Each virtual network in a network virtualization environment is a collection of virtual nodes and virtual links. Essentially, a virtual network is subset of underlying physical network resources. Network virtualization proposes decoupling of functionalities in a networking environment by separating the role of traditional ISPs into InP’s (Infrastructure Providers) who manages the physical infrastructure and SP’s (Service Providers) who creates virtual networks by aggregating resources from multiple InP’s and offers end-to-end network services. In order to build virtual network enabled networks the following specifications must be fulfilled. Robustness: The network should continue to operate in the event of node or link failure. Manageability: The InP must have a view of the underlying physical topology, state and other parameters associated with the equipment providing the virtual network. Traffic and network resource control: Traffic engineering and management techniques performed by the InP must not restrict the basic operation of a Virtual network. Isolation: Mechanisms for isolation between virtual networks must be provided. It must be guaranteed that malfunctioning virtual networks do not affect the performance of other virtual networks sharing the same resources. Scalability: Any technical solution must be scalable to cope up with any number of virtual networks. On-demand provisioning: It must be possible to create, modify and remove virtual networks dynamically on request. In general a virtual network will have a limited lifespan.
6.2 Virtual network ID, Virtual link ID:
In order to control virtual networks spanning multiple infrastructure domains, the virtual networks must be identified by a virtual network ID. Additionally the virtual links are also needed to be identified which can be done by using virtual link ID. One of the solution would consist of simply mapping the virtual link ID to whatever data link layer specific tag is in use. A number of available link virtualization techniques such as ATM, Ethernet VLAN could be used for this purpose. This Virtual link ID can be used for both virtual link identifier and a tag for data forwarding.
Scalability is a major requirement for virtual networks. For this reason, virtual link aggregation will constitute an important requirement for network virtualization. Virtual link aggregation can be defined as a set of virtual links that follow a common path and are similarly treated between a pair of virtual nodes. It can be performed by carrying at least two types of identifiers in the data plane, one for virtual network identification and another for hop-by-hop forwarding. Hence, virtual link aggregation enhances scalability and also improves performance.
7. Building Virtual Networks
7.1 The VNP- InP interface:
The VNP (virtual network provider) / InP interface is a key component of network virtualization architecture. The virtual network provider is able to request the...