Cisco Smart Care Services Questions and Answers About the Voice Quality Monitor Service

Transcription

1 Cisco Smart Care Services Questions and Answers About the Voice Quality Monitor Service For Qualified Cisco Partners October 2008 Americas Headquarters Cisco Systems, Inc. 170 West Tasman Drive San Jose, CA USA Tel: NETS (6387) Fax: Customer Order Number: Text Part Number: OL VQMQ&A

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3 This document answers common questions about the Voice Quality Monitor (VQM) service. High Level Topics The following Q&A addresses general questions about the VQM service. When should I use the Voice Quality Monitor service? How many concurrent calls are supported? What codecs are supported? You should use the Voice Quality Monitor (VQM) service to forecast the quality of voice traffic before you deploy a converged network over one or more sites. This makes it possible to determine the effectiveness of Quality of Service (QoS) policies, as well as the effects of voice traffic on existing applications, before deployment. You can also use the VQM service to monitor and report on voice quality for one or more sites where a converged voice and data network is already deployed. The VQM service eliminates the need to rely on end users for subjective assessments of voice quality. Beginning with the release of Cisco Smart Care Service , 20 concurrent calls are supported. The Voice Quality Monitor (VQM) service supports the G.711 codec and the G.729 codec. Can I use this service to assess and monitor multiple sites at the same time? Yes. For more information about scheduling tasks, see the Smart Care Partner User Guide. This document accompanies version of the Cisco Smart Care Service application, providing late-breaking information about the release. This document also provides information about new features in this release, in addition to information about known issues that affect this release. What is the difference between the VQM and the existing Voice Assessment service? The voice assessment feature recommends the maximum number of G.711 and G.729 calls for a given link based on link bandwidth and best practice. The VQM, in contrast, assesses voice quality by injecting G.711 or G.729 traffic into the network and measuring key parameters. Americas Headquarters: Cisco Systems, Inc., 170 West Tasman Drive, San Jose, CA USA

4 Detailed Specifications Both the Voice Assessment and Voice Quality Monitor services provide information that can help you to determine the optimal number of calls to provision over a given link. Detailed Specifications The following Q&A addresses the detailed specifications for registration of the Smart Care Network Appliance. Does this service inject traffic into the network? Yes. The VQM injects voice traffic using either of the G.711 or G.729 codecs. How much traffic will be injected into the network? The injected traffic is identical to that of a real voice call from an IP phone. If you specify the G.711 codec, the VQM service injects 80 kilobits per second for each call at Layer 3. If you specify the G.729 codec, the VQM service injects 24 kilobits per second for each call at Layer 3. For information about the actual bandwidth utilization, including the Layer 2 overhead for each call, see the QoS Requirements of VoIP section of the Enterprise QoS SRND document located at How many packets are generated per second per call? For both G.711 and G.729 codecs, the VQM generates 50 packets per second for each call. What type of packets does the appliance send? The VQM service uses a TCP control connection between the appliance and the reflector to negotiate Real-Time Transport Protocol (RTP) ports. After the TCP connection is established, the VQM service generates RTP packets between the appliance and the Reflector PC. At the end of the RTP session, the TCP connection is closed. What DSCP (Differentiated Services Code Point) marking is used for the TCP control connection and the RTP media traffic? TCP control packets are marked for forwarding at a Best Effort level. RTP packets are marked for Expedited Forwarding. How much bandwidth should I provision in the infrastructure to run the VQM service? The bandwidth that is required to run the VQM service depends on the number of calls that you inject into the network and the type of codec that you use. For more information about the actual bandwidth utilization of the VQM service, including Layer 2 overhead for each call, see the QoS Requirements of VoIP section in the Enterprise QoS SRND document located at Does the VQM service provide integration with Locations-based or Gatekeeper-based Call Admission Control mechanisms? 1 No. 1. Call Admission Control mechanisms (both Locations and Gatekeeper) limit the number of administrator-specified calls that can be concurrently sent over a given link. Because VQM does not integrate with these admission control mechanisms, Partners must ensure that additional bandwidth is provisioned on the links that will carry assessment traffic. This is also clarified in the Solution Overview entitled Cisco Smart Care Service Voice Quality Monitor. 2 Questions and Answers about the VQM Service

5 Reflectors Can this service report on the quality of inbound or outbound public switched telephone network (PSTN) calls? No. The VQM service reports only on the quality of the Voice over IP (VoIP) calls that it injects between the appliance and the Reflector PC. Can this service report on the quality of other VoIP calls in the network? No. The VQM service reports only on the quality of calls that it initiates. This service does not monitor other network traffic. Can this service report on the quality of signaling packets such as those provided by Skinny Call Control Protocol (SCCP) or Media Gateway Control Protocol (MGCP)? No. The VQM service reports only on the quality of RTP media packets. It does not inject signaling packets into the network. Before I run the VQM service, are there any other network requirements that I need to know about? Yes. Read the Voice Quality Monitor Solution Overview at Reflectors What is a reflector? The following Q&A provides information about the Smart Care reflector software. As part of the VQM service, Smart Care provides a software-based reflector that is used to receive RTP media traffic from, and return it to, the appliance. The appliance analyzes the delay, jitter, and packet loss that occurs during the round trip. The reflector software is installed on a compliant laptop or desktop computer called the Reflector PC or the Reflector. Each Reflector PC must be registered with Smart Care. The VQM service sends voice traffic from the appliance to the specified Reflector PC. The Reflector PC returns the voice traffic to the appliance, and the appliance then computes values for round-trip delay, jitter, and packet loss (DJL). These values are then used to compute the Mean Opinion Score (MOS), a widely used measurement of voice quality. Can I measure the voice quality from one reflector to another reflector? No. The VQM service always measures voice quality between the Smart Care appliance and a Reflector PC. Voice quality cannot be measured between two Reflector PCs. Where can I download the reflector software? To download the reflector software visit the Support section of the Smart Care partner portal. You can also download the reflector software from Questions and Answers about the VQM Service 3

