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Software Defined Networking COMS 6998-10, Fall 2014

Software Defined Networking COMS 6998-10, Fall 2014. Instructor: Li Erran Li ( lierranli@cs.columbia.edu ) http://www.cs.columbia.edu/ ~lierranli/coms6998-10SDNFall2014/ 9 /29/2014: SDN Programming Language. Outline. Announcements Homework 2 will be posted on Thursday, due in 18 days

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Software Defined Networking COMS 6998-10, Fall 2014

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  1. Software Defined NetworkingCOMS 6998-10, Fall 2014 Instructor: Li Erran Li (lierranli@cs.columbia.edu) http://www.cs.columbia.edu/~lierranli/coms6998-10SDNFall2014/ 9/29/2014: SDN Programming Language

  2. Outline • Announcements • Homework 2 will be posted on Thursday, due in 18 days • Review of previous lecture • Project ideas on scalable controller for cellular WAN • SDN programming language • Maple: generic programming language syntax such as Java, Python • NetKAT: domain specific programming language Software Defined Networking (COMS 6998-10)

  3. Review of Previous Lecture • How do we design scalable software defined networks? • Design scalable controllers • Offload control plane processing to switches • How do we design scalable controllers? • Flat structure multiple controllers • Recursive controller design • Hierarchical controller design Software Defined Networking (COMS 6998-10)

  4. Review of Previous Lecture (Cont’d) • How to offload control plane processing to switches? • Offload to switch control plane • Controller proactively generates the rules and distributes them to authority switches • Authority switches keeppackets always in the data plane and ingress switches reactively cache rules • Offload to switch data plane • Try to stay in data-plane, by default • Provide enough visibility: for significant flows & sec-sensitive flows; Otherwise, aggregate or approximate statistics Software Defined Networking (COMS 6998-10)

  5. Review of Previous Lecture (Cont’d) How do wedividetasksamongcontrollerinstances? • Partition • Controller instances with different computations tasks • Controller instances have only subsets of the NIB • Switches connect to a subset of controller instances • Aggregation • Reduce fidelity of information Software Defined Networking (COMS 6998-10)

  6. Review of Previous Lecture (Cont’d) • How to maintain network information base (NIB)? • Replicated transactions (SQL) storage for strong consistency (more static information) • One-hop memory-based DHT for weak consistency (more dynamic information) Software Defined Networking (COMS 6998-10)

  7. Review of Previous Lecture (Cont’d) Authority Switch Feedback: Cache rules Ingress Switch Forward Egress Switch Redirect First packet Following packets Hit cached rules and forward Offload to switch control plane Software Defined Networking (COMS 6998-10) Source: Minlan Yu

  8. Review of Previous Lecture (Cont’d) • Rule cloning • ASICclones a wildcard rule as an exact match rule for new microflows • Timeout or output port by probability Software Defined Networking (COMS 6998-10)

  9. Review of Previous Lecture (Cont’d) • Rule cloning • ASIC clones a wildcard rule as an exact match rule for new microflows • Timeout or output port by probability Software Defined Networking (COMS 6998-10)

  10. Review of Previous Lecture (Cont’d) • Rule cloning • ASIC clones a wildcard rule as an exact match rule for new microflows • Timeout or output port by probability Software Defined Networking (COMS 6998-10)

  11. Review of Previous Lecture (Cont’d) • Local actions • Rapid re-routing: fallback paths predefinedRecover almost immediately • Multipath support: based on probability dist.Adjusted by link capacity or loads Software Defined Networking (COMS 6998-10)

  12. Outline • Announcements • Homework 2 will be posted on Thursday, due in 18 days • Review of previous lecture • Project ideas on scalable controller for cellular WAN • SDN programming language • Maple: generic programming language syntax such as Java, Python • Frenetic: domain specific programming language Software Defined Networking (COMS 6998-10)

  13. LTE Cellular Network Architecture Base Station (BS) Serving Gateway Packet Data Network Gateway Serving Gateway Internet User Equipment (UE) access core Software Defined Networking (COMS 6998-10)

  14. Current Mobile WANs Two Regions • Organized into rigid and very large regions • Minimal interactions among regions • Centralized policy enforcement at PGWs Software Defined Networking (COMS 6998-10)

  15. Mobile WANs Problems • Suboptimal routing in large carriers • Lack of sufficiently close PGW is a major cause of path inflation • Scalability and reliability • The sheer amount of traffic and centralized policy enforcement • Ill-suited to adapt to the rise of new applications • E.g., machine-to-machine • All users’ outgoing traffic traverses a PGW to the Internet, even for reaching a user served by a close base station in a neighbor region Software Defined Networking (COMS 6998-10)

