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Software Defined Networking COMS 6998-8, Fall 2013 Instructor: Li Erran Li 6998-8SDNFall2013/

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Presentation on theme: "Software Defined Networking COMS 6998-8, Fall 2013 Instructor: Li Erran Li 6998-8SDNFall2013/"— Presentation transcript:

1 Software Defined Networking COMS 6998-8, Fall 2013 Instructor: Li Erran Li (lierranli@cs.columbia.edu) http://www.cs.columbia.edu/~lierranli/coms 6998-8SDNFall2013/ 9/24/2013: SDN Programming Language

2 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 9/24/13 Software Defined Networking (COMS 6998-8) 2

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 9/24/13 Software Defined Networking (COMS 6998-8) 3

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 keep packets 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 9/24/13 Software Defined Networking (COMS 6998-8) 4

5 Review of Previous Lecture (Cont’d) How do we divide work among controller instances? 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 9/24/13 Software Defined Networking (COMS 6998-8) 5

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) 9/24/13 Software Defined Networking (COMS 6998-8) 6

7 Following packets Review of Previous Lecture (Cont’d) Ingress Switch Authority Switch Egress Switch First packet Redirect Forward Feedback: Cache rules Hit cached rules and forward Offload to switch control plane Source: Minlan Yu 9/24/13 Software Defined Networking (COMS 6998-8) 7

8 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 9/24/13 Software Defined Networking (COMS 6998-8) 8

9 A Key Source of Complexity in Openflow Controllers onPacketIn(p): examine p and decide what to do with p.Step 1 construct and install OF rules so that similar packets are processed at switches with same action. Step 2 9/24/13 Software Defined Networking (COMS 6998-8) 9 Source: Andreas Voellmy, Yale

10 Simple, generic solution using exact matches onPacketIn(p): examine p and decide what to do with p.Step 1 insert rule with “exact match” for p, i.e. match on ALL attributes, with action determined above. Step 2 Every flow incurs flow setup delay. 9/24/13 Software Defined Networking (COMS 6998-8) 10 Source: Andreas Voellmy, Yale

11 Step 1Step 2 p.TcpDst=22 ? dropdrop match:{TcpDst=22} action:drop send to next hop for p.EthDst match:{EthDst=p.EthDst} action:nextHop(p) yes no priority:HIGH priority:LOW tcpDst!=22 9/24/13 Software Defined Networking (COMS 6998-8)Source: Andreas Voellmy, Yale 11

12 EthDst:A, TcpDst:8 0 Controller Switch EthDst:A, TcpDst:2 2 LowEthDst:APort 1 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) 9/24/13 Software Defined Networking (COMS 6998-8) 12

13 OF Switches User Level Under the hood OF Controller Library Step 1. Make Decisions Step 2. Generate Rules 9/24/13 Software Defined Networking (COMS 6998-8) 13 Source: Andreas Voellmy, Yale

14 Algorithmic Policy OF Switches OF Controller Library Step 1. Make Decisions Step 2. Generate Rules User Level Under the hood 9/24/13 Software Defined Networking (COMS 6998-8) 14 Source: Andreas Voellmy, Yale

15 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 9/24/13 Software Defined Networking (COMS 6998-8) 15 Source: Andreas Voellmy, Yale

16 Example Algorithmic Policy in Java Route f(Packet p, Env e) { if (p.tcpDstIs(22)) return null(); else { Location sloc = e.location(p.ethSrc()); Location dloc = e.location(p.ethDst()); Path path = shortestPath(e.links(), sloc,dloc); return unicast(sloc,dloc,path); } Does not specify flow table configutation 9/24/13 Software Defined Networking (COMS 6998-8) 16 Source: Andreas Voellmy, Yale

17 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 9/24/13 Software Defined Networking (COMS 6998-8) 17 Source: Andreas Voellmy, Yale

18 Maple ’ s approach: runtime tracing PrioMatchAction 1tcpDst:22 ToControlle r 0ethDst:2discard 0ethDst:4, ethSrc:6port 30 PrioMatchAction 1tcpDst:22 ToControlle r 0ethDst:2discard 0ethDst:4, ethSrc:6port 30 PrioMatchAction 1tcpDst:22 ToControlle r 0ethDst:2discard 0ethDst:4, ethSrc:6port 30 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. 9/24/13 Software Defined Networking (COMS 6998-8) 18 Source: Andreas Voellmy, Yale

