The Networking Philosopher’s Problem

1. The Networking Philosopher’s Problem Jennifer Rexford Computer Science Department Princeton University http://www.cs.princeton.edu/~jrex

2. The Internet: An Exciting Time • One of the most influential inventions • A research experiment that escaped from the lab • … to be a global communications infrastructure • Ever wider reach • Today: 1.7 billion users • Tomorrow: more users, computers, sensors • Near-constant innovation • Apps: Web, P2P, social networks, virtual worlds • Links: optics, WiFi, cellular, WiMax, …

3. So, why every two years, when I teach graduate networking, I have all sorts of angst...

4. What is Networking?

5. A Plethora of Protocol Acronyms? WAP SNMP IPX SIP PPP MAC FTP LLDP UDP HIP ICMP OSPF RTP IMAP IGMP BGP HTTP ECN PIM RED ARP IP TCP RIP MPLS RTCP SMTP BFD CIDR RTSP NNTP TLS NAT SACK STUN SSH DNS DHCP VTP VLAN LDP POP LISP TFTP

6. A Heap of Header Formats?

7. TCP/IP Header Formats in Lego

8. A Big Bunch of Boxes? Load balancer Label Switched Router Switch Router Scrubber Repeater Gateway Bridge Intrusion Detection System Route Reflector Deep Packet Inspection DHCP server Packet shaper Firewall NAT Hub Packet sniffer DNS server WAN accelerator Base station Proxy

9. A Ton of Tools? arpwatch tcpdump syslog wget nslookup traceroute trat snort nmap whois ipconfig rancid ntop bro net-snmp dig ping iperf wireshark NDT dummynet mrtg

10. What Do Peers in Other Fields Say? • “You networking people are very curious.  You really love your artifacts.” • “In my college networking class I fell asleep at the start of the semester when the IP header was on the screen, and woke up at the end of the semester with the TCP header on the screen.” • “Networking is all details and no principles.” Is networking “just the (arti)facts”?

11. An Application Domain?

12. Application Domain for Theory? • Algorithms and data structures • Control theory • Queuing theory • Optimization theory • Game theory and mechanism design • Formal methods • Information theory • Cryptography • Programming languages • Graph theory

13. Application Domain for Systems? • Distributed systems • Operating systems • Computer architecture • Software engineering • …

14. An Exercise in Entrepreneurship? • Identify a need or desirable capability • Whether previously known or not • Invent a new feature or system that provides it • Determine how it fits in the existing network • Build and/or evaluate your solution • Pitch or $ell the problem and solution to others • Whether to investors or a program committee • Bask in glory, or lick your wounds

15. What Peers in Other Fields Say? • “Networking papers are strange.  They have a lot of text.” • “What are the top ten classic problems in networking?  I would like to solve one of them and submit a paper to SIGCOMM.” After hearing that we don't have such a list: "Then how do you consider networking a discipline?” • “So, these networking research people today aren't doing theory, and yet they aren't the people who brought us the Internet.  What exactly are they doing?” • “Networking is an opportunistic discipline.” Is networking a problem domain or a scholarly discipline?

16. What Do We Teach Networking Students?

17. How Practitioners Learn Networking • Certification courses • On how to configure specific pieces of equipment • “On the job” training • Aka “trial by fire”

18. How Colleges Teach Networking • Undergraduates: how the Internet works • Graduates: read the 20 “best” papers • Few general principles, little “hands-on” experience • (I’m as guilty as anyone) “There is a tendency in our field to believe that everything we currently use is a paragon of engineering, rather than a snapshot of our understanding at the time.  We build great myths of spin about how what we have done is the only way to do it to the point that our universities now teach the flaws to students (and professors and textbook authors) who don't know better.” -- John Day

19. Now That I’ve Bummed You Out… Or, Why Should You Stay in This Field?

20. So, Why is Networking Cool? • Tangible, relates to reality • Can measure/build things (we do “love our artifacts”) • Can truly effect far-reaching change in the real world • Inherently interdisciplinary • Well-motivated problems + rigorous solution techniques • Interplay with policy, economics, and social science • Widely-read papers • Many of the most cited papers in CS are in networking • Congestion control, distributed hash tables, resource reservation, self-similar traffic, multimedia protocols,… • Three of top-ten CS authors (Shenker, Jacobson, Floyd) • So, somebody is interested in reading this stuff… 

21. So, Why is Networking Cool? (Cont) • Young, relatively immature field • Great if you like to make order out of chaos • Tremendous intellectual progress is still needed • You can help decide what networking really is • Defining the problem is a big part of the challenge • Recognizing a need, formulating a well-defined problem • … is at least as important as solving the problem… • Lots of platforms for building your ideas • Programmability: Click, OpenFlow/NOX, NetFPGA • Routing software: Quagga, XORP, and Bird • Testbeds: Emulab, PlanetLab, Orbit, GENI, … • Measurements: RouteViews, traceroute, Internet2, …

22. But, That Doesn’t Say What Networking Really Is

23. Maybe networking is defined more by the questions we ask, than the techniques we use

24. Decomposition of Function • How to • Design and operate components and protocols • That can be used and combined in many ways • To do many things • Definition and placement of function • What to do, and where to do it • The “division of labor” • Between the host, network, and management systems • Across multiple concurrent protocols and mechanisms • How do we know if we got it right? • Soul searching? A proof or analysis? A prototype?

25. UDP TCP Today’s Divisions of Labor • End host and the network • Packet switching • Best-effort delivery • Fixed end-points withIP addresses • Protocol layers • IP as the center of the universe • IP above the link layer • IP below transport and application network Applications Data Link Physical

26. 2 Today’s Divisions of Labor • Network elements • Data plane: packets • Control plane: events • Management: policies • Administrative domains • Autonomous Systems • Destination IP prefixes • Policy-based path-vector routing “d: path (2,1)” “d: path (1)” 3 1 data traffic data traffic d

27. Beyond Today’s Division of Labor

28. Between Hosts and the Network • Networked services hosted in data centers • Web sites, social networks, video streaming, online gaming, virtual worlds, ... • Replicated on servers in multiple data centers • Churn from mobile users, migrating VMs, failures, … • Time to rethink • Naming and addