WHAT IS MPLS
The Wide Area Network (WAN) is the backbone of enterprises today and ties together remote locations, headquarters, and data centers into an integrated network. Since becoming widely available in 2001, the Multiprotocol Label Switching (MPLS) protocol has been the primary means by which service providers and enterprises have built WANs. The protocol sits between layer 2 and layer 3 and was designed to support multiple types of transports.With MPLS, a telecommunications provider provisions two or more physical locations with a managed connection and routes traffic between these locations using the most efficient route over the provider’s private backbone.
What makes MPLS unique from previous WAN transports is its reliability and performance.It was designed back in the days of ATM and Frame Relay as an overlay technique intended to simplify and improve performance. As Richard A Steenbergen, of nLayer Communications, notes what what differentiates MPLS from traditional IP routing is MPLS does “label switching” instead of an IP lookup at each router hop. The first device does a routing lookup, just like IP routing, but instead of finding a next-hop, it finds the final destination router and calculates a predetermined path to that final router.
As enterprise data enters the carrier network, a label is attached to each packet. This label uniquely identifies your Virtual Private Network (VPN) in a shared infrastructure and keeps it private. Upon reaching its destination, the label is removed, returning the data packet to its original state. In theory, since the traffic does not traverse the Internet, encryption is optional and is not vulnerable to denial of service attacks, which might impact pure-IP-based networks.
MPLS controls where and how traffic is routed on your network, manages capacity, prioritizes different services, and prevents congestion. The carrier can commit to up-time and latency service level agreements (SLA) because the carrier manages the entire connection. Generally, MPLS services are highly available with 99.99% being a typical target for an SLA and engineered to deliver low packet loss (.1% is typical of SLAs). MPLS also supports applications with strict up-time and latency requirements, such as voice and video applications.
When comparing MPLS services against Internet services, there are a couple of challenges to note:
Agility and costs
MPLS connections require specific, complex configurations by the carrier that usually create lengthy provisioning of MPLS services. Providing up-time, bandwidth, and latency guarantees via SLAs makes MPLS more expensive compared to Internet services.
The networks of MPLS service providers do not reach into every region of the globe. Typically, service providers piece together global coverage through partnerships with other service providers, which can be costly.
Why Use MPLS
Initially, the primary benefit of MPLS came about because routing lookups was difficult to implement efficiently in software.By minimizing them, MPLS offered a significant reduction in latency and provided improved performance. Improvements in silicon ASIC chipsets have largely eliminated lookup problems, but MPLS still brings major benefits:
Traffic engineering allows fine-grained control over how the network routes traffic. The network engineer can then prevent traffic congestion, manage line capacity, and prioritize services more effectively.
Network uptime is improved because of the inherent meshed architecture as well as the ability to reroute to an alternative path in less than 50ms.
Outsourced routing frees users from having to handle WAN routing themselves.
Quality-of-Service (class of service (COS) in MPLS parlance) support enables network managers to support different applications by reducing latency, jitter and packet loss to prioritize With QOS/COS, MPLS could support different types of networks on one physical network. Until MPLS, organizations maintained separate networks for voice and data, for example, which was very expensive.
These features combine to create a solution that provides high-speed and reliable connections backed with an SLA by the carrier. MPLS is a definite upgrade over previous technologies of Frame Relay and ATM and by allowing for improvements such as the ability for organizations to combine voice and data onto a single network.
MPLS brought about some cost savings by consolidating services into one network, but any monetary savings are generally offset by the overall cost of bandwidth of MPLS services. Today’s enterprises are increasingly adding bandwidth-hogging applications and media to their network, and the high per-megabit cost that MPLS demands can strain IT budgets. The Internet has become reliable enough for certain applications on some routes. Internet circuits are inherently cheaper than MPLS and underscore the high price point of MPLS.
Although cost is probably the biggest hindrance for MPLS, it does present other potential challenges. If configured correctly an MPLS network doesn’t offer built-in data protection. Traffic is isolated between MPLS customers but not encrypted exposing the traffic to wiretapping.
Deployment times can also be a major concern, as MPLS circuits can take months to install. Today’s rapidly changing business requirements can end up delayed because of the long lead times required by MPLS. As adoption of cloud services and Software-as-a-Service (SaaS) delivery models grow, traditional MPLS network architectures become less effective. Cloud and SaaS traffic must be first brought from the branch to a secured Internet access point at a central location for delivery through a secured Internet access portal onto the public Internet. As such, traditional MPLS services find it difficult to offer low latency/high-performance access to cloud and SaaS applications and services.
Despite some drawbacks, MPLS transformed the WAN to become the de facto standard for enterprise networks. Just as MPLS came along as a noteworthy improvement over its predecessors, no doubt another technology will eventually usurp MPLS as the most common WAN deployment. Until then, organizations can rely on MPLS today to provide a reliable and effective network.