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1、,Software-defined Networking,Nick McKeown nickmstanford.edu,Infocom, April 2009,Part 1: Inside the boxSwitch and Router DesignPart 2: Outside the boxSoftware-defined networking,How big should buffers be? 1/N,How to build really fast buffers? Nemo,Which schedulers give 100% throughput? MWM,Which sche
2、dulers are practical in hardware? iSLIP,How to schedule multicast? ESLIP,How to run the scheduler slower? PPS,How to avoid scheduling altogether? VLB,How to emulate an output queued switch? MUCFA,How to lookup quickly in hardware? 24-8,Heuristic classification algorithms HiCuts,Three Open Topics,The
3、res something special about “2x speedup”Deterministic (instead of probabilistic) switch designMaking routers simpler,Three Open Topics,Theres something special about “2x speedup” A maximal match crossbar scheduler gives 100% throughput Dai&Prabhakar Makes a Clos network strictly non-blocking Clos Al
4、lows a CIOQ switch to precisely emulate an output-queued switch Chuang,Three Open Topics,Theres something special about “2x speedup” (contd.) Allows a parallel stack of small switches to precisely emulate one big switch Iyer Valiant Load-Balanced switch (or network) can give 100% throughput Valiant,
5、Related observations,“2x speedup” is key for both deterministic & probabilistic systems A maximum size bipartite match is at most twice the size of a maximal match A switch has two simultaneous constraints: input and output Local “selfish” routing decisions cost twice as much as “global” ones Roughg
6、arden,Three Open Topics,Theres something special about “2x speedup”Deterministic (instead of probabilistic) switch design We need more analytical tools for “mimicking” Generalized pigeon-hole principles Making routers simpler,Three Open Topics,Theres something special about “2x speedup”Deterministic
7、 (instead of probabilistic) switch designMaking routers simpler,5389 RFCs,Barrier to entry,Bloated,Power Hungry,Many complex functions baked into the infrastructure OSPF, BGP, multicast, differentiated services, Traffic Engineering, NAT, firewalls, MPLS, redundant layers, ,We have lost our way,Proce
8、ss of innovation,Almost no technology transfer from academia,Deployment,Idea,Standardize,Personal regret,I wish I had said it sooner and louderOur “dumb, minimal” datapath turned into a bloated 1960s mainframe!,The essence of my talk (1 of 2),Hardware Substrate The PC industry found a simple, common
9、, hardware substrate (x86 instruction set) Software-definition Innovation exploded on top (applications) and in the infrastructure itself (operating systems, virtualization) Open-source 100,000s of developers blew apart the standards process, accelerated innovation,The essence of my talk (2 of 2),It
10、 is up to us to make it happen. Until we (someone) does, it remains ossified.Lets define the substrate.,Hardware Substrate,Open Source Culture,Software-Defined Network,Innovation!,Part 1: Inside the boxPart 2: Outside the box The need for a substrate The inevitability of software-defined networking,
11、Computer,Application,OS abstracts hardware substrate Innovation in applications,x86 (Computer),Windows (OS),Application,Application,Simple, common, stable, hardware substrate below + Programmability + Competition Innovation in OS and applications,Linux,Mac OS,x86 (Computer),Windows (OS),or,or,Applic
12、ation,Application,Simple, common, stable, hardware substrate below + Programmability + Strong isolation model + Competition above Innovation in infrastructure,A simple stable common substrate,Allows applications to flourish Internet: Stable IPv4 lead to the web Allows the infrastructure on top to be
13、 defined in software Internet: Routing protocols, management, Rapid innovation of the infrastructure itself Internet: er.? Whats missing? What is the substrate?,Mid-1990s: “To enable innovation in the network, we need to program on top of a simple hardware datapath”,Problems: isolation, performance,
14、 complexity,Late-1990s: “To enable innovation in the network, we need the datapath substrate to be programmable”,Problem: Accelerated complexity of the datapath substrate,(Statement of the obvious),In networking, despite several attemptsWeve never agreed upon a clean separation between: A simple com
15、mon hardware substrate And an open programming environment on top,But things are changing fast in data centers and service provider networks.,Observations,Prior attempts have generally Assumed the current IP routing substrate is fixed, and tried to program it externally Including the routing protoco
16、ls Defined the programming and control model up-front But to pick the right x86 instruction set, Intel didnt define Windows XP, Linux or VMware,We need,A clean separation between the substrate and an open programming environment A simple hardware substrate that generalizes, subsumes and simplifies the current substrate Very few preconceived ideas about how the substrate will be programmed Strong isolation,
