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Software Networks. Guy PujolleЧитать онлайн книгу.

Software Networks - Guy Pujolle


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as much as we want. Finally, the third principle is that of automation – the best possible automation – of the operations carried out on the network, whether for management or for control. This automation is obtained thanks to centralization.

      The storage, processing and the network use virtual machines associated with each of these domains that share the hardware resources. We can equally find three types of virtual machines on the same server. In order for the environment to be able to be executed without problems, we must add security, management and control virtual machines. Today, a company needs to have all five of these groups of virtual machines set up in order to constitute an operational information system. These five domains are shown in Figure 2.2.

      Figure 2.1. The three basic principles. For a color version of the figure, see www.iste.co.uk/pujolle/software2.zip

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      Figure 2.2. The five domains necessary for the life of a company

      The five domains described above can be put in place by way of virtual machines associated with each of the domains. The whole computing environment of a company can thus be concentrated in the Cloud in the form of virtual machines distributed in datacenters. This environment is illustrated in Figure 2.3 by datacenters containing the virtual machines necessary for the construction of the company’s computing system.

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      Figure 2.3. Virtualization of the five domains

      In addition to this environment, there are applications that may be of two types: business applications and applications to control or orchestrate the environment itself. The search for new products has therefore turned towards autopilot systems, which are also referred to as orchestrators in the literature. The complete environment, which is vital to the functioning of a company, is shown in Figure 2.4, which shows the importance of the orchestrator in the general architecture of informational and operational systems.

      Figure 2.4. The pilot program

      In order for this new world of SDN to have a chance of being successful, it has to be standardized. This standardization was carried out by the ONF (Open Networking Foundation), which was set up under the auspices of large companies in the USA, following the proposal of this architecture by Stanford University and Nicira.

      The architecture proposed by the ONF is shown in Figure 2.5. It comprises three layers. The bottom layer is an abstraction layer, which decouples the hardware from the software, and is responsible for data transport. This level describes the protocols and algorithms that enable IP packets to advance through the network to their destination. This is called the infrastructure plane. The second layer is the control plane. This plane contains the controllers providing control data to the data plane so that the data are channeled as effectively as possible. The ONF’s vision is to centralize control in order to facilitate the recovery of a great deal of information on all the clients. The centralized controller enables obtaining a sort of intelligence. The infrastructure to be managed is distributed between the controllers. Of course, we need to take account of the problems caused by a centralized environment, and therefore duplicate the decision elements.

      Finally, the uppermost layer, the application plane, is responsible for the applications needed by the clients and storage, computation, network, security and management applications. This layer introduces the programmability of the applications, and sends the controller all of the necessary information to allow the opening of the software networks meeting the needs of the applications. This layer also includes control, orchestration and management applications that are vital to the good functioning of the company’s computing system. The application plan must be able to channel the information required to open up the network that corresponds to the application towards the controller. Any new service can be introduced quickly, and will give rise to a specific network if it cannot be embedded on a pre-existing network.

      The ONF architecture is shown in Figure 2.5, with its three layers: the application layer and programmability, the control layer with centralized intelligence, and abstraction at the infrastructure layer. We will come back to look at the interfaces between these layers, which are important for the compatibility of products from different vendors. The ONF has standardized the intermediary layer and the interfaces. Certain parts of the architecture are taken up by other standardization organizations so as to conform to the legal standards.

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      Figure 2.5. The ONF architecture

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      Figure 2.6. The SDN architecture

      In addition to the two interfaces described above, there are also the eastbound and westbound interfaces. The eastbound interface enables two controllers of the same type to communicate with one another and make decisions together. The westbound interface must


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