6 Using the VQM Service Can customers download the reflector software? Partners and customers with valid Cisco.com user IDs can download the reflector software from Do I need to install the reflector software on a computer before I can use the VQM service? Yes. The VQM service requires the reflector to be installed on a compliant computer. What are the minimum requirements for a computer to be used as a Reflector PC? The Smart Care reflector software requires the following: Microsoft Windows XP with Service Pack 2 or higher, or Microsoft Windows 2000 with Service Pack 2 or higher 1.6 GHz Pentium 4 or higher An average CPU utilization of 15% or less At least 1 GB RAM Where do I deploy the Reflector PCs? At least 10 MB disk space You should deploy one or more Reflector PCs at customer sites for which you want to assess or monitor call quality. The VQM service measures voice call quality between the appliance and the Reflector PCs. The Reflector PCs can be installed on networks used by end users. These are usually main office or remote branch office locations. Typically, Reflector PCs are installed in branch offices that are connected to a main office through WAN links. Because bandwidth is at a premium in such a scenario, the QoS policies must be more finely tuned to achieve the best voice quality. How many calls can a Reflector handle at one time? A Reflector PC can handle one call at a time. What are the connectivity requirements between the appliance and the Reflector PC? The appliance must be able to reach the IP address of the Reflector PC, in addition to the nominated port for TCP control and the negotiated ports for RTP media. If the Reflector PC is installed behind a device using Network Address Translation (NAT), the NAT IP address must be entered in the reflector registration page of the portal. The Reflector PC uses a default port range of to Using the VQM Service The following Q&A addresses questions about how to use the VQM service. How do I select assessment or monitoring mode in the user interface? You do not need to select one mode or the other. You can schedule one service run to do both. For example, if you want to assess voice quality, you should schedule a service run of longer duration. This is because a useful assessment may require the maximum number of concurrent calls for a site to be simulated over a longer period of time. 4 Questions and Answers about the VQM Service

7 Reporting When do I use the Run Now option? In contrast, you can obtain useful information about call quality by monitoring a single call over a shorter period of time. This means that when you want to monitor voice quality, you can schedule a run of shorter duration. You can create a long assessment period by scheduling a series of service runs with a minimum duration of time between them. This causes the service to run nearly continuously. Note that the maximum duration of a service run is 590 seconds (10 seconds less than 10 minutes). The minimum duration of a service run is 10 seconds. This is used for ad hoc service runs. You can use the Run Now option of the VQM service to check for ongoing network issues that contribute to poor voice quality. The Run Now option can be used to run the VQM service for a minimum of 10 seconds or a maximum of 30 minutes. Can I generate multiple calls by using the Run Now option or by creating a scheduled task? Yes. Whether you use the Run Now option or create a scheduled task, you can generate up to 20 concurrent calls. To do so, just specify 20 Reflector PCs when you start the run or schedule the task. Note that before you specify the Reflector PCs that the VQM service will use, you must first add and register the Reflector PCs in the Reflector Management section of Smart Care. Can I have more than one concurrent scheduled session? No. If I specify more than one Reflector PC for use in a scheduled task, can I select the G.711 codec for use with some Reflector PCs and the G.729 codec for use with others? No. In a single VQM session, only one type of codec can be used. Reporting What values are reported in the graph? The following Q&A addresses how the VQM service reports data. The graph displays round-trip average values for delay, jitter, and loss (DJL), and for MOS. Where can I get information about the minimum and maximum DJL values that were obtained during the service run? Click the View Details link to obtain information about the minimum, average, and maximum values for delay and jitter, as well as for the number of packets that were lost during the VQM service run. Delay and jitter values are shown in milliseconds. The report also provides the names and IP addresses of all specified Reflector PCs, the codec that was used, the date, time, and duration of the service run, and the MOS value. When I click the Quality Monitor tab, I always see a graph. What does this graph show? This graph, provided by default, shows the results for all voice quality tests that were run in the last 24 hours. Questions and Answers about the VQM Service 5

8 Further Information Do the DJL reports summarize one way or round-trip traffic? The DJL reports provide values that are calculated based on the round trip from the appliance, to the Reflector PC, and back to the appliance. Can the tool report the DJL and MOS values for every hop between the appliance and the Reflector PC? No. The VQM service reports only the end-to-end value. It does not report DJL and MOS values for each hop between the appliance and the Reflector PC. Further Information The following Q&A provides other resources for the VQM Service. Where can I get more details about this service? For more information about the VQM service, see the Voice Quality Monitor Solution Overview at 6 Questions and Answers about the VQM Service