I m Madhu Yarlagadda, responsible for Real TimeCommunications at Yahoo! Today I am going to talk about VoIP ready forprimetime. 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 someof the reliability issues and how we can make it 100% reliable.
Today most of the households use a NAT in order to connectto the internet. Traditionally, people would connect to the internet directly.However, there are not enough addresses for every device that s there. And as aresult, a NAT, which stands for network address translator, allows us toconnect to the internet and use a single address and have multiple devicesshare it.
However, a NAT poses a huge problem for voice over IPapplications. When there is an incoming call that comes in from thedestination, it would reach the device directly if it is directly connected tothe internet. However, if there is a NAT, then the corresponding call comesthrough the internet, reaches the NAT, and now the NAT does not know to whichdevice the call needs to be handed off, and as a result, it drops the call. Theuser who is making the call suddenly has this experience that at times thecalls go through and other times they do not.
There is a solution in order to effectively traverse theNAT and make that call go through. And the solution is called STUN. STUN standsfor Simple Traversal of UDP through NAT. And it s primarily used forresidential NATs. STUN is a protocol that allows two destinations to have apeer-to-peer connection through the NAT. However, STUN is not 100% reliable. Itworks between two consumer NATs. Any time we have an enterprise, STUN does notwork through enterprise NATs which are generally a lot more secure and do notallow UDP traffic to go through. UDP is the means in which all the voice overIP data is sent.
In the case of the enterprise NAT, we would like the PC tosend the data to every listserver which in turn will relay it to thedestination. And the standard that allows us to do it is called TURN. TURNstands for traversal using relay NAT. Even though TURN is 100% reliable, onehas to pay for excess bandwidth and the delay associated. As a result, it isbest to use STUN whenever possible and only use TURN as a last resort to gain100% reliability.
There is a framework called ICE. ICE primarily states thatwe should use STUN to the maximum extent possible and whenever STUN doesn twork, at that point we should use TURN. With the combination of STUN, TURN andICE, now we ll be able to have 100% reliability for every single voiceover IPcall that is being made. And as a result, VoIP is now ready for primetime.