19 Route f(Packet p, Env e) { if (p.tcpDstIs(22)) return null(); else { Location sloc = e.location(p.ethSrc()); Location dloc = e.location(p.ethDst()); Path path = shortestPath( e.links(),sloc,dloc); return unicast(sloc,dloc,path); } EthDest:1, TcpDst:80 Assert(TcpDst, 22) false Read(EthSr c) Read(EthDs t) path1 1 2 Policy 9/24/13 Software Defined Networking (COMS 6998-8) 19 Source: Andreas Voellmy, Yale

20 EthDst:1, TcpDst:2 2 1 2 ? true null true Assert(TcpDst,22) Policy Trace Tree false Route f(Packet p, Env e) { if (p.tcpDstIs(22)) return null(); else { Location sloc = e.location(p.ethSrc()); Location dloc = e.location(p.ethDst()); Path path = shortestPath( e.links(),sloc,dloc); return unicast(sloc,dloc,path); } Assert(TcpDst, 22) Read(EthSr c) Read(EthDs t) path1 9/24/13 Software Defined Networking (COMS 6998-8) 20 Source: Andreas Voellmy, Yale

21 Compile recorded executions into flow table tcpDst==2 2 False ethDst 2 drop 4 port 30 ethSrc 6 drop True match:{tcpDst==22} action:ToController match:{ethDst:4,ethSrc:6} action:[port 30] Priority barrier rule: 1 2 3 9/24/13 Software Defined Networking (COMS 6998-8) 21 Source: Andreas Voellmy, Yale

22 Basic compilation: in-order traversal & barrier rules accumulated match: {} {tcpDst:22} (prio:3,{tcpDst:22},action:drop) {} {ethDst:2} {ethDst:4} {ethDst:4, ethSrc:6} (prio:0,{ethDst:4, ethSrc:6},action:[port 30]) (prio:1,{ethDst:2},action:drop) (prio:2,{tcpDst:22},action:ToController) Priority := 0Priority := 1Priority := 2Priority := 3 barrier rule: tcpDst==2 2 ethDst 2 null 4 port 30 6 null True ethSrc False 9/24/13 Software Defined Networking (COMS 6998-8) 22 Source: Andreas Voellmy, Yale

23 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:0,{ethDst:4, ethSrc:6},action:[port 30]) (prio:1,{ethDst:2},action:drop) (prio:2,{tcpDst:22},action:ToController) No effect Can use priority 0 9/24/13 Software Defined Networking (COMS 6998-8) 23 Source: Andreas Voellmy, Yale

24 Optimization 1: Annotate TT nodes with completeness tcpDst==2 2 False ethDst 2 drop 4 port 30 ethSrc 6 drop True {} {tcpDst:22} (prio:2,{tcpDst:22},action:drop) {} {ethDst:2}{ethDst:4} {ethDst:4, ethSrc:6} (prio:0,{ethDst:4, ethSrc:6},action:[port 30]) (prio:1,{ethDst:2},action:drop) no barrier complete 9/24/13 Software Defined Networking (COMS 6998-8) 24 Source: Andreas Voellmy, Yale

25 Optimization 2: Annotate nodes with priority dependencies tcpDst==2 2 False ethDst 2 drop 4 port 30 ethSrc 6 drop True {} {tcpDst:22} (prio:1,{tcpDst:22},action:drop) {} {ethDst:2} {ethDst:4} {ethDst:4, ethSrc:6} (prio:0,{ethDst:4, ethSrc:6},action:[port 30]) (prio:0,{ethDst:2},action:drop) 1 9/24/13 Software Defined Networking (COMS 6998-8) 25 Source: Andreas Voellmy, Yale

26 Improved compilation result (prio:1,{tcpDst:22},action:drop) (prio:0,{ethDst:4, ethSrc:6},action:[port 30]) (prio:0,{ethDst:2},action:drop) 9/24/13 Software Defined Networking (COMS 6998-8) 26 Source: Andreas Voellmy, Yale

