Thank Cisco for IP Service Level Agreement…… you will, I promise!

There are many uses for IP SLA  and one use for this technology is to monitor traffic for a certain IP application, you can use it to simulate traffic and have it report back with information such as latency, jitter, packet loss etc. I will cover other uses for IPSLA in future blogs.

I will give you a real world example so you can understand just what it can do. This SLA measures UDP-Jitter for VOIP.



ip sla 10
udp-jitter 5000 source-ip source-port 17386 codec g711ulaw                                                                                     tos 184
tag site A to site B UDP VOIP
frequency 150
ip sla schedule 10 life forever start-time now

That’s one side done, the other router you specify has to be setup to respond, so this is actually called a responder funnily enough


ip sla responder
ip sla responder udp-echo ipaddress port 17386

Now that you have both ends setup, our schedule states that the frequency is every 150 seconds, so wait this time and you will start to see statistics. the command you would use is “show ip sla statistics 10” this will bring up all the information based on your UDP-Jitter setting and in our case we are simulating a voice packet with G711 codec.

IPSLAs Latest Operation Statistics

IPSLA operation id: 10
Type of operation: udp-jitter
Latest RTT: 147 milliseconds
Latest operation start time: 06:29:19
Latest operation return code: OK
RTT Values:
Number Of RTT: 1000             RTT Min/Avg/Max: 146/147/151 milliseconds
Latency one-way time:
Number of Latency one-way Samples: 1000
Source to Destination Latency one way Min/Avg/Max: 116/116/118 milliseconds
Destination to Source Latency one way Min/Avg/Max: 30/31/34 milliseconds
Jitter Time:
Number of SD Jitter Samples: 999
Number of DS Jitter Samples: 999
Source to Destination Jitter Min/Avg/Max: 0/1/2 milliseconds
Destination to Source Jitter Min/Avg/Max: 0/1/3 milliseconds
Packet Loss Values:
Loss Source to Destination: 0
Source to Destination Loss Periods Number: 0
Source to Destination Loss Period Length Min/Max: 0/0
Source to Destination Inter Loss Period Length Min/Max: 0/0
Loss Destination to Source: 0
Destination to Source Loss Periods Number: 0
Destination to Source Loss Period Length Min/Max: 0/0
Destination to Source Inter Loss Period Length Min/Max: 0/0
Out Of Sequence: 0      Tail Drop: 0
Packet Late Arrival: 0  Packet Skipped: 474
Voice Score Values:
Calculated Planning Impairment Factor (ICPIF): 2
MOS score: 4.32
Number of successes: 21
Number of failures: 0
Operation time to live: Forever

The main parts you will probably look at here are MOS (mean opinion score) and ICPIF (planning impairment factor) Jitter and of course RTT. The TOS option is for adding a QOS value for my example i’ve used 184 which is DSCP 46 or EF, which is what you would normally use for VoIP. This of course only matters if you have QOS setup in the first place.

As you can see there’s lots of information here but what’s even better if you use a tool such as PRTG or MRTG you can output this data to a very nice graph where you can monitor it over a long period of time. Here’s an example.


Look out for my QOS blog next!