IP SLA is a feature that measures the ongoing behavior of the network, it acts as a tool to test and gather data abouth the network. Network management tools can then collect that data and report whether the network reached the desired SLAs for the network, many management tools support the ability to configure IP SLA from the management tool's gui. When configure, the routers gather the results of network operation, storing the statistics in the IOS RTTMON MIB, management applications can later gather the statistics from this MIB on various routers and report whether the SLAs are met.

CCNP ROUTE (4th printing) p. 371.

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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 .– Probably the most 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 overall Connectivity.
* ICMP Path Jitter .– Hop-by-hop Jitter, Packet Loss, and Delay.
* 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.
* UDP Echo .– Round-trip Delay for UDP traffic.
* ICMP Echo .– Round-trip Delay, full path.
* ICMP Path Echo .– Round-trip Delay and Hop-by-hop round trip delay.
* HTTP .– Round-trip time using simulated http traffic.
* TCP Connect .– Allows us to sample the time to connect to a target using TCP.
* FTP .– Round-trip time for file transfers.
* DHCP .– Round-trip time for dynamic host configuration.
* Frame-Relay .-–Round-trip Delay, and the Frame Delivery Ratio. Mostly used for circuit availability.

http://routerjockey.com/2011/05/06/ip-sla-basics/

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Cisco IP SLA is an embedded feature set in Cisco IOS Software that allows you to analyze service levels for IP applications and services. It is one of those Cisco device instrumentation features with a long history. IOS 11.2 introduced the Response Time Reporter (RTR), which supported three functions: ICMP Ping, ICMP Echo Path, and SSCP (IBM SNA native echo). In those days, multiple customers migrated their dedicated IBM SNA infrastructure to an IP network and realized how limited IP reporting functions were compared to IBM's SNA network. RTR addressed this issue and significantly increased functionality over the years. Cisco renamed RTR Service Assurance Agent (SAA) in Cisco IOS Software Release 12.0(5)T. New features were continuously added and, in 2004, Cisco changed the name to IP SLA. Despite the name changes, the basic principle of IP SLA remained the same: an active measurement that uses injected test packets (synthetic traffic) marked with a time stamp to calculate performance metrics. The results allow indirect assessment of the network, such as Service-Level Agreements (SLA) and QoS class definitions.

http://etutorials.org/Networking/networ ... 1.+IP+SLA/

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Also: See Cisco's NetFlow

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