What  is UDP Lite ?

Introduction

We use TCP and UDP all the time but are you familiar with the newer UDP light isn't UDP already lightweight how much lighter can it get stick around.

Fig 1: UDP Lite

UDP Lite

And we'll see the first thing we need to look at is the checksum in UDP we're talking regular UDP at this point not UDP light UDP may have a checksum this means UDP can protect against payload corruption or it can ignore it entirely if there's no checksum a payload may be corrupted beyond use and UDP won't know if there is a checksum a single bad bit in the payload will cause validation to fail and the entire UDP datagram will be thrown away it won't be resent as UDP does not have any mechanism to resend missing data so UDP has an all or nothing approach to data loss UDP light is nearly the same as regular UDP it is still connectionless it still uses ports and so on but it has a different approach to the way it handles the checksum in fact it has a partial checksum the idea behind this is that the application that uses the data in the payload knows best and may be able to recover from small errors think of a voice codec for example it knows how to handle voice errors better than UDP does so to achieve this UDP light sees two parts of each payload one part is sensitive and the other part is insensitive the partial checksum covers the sensitive area this is the part of the payload that cannot withstand corruption if a single bit is wrong here the UDP datagram is discarded as normal if there's any errors in the insensitive part UDP lite just will not care and will deliver the datagram to the application as normal UDP lite is useful for multimedia applications like voice and streaming video to these applications a damaged packet is still better than no packet at all these applications will use advanced codecs which will be able to correct or conceal small errors it's easier to hide an error from a few bad bits than it is to hide an entire missing packet and that's all there is to UDP lite nearly the same as regular UDP just with some better handling for damage datagrams.

Conclusion

UDP Lite is a very efficient version of UDP. UDP may have a checksum. If it does use a checksum and a single bit is off, the checksum won’t match and the entire datagram will be discarded. UDP Lite takes a different approach. It uses a partial checksum. This means that the checksum covers only an area of the payload marked as ‘sensitive’. If a bit changes in the ‘insensitive’ area, the UDP segment is still delivered as normal. This is used with voice and video traffic, which will usually have advanced codecs to detect problems and conceal or repair them.