These topologies are composed of virtual routers, which use a portion of the resources available in physical ones, and virtual links, which are mapped to physical paths composed of one or more physical links and their respective intermediate routers.
Those based on network virtualization allow the definition of virtual networks composed of virtual routers and links; these are then hosted by routers and links of the real network called "substrate network".
Table 3 Types of virtual networks Type # of virtual routers # of cores Bandwidth (uniformly distributed) 1 5 2 100Mbps–200Mbps 2 8 3 200Mbps–300Mbps 3 10 6 300Mbps–400Mbps.
Constraint (C 2) limits the number of virtual routers that can be allocated on a physical router per request, with only a single virtual router can be allocated to a given physical router per request.
In several studies[5, 6], the mapping of virtual links is separated from the mapping of virtual routers.
In virtual network environments, providing proper authentication is complicated by factors such as the federation of virtual networks or mobility of virtual routers and links.
Information interception, physical resource overloading, physical resource failure, and software vulnerability exploitation are aggravated by the fact that a number of virtual routers may share a physical router.
As network virtualization is new emerging field, there is few literature on some important field like the migration of virtual router and link etc. Chen et al. uses VROOM [56] router architecture to provide energy-saving IP-WDM network architecture [83] by the process of virtual router migration.
Virtual Machine Monitors are used to instantiate virtual routers, and virtual links are established between them, regardless of physical network topology.
They differ in terms of the number of requested virtual routers, the number of cores to instantiate each virtual router and in the guaranteed bandwidth per virtual link being requested.
