Towards a Framework for Network Control Composition

1. Towards a Framework for Network Control Composition T. S. Eugene Ng Rice University Hong Yan Carnegie Mellon University

2. Many Network Controls Manage Network State • Best effort routing • Traffic engineering • QoS routing • VPN tunneling • Packet filtering • Planned maintenance • Policy based inter-domain routing • … • Implemented by a variety of • Distributed protocols • Remote configurations • How do they coordinate?

3. Comparing Network Controls to Processes Operating System Internet Control Plane vs Processes Dist. protocols, remote config. Process scheduling ? Process synchronization ?? Inter-process communication ??? Memory management ????

4. ISP Z ISP Y B3 B4 B1 B2 A4 C1 C2 C3 A3 ISP X A1 A2 “Inter-Process Communication” • ISP Y is the preferred egress • How to “tell” OSPF this policy? • Overload semantics of OSPF link weight • Prone to policy violations • Traffic engineering, link failure, etc

5. ISP Z ISP Y B3 B4 B1 B2 A4 C1 C2 C3 A3 ISP X A1 A2 “Process Scheduling” • A packet filter needs to be placed on the flow path • OSPF re-routes when network changes • Who “schedules” the packet filter control to run after routing changes?

6. ISP Z ISP Y B3 B4 B1 B2 A4 C1 C2 C3 A3 ISP X A1 A2 “Process Synchronization” • Want to perform planned maintenance on C1 • How to re-config network in a systematic manner? • How to ensure re-config is completed before taking down C1? QoS Routed Traffic

7. “Memory Management” • Hardware tables shared by all network controls • What does each network control see? • All table space? • Only free table space? • How to share limited physical space? • Virtual table abstraction? Paging?

8. Operating Platform Approach • Re-factor existing nuts and bolts network controls into simple control applications • Applications are not distributed protocols • Run control applications on operating platform to achieve control objectives • Distributed nature of network control handled by underlying system

9. 4D-like Architecture Network Control Applications Operating Platform Meta Management System Node 2 Node 3 Node 1

10. Operating Platform Services • Network and node abstractions • Topology, hardware tables, link characteristics, load, etc • Interfaces for writing network state • Control coordination • Inter-process communication • Synchronization • Scheduling • Resource management • Coordinated sharing of hardware resources • Network protection • Prevent exceeding hardware resource limits • Link bandwidth, hardware tables, etc

11. ISP Z ISP Y QoS Routing Shortest Path Routing Network Maintenance B3 B4 Inter-Domain Routing Policy B1 B2 A4 C1 C2 C3 A3 ISP X A1 A2 Operating Platform Network View Virtualization Operating Platform Meta Management Interface

12. Potential Benefits • Remove implicit dependencies between controls • Prevent unintended side-effects of ad hoc control composition • Network control re-configurations are triggered systematically • Protect network from faulty network controls • A better environment for innovation and evolution

13. Summary • Ad hoc network control composition leads to unwanted complexity and fragile systems • It is time to move towards a more principled framework analogous to an operating system • Challeges: Develop abstractions and services for a network control platform • Network abstractions and interfaces • Inter-process communication • Scheduling • Synchronization • Resource management • Protection