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IP SLA

IP SLAs enable you to monitor network performance between two Cisco routers. IP SLA is a feature embedded in the Cisco IOS software that the IP SLA plugin polls to help Cisco customers understand IP service levels, increase productivity, lower operational costs, and reduce the frequency of network outages. IP SLA actively monitors network performance and helps troubleshoot your network, assess network readiness, and monitor network health. The Probe Manager enables you to manage how SevOne NMS monitors the Cisco IOS IP SLAs on the devices for which you enable the IP SLA plugin.

IP SLA technology allows remote configuration over SNMP. SevOne NMS uses this remote aspect to create IP SLAs on a router without the need to log in and run the router commands and without writing to the router startup config file. The IP SLA plugin detects and monitors all IP SLAs on the router including the IP SLAs you create.

IP SLA Identity

Unlike interfaces, IP SLAs are not physical which poses a challenge for performance monitors.

Example: When a device reboots there is no rule to preserve the IDs of the IP SLAs or even to preserve the IP SLA.

To avoid duplicate IP SLAs, SevOne NMS uses three criteria to determine if an IP SLA is one SevOne NMS has already encountered.

  • IP SLA Type - SevOne NMS compares the IP SLA type to see if it is the same as an existing IP SLA.

  • Owner - SevOne NMS compares the owner to see if it is the same as an existing IP SLA. The owner is the string that the creator of the IP SLA uses to identify itself.

  • Tag - SevOne NMS compares the tag to see if it is the same as an existing IP SLA. The tag is the unique identifier that the creator uses to distinguish the IP SLA.

If the IP SLA type, owner, and tag are the same, then SevOne NMS assumes that the two IP SLAs refer to the same thing and does not create a duplicate IP SLA. Whereas the router can use the IP SLA identifier number to distinguish between IP SLAs (because the router does not need to track the IP SLAs it created before the reboot), SevOne NMS does not rely on the IP SLA numeric identifier.

IP SLA Compliance Revisions

The information on the Cisco IP SLA Compliance Revision page applies to the Cisco IP SLA MIB known as CISCO-RTTMON-MIB. The page displays a list of compliance revisions for the MIB. Cisco devices that support IP SLA also support one of these revisions. SevOne NMS checks for the existence of certain values of rttMonSupportedProtocolsValid and rttMonSupportedRttTypesValid to detect the compliance revision for a device.

Supported IP SLAs

SevOne NMS supports the following IP SLAs.

  • Dhcp - This has the router perform an IP address lease request/tear down operation.

  • Dlsw - This has the router perform a keep alive operation to measure the response time of a DLSw peer.

  • DNS - This has the router perform a name lookup of an IP address or host name.

  • Echo - This has the router perform a timed echo request/response operation.

  • Ethernet Jitter - This has the router send and receive Ethernet data frames between Ethernet Connectivity Fault Management (CFM) maintenance end points (MEPs) to measure the latency, jitter, and frame loss between two MEPs.

  • Ethernet Ping - This has the router send and receive Ethernet data frames between Ethernet Connectivity Fault Management (CFM) maintenance end points (MEPs) to measure the latency between two MEPs.

  • FTP – This has the router download an FTP file and record how long it takes. This is a good way to determine if an important FTP site/file is available at a remote location.

  • HTTP - This has the router perform a round-trip time to get a web page.

  • ICMP jitter - This has the router perform delay variance analysis.

  • RTP – This has the router gather network performance related statistics for a call. Available statistical measurements for VoIP networks include jitter, frame loss, Mean Opinion Score for Conversational Quality (MOS-CQ), and Mean Opinion Score for Listening Quality (MOS-LQ).

  • tcpConnect - This has the router perform a timed TCP connect operation.

  • udpEcho - This has the router perform a timed UDP packet send/receive operation.

  • UDP Jitter - This has the router perform a delay variance analysis over UDP, usually to simulate voice traffic.

  • Video - This has the router perform a one way video operation, streamed from the source to the destination.

  • VoIP - This has the router measure network response time to set up a VoIP call.

dhcp

The IP SLA plugin collects the following dhcp data.

  • Availability - Whether the IP SLA succeeded or not.

  • Average Time - How long the operation took.

dlsw

The IP SLA plugin collects the following dlsw data.

  • Availability - Whether the IP SLA succeeded or not.

  • Response Time - How long the operation took.