  16. SoftMoW Motivation Question: How to make the packet core scalable, simple, and flexible for hundreds of thousands of base stations and hundreds of millions of mobile users? • Mobile networks should have fully connected core topology, small logical regions, and more egress points • Operators should leverage SDN to manage the whole network with a logically-centralized controller: • Directs traffic through efficient network paths that might cross region boundaries • Handles high amount of intra-region signaling load from mobile users • Supports seamless inter-region mobility and optimizes its performance • Performs network-wide application-based such as region optimization Software Defined Networking (COMS 6998-10)

  17. SoftMoW Solution Union of Coverage Sum of capacities Latency Matrix VBS GS VMB Policy Core Net RadioAccess Network • Hierarchically builds up a network-wide control plane • Lies in the family of recursive SDN designs (e.g. XBAR, ONS’13) • In each level, abstracts both control and data planes and exposes a set of “dynamically-defined” logical components to the control plane of the level above. • Virtual Base stations (VBS), Gigantic Switches (GS), and Virtual Middleboxes (VMB) Software Defined Networking (COMS 6998-10)

  18. SoftMoW Solution Merge/Split Move and Split • New Dynamic Feature: In each level, the control logic can modify its logical components for optimization purposes • E.g., merge/spilt and move operations Software Defined Networking (COMS 6998-10)

  19. First Level-SoftMoW Architecture Bootstrapping phase: based on location and processing capabilities of child controllers Replace inflexible and expensive hardware devices (i.e., PGW, SGW) with SDN switches Perform distributed policy enforcement using middle-box instances Partition the network into independent and dynamic logical regions A child controller manages the data plane of each regions Software Defined Networking (COMS 6998-10)

  20. Second Level-SoftMoW Architecture • A parent runs a global link discovery protocol • Inter-region links are not detected by BDDP and LLDP • A parent participates in the inter-domain routing protocol • A parent builds virtual middleboxchains and egress-point policies, and dictates to GSs Software Defined Networking (COMS 6998-10)

  21. Hierarchical Traffic Engineering • A parent pushes a global label into each traffic group • Child controllers perform label swapping • Ingress point: pop the global label and push some local labels for intra-region paths • Egress point: pop the local labels and push back the global label Push W Web Voice Pop W2 Push W Pop W1 GS Rules Latency (P1,E2)=300 Latency (P1,E4)=100 Push W Push W2 Pop W Pop W Push W1 Software Defined Networking (COMS 6998-10)

  22. Time-of-day Handover Optimization Abstraction update Handover graph coordination GS Rule: Move Border VBS1 Q: How can an operator reduce inter-region handovers in peak hours? Software Defined Networking (COMS 6998-10)

  23. Project Ideas • Implement a G-switch driver/agent: acts as a shim to allow a G-switch to act like an actual OF switch. • This driver helps to connect any OF controller as a G-switch to its parent OF controller. In this way, installing rule-actions into G-switches and setting up paths on abstract topology becomes like the physical topology. • Driver should translate the messages or states received from the parent OF controller to the underlying topology and periodically pulls states from the local NIB to expose to the parent. • Implement HazelCast on a single controller • Show performance improvement on various applications such as traffic engineering, routing, and failure recovery over the standard in-memory data structures for a single controller. Software Defined Networking (COMS 6998-10)

  24. Project Ideas (Cont’d) • Implement recursive link discovery protocol and the necessary translations in the shim. • Implement RamCloud on a single controller • Show performance improvement on various applications such as traffic engineering, routing, and failure recovery compared with the standard NIB. • Implement an orchestration layer to provide global network view • Use ZooKeeper to dynamically assign controllers to data plane switches as the network becomes larger on top of a single/flat controller. • Implement the hierarchical control plane Software Defined Networking (COMS 6998-10)

  25. Outline • Announcements • Homework 2 will be posted on Thursday, due in 18 days • Review of previous lecture • Project ideas on scalable controller for cellular WAN • SDN programming language • Maple: generic programming language syntax such as Java, Python • Frenetic: domain specific programming language Software Defined Networking (COMS 6998-10)

  26. construct and install OF rules so that similar packets are processed at switches with same action. Step 1 Step 2 examine p and decide what to do with p. A Key Source of Complexity in Openflow Controllers • onPacketIn(p): Software Defined Networking (COMS 6998-10) Source: Andreas Voellmy, Yale