27 Maple Status Maple has been implemented in Haskell using the McNettle Openflow 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 cha nges. 9/24/13 Software Defined Networking (COMS 6998-8) 27 Source: Andreas Voellmy, Yale

28 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. 9/24/13 Software Defined Networking (COMS 6998-8) 28 Source: Andreas Voellmy, Yale

29 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 9/24/13 Software Defined Networking (COMS 6998-8) 29

30 Key questions: What are the right abstractions for programming software-defined networks? How can we engineer trustworthy implementations that provide assurance? 9/24/13 Software Defined Networking (COMS 6998-8) 30 Source: Nate Foster, Cornell

31 Modular Abstractions 9/24/13 Software Defined Networking (COMS 6998-8) 31 Source: Nate Foster, Cornell

32 Combining Functionality Challenges: Writing, testing, and debugging programs Reusing code across applications Porting applications to new platforms Controller Platform Monitor + Route + Load Balance + Firewall One monolithic application 9/24/13 Software Defined Networking (COMS 6998-8) 32 Source: Nate Foster, Cornell

33 Route PatternActions dstip=10.0.0.1Fwd 1 dstip=10.0.0.2Fwd 2 PatternActions srcip=1.2.3.4Count Monitor + PatternActions srcip=1.2.3.4, dstip=10.0.0.1Fwd 1, Count srcip=1.2.3.4, dstip=10.0.0.2Fwd 2, Count srcip=1.2.3.4Count dstip=10.0.0.1Fwd 1 dstip=10.0.0.1Fwd 2 Route + Monitor 9/24/13 Software Defined Networking (COMS 6998-8) 33 Source: Nate Foster, Cornell

34 + PatternActions srcip=1.2.3.4, dstip=10.0.0.1Fwd 1, Count srcip=1.2.3.4, dstip=10.0.0.2Fwd 2, Count srcip=1.2.3.4Count dstip=10.0.0.1Fwd 1 dstip=10.0.0.2Fwd 2 Route + Monitor PatternActions tcpdst = 22Drop *Fwd ? Firewall PatternActions srcip=1.2.3.4, tcpdst = 22Count, Drop srcip=1.2.3.4, dstip=10.0.0.1Fwd 1, Count srcip=1.2.3.4, dstip=10.0.0.2Fwd 2, Count srcip=1.2.3.4Count tcpdst = 22Drop dstip=10.0.0.1Fwd 1 dstip=10.0.0.2Fwd 2 Route Monitor Firewall ++++ 9/24/13 Software Defined Networking (COMS 6998-8) 34 Source: Nate Foster, Cornell

35 Modular Applications Controller Platform MonitorRouteLoad BalanceFirewall Benefits: Easier to write, test, and debug programs Can reuse modules across applications Possible to port applications to new platforms One module for each task 9/24/13 Software Defined Networking (COMS 6998-8) 35 Source: Nate Foster, Cornell

36 Beyond Multi-Tenancy Relatively straightforward to split rule, bandwidth, and network events across these modules Slice 1Slice 2Slice 3 Slice N... Controller Platform Each module controls a different portion of the traffic 9/24/13 Software Defined Networking (COMS 6998-8) 36 Source: Nate Foster, Cornell

37 Modules Affect the Same Traffic How should we combine a collection of such modules into a single application? Controller Platform MonitorRouteLoad BalanceFirewall Each module partially specifies handling of all traffic 9/24/13 Software Defined Networking (COMS 6998-8) 37 Source: Nate Foster, Cornell

38 Language-Based Approach Design languages based on modular programming abstractions, and engineer efficient implementations using a compiler and run-time system Compiler + Run-Time System Controller Platform MonitorRouteLoad BalanceFirewall 9/24/13 Software Defined Networking (COMS 6998-8) 38 Source: Nate Foster, Cornell

39 Language Constructs [POPL ’ 12, NSDI ’ 13] 9/24/13 Software Defined Networking (COMS 6998-8) 39 Source: Nate Foster, Cornell

