Network technologies and trends

Mar 27 2011   5:46AM GMT

What is IP SLA?

Yasir Irfan Yasir Irfan Profile: Yasir Irfan

 When you are preparing for Cisco CCNP- Switch Exam, IP SLA is one of the key topics included at quite later stage even surprised David Hucaby the author of the title “CCNP Switch Official Certification Guide”  Even he included the supplementary material for the “CCNP Switch Official Certification Guide”

 The Cisco IOS IP Service Level Agreement better known as IPSLA is a feature which was introduced in the IOS version 11.2 under the name of Response Time Responder (RTR). Later on Cisco sensed RTR is creating some sort of confusion as some of reference texts referred RTR as Real time responder; hence they renamed RTR as Service Assurance Agent (SAA). Even SAA didn’t stick for long time and now it’s known as IP SLA.  IP SLA is truly excellent for built-in network testing. In fact, it is a key ingredient for sophisticated implementations of Performance Routing (PfR).

 At its introduction in IOS 11.2 version under the name of RTR it had very limited offerings  

  • ICMP Ping
  • ICMP Echo Path
  • IBM SNANativeEcho

The Cisco IOS IP Service Level Agreement (IP SLA) feature can be used to gather realistic information about how specific types of traffic are being handled end-to-end across a network. To do this, an IP SLA device runs a preconfigured test and generates traffic that is destined for a far end device. As the far end responds with packets that are received back at the source, IP SLA gathers data about what happened along the way.

IP SLA is capable of running following tests in Cisco Switches and routers

Test Type Description IP SLA Required on Target?
icmp-echo ICMP Echo response time No
path-echo Hop-by-hop and end-to-end response times over path discovered from ICMP Echo No
path-jitter Hop-by-hop jitter over ICMP Echo path Yes
dns DNS query response time No
dhcp DHCP IP address request response time No
ftp FTP file retrieval response time No
http Web page retrieval response time No
udp-echo End-to-end response time of UDP echo No
udp-jitter Round trip delay, one-way delay, one-way jitter, one-way packet loss, and connectivity using UDP packets Yes
tcp-connect Response time to build a TCP connection with a host No

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