Enhance MPLS QoS

Procedures to make PacketWise and MPLS collaborate for optimum performance improvements

MPLS (Multiprotocol Label Switching) is a standards-based technology that can improve network performance and quality of service (QoS) for select traffic. MPLS offers multiple classes of service, each associated with different types of traffic. For instance, an enterprise's mission-critical applications (such as Oracle) might be in a Gold class of service, less-important applications might be in a Silver service, recreational applications (such as games, instant messaging, and P2P) might be in a Best Effort service, and VoIP traffic might be in its own class of service that would reduce jitter.

Typically, MPLS operates in the carrier's network, requiring the WAN router on the customer premise (the CPE router) to differentiate between different traffic types. Based on the type of application and the class of service the application is assigned to, the CPE router applies a Diffserv or ToS (Type of Service) mark to each packet, indicating the class of service. When the packet arrives at the Label Edge Router (LER) in the carrier network, the LER can look at the Diffserv label and translate that into the appropriate MPLS tag.

However, because routers' application classification capabilities are limited, the CPE router lacks precision and accuracy when tagging traffic with Diffserv labels. PacketShaper, on the other hand, has extensive classification abilities. It can detect, identify, and classify applications, and then assign appropriate QoS tags (such as Diffserv labels). For example, suppose Oracle is one of your mission-critical "gold service" applications. PacketShaper can identify and classify this traffic into the Oracle traffic class and assign it a DSCP label, such as 23. When the packet arrives at the LER in the carrier network, the router looks at the DSCP tag and assigns it the corresponding MPLS label (for example 5, the label associated with gold service). The LER then forwards the packets on the MPLS path for gold service, ensuring that the requisite bandwidth, jitter, and latency specifications are met.

PacketShapers are deployed at the network edge, as shown in the topology below.

PacketShaper can do more than just label the traffic. Using its policies and partitions, PacketShaper is able to ease the bottlenecks that form at the entry points to the MPLS core network. (The link from the local LAN to the MPLS core is typically the lowest capacity portion of the network and can back up with deep queues.) With PacketShaper, you can protect the performance of applications in the premium MPLS class of service, enforce limits on traffic volume in each MPLS class of service, provision steady streams for voice or video traffic to ensure smooth performance, and prevent applications or users from monopolizing the link.

For instructions on setting up the MPLS traffic configuration described here, see Classify and Control MPLS Traffic.

In addition, PacketShaper's analysis capabilities allow you to determine the bandwidth requirements of an application prior to MPLS deployment. For example, suppose you want to see how much bandwidth you need for SAP. Using the average rate that PacketShaper measures for the SAP traffic class, you can calculate the amount of bandwidth required for SAP by mulitplying the rate by the number of concurrent SAP sessions you want to support.

To summarize, PacketShaper's functionality complements MPLS installations in the following ways:

• It detects, identifies, and classifies diverse applications, assigning distinct QoS tags (such as Diffserv labels).
• It helps you determine an application' s bandwidth requirements before an MPLS deployment.
• It eases the bottlenecks that form at the entry points to the MPLS core network.
• It extends MPLS performance benefits to the network edge and user's premises.
• It helps companies assess and manage transition to MPLS-based WAN services by allowing them to accurately specify capacity and measure performance for different service classes; for instance, gold, silver, and bronze classes of service.
• It measures and graphs per-application and per-MPLS-class performance, enabling assessment of service level agreement (SLA) compliance. See Assess MPLS Performance.

Note: This Recommendation assumes that the Label Edge Router will be doing MPLS tagging based on Diffserv or IP ToS tags. If you would like PacketShaper (instead of the LER) to assign the MPLS labels, see Classify Traffic with an MPLS Label.