TCP splits data into packets, and the size of the packets is dictated by the TCP Window size: bigger this value, more data can be transferred in a single transmission. But on top of it, we need to run multiple protocols, one above the other, like TCP over IP. What’s the catch? The link speed we usually talk about is the pure cable link speed. I’m not going to repeat what has been already written in a perfect way by others, so if you want to learn more, read this post by Brad Hedlund. Even on a local network, where latency is close to zero, there are other parameters that may impact the final speed. Why latency is important?īecause to ignore it, together with other parameters, leads to false results!

And if my bandwidth is 125MBps, it means I can transfer 125MB every second. – 1 Gb ethernet link, divided by 8, gives me 125 MBpsĪnd so on. After all, when we run a ping command to check if a host is connected, latency is always “below 1 ms” :įor this reason, it’s not uncommon to calculate the maximum transfer speed by simply looking at the available bandwidth: In a local network it’s easy to apply some approximation and declare that the processing delay is 0, and also that the multiple switches in between two hosts don’t add additional latency.

So, simply said, latency is the time that it takes to a packet to go from source to destination. The source host, switches, routers, firewalls, the target host each “hop” adds time to the total time that a packet needs to reach its destination. Our computer networks are not even close to that speed, because first of all usually our connections are not made with optical fiber (which would eventually be as fast as light) but with electric cables and so transmissions over these media are slower, but also because there are many appliances between source and destination that need to manipulate the packet. It takes time to a photon to go from point A to point B, and for example the light generated by the Sun takes 8 minutes to reach the Earth. What is latency?Īs fast as it can be, even light speed is not infinite. There are some topics that are obscure for many, like Layer2 vs Layer3, BGP, Spanning Tree, but there is one topic that is really important even for infrastructure guys, yet it’s almost unknown to them: Latency. Especially in the virtualization market, many people are usually well prepared when it comes to infrastructure, servers and storage, but I found out that the weakest point is many times networking.

In my job, I have to learn a lot about multiple topics of IT. 0 Flares Twitter 0 Facebook 0 LinkedIn 0 Email - 0 Flares ×

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