VoIP traffic: Could it be managed inside a data center?

We will start with a brief introduction, where we will give you a general overview of what VoIP is and how it works. We call VoIP the voice over Internet: it is based on a way of making calls over the same network. The audio data collected from the microphone of the originating device is converted to digital information, allowing it to be transmitted over the network and once the destination device receives it, it is processed to retrieve the voice. In this way, an apparently analog connection is established.

The transport of VoIP packets travels over UDP, which is a non-connection-oriented protocol that does not confirm the delivery of packets because it is not critical to lose any of them and it also requires very low latency. This is why for this type of use it is more efficient than using TCP, since we avoid the initial negotiation and subsequent confirmation of the arrival of each packet, which would directly affect the quality of the call, since the users, for example, could hear each other with some delay.

As VoIP is a type of traffic that is very sensitive to packet loss and requires low latency, there is a need to implement protocols to try to ensure that packets arrive as soon as possible. One of the most widely used by telecommunications operators and companies is QoS (Quality of Service), which allows the integration of all kinds of different services in the same network, offering better control and a more positive experience for users in the use of different applications.

One of the main utilities of QoS is to prioritize certain traffic over the rest through the Differentiated Services (Diffserv) architecture defined by the IETF, ensuring lower latency and avoiding packet loss in the event of network congestion by differentiating traffic, which is divided into classes. The resources used to achieve this classification according to the required quality of service are obtained through the following functional blocks: traffic conditioners, which are typically implemented in the ingress interface of the router that delimits the DiffServ domain, and PHBs (Per-hop behaviors), which are implemented in all the routers of the domain. The later have a series of classes already predefined by the service itself, of which we are interested in the Expedited Forwarding (EF), which is the one that defines the premium or top priority user traffic, which usually includes voice and video traffic.

Having seen its operation more closely and taking into account several of the proposals that were discussed during the interesting talk by the company Fortinet which we attended as students a couple of weeks ago, one of the solutions proposed to implement VoIP in a CPD is to use, on the one hand, a virtualized physical server containing a virtual machine with software that acts as a PBX server providing the functionality of a PBX among others in the same local network and all this accompanied by a web interface such as Asterisk for managing the users this way. 

On the other hand, it could also be interesting to include the QoS service in all the routers that make up the DPC domain (boundary & core), taking into account the possible routers or switch-routers as well as firewalls that may be found in the path traced by the communication of a call between users. Currently, there are other alternatives in terms of VoIP implementations in a DPC, going fully into the world of the cloud with the same PBX. A cloud PBX implements a telephone system using a PBX in the cloud as described above, allowing the classic calls to be made with the added benefit of having better control of the network and not having to bear the burden of maintaining this service.

In the preparation of the project that we have to do in the subject of "Network Management and Planning", we will investigate further on the inclusion of this service studying what could be the limitations that should be dealt with and we will keep you informed about our progress in subsequent posts. Thank you very much for your time spent reading us!

Arturo Moseguí and Enric Sasselli