40 Parallel Composition Controller Platform MonitorRoute PatternActions dstip=3.4.5.6Fwd 1 dstip=6.7.8.9Fwd 2 PatternActions srcip=1.2.3.4Count + PatternActions srcip=1.2.3.4, dstip=3.4.5.6Fwd 1, Count srcip=1.2.3.4, dstip=6.7.8.9Fwd 2, Count srcip=1.2.3.4Count dstip=3.4.5.6Fwd 1 dstip=6.7.8.9Fwd 2 9/24/13 Software Defined Networking (COMS 6998-8) 40 Source: Nate Foster, Cornell

41 Sequential Composition Controller Platform Load BalanceRoute PatternActions dstip=10.0.0.1Fwd 1 dstip=10.0.0.2Fwd 2 PatternActions srcip=*0dstip:=10.0.0.1 srcip=*1dstip:=10.0.0.2 ; PatternActions srcip=*0dstip:=10.0.0.1, Fwd 1 srcip=*1dstip:=10.0.0.2, Fwd 2 9/24/13 Software Defined Networking (COMS 6998-8) 41 Source: Nate Foster, Cornell

42 Dividing Traffic Over Modules Load BalanceRoute ; MonitorRoute + if then else if then dstport=80 dstport=22 else Drop Predicates specify which packets traverse which modules, using ingress port and packet-header fields 9/24/13 Software Defined Networking (COMS 6998-8) 42 Source: Nate Foster, Cornell

43 The NetKAT Language field ::= switch | inport | srcmac | dstmac |... val ::= 0 | 1 | 2 | 3 |... a,b,c ::= true (* true constant *) | false (* false constant *) | field = val (* test value *) | a 1 | a 2 (* disjunction *) | a 1 & a 2 (* conjunction *) | ! a (* negation *) p,q,r ::= filter a (* filter by predicate *) | field := val (* modify value *) | p 1 + p 2 (* parallel composition *) | p 1 ; p 2 (* sequential composition *) | p * (* iteration *) Syntactic sugar: if a then p 1 else p 2 = filter a ; p 1 + filter ! a ; p 2 9/24/13 Software Defined Networking (COMS 6998-8) 43 Source: Nate Foster, Cornell

44 Example: Topology Abstraction Abstract topology Physical topology It is often useful to write programs in terms of a simplified abstract network topology Benefits: Information hiding: limit what each module sees Protection: limit what each module does Reuse: write code for appropriate interface Example: load balancer 9/24/13 Software Defined Networking (COMS 6998-8) 44 Source: Nate Foster, Cornell

45 Simplest example of topology abstraction Can be used in many applications, including access control, load balancing, distributed middleboxes, etc. Abstract Network Physical Network Example: “ One Big Switch ” (ingress; raise; application; lower; fabric; egress) Implementation: 9/24/13 Software Defined Networking (COMS 6998-8) 45 Source: Nate Foster, Cornell

46 Formal Reasoning 9/24/13 Software Defined Networking (COMS 6998-8) 46 Source: Nate Foster, Cornell

47 Program Equivalence A A B B Given a program and a topology: Formally, does the following equivalence hold? ( filter switch = A ; firewall; routing + filter switch = B ; routing) ~ ( filter switch = A ; routing + filter switch = B ; firewall ; routing) Want to be able to answer questions like: “ Will my network behave the same if I put the firewall rules on A, or on switch B (or both)? ” 9/24/13 Software Defined Networking (COMS 6998-8) 47 Source: Nate Foster, Cornell

48 NetKAT Equational Theory Boolean Algebra a | (b & c) ~ (a | b) & (a | c) a | true ~ true a | ! a ~ true a & b ~ b & a a & ! a ~ false a & a ~ a Packet Algebra f := n ; f ’ := n ’ ~ f ’ := n ’ ; f := n if f ≠ f ’ f := n ; f ’ = n ’ ~ f ’ = n ’ ; f := n if f ≠ f ’ f := n ; f = n ~ f := n f = n ; f := n ~ f = n f := n ; f ’ = n ’ ~ f := n ’ f = n; f = n ’ ~ filter drop if n ≠ n ’ Kleene Algebra p + (q + r) ~ (p + q) + r p + q ~ q + p p + filter false ~ p p + p ~ p p ; (q ; r) ~ (p ; q) ; r p; (q + r) ~ p ; q + p ; r (p + q) ; r ~ p ; r + q ; r filter true ; p ~ p ~ p ; filter true filter false ; p ~ filter false p ; filter false ~ filter false filter true + p ; p * ~ p * filter true + p * ; p ~ p * p + q ; r + r ~ r ⟹ p * ; q + r ~ r p + q ; r + q ~ q ⟹ p ; r * + q ~q 9/24/13 Software Defined Networking (COMS 6998-8) 48 Source: Nate Foster, Cornell

