Latency?

[bluesjunior 43]

For someone who is not very PC savvy, what is Latency?. I am talking about the header in the Services screen, The British ones run from 16-25ms, the Dutch ones from 35-37ms right up to the Hong Kong ones which go up to 365ms. What exactly does this mean and how should this affect which server I choose to connect, is it better to connect to lower or higher latency?.

[Staff 10018]

Hello!
 
Please see here:
https://en.wikipedia.org/wiki/Latency_(engineering)
 
in particular
https://en.wikipedia.org/wiki/Latency_(engineering)#Packet-switched_networks
 
You should prefer servers with lower latency. The lower the better.
 
Kind regards

[OpenSourcerer 1442]

Network latency is a term that expresses how much a packet is delayed while it travels through the internet for example.

This number is important since the internet is not as easy as "A connects to B".

Truth is, the internet is a global network consisting of many Asynchronous Systems (AS) that are interconnected. These Asynchronous Systems are routers and generally belong to certain providers: Hosters and ISPs for example.

It's economically not feasible to connect an AS to every AS in that network. That's why providers only connect to the ones who route their traffic through cheaper providers.

 

Let's say, an AirVPN user connected to a german server (LeaseWeb, the hoster of the german AirVPN servers, it's AS number is 16265) wants to access google.com (Google has it's own AS number: 15169). If LeaseWeb's AS is connected to Google - best case - your request will be processed very fast. The number representing the network latency will thus be very low.

This case is rare, though. Usually LeaseWeb will route your request through an AS that's - ideally - nearer to Google's. If the next AS is not Google, that AS will route it through another AS that's ideally nearer to Google's. That process repeats until Google's AS is reached. The more of these AS you chain the more time it will take to answer your request, thus raising the network latency value, sometimes even to 0.365 seconds which is intolerably high.

We speak of routing issues because the choice which AS will be the next to route your request through is the choice of the companies running the AS. Which of course choose their routes from an economical point of view most of the time. The cheaper the better.

 

how should this affect which server I choose to connect

 

There's a thing called the bandwidth-delay product. It's a value expressing how much data can be sent simultaneously before it has to stop and wait for the response ("Hey, B! Did you receive my data?" or "data sent but not acknowledged"). A higher line capacity (higher bandwidth) means I can send more data, but a higher latency means more time an acknowledgement will need, thus lowering speed. Explanation:

Taking the residential DSL example from Wikipedia with a capacity of 2 MBit/s and a network latency of 50 ms. The BDP is 12.5 kB, means: I can send 12.5 kB of data simultaneously, then I will have to wait for the acknowledgement from the one I send those data to. In this case I have to wait 50 ms. During these 50 ms it won't send more data. When I get an ACK, I will send the next 12.5 kB of data. And so on until I transmitted all of it.

You should keep the latency low, because if you double it, your transmission speed will effectively be halved.

That's why you choose servers with the lowest ping results.

 

Now a wonderful explanation of why you lose 10%, sometimes even more, of your speed: Bigger latency. You redirect your encrypted OpenVPN data through LeaseWeb's AS which just lengthens the routing chain: Your ISP uses their routes to route your request to LeaseWeb. LeaseWeb uses their own routes to route your request to your destination. It inevitably means longer routing chains, and that inevitably means higher network latency, and that inevitably means lower speeds.

Given all that it's no surprise your requests through TOR can take a very long time to succeed. The routing chain is just extraordinary long.

[bluesjunior 43]

Thanks guys for the clarification.