1. Department of Electrical and Computer Engineering Abhishek Dwaraki 1 Srini Seetharaman 2, Sriram Natarajan 3, Tilman Wolf 1 1. Department of Electrical and Computer Engineering, University of Massachusetts, Amherst, MA, USA 2. Infinera Inc., San Francisco, CA, USA 3. Deutsche Telekom Inc., Silicon Valley Innovation Center, Mountain View, CA, USA This material is based upon work supported by the National Science Foundation under Grant No. 1421448 GitFlow: Flow Revision Control for Software- Defined Networks

2. 2 Department of Electrical and Computer Engineering Inconsistencies in SDNs Device X Data plane Controller App 1App 2 Rule #Ingress Port Source IPDest IPInstructions 1Port 11.2.*.*3.4.5.*DROP 2Port 2**FWD(Port3) 3Port 2*10.1.1.1FWD(Port 4) 1. App1 inserts specific flow rule to direct traffic 2. App2 inserts general rule that diverts traffic elsewhere  Fundamental example, other complex ones may exist  Can be introduced through alternate interfaces, e.g., data plane devices, configuration points

3. 3 Department of Electrical and Computer Engineering Unified Consistent State – Goals and Challenges  Network state abstracted into the SDN framework Goal – Updated network state always available Challenge – Real time performance  Unified, consistent view across framework Goal – Support multiple interfaces Challenge – Concurrency mechanisms to ensure consistency  Up-to-date network state to make control plane decisions Goal – Ensure availability to all entities Challenge – Clean abstraction required Existing approaches Statesman, FortNOX, VeriFlow

4. 4 Department of Electrical and Computer Engineering Required Concurrency Safeguards Author identification Safety and provenance Author Tracking Track state transformation Information generation Change Tracking Control ownership Prevent unauthorized modification State Safety Detect and resolve conflicts Generate matches for mutability, safety Conflict Resolution Metadata generation, storage Useful to tools on top of framework Annotations

5. 5 Department of Electrical and Computer Engineering Network State versus Software Code  Network State State evolves over time Multiple players involved Programmability challenges State conflicts Security violations  Software Code Code evolves over time Multiple code authors Programmability challenges Merge conflicts Authorization violations Revision control (Git) manages this elegantly. Why not treat network state like software code?

6. 6 Department of Electrical and Computer Engineering Existing Solutions Current Solution Author Tracking Change Tracking State SafetyConflict Detection/Resol ution Annotations Statesman ✕✕✔✔✕ FortNOX ✕✕✔✔✕ FlowSpace Firewall ✔✕ partial ✕✕ VeriFlow ✕✕✔✔✕

7. 7 Department of Electrical and Computer Engineering GitFlow Architecture

8. 8 Department of Electrical and Computer Engineering Scenario 1 – Flow Table Evolution  Flow state – evolves over time  Revision control – aids understanding state evolution Controller Rule #Ingress PortSource IPDest IPInstructions 1Port 11.2.*.*3.4.5.*DROP 2Port 2**FWD(Port3) 3Port 2*10.1.1.1FWD(Port 4) Rule #Ingress PortSource IPDest IPInstructions 1Port 11.2.*.*3.4.5.*DROP 2Port 2**FWD(Port3) Rule #Ingress PortSource IPDest IPInstructions 1Port 11.2.*.*3.4.5.*DROP 2Port 2**FWD(Port5) 3Port 2*10.1.1.1FWD(Port 4) Switch Add Flow Modify Flow

9. 9 Department of Electrical and Computer Engineering Scenario 2 – Identifying security violations  Malicious updates affect packet forwarding behavior  AAA – vets applications/bundles for malicious activity  Revision control + AAA = higher security Revision control – can identify when what was changed and who authorized it AAA – corrective measures to ensure secure operation in future

10. 10 Department of Electrical and Computer Engineering Scenario 3 – Troubleshooting  Previous approaches - identify errant states, cannot prevent reoccurrence  Revision control – can avoid transitions to errant states using annotations  Networks as autonomous entities What is important - Self-healing How it is achieved - automated troubleshooting tools How can revision control help - exercising more intricate level of inspection

11. 11 Department of Electrical and Computer Engineering Summary  Inconsistencies exist in network state information  Revision control is a comprehensive solution  Treat network state like code/files  revision and abstract  Revision control provides required concurrency guarantees  Very relevant use cases in state evolution, troubleshooting  Please refer paper for more details