http://dl.acm.org/citation.cfm?id=1921162
http://yuba.stanford.edu/~casado/virt-presto.pdf
ref [9] distributed firewall
ref [16] virtual routers on the move VROOM
network services (e.g., policy routes, ACLs, QoS, isolation domain) relies on topology-dependent configuration state [4,9,16] … manual reconfiguration
virtualization not foreign to networks, … component failover (e.g., VRRP). However, these primitives have not significantly changed the operational model of networking, and operates continue to screen scrape CLIs with scripts in order to achieve a limited degree of automation
roughly, the idea is to introduce a new network-wide software layer that exposes one or more logical forwarding elements (similar to [10])
the control software reads and writes to these logical forwarding elements… allows network state (forwarding and configuration) to be largely decoupled from the underlying hardware
the compelling use cases demand a many-to-many mappnig between the logical and physical forwarding elements …
not provide an adequate abstraction upon which to build topology-independent control software
resource pool of forwarding capacity, and hardware changes do not disrupt the logical view of the system
in order to provide application-independent virtualization, we chose to virtualize the forwarding plane
“network hypervisor” for our proposed software layer to intentionally call to mind the concept of virtualization
network "slicing" are not independent of the underlying physical infrastructure, but instead are a way of multiplexing infrastructure
our hypervisor maintains these abstractions, providing the ability to create one or more logical (possibly interconnected) forwarding elements, … these elements also have associated capacities (line speeds, cross-section bandwidth, table sizes) … use this logical abstraction to express the desired network functionality …
a recent line of research (onix, nox, 4D) that provides global network control
if a logical forwarding decision is distributed across multiple physical components, the "next hop" will be the next physical component that will continue to execute the logical forwarding component ...
In our implementation, the network hypervisor is being built as a distributed system that operates as an OpenFlow controller.
End-host virtualization requires switching capability on a host (implemented in the host hypervisor [13]). This is generally realized as an L2 software switch (generally termed vswitch) which connects all co-resident VMs on a physical host.