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Implementing Quality of Service Over Cisco MPLS VPNs

Chapter Description

This chapter covers the requirements for supporting the converged world of Multiprotocol Label Switching (MPLS) VPNs and how this maps to QoS policy applicable in the enterprise. The aim is to provide a deployable set of policies that the enterprise can use as guidelines. You'll also see how to address these policies to the service provider. Specifically, the QoS needs of Acme, Inc. are addressed in the case study.

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Selecting MPLS VPN Services

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QoS Reporting

The service provider should offer a minimum level of QoS reporting to provide you with statistics on the QoS you are receiving. This reporting should include the following metrics:

  • Observed traffic ratio for classes
  • Number of packet drops per class as a number and percentage
  • Average offered load per class

The network administrator may specify additional parameters as necessary to ensure the network's maintenance and operation.

You can use the Cisco IP SLA Response Time Reporter (RTR) feature in Cisco IOS to measure the response time between IP devices. A source router configured with IP SLA configured can measure the response time to a destination IP device that can be a router or an IP device. The response time can be measured between the source and the destination or for each hop along the path. Simple Network Management Protocol (SNMP) traps can be configured to alert management consoles if the response time exceeds the predefined thresholds.

Key areas that can be measured with IP SLA include

  • Interpacket delay variance (jitter) of VoIP traffic
  • Response time between endpoints for a specific QoS
  • IP ToS bits
  • Packet loss using IP SLA generated packets

You can configure the IP SLA feature on routers using the Cisco Internetwork Performance Monitor (IPM) application. The IP SLA/RTR is imbedded in many but not all feature sets of the Cisco IOS software. A release of the Cisco IOS software that supports IP SLA/RTR must be installed on the device that IPM uses to collect performance statistics.

Chapter 8, "Network Management, SLA, and Support Requirements," contains more information on reporting, monitoring, and managing QoS.