49 NetKAT and Kleene Algebras Theorems Soundness: programs related by the axioms are equivalent Completeness: equivalent programs are related by the axioms Decidabilty: program equivalence is decidable (PSPACE) Its foundations rest upon canonical mathematical structure: Regular operators ( +, ;, and * ) encode paths through topology Boolean operators ( &, |, and ! ) encode switch tables The design of NetKAT is not an accident! This is called a Kleene Algebra with Tests [Kozen ’ 96] 9/24/13 Software Defined Networking (COMS 6998-8) 49 Source: Nate Foster, Cornell

50 NetKAT Verification Model programs and topologies in the Z3 SMT solver Encode network-wide function as the transitive closure of the sequential composition of the program and topology Verify reachability properties automatically 9/24/13 Software Defined Networking (COMS 6998-8) 50 Source: Nate Foster, Cornell

51 Machine-Verified Controllers 9/24/13 Software Defined Networking (COMS 6998-8) 51 Source: Nate Foster, Cornell

52 Inductive pred : Type := | OnSwitch : Switch -> pred | InPort : Port -> pred | DlSrc : EthernetAddress -> pred | DlDst : EthernetAddress -> pred | DlVlan : option VLAN -> pred |... | And : pred -> pred -> pred | Or : pred -> pred -> pred | Not : pred -> pred | All : pred | None : pred Inductive act : Type := | ForwardMod : Mod -> PseudoPort -> act |... Inductive pol : Type := | Policy : pred -> list act -> pol | Union : pol -> pol -> pol | Restrict : pol -> pred -> pol |... Certified Software Systems Recent Successes seL4 [SOSP ’ 09] CompCert [CACM ’ 09] F* [ICFP ’ 11, POPL ’ 12, ’ 13] Tools Textbooks Certified Programming with Dependent Types Write code Lemma inter_wildcard_other : forall x, Wildcard_inter WildcardAll x = x. Proof. intros; destruct x; auto. Qed. Lemma inter_wildcard_other1 : forall x, Wildcard_inter x WildcardAll = x. Proof. intros; destruct x; auto. Qed. Lemma inter_exact_same : forall x, Wildcard_inter (WildcardExact x) (WildcardExact x) = WildcardExact x. Proof. intros. unfold Wildcard_inter. destruct (eqdec x x); intuition. Qed. Prove correct Extract code (** val handle_event : event -> unit Monad.m **) let handle_event = function | SwitchConnected swId -> handle_switch_connected swId | SwitchDisconnected swId -> handle_switch_disconnected swId | SwitchMessage (swId, xid0, msg) -> (match msg with | PacketInMsg pktIn -> handle_packet_in swId pktIn | _ -> Monad.ret ()) (** val main : unit Monad.m **) let main = Monad.forever (Monad.bind Monad.recv (fun evt -> handle_event evt)) Certified binary 9/24/13 Software Defined Networking (COMS 6998-8) 52 Source: Nate Foster, Cornell

53 NetKAT Flow tables OpenFlow messages Compiler Run-time system Optimizer Each level of abstraction formalized in Coq Machine-checked proofs that the transformations between levels preserve semantics Code extracted to OCaml and deployed with real switch hardware Certified NetKAT Controller 9/24/13 Software Defined Networking (COMS 6998-8) 53 Source: Nate Foster, Cornell

54 NetKAT Compiler Correctness Theorem Overview Compiler: maps NetKAT programs to flow tables Optimizer: eliminates “ empty ” and “ shadowed ” rules Formalization Highlights Library of algebraic properties of flow tables New tactic for proving equalities on bags Key invariant: all packet patterns “ natural ” Theorem compile_correct : forall opt pol sw pt pk bufId, SemanticsPreserving opt -> netcore_eval pol sw pt pk bufId = flowtable_eval (compile pol sw) sw pt pk bufId. 9/24/13 Software Defined Networking (COMS 6998-8) 54 Source: Nate Foster, Cornell

