PDD is one of the main reasons for other rates in a traffic. PDD may appear as a result in some cases or maybe the reason itself. Let’s start to explain our topic.
What is the meaning of Post Dial Delay, PDD? 
Post Dial Delay is the average time before hearing the ringtone.
What are the consequences of high PDD rates?
High PDD values are the main reasons for the low Average Success Rate, ASR. People don’t want to wait too long before hearing the ringtone, and they close the phone when it’s not connected. This will cause to miss calls. When the caller closes, call ends and there will be no re-route. Post dial delay is more common on wholesale termination (LCR) products, which provide aggressive rating as a product of having multiple carriers to attempt to complete the call. This occurs because each carrier can take a few seconds to acknowledge their ability to complete the call. Most carriers within the telecommunications industry consider anything under 7 seconds as an acceptable amount of PDD, and most will not troubleshoot PDD that is less than 7 seconds
What are the main reasons for getting high PDD rates?
There are several reasons for receiving high Post Dial Delay. If you are seeing high PDD values in traffic, you should focus on those things to solve the problem.
- Destination based
- Exceeded HOP
- Provider
- NCLI
Destination Based
Some destinations have standard PDD profiles. For example this rate is between 8 to 9 seconds for Syria, but it is around 3 to 4 seconds for Turkmenistan. This rate can change according to the traffic profile. We need to test these destinations’ traffic profiles by sending them to the direct route. After all, if there are higher values than the average, we can understand that there is a problem with the provider.
Exceeded Hop
There is a big PDD difference between sending the traffic directly and and sending them through 6-7 different vendors. Because high delay times and package loses are very normal when you sending the traffic over many different servers.
Provider Problem
There can be a problem with the carrier service internet and because of this, delay times can be high with the provider. It’s also possible to be NCLI.
NCLI Problem
Some NCLI routes can use low speed home internet connection so it takes too much to open packages and this will cause high delay times. Providers can use fake RBT and fake RBT will help to decrease PDD rates. But ASR rates still will be low because people will hear the fake ringtone and still wait for too much and think that the person is busy to open the phone. Eventually they will give up on calling.
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