi-Protocol Label Switching, a technology that simplifies and improves IP-packet exchange. This packet-forwarding technology uses labels to make data forwarding decisions.

With MPLS, the Layer 3 header analysis is done just once, when the packet enters the MPLS domain. The label that gets inserted at this point, decides subsequent packet forwarding, eliminating the decision-making necessary at every hop on the way to the destination in traditional networks.

In traditional networks, IP-packet forwarding uses the IP destination address in the packet's header to make an independent forwarding decision at each router in the network. These hop-by-hop decisions are based on network layer routing protocols that are designed to find the shortest path through the network, without considering other factors, such as latency or traffic congestion.

Data transfer on MPLS
MPLS builds on Internet Protocol (IP), combining the intelligence of routing, which is fundamental to the operation of the Internet and IP networks, with the high performance of switching. When a packet enters an MPLS-based network, the Label Edge Router (LSR) gives it a label, identifying it with an MPLS path, it would take. Once this classification is complete and mapped, different packets are assigned to corresponding Labeled Switch Paths (LSPs), where Label Switch Routers (LSRs) place outgoing labels on the packets.

Labels are inserted when the packets enter the MPLS network, and ultimately removed before they leave the MPLS network, so nothing remains to be done by the non-MPLS devices outside the MPLS network. This whole MPLS scheme is totally transparent to the world outside the MPLS network. 

MPLS provides a variety of benefits:
Virtual Private Networking: MPLS VPNs are maintained on the service provider's equipment, which can provide significant cost savings and increased scalability, compared to other VPN technologies. MPLS VPNs keep different customers' traffic separated by uniquely identifying each VPN flow and setting up circuit-like connections. VPNs based on MPLS have inherent self-healing ability by automatically re-routing traffic and also ensures quality of service including high throughput with low latency and jitter.

Traffic Engineering: A shortcoming of IP in public networks is its inability to optimize network resource utilization. Using standard IP routing, all traffic between two points is sent over the shortest path, even though multiple paths may exist. During periods of high traffic volume, this can result in traffic congestion on certain routes while alternative routes are underused. MPLS enables traffic engineering to squeeze more data into available bandwidth by allowing packets to be routed along explicit routes and with specific bandwidth guarantees. MPLS traffic engineering also enables resiliency and reliability to be built into the networks.

Quality of Service: MPLS supports the delivery of services with Quality of Service (QoS) guarantees. Packets can be marked for high quality, enabling providers to maintain a specified low end-to-end latency for voice and video.

Flexibility: MPLS gives a great deal of flexibility to divert and route traffic around link failures, congestion and bottlenecks. ISPs are better able to manage different kinds of data streams based on priority and service plans. MPLS is currently the best approach for simplified implementation of very large IP infrastructures.

Other benefits: MPLS decreases the forwarding overheads on core routers, since routers simply forward packets based on fixed labels. It also provides the appropriate level of security while reducing the need for encryption on public IP networks. An ISP with MPLS services can also provide bandwidth on demand for customers who have high bandwidth requirements periodically for a short duration.

The MPLS VPN reduces network complexity and cost, as customers need to provide only one connection from their office router to the service provider's edge router at each location. Fully managed services are also possible using a VPN network where the service provider also manages the customer's routers, thus removing the need for highly skilled human resources for the customer.

Services that run on MPLS VPN
This is where systems integrators and solutions providers can ride the MPLS wave and make effective use of the technology for the benefit of their clients. Using the MPLS VPN infrastructure provided by service providers like BSNL, which has all-India coverage under their own control, many services and solutions can be tailored for customers.

Many corporate customers are looking at solutions to interconnect all the branches, depots, plants and even their mobile sales force for enhanced communications and efficiency. Travel, STD bills and delays in data communication can be drastically cut down by deploying different services over an MPLS-based VPN, at costs ranging from a few lakhs to a crore of Rupees, depending on the number of services deployed and number of locations connected. Implementing enterprise solutions like ERP may, of course, add a crore or two more to the budget.

As the service provider handles the deployment of the MPLS VPN services, the systems integrators and solutions providers need only to provide the infrastructure and software solutions at the customer end, sometimes, even without knowing much about MPLS, the technology that really makes it all work!

The author is an independent consultant and can be reached at: dongre@usa.net

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