How are the simulated VoIP calls created by IPSLAM considered by QoS? Is it considered to be voice traffic or data traffic?
Good question freemen. SolarWinds?
bump!! Solarwinds please?
Hi,
The VoIP related IP SLA operations (and their data) created by IPSLA Manager contain informations like UDP Jitter (for calculating MOS) and voice codec type (this can be set as one of the criteria when you creating a new operation). Also requested data size value is being automatically set according to used codec. This mean than QoS should really recognize this kind of data traffic as voice data.
thanks,
Michal
An additional point that is worth mentionning is that you can tag your IP SLA operations with the Type Of Service (TOS) byte (bit mask) to make sure the traffic generated by this operation is properly categorized by the CB QOS queuing mechanism (if this is what you mean by QOS).
To do this, go to advanced screen in the IP SLA Operation creation wizard and set the TOS approprietaly (i.e. matching the TOS used in your router's CB QOS setting).
I just wanted to add a little clarification to this issue:
1) The IP SLA operation generally used to measure synthetic voice quality is UDP jitter.
2) Normally, IOS routers are configured use the strict priority queue only for voice packets marked with DSCP 46 (Expedited Forwarding).
3) By default, IOS sets the ToS byte to 0 for UDP jitter operations. This equates to a DSCP value of zero, meaning that the router will NOT prioritize IP SLA packets under normal circumstances. A TOS/DSCP of zero normally goes into the default class and gets queued according to whatever you configure for that class.
4) If you want your IP SLA packets to go in the priority queue (which makes things more realistic), you need to set the TOS field shown by fcaron to 184. This is because the DSCP field is 6 bits, and the IP SLA operation annoyingly requires you to set a decimal equivalent for all 8 bits.
5) Remember that if you do this, you will slightly decrease the amount of bandwidth available in your voice queue for real voice calls, since you're putting synthetic IP SLA packets in the same queue. Usually this won't matter, but if you have a small voice queue or a lot of voice traffic, it might!
