Cisco IOS IP SLA Basics and Operation Types

Benefits of Cisco IOS IP SLAs:

1. Cisco IOS IP SLAs monitoring – Provides service level agreement monitoring, measurement, and verification.

2. Network performance monitoring – Measures the jitter, latency, or packet loss in the network and Provides continuous, reliable, and predictable measurements.

3. IP service network health assessment – Verifies that the existing QoS is sufficient for new IP services.

4. Edge-to-edge network availability monitoring Provides proactive verification and connectivity testing of network resources.

5. Troubleshooting of network operation Provides consistent, reliable measurement that immediately identifies problems and saves troubleshooting time.

6. Voice over IP (VoIP) performance monitoring

7. Multiprotocol Label Switching (MPLS) performance monitoring and network verification

Cisco IOS IP SLAs Operation Types:

IP SLA is a function of Cisco’s IOS enabling you to analyze a Service Level Agreement (SLA) for an IP application or service. IP SLAs use active traffic-monitoring to continuously monitor traffic across the network. This is very different from SNMP or Netflow data which give you more volume oriented statistics. Many different metrics can be analyzed using IP SLA, here is a break down of a few.

UDP Jitter – This is the most commonly used operation in all of IP SLA. This IP SLA generates UDP traffic and Measures round-trip delay, one-way delay, one-way jitter, one-way packet loss, and connectivity testing of networks that carry UDP traffic, such as voice. This is used to monitor Voice and Data Network performance.

ICMP Path Jitter – Hop-by-hop Jitter, Packet Loss, and Delay. This is also used to monitor voice and data network performance.

UDP Jitter for VoIP – Enhanced test for VoIP monitoring. It can simulate various codecs and spits out voice quality scores (MOS, and ICPIF). Also shows us Round-trip Delay, One-way Delay, One-way Jitter, and One-way Packet Loss. It is used to monitor VOIP network and performance.

UDP Echo – Round-trip Delay for UDP traffic. It is used to monitor Server and IP application performance.

ICMP Echo – Round-trip Delay, full path. It is used to monitor IP and Connectivity measurement.

ICMP Path Echo – Round-trip Delay and Hop-by-hop round trip delay. It is used identify bottlenecks in Path and connectivity.

HTTP – Round-trip time using simulated http traffic. It is used to monitor Web server performance.

TCP Connect – Allows us to sample the time to connect to a target using TCP. It is used to monitor server and application performance.

FTP – Round-trip time for file transfers. It is used to monitor FTP server performance.

DHCP – Round-trip time for dynamic host configuration. It is used to monitor DHCP server response time.

DNS – It measures DNS lookup time, It is used to monitor Web or DNS server performance.

Frame-Relay –Round-trip Delay, and the Frame Delivery Ratio. Mostly used for circuit availability.

Cisco IP SLA Configuration

Cisco IOS IP SLAs uses generated traffic to measure network performance between two networking devices such as routers. Cisco IOS IP SLAs starts when the Cisco IOS IP SLAs device sends a generated packet to the destination device. After the destination device receives the packet, and depending on the type of Cisco IOS IP SLAs operation, the device will respond with time-stamp information for the source to make the calculation on performance metrics. A Cisco IOS IP SLAs operation performs a network measurement from the source device to a destination in the network using a specific protocol such as UDP. Using Cisco IOS IP SLAs, a network engineer can monitor the performance between any areas in the network: core, distribution, and edge.

There are 2 parts in the IP SLA configuration. One is testing source, and second is the responder. Typically our responder is a device local to the data center, while the test host is device at a remote site. The test host sends data to the responder and the responder sends a reply back. The configuration for the responder is very simple.

ip sla responder

Now let’s take a look at the configuration of the testing source. Find below configuration example.

ip sla 10                                                ! New IP SLA Instance #10
  udp-jitter 16800 source-ip codec g711ulaw    ! udp jitter w/Voice codec
  tos 184                                                 ! TOS bit, using EF here
  frequency 300                                            ! testing interval
ip sla schedule 10 life forever start-time now            ! start now, never stop

Below find the stats output by our IP SLA source..

Router#sh ip sla statistics 10    ! Omit the # to view all SLA stats.
IPSLAs Latest Operation Statistics
IPSLA operation id: 10
Type of operation: udp-jitter
        Latest RTT: 42 milliseconds
Latest operation start time: 18:28:06.603 UTC Thu May 5 2011
Latest operation return code: OK
RTT Values:
        Number Of RTT: 1000             RTT Min/Avg/Max: 39/42/154 milliseconds
Latency one-way time:
        Number of Latency one-way Samples: 1000
        Source to Destination Latency one way Min/Avg/Max: 25/26/41 milliseconds
        Destination to Source Latency one way Min/Avg/Max: 13/15/127 milliseconds
Jitter Time:
        Number of SD Jitter Samples: 999
        Number of DS Jitter Samples: 999
        Source to Destination Jitter Min/Avg/Max: 0/2/15 milliseconds
        Destination to Source Jitter Min/Avg/Max: 0/2/90 milliseconds
Packet Loss Values:
        Loss Source to Destination: 0           Loss Destination to Source: 0
        Out Of Sequence: 0      Tail Drop: 0
        Packet Late Arrival: 0  Packet Skipped: 0
Voice Score Values:
        Calculated Planning Impairment Factor (ICPIF): 1
MOS score: 4.34
Number of successes: 7
Number of failures: 0
Operation time to live: Forever

Filed Under: IP SLA


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