VoIP: Ready for prime time

I m Madhu Yarlagadda, responsible for Real Time Communications at Yahoo! Today I am going to talk about VoIP ready for primetime. There are primarily two reasons why VoIP has not really taken off. One is reliability and the other is quality. Today I m going to talk about some of the reliability issues and how we can make it 100% reliable.

Today most of the households use a NAT in order to connect to the internet. Traditionally, people would connect to the internet directly. However, there are not enough addresses for every device that s there. And as a result, a NAT, which stands for network address translator, allows us to connect to the internet and use a single address and have multiple devices share it.

However, a NAT poses a huge problem for voice over IP applications. When there is an incoming call that comes in from the destination, it would reach the device directly if it is directly connected to the internet. However, if there is a NAT, then the corresponding call comes through the internet, reaches the NAT, and now the NAT does not know to which device the call needs to be handed off, and as a result, it drops the call. The user who is making the call suddenly has this experience that at times the calls go through and other times they do not.

There is a solution in order to effectively traverse the NAT and make that call go through. And the solution is called STUN. STUN stands for Simple Traversal of UDP through NAT. And it s primarily used for residential NATs. STUN is a protocol that allows two destinations to have a peer-to-peer connection through the NAT. However, STUN is not 100% reliable. It works between two consumer NATs. Any time we have an enterprise, STUN does not work through enterprise NATs which are generally a lot more secure and do not allow UDP traffic to go through. UDP is the means in which all the voice over IP data is sent.

In the case of the enterprise NAT, we would like the PC to send the data to every listserver which in turn will relay it to the destination. And the standard that allows us to do it is called TURN. TURN stands for traversal using relay NAT. Even though TURN is 100% reliable, one has to pay for excess bandwidth and the delay associated. As a result, it is best to use STUN whenever possible and only use TURN as a last resort to gain 100% reliability.

There is a framework called ICE. ICE primarily states that we should use STUN to the maximum extent possible and whenever STUN doesn t work, at that point we should use TURN. With the combination of STUN, TURN and ICE, now we ll be able to have 100% reliability for every single voiceover IP call that is being made. And as a result, VoIP is now ready for primetime.