Information Technology Reference
In-Depth Information
Each path computing APP on NOS can compute the routing path (just a routing
path segment such as VP1 or VP2) within its domain. To compute a complete end to
end or global routing path, the NOS should at least know other abstracted virtual net-
work view. The abstracted virtual network view is the minimum information for glob-
al network reachability. Then the path computing APP can compute and install a
routing path by the restful API provided by NOS into OpenFlow switches.
For the virtual network view, each NOS should store a mapping table between the
physical network and the abstracted virtual network views which is showed in the
table of Figure 3. To achieve large-scale scalability, each SDN domain can be ab-
stracted to a node with multi-ports and multiple bandwidths like network 2. Other
NOSes treat the network domain 2 as an abstract node with 3 ports and 3 links. After
exchanging the network views, each NOS can further provide additional specific net-
work view [1] like access network view, edge network view.
3.3
High Speed Bridge Exchange Mechanism
After the controller discovery process, each controller learns all the addresses of their
peers. Then all the controllers can establish a virtual full mesh topology based on
TCP/ SSL shown in Figure 4.
Fig. 4.
TCP/SSL based full mesh topology for EWBridge
All the SDN peers are equal to each other. For the network event such as link fail-
ure, adding/ deleting switch, adding/ deleting IP prefixes, each controller can sub-
scribe to other controllers' database events. EWBridge adopts the publish/ subscribe
system to deliver update messages. Once an event is triggered, the corresponding
controller will push the event to all the subscribers simultaneously. Each controller
can get the update message directly from the controller it cares.
Considering the success of BGP (Border Gateway Protocol), similarly we design a
network view message exchange protocol with a finite state machine and define 5
types of messages: OPEN, UPDATE, NOTIFICAION, KEEPALIVE, VIEW-
REFRESH. In which, the UPDATE message is delivered by the format of JSON file,
and the rest of messages are by the format of data packet. Compared with the BGP
protocol, the EWBridge system mainly changes the UPDATE message into JSON file
format, and simplifies the finite state machine.
