Packet Loss: Difference between revisions

=What is Packet Loss?=

 

 

 

Each of these packets carries some addressing information, and some data. The fact that packets are used means it is possible to have lots of things happening at once, with bits of one thing in one packet followed by bits of something else in another packet and so on, mixing up multiple things on one Internet connection. This is how it is possible for lots of people to use an Internet connection at once. The addressing data in the packet makes sure the right things go to the right place and are put back together at the far end.

 

==How Does AAISP Monitor Packet Loss==

 

==So packet loss is normal. It is what happens when a link is full.==

 

However, there is another scenario where you can get packet loss, and this is where there is a fault. In the case of a fault you will find some packets are dropped at random. What usually happens is some of the data in the packet is corrupted (changed) by random noise or errors from the fault, and this means that the packet no longer checks out when it gets to the other end. Packets have built in checks to confirm nothing was changed, and if that check fails the packet is dropped.

 

==The effect of fault based packet loss depends on the protocol.==

 

This means that even low levels of random packet loss can massively slow down a data transfers.

 

==Packet loss when a link is otherwise idle is a fault.==

The best measure of loss as a simple percentage is the loss when sending full size packets (1500 bytes) which is what the data transfer protocols (like TCP) use. Even a 1% or 2% of loss of such packets can cause TCP to slow down massively. It does not work like taking away a couple of percent of speed - the data transfers keep slowing down as they keep thinking the line must be full.

 

 

Packet loss on an idle line is always bad news...

 

 

...even if only 1% (one red dot at the top is 1%)

 

 

A simpler, and less intrusive measure of loss, is a simple short LCP echo. LCP echoes are a normal part of most Internet links, and A&A do them every second and record the loss for every line. This is only a few bytes, and so packet loss that is a fraction of a percentage could mean several percent at full packet sizes. This is why it is so important to take even very low levels of LCP echo loss seriously.