Suddenly the voice market in India is becoming very interesting. Earlier it was the case of Jio (and competitors) launching unlimited voice plans and now it’s the case of Govt. of India permitting IP telephony. IP Telephony i.e networks where telephony happens over IP (not to be confused with IP to IP calls but) where IP to PSTN interconnects happen. Till a few months ago IP telephony (or IP-PSTN) interconnection was allowed only under certain conditions like doing it inside a building only for purpose of call centres (with OSP license) or running SIP trunks over private networks.
I usually find that Gmail phone performs lot better then Skype for calls to PSTN. Usually latency on Skype is high as compared to Gmail phone in India (in US it was almost no difference). I looked around today and here’s bit of test data I collected by calling couple of numbers from Skype & Gmail phone & monitored UDP traffic to collect information about destination servers which is very likely IP-PSTN gateway.