Performance metrics
Revision as of 14:40, 14 December 2009
This page provides information on the performance of TelcoBridges products. Performance of each TelcoBridges device described here is based on a specific testing scenario and system configuration. Please note that TelcoBridges makes no claims, promises or guarantees regarding the actual performance of its products in a real-world production environment.
The TDM/VoIP resources required by a telephony system can be calculated using a simple equation:
CPS X average call duration = amount of resources required
To better estimate the amount of TDM and/or VoIP resources required by an application, it is important to define the call duration.
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Call Duration
A call consist of 3 parts:
- The establish part of a call consists of the signaling to establish the call (i.e. INVITE, 180 Ringing, 200 OK for SIP). It also contains the allocation and the connection of TDM and/or VoIP resources.
- The active part consist of the 'useful' part of the call (i.e. users can now talk). The call is established and the media is connected.
- The tear down of the call consists of the signaling of the call (i.e. BYE for SIP). It also contains the dis-connection and the de-allocation of the media (TDM and/or VoIP) resources.
These three concepts are displayed in the figure below.
The call duration is the sum of those 3 parts and the duration of each may vary greatly according to the type of application. For example, voice mail applications will most likely have a very short 'Establish' time, since the application will answer the call immediately because it will not let it ring for long. For fax applications, the average 'Active' time will be longer than other types of calls (because of fax negotiation requirements).
Performance variables
Different factors may influence the performance expressed in calls per second (CPS) and call duration.
Establish
Calls, whether answered or not, will reserve outgoing resources even they are not connected until the end user answers. An exception to this is the case of early media and ring/ring-back tones, which require allocation and connection.
The Establish CPS performance will vary according to these factors:
- Signaling protocol used: SIP is the most CPU-intensive protocol, much more than ISDN or SS7
- IVR resources: if the application requires IVR, it will increase CPU usage on the device
- VoIP resources: if the application requires VOIP, it will increase CPU usage on the device, much more than TDM resources do
- Percentage of unanswered calls: calls that are never answered require less CPU, since resources are not allocated and connected
- Early media: this call option forces resources to be allocated and connected even if the call is not answered yet; it is as CPU-intensive as a regular call that is answered even if the early media call is not answered yet
- Ring tone /ring-back tone: same as early media
The Establish length will vary mostly because of these factors:
- Signaling protocol used: SIP takes a little longer to process, longer than ISDN or SS7
- Answer time: if the Tmedia terminates the call, the Establish length will be a lot shorter since the call will be answered immediately
- Average unanswered ring time: even though the call is not answered, it still reserves resources for the time it is ringing
NOTE: A ring is 6 seconds long, that is 2 seconds on and 4 seconds off.
Active
An Active call does not cost a lot of CPU time compared to those required for allocating and connecting resources.
The Active length will vary according to the type of application. IVR applications average call lengths of 20 seconds, while fax applications can be 4-5 minutes.
Tear down
Answered calls will eventually require disconnecting and deallocating the resources used, therefore they can be quite CPU intensive. As for unanswered calls (except when using early media or ring back tone), they only use signaling and are nominally CPU-intensive.\\ The Tear down CPS performance will vary according to these factors:
- Signaling protocol use: SIP is the most CPU intensive protocol, more than ISDN or SS7.
- IVR resources: if the application requires IVR it will increase CPU usage on the Tmedia.
- VoIP resources: if the application requires VoIP it will increase CPU usage on the Tmedia, much more than TDM resources will.
- Percentage of unanswered calls: calls that are never answered requires less CPU since the resources are not allocated or connected.
- Early media, this call option force the resources to be allocated and connected even if the call is not answered yet, it is as CPU-intensive as a regular call that is answered even if the early media call is not answered yet.
- Ring tone / ring-back tone, same as early media.
The Tear down length will vary mostly because of these factors:
- Signaling protocol use, SIP takes a little longer to process, longer than ISDN or SS7.
Performance results
ISDN-SIP
Results expressed in bridged calls per second (BCPS)
