Jennifer Rexford - PowerPoint Presentation

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Jennifer RexfordPrinceton UniversityMW 11:00am-12:20pm

Programmable Data Planes

COS 597E: Software Defined NetworkingSlide2

Data PlaneStreaming algorithms that act on packets

Matching on some bits, taking a simple action

… at behest of control and management plane

Wide range of functionalityForwarding and access controlBuffering, marking, shaping, and schedulingRewriting header fields (e.g., NAT)Traffic monitoring and deep packet inspectionEncryption, compression, and transcoding

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A Need for SpeedHigh link speed10

Gbps

, 40

Gbps, 100 GbpsSmall packets40-byte TCP ACK packetsSmall time per packet40 Gbps =124 Mpps with 320-bit packets8 ns to process a packetRouters need low latencyRelatively limited opportunity to batch or pipeline3Slide4

A Range of TechnologiesASIC (App-Specific Integrated Circuit)

Fast, dense chip, but expensive to change

FPGAs and network processors

Fast, reconfigurable, hard to program Graphics Processing UnitsMassive parallel computation on small coresSoftware on commodity computerEasy to program, but I/O bandwidth, memory copying, and interrupt overheads4Slide5

Click Modular Router

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Click Motivation

Flexibility

Add new features and enable experimentation

OpennessAllow users/researchers to build and extend(In contrast to most commercial routers)ModularitySimplify the composition of existing featuresSimplify the addition of new featuresSpeed/efficiencyOperation (optionally) in the operating systemWithout user needing to grapple with OS internals

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Router as a Graph of Elements

Large number of small elements

Each performing a simple packet function

E.g., IP look-up, TTL decrement, bufferingConnected together in a graphElements inputs/outputs snapped togetherBeyond elements in series to a graphE.g., packet duplication or classificationPacket flow as main organizational primitiveConsistent with data-plane operations on a router(Larger elements needed for, say, control planes)7Slide8

Push vs. Pull

Packet hand-off between elements

Directly inspired by properties of routers

Annotations on packets to carry temporary statePush processingInitiated by the source endE.g., when an unsolicited packet arrives (e.g., from a device)Pull processingInitiated by the destination endE.g., to control timing of packet processing (e.g., based on a timer or packet scheduler)8Slide9

Click Language

Declarations

Create elements

ConnectionsConnect elementsCompound elementsCombine multiple smaller elements, and treat as single, new element to use as a primitive classLanguage extensions through element classesConfiguration strings for individual elementsRather than syntactic extensions to the language9

src :: FromDevice(eth0);

ctr :: Counter;

sink :: Discard;

src -> ctr;

ctr -> sink;Slide10

Handlers and Control Socket

Access points for user interaction

Appear like files in a file system

Can have both read and write handlersExamplesInstalling/removing forwarding-table entriesReporting measurement statisticsChanging a maximum queue length Control socketAllows other programs to call read/write handlersCommand sent as single line of text to the server10Slide11

An Observation…

Click is widely used

And the paper on Click is widely cited

Click elements are created by othersEnabling an ecosystem of innovationTake-away lessonCreating useful systems that others can use and extend has big impact in the research communityAnd brings tremendous professional valueCompensating amply for the time and energy 11