Quality of Service

Hi guys!

Welcome again to this new post, where we are going to talk about Quality of Service (QoS). This is an important item in nowadays networks and sometimes it doesn’t have all the importance it should, so in this post we are going to explain how does it works and why is it so important.

Some years ago, different types of traffic were sent through different networks, but nowadays the idea is to integrate all services in the same network because it simplify the management of the networks and also reduce the cost of them. To manage all the traffic in a unique network, providing the service we want at every type if traffic, we must use QoS, a method to send different types of traffic with different priorities in a network.

There are various aspects we can consider to determine the quality of service of a network. The most used are the following:

• Throughput: bit rate
• Latency: time for each packet to reach its destination
• Jitter: different delays of packets from the source to reach the destination
• Packet loss: packets arriving to the destination
• Errors: bit errors in some packets

So analyzing these factors, we can determine the quality of service of our network and we can try to improve it as much as posible.

In the case of a data center, the use of QoS is very important because it manages a lot of traffic types, some more important (in terms of order of arrival) than others. For example, video streaming traffic must be priority in front of database traffic, because if two persons are doing a videoconference (for example) the video must arrive in (nearly) real time, otherwise these two person won’t understand each other, but if database traffic arrives a little bit later, no one is going to notice it.

Many of the methods we use to configure nowadays networks supports QoS, and provides different ways to implement it. So Ethernet (802.1q (VLANs)), MPLS (diffserv), ATM, FiberChannel… give us the opportunity to easily implement QoS and give the appropriate priority level to each type of traffic that circulates through a network. It’s important also to know that we have to separate the different types of traffic in a network (which will circulate in the same wire), a thing that we can do through various methods like VLANs, SLAs, virtual switching… It can also be very useful some methods that give us some manufacturers like VMWare, Cisco, Arista Networks…

To resume, we can say that QoS is a very important method used in all the modern data centers to get a well behavior of the traffic transmitted and received. But also it can harm non-priority traffic that is transmitted through our network, although in most cases it won’t affect the network performance. 

Hope you have learned something new in this post, and we will extend the explanation of this topic in a next post, explaining some devices and methods to implement QoS on the data center we are designing.

See you soon!