  27. insert rule with “exact match” for p, i.e. match on ALL attributes, with action determined above. Step 1 Step 2 examine p and decide what to do with p. Simple, generic solution using exact matches • onPacketIn(p): Every flow incurs flow setup delay. Software Defined Networking (COMS 6998-10) Source: Andreas Voellmy, Yale

  28. Step 1 Step 2 drop match:{TcpDst=22} action:drop priority:HIGH yes p.TcpDst=22? tcpDst!=22 send to next hop for p.EthDst match:{EthDst=p.EthDst} action:nextHop(p) priority:LOW no Software Defined Networking (COMS 6998-10) Source: Andreas Voellmy, Yale

  29. EthDst:A, TcpDst:80 Switch EthDst:A, TcpDst:22 Controller If p.TcpDst=22: insert rule {prio:HIGH, match:{TcpDst=22}, action:drop } Else: insert rule {prio:LOW, match:{EthDst=p.EthDst},action:nextHop(p.EthDst) Software Defined Networking (COMS 6998-10)

  30. Step 1. Make Decisions User Level Step 2. Generate Rules OF Controller Library Under the hood OF Switches Software Defined Networking (COMS 6998-10) Source: Andreas Voellmy, Yale

  31. Algorithmic Policy Step 1. Make Decisions User Level Step 2. Generate Rules OF Controller Library Under the hood OF Switches Software Defined Networking (COMS 6998-10) Source: Andreas Voellmy, Yale

  32. Algorithmic Policies • Function in a general purpose language that describes how a packet should be routed, not how flow tables are configured. • Conceptually invoked on every packet entering the network; may also access network environment state; hence it has the form: • Written in a familiar language such as Java, Python, or Haskell Software Defined Networking (COMS 6998-10) Source: Andreas Voellmy, Yale

  33. Example Algorithmic Policy in Java Does not specify flow table configutation Route f(Packet p, Env e) { if (p.tcpDstIs(22)) returnnull(); else { Locationsloc = e.location(p.ethSrc()); Locationdloc = e.location(p.ethDst()); Path path = shortestPath(e.links(), sloc,dloc); if (p.ethDstIs(2) return null(); elsereturnunicast(sloc,dloc,path); } } Software Defined Networking (COMS 6998-10) Source: Andreas Voellmy, Yale

  34. How to implement algorithmic policies? • Naive solutions -- process every packet at controller or use only exact match rules -- perform poorly • Static analysis to determine layout of flow tables is possible, but has drawbacks: • Static analysis of program in general-purpose language is hard and is typically conservative • System becomes source-language dependent Software Defined Networking (COMS 6998-10) Source: Andreas Voellmy, Yale

  35. Maple’s approach: runtime tracing 1. Maple observes the dependency of f on packet data. 2. Build a trace tree (TT), a partial decision tree for f. 3. Compile flow tables (FTs) from a trace tree. Software Defined Networking (COMS 6998-10) Source: Andreas Voellmy, Yale

  36. Policy EthDest:1, TcpDst:80 Assert(TcpDst,22) Route f(Packet p, Env e) { if (p.tcpDstIs(22)) returnnull(); else { Locationdloc = e.location(p.ethDst()); Locationsloc = e.location(p.ethSrc()); Path path = shortestPath( e.links(),sloc,dloc); if (p.ethDstIs(2) returnnull(); else returnunicast(sloc,dloc,path); } } false Read(EthDst) 4 Read(EthSrc) 6 path1 Software Defined Networking (COMS 6998-10) Source: Andreas Voellmy, Yale

  37. EthDst:1, TcpDst:22 Trace Tree Policy Assert(TcpDst,22) Route f(Packet p, Env e) { if (p.tcpDstIs(22)) returnnull(); else{ Locationdloc = e.location(p.ethDst()); Locationsloc = e.location(p.ethSrc()); Path path = shortestPath( e.links(),sloc,dloc); if (p.ethDstIs(2) return null(); else returnunicast(sloc,dloc,path); } } Assert(TcpDst,22) true null true false Read(EthDst) ? 4 Read(EthSrc) 6 path1 Software Defined Networking (COMS 6998-10) Source: Andreas Voellmy, Yale

  38. Compile recorded executions into flow table tcpDst==22 3 1 True False 2 ethDst drop 4 2 ethSrc drop 6 port 30 barrier rule: match:{ethDst:4,ethSrc:6} action:[port 30] match:{tcpDst==22} action:ToController Priority Software Defined Networking (COMS 6998-10) Source: Andreas Voellmy, Yale

