Some telecommunication companies in Europe and maybe in other parts of the world now want to charge their customers for the VOIP traffic (maybe some already are doing it), e.g. the use of Viber, Skype etc since it´s "free" to use in Android and IOS.

I guess they will use deep packet inspection to read the headers of the packets to figure out that it comes from services like Viber and Skype.

I want to discuss the security view about this and in what ways it is possible for a customer to bypass the packet inspection and what a telecommunication company can do to inspect the packets even if a customer tries to bypass the inspection.

This is what I know that will make a customer bypassing the inspection, and what a company can do to inspect the packets even if they are encrypted.

To bypass packet inspection:

  • Use VPN
  • Use a SSH tunnel
  • The developers of Viber and Skype adds SSL support into their application

To inspect:

  • Read packet headers to see from which application the packets are coming from
  • Read the time interval and packet size

What else can a customer do get around the inspection and what else can a company do to inspect the packets?

1 Answer 1


I couldn't find any articles stating this and I highly doubt they would charge you for it (unless you are using their VOIP services instead of skype). The reason for this is that some providers prioritize this type of traffic on their network and some even have special separated networks (this only works for their VOIP phones/services).

You can't really encrypt voip itself with SSL. The reason for this is that VOIP uses UDP. SSL requires a stateful protocol like TCP. So a VPN tunnel would be the only option.

If they want to know if you are using VOIP you would indeed need to do DPI with IPv4. With IPv6 this isn't necessary as IPv6 has a special header field to identify the traffic.

Your best option would still be a VPN. I don't really know of any other ways.


Bruno suggested you can also use DTLS at implementation level.

  • 2
    VOIP with DTLS instead of SSL/TLS perhaps?
    – Bruno
    Apr 20, 2012 at 10:23
  • @Bruno: Is that header field in IPv6 the QoS field? Doesn´t IPv4 also has a simillar field (the one with bitset 8-13)?
    – Rox
    May 7, 2012 at 8:00
  • VOIP uses UDP can you please confirm this statement by sources? I read that SIP and VOIP use both TCP and UDP.
    – Suncatcher
    Apr 22, 2017 at 21:36

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