MPLS and Quality of Service (QoS)

Written by: Ls Harper - Feb 4, 2012

The greatest benefit that is derived from implementing MPLS technology is the ability to provide Quality of Service (QoS) guarantees to customers. Providers can now offer service level agreements that promise to carry the customer’s mission critical applications in real time. They can support VoIP and Video over IP and integrate several diverse applications on a pure IP backbone.

The advantage of MPLS is that service providers can define specific packet delivery paths for traffic through IP networks. They can move traffic flows into less congested paths and balance network traffic load and overall network response time and throughput. The technique marries connectionless IP technology to connection oriented technologies like ATM and assigns labels to IP flows placing them in IP frames. The packets can then be transported across packet or cell based networks and switched on labels. MPLS in other words makes it possible to set up explicit routes for data flows that are constrained by path, resource availability and requested quality of service.

It follows that providers can also give explicit guarantees on performance metrics. They can define an overall QoS architecture and the subset of services they can deliver to each customer. They can define multiple classes of service that must be aligned by the customer if they want to leverage the benefits of the service. The QoS in a point to point MPLS network is built on the “pipe” model. This model allows the provider to build virtual QoS pipes between the customer edge routers that are used for providing guarantees regarding bandwidth and delay. This is similar to legacy ATM and Frame Relay PVC meshings. The provider in this instance takes responsibility for the virtual mesh and provides the necessary traffic engineering across a virtual mesh. Each tunnel has its own QoS characteristics. CE to CE QoS guarantees are also established before the transmission of data commences. QoS approaches can be extremely granular and the more granular the approach the more complicated the provider’s configuration. However, it must be noted that in MPLS-QoS the service providers QoS architecture has a definite impact on the internal architecture of the customer’s network and how the customer applications are serviced on the network. Most MPLS service providers support 3-4 classes of service. A few may provide as much as 5 classes, but they are not common. It follows that customers will have to limit the number of classes they define to the maximum provided by the service provider. They can put any application they want into a class defined by the provider and expect the performance guarantees defined for that class.

In short, MPLS technology solves many traffic and IT management and bandwidth management problems for service providers. However, the implementation requires traffic classification, traffic prioritization, bandwidth management and traffic monitoring at very intense levels. Highest level planning and granular level implementation is required to meet the QoS standards that are promised and even guaranteed to customers. For MPLS prices use MPLS-IETF.com