  39. Basic compilation: in-order traversal & barrier rules tcpDst==22 Priority := 0 Priority := 2 Priority := 1 Priority := 3 accumulated match: {} False True ethDst null {tcpDst:22} {} 4 2 ethSrc null {ethDst:2} (prio:3,{tcpDst:22},action:drop) {ethDst:4} 6 {ethDst:4, ethSrc:6} port 30 (prio:2,{tcpDst:22},action:ToController) barrier rule: (prio:1,{ethDst:2},action:drop) (prio:0,{ethDst:4, ethSrc:6},action:[port 30]) Software Defined Networking (COMS 6998-10) Source: Andreas Voellmy, Yale

  40. Can use priority 0 No effect Basic compilation example result • Trace tree method converts arbitrary algorithmic policies into correct forwarding tables that effectively use wildcard rules. • Deficiencies: • More priorities levels than necessary • More rules than necessary • Annotate TT nodes with extra information to improve compilation (prio:3,{tcpDst:22},action:drop) (prio:2,{tcpDst:22},action:ToController) (prio:1,{ethDst:2},action:drop) (prio:0,{ethDst:4, ethSrc:6},action:[port 30]) Software Defined Networking (COMS 6998-10) Source: Andreas Voellmy, Yale

  41. Optimization 1: Annotate TT nodes with completeness tcpDst==22 {} False True no barrier ethDst drop {tcpDst:22} {} complete 4 2 complete ethSrc drop {ethDst:2} {ethDst:4} (prio:2,{tcpDst:22},action:drop) 6 complete port 30 {ethDst:4, ethSrc:6} (prio:1,{ethDst:2},action:drop) (prio:0,{ethDst:4, ethSrc:6},action:[port 30]) Software Defined Networking (COMS 6998-10) Source: Andreas Voellmy, Yale

  42. Optimization 2: Annotate nodes with priority dependencies tcpDst==22 {} False True 1 ethDst drop {tcpDst:22} {} 4 2 ethSrc drop {ethDst:2} {ethDst:4} (prio:1,{tcpDst:22},action:drop) 6 port 30 {ethDst:4, ethSrc:6} (prio:0,{ethDst:2},action:drop) (prio:0,{ethDst:4, ethSrc:6},action:[port 30]) Software Defined Networking (COMS 6998-10) Source: Andreas Voellmy, Yale

  43. Improved compilation result (prio:1,{tcpDst:22},action:drop) (prio:0,{ethDst:2},action:drop) (prio:0,{ethDst:4, ethSrc:6},action:[port 30]) Software Defined Networking (COMS 6998-10) Source: Andreas Voellmy, Yale

  44. Maple Status • Maple has been implemented in Haskell using the McNettleOpenflow controller, which implements Openflow 1.0. • The implementation includes several other features: • Incremental TT compilation, to avoid full recompilation on every update. • Trace reduction, to ensure traces and trace trees do not contain redundant nodes. • Automatic and user-specified invalidation, to support removing and updating TT and FT when network state changes. Software Defined Networking (COMS 6998-10) Source: Andreas Voellmy, Yale

  45. Summary: Contributions • Algorithmic policies provide a simple, expressive programming model for SDN, eliminating a key source of errors and performance problems. • Maple provides a scalable implementation of algorithmic policies through several novel techniques, including: • runtime tracing of algorithmic policies, • maintaining a trace tree and compiling TT to flow tables to distribute processing to switches; • using TT annotations to implement compiler optimizations such as rule and priority reductions. Software Defined Networking (COMS 6998-10) Source: Andreas Voellmy, Yale

  46. Outline • Announcements • Homework 2 posted due in 18 days • Next lecture: first half by Josh Reich from Princeton on Pyretic • Review of previous lecture • SDN programming language • Maple: generic programming language syntax such as Java, Python • Frenetic: domain specific programming language Software Defined Networking (COMS 6998-10)

  47. Key questions: • What are the right abstractions for programming software-defined networks? • How can we engineer trustworthy implementations that provide assurance? Software Defined Networking (COMS 6998-10) Source: Nate Foster, Cornell

  48. Modular Abstractions Software Defined Networking (COMS 6998-10) Source: Nate Foster, Cornell

  49. Combining Functionality • One monolithic • application Monitor + Route + Load Balance + Firewall Controller Platform • Challenges: • Writing, testing, and debugging programs • Reusing code across applications • Porting applications to new platforms Software Defined Networking (COMS 6998-10) Source: Nate Foster, Cornell

  50. Route Monitor + Route + Monitor Software Defined Networking (COMS 6998-10) Source: Nate Foster, Cornell

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