55 OpenFlow 1.0 Specification 42 pages......of informal prose...and C struct definitions...diagrams and flow charts 9/24/13 Software Defined Networking (COMS 6998-8) 55 Source: Nate Foster, Cornell

56 Featherweight OpenFlow Syntax Semantics Key Features: Models all features related to packet forwarding and all essential asynchrony Supports arbitrary controllers 9/24/13 Software Defined Networking (COMS 6998-8) 56 Source: Nate Foster, Cornell

57 Forwarding Definition Pattern_inter (p p':Pattern) := let dlSrc := Wildcard_inter EthernetAddress.eqdec (ptrnDlSrc p) (ptrnDlSrc p') in let dlDst := Wildcard_inter EthernetAddress.eqdec (ptrnDlDst p) (ptrnDlDst p') in let dlType := Wildcard_inter Word16.eqdec (ptrnDlType p) (ptrnDlType p') in let dlVlan := Wildcard_inter Word16.eqdec (ptrnDlVlan p) (ptrnDlVlan p') in let dlVlanPcp := Wildcard_inter Word8.eqdec (ptrnDlVlanPcp p) (ptrnDlVlanPcp p') in let nwSrc := Wildcard_inter Word32.eqdec (ptrnNwSrc p) (ptrnNwSrc p') in let nwDst := Wildcard_inter Word32.eqdec (ptrnNwDst p) (ptrnNwDst p') in let nwProto := Wildcard_inter Word8.eqdec (ptrnNwProto p) (ptrnNwProto p') in let nwTos := Wildcard_inter Word8.eqdec (ptrnNwTos p) (ptrnNwTos p') in let tpSrc := Wildcard_inter Word16.eqdec (ptrnTpSrc p) (ptrnTpSrc p') in let tpDst := Wildcard_inter Word16.eqdec (ptrnTpDst p) (ptrnTpDst p') in let inPort := Wildcard_inter Word16.eqdec (ptrnInPort p) (ptrnInPort p') in MkPattern dlSrc dlDst dlType dlVlan dlVlanPcp nwSrc nwDst nwProto nwTos tpSrc tpDst inPort. Definition exact_pattern (pk : Packet) (pt : Word16.T) : Pattern := MkPattern (WildcardExact (pktDlSrc pk)) (WildcardExact (pktDlDst pk)) (WildcardExact (pktDlTyp pk)) (WildcardExact (pktDlVlan pk)) (WildcardExact (pktDlVlanPcp pk)) (WildcardExact (pktNwSrc pk)) (WildcardExact (pktNwDst pk)) (WildcardExact (pktNwProto pk)) (WildcardExact (pktNwTos pk)) (Wildcard_of_option (pktTpSrc pk)) (Wildcard_of_option (pktTpDst pk)) (WildcardExact pt). Definition match_packet (pt : Word16.T) (pk : Packet) (pat : Pattern) : bool := negb (Pattern_is_empty (Pattern_inter (exact_pattern pk pt) pat)). /* Fields to match against flows */ struct ofp_match { uint32_t wildcards; /* Wildcard fields. */ uint16_t in_port; /* Input switch port. */ uint8_t dl_src[OFP_ETH_ALEN]; /* Ethernet source address. */ uint8_t dl_dst[OFP_ETH_ALEN]; /* Ethernet destination address. */ uint16_t dl_vlan; /* Input VLAN. */ uint8_t dl_vlan_pcp; /* Input VLAN priority. */ uint8_t pad1[1]; /* Align to 64-bits. */ uint16_5 dl_type; /* Ethernet frame type. */ uint8_t nw_tos; /* IP ToS (DSCP field, 6 bits). */ uint8_t nw_proto; /* IP protocol or lower 8 bits of ARP opcode. */ uint8_t pad2[2]; /* Align to 64-bits. */ uint32_t nw_src; /* IP source address. */ uint32_t nw_dst; /* IP destination address. */ uint16_t tp_src; /* TCP/UDP source port. */ uint16_t tp_dst; /* TCP/UDP destination port. */ }; OFP_ASSERT(sizeof(struct ofp_match) == 40); Record Pattern : Type := MkPattern { dlSrc : Wildcard EthernetAddress; dlDst : Wildcard EthernetAddress; dlType : Wildcard EthernetType; dlVlan : Wildcard VLAN; dlVlanPcp : Wildcard VLANPriority; nwSrc : Wildcard IPAddress; nwDst : Wildcard IPAddress; nwProto : Wildcard IPProtocol; nwTos : Wildcard IPTypeOfService; tpSrc : Wildcard TransportPort; tpDst : Wildcard TransportPort; inPort : Wildcard Port }. Detailed model of matching, forwarding, and flow table update 9/24/13 Software Defined Networking (COMS 6998-8) 57 Source: Nate Foster, Cornell

