Quality of service implementations that utilize Integrated Services (IntServ) provides end-to-end service guarantees to IP traffic traversing campus networks. IntServ allows applications to signal their QOS requirements to the network while providing strong guarantees to individual traffic flows from sender to receiver,however IntServ quality of service architectures require all routers to implement a reservation protocol and maintain state information for all flows.
Computation of routes and the maintenance of states requires copious amounts of RAM and Processing power in order to scale to support large route and flow tables. Routers and switches built on merchant Asic are typically equipped with a limited amounts of ram and processing power when compared to the typical X86 computer. The price of multi-core CPUs and DDR memory modules are at an all time low and this reality should allow the development of a x86 based SDN controller that will be able to incrementally store router flow and link states.
SNMP or NETFLOW could be used to measure various constraints such as bandwidth,latency and delay. The values measured could be used to perform constrained shortest path route calculations for each node and also to modify route or congestion management characteristics on a per interface basis.