DNS

The IP SLA plugin collects the following DNS data.

  • Availability - Where the IP SLA succeeded or not.

  • Response Time - How long the operation took.

echo

The IP SLA plugin collects the following echo data.

  • Availability - Whether the IP SLA succeeded or not.

  • Ping Time - How long the operation took.

Ethernet Jitter

The IP SLA plugin collects the following Ethernet Jitter data.

  • Availability - Where the IP SLA succeeds or not.

  • Average Delay DS - The average delay from the destination to the source.

  • Average Delay SD - The average delay from the source to the destination.

  • Average Jitter - The average jitter. See calculation description below.

  • Average Jitter SD - The average jitter from the source to the destination.

  • Average Jitter DS - The average jitter from the destination to the source.

  • Average RTT - The average round trip time.

  • Frames Unprocessed - The number of frames that were not processed due to high CPU load.

  • Interarrival Jitter In - The mean deviation (smoothed absolute value) of the difference in frame spacing for a pair of packets from destination to source.

  • Interarrival Jitter Out - The mean deviation (smoothed absolute value) of the difference in frame spacing for a pair of packets from source to destination.

  • Late Frames - The number of frames that arrived late.

  • Lost Frames - The number of frames that did not arrive.

  • Frames Skipped - The number of frames skipped.

  • Negative Jitter Average - The number of frames that reduced jitter.

  • Negative Jitter Percent - The percentage of frames that reduced jitter.

  • Lost Frames DS - The frame lost from the destination to the source.

  • Frame Loss Ratio - The ratio of lost frames to total frames.

  • Lost Frames SD - The frames lost from source to the destination.

  • Frames Out of Sequence - The number of frames received out of sequence.

  • Positive Jitter Average - The number of frames it takes to compensate for jitter.

  • Positive Jitter Percent - The percentage of frames that introduced jitter.

  • Sent Frames - The number of frames sent.

Ethernet Ping

The IP SLA plugin collects the following Ethernet Ping data.

  • Availability - Where the IP SLA succeeded or not.

  • Response Time - How long the operation took.

FTP

The IP SLA plugin collects the following FTP data.

  • Availability - Where the IP SLA succeeded or not.

  • Response Time - How long the operation took.

HTTP

The IP SLA plugin collects the following HTTP data.

  • Availability - Whether the IP SLA succeeded or not.

  • Response Time - How long the operation took.

ICMP jitter

The IP SLA plugin collects the following ICMP jitter data.

  • Availability - Where the IP SLA succeeded or not.

  • Average Delay DS - The average delay from the destination to the source.

  • Average Delay SD - The average delay from the source to the destination.

  • Average Jitter - The average jitter. See calculation description below.

  • Average RTT - The average round-trip time. See calculation description below.

  • Interarrival Jitter In - The mean deviation (smoothed absolute value) of the difference in packet spacing for a pair of packets from destination to source.

  • Interarrival Jitter Out - The mean deviation (smoothed absolute value) of the difference in packet spacing for a pair of packets form source to destination.

  • Late Packets - The number of packets that arrived late.

  • Lost Packets - The number of packets that did not arrive.

  • Negative Jitter Average - The number of packets that introduced jitter.

  • Negative Jitter Percent - The percentage of packets that introduced jitter.

  • Packet Loss Ratio - The ratio of lost packets to total packets.

  • Packets Out of Sequence - The number of packets received out of sequence.

  • Positive Jitter Average - The number of packets it takes to compensate for jitter.

  • Sent Packets - The number of packets sent.

RTP

The IP SLA plugin collects the following RTP data.

  • Availability - Where the IP SLA succeeded or not.

  • Connection Time - How long the operation took.

tcpConnect

The IP SLA plugin collects the following tcpConnect data.

  • Availability - Where the IP SLA succeeded or not.

  • Connection Time - How long the operation took.

udpEcho

The IP SLA plugin collects the following udpEcho data.

  • Availability - Where the IP SLA succeeded or not.

  • Echo Time - How long the operation took.

UDP Jitter

The IP SLA plugin collects the following UDP Jitter data.

  • Availability - Where the IP SLA succeeded or not.

  • Average Delay DS - The average delay from the destination to the source.

  • Average Delay SD - The average delay from the source to the destination.

  • Average Jitter - The average jitter. See calculation description below.

  • Average RTT - The average round-trip time. See calculation description below.

  • Bandwidth - The bandwidth measure of the volume of data used for the operation over a known period of time, measured in bits per second. This uses the following calculation: the number of packets, multiplied by the request size (plus 12 bytes for protocol overhead). Multiply that by 8 (to convert from bytes to bits), and then divide by the interval between tests.

  • Calculated Planning Impairment Factor (ICPIF) - Attempts to quantify, for comparison and planning purposes, the key impairments to voice quality that are encountered in the network.

  • Interarrival Jitter In - The mean deviation (smoothed absolute value) of the difference in packet spacing for a pair of packets from destination to source.

  • Interarrival Jitter Out - The mean deviation (smoothed absolute value) of the difference in packet spacing for a pair of packets from source to destination.

  • Late Packets - The number of packets that arrived late.

  • Lost Packets - The number of packets that did not arrive.

  • Mean Opinion Score (MOS) - A common benchmark to determine the quality of sound produced by codes on a scale of 1 (poor quality) to 5 (excellent quality).

  • Negative Jitter Average - The number of packets that reduced jitter.

  • Negative Jitter Percent - The percentage of packets that reduced jitter.

  • NTP State - The NTP state of the operation.

  • Packet Loss DS - The packets lost from the destination to the source.

  • Packet Loss Ratio - The ratio of lost packets to total packets.

  • Packet Loss SD - The packets lost form the source to the destination.

  • Packets Out of Sequence - The number of packets received out of sequence.

  • Positive Jitter Average - The number of packets that introduced jitter.

  • Positive Jitter Percent - The percentage of packets that introduced jitter.

  • Sent Packets - The number of packets sent.

  • Sigma Delay DS - Standard deviation of the destination-to-source delay.

  • Sigma Delay SD - Standard deviation of the source-to-destination delay.

  • Sigma Jitter DS - Standard deviation of the destination-to-source jitter.

  • Sigma Jitter SD - Standard deviation of the source-to-destination jitter.

  • Sigma RTT - Standard deviation of the round-trip time.

  • UnSync RTTs - The number of probes received that were out of sync with NTP.

Video

The IP SLA plugin collects the following Video data.

  • Availability - Where the IP SLA succeeded or not.

  • Average Delay DS - The average delay from the destination to the source.

  • Average Delay SD - The average delay from the source to the destination.

  • Interarrival Jitter Out - The mean deviation (smoothed absolute value) of the difference in packet spacing for a pair of packets from source to destination.

  • IPDV Average Jitter - The instantaneous packet delay variation.

  • Late Packets - The number of packets that arrived late.

  • Lost Packets - The number of packets that did not arrive.

  • Negative Jitter Average - The number of packets that reduced jitter.

  • Negative Jitter Percent - The percentage of packets that reduced jitter.

  • NTP State - The NTP state of the operation.

  • Packet Loss Ratio - The ratio of lost packets to total packets.

  • Packet Loss SD - The packets lost form the source to the destination.

  • Packets Out of Sequence - The number of packets received out of sequence.

  • Positive Jitter Average - The number of packets that introduced jitter.

  • Positive Jitter Percent - The percentage of packets that introduced jitter.

  • Sent Packets - The number of packets sent.

  • UnSync RTTs - The number of probes received that were out of sync with NTP.

VoIP

The IP SLA plugin collects the following VoIP data.

  • Availability - Whether the IP SLA succeeded or not.

  • Time Until Ring - How long it takes the sender to ring the receiver.

IP SLA Jitter Operation

SevOne NMS calculates the following metrics for IP SLA jitter tests.

Metric

> Compliance Version 10

< Compliance Version 9

Average Round-Trip-Time (RTT)

= rttMonLatestJitterOperRTTSum / rttMonLatestJitterOperNumOfRTT

Average Jitter

= rttMonLatestJitterOperAvgJitter 

= ( rttMonLatestJitterOperSumOfPositivesDS 
 + rttMonLatestJitterOperSumOfNegativesDS 
 + rttMonLatestJitterOperSumOfPositivesSD 
 + rttMonLatestJitterOperSumOfNegativesSD ) 
/ ( rttMonLatestJitterOperNumOfPositivesDS 
  + rttMonLatestJitterOperNumOfNegativesDS 
  + rttMonLatestJitterOperNumOfPositivesSD 
  + rttMonLatestJitterOperNumOfNegativesSD)
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