58 Asynchrony “ In the absence of barrier messages, switches may arbitrarily reorder messages to maximize performance. ” “ There is no packet output ordering guaranteed within a port. ” Definition InBuf := Bag Packet. Definition OutBuf := Bag Packet. Definition OFInBuf := Bag SwitchMsg. Definition OFOutBuf := Bag CtrlMsg. Essential asynchrony: packet buffers, message reordering, and barriers 9/24/13 Software Defined Networking (COMS 6998-8) 58 Source: Nate Foster, Cornell

59 PriorityPredicateAction PriorityPredicateAction 10SSHDrop 5dst_ip = H1Fwd 1 5dst_ip = H2Fwd 2 PriorityPredicateAction 5dst_ip = H1Fwd 1 PriorityPredicateAction 5dst_ip = H1Fwd 1 5dst_ip = H2Fwd 2 update re-ordering PriorityPredicateAction 10SSHDrop PriorityPredicateAction 10SSHDrop 5dst_ip = H1Fwd 1 ⊆ ⊆ ⊆ Distributed Programming : non-atomic table updates Asynchrony (Cont’d) 9/24/13 Software Defined Networking (COMS 6998-8) 59 Source: Nate Foster, Cornell

60 Controllers : abstract type of controller state f in : f out : Controller Parameters Ultimately we want to prove theorems about controllers that implement the NetKAT run-time system......but we didn ’ t want to bake specific controllers into Featherweight OpenFlow! Controller model: fully abstract 9/24/13 Software Defined Networking (COMS 6998-8) 60 Source: Nate Foster, Cornell

61 (H 1, )(S 1,pt 1, ) (S 2,pt 1, )(H 2, ) ≈ ≈ ≈ ≈ ≈ ≈ ≈ ≈ add rules Weak Bisimulation Theorem fwof_abst_weak_bisim : weak_bisimulation concreteStep abstractStep bisim_relation. 9/24/13 Software Defined Networking (COMS 6998-8) 61 Source: Nate Foster, Cornell

62 Frenetic OX implemented using OCaml embedding predicates and policies queries OCaml OpenFlow Platform similar to Nox, Pox, Floodlight, etc. predicates policies queries stream of snapshots over time predicates policies queries predicates policies queries Frenetic Ox The System 9/24/13 Software Defined Networking (COMS 6998-8) 62 Source: Nate Foster, Cornell

63 Frenetic DSL Frenetic OX implemented using Domain-specific language predicates and policies monitoring mac learning network address translation OCaml embedding predicates and policies queries OCaml OpenFlow Platform similar to Nox, Pox, Floodlight, etc. Frenetic Ox The System 9/24/13 Software Defined Networking (COMS 6998-8) 63 Source: Nate Foster, Cornell

64 Conclusion Modularity is a key concern in the design of any language NetKAT provides rich abstractions for building modular network programs, including parallel and sequential composition operators By leveraging recent advances in formal methods, can build trustworthy compilers, run-time systems, and verification tools Implementation status: Stand-alone controller platform implemented in OCaml Sophisticated, proactive compiler for OpenFlow rules Large parts of the system formally verified in Coq Experimental support for OpenFlow 1.3 9/24/13 Software Defined Networking (COMS 6998-8) 64 Source: Nate Foster, Cornell

65 Questions? 9/24/13 Software Defined Networking (COMS 6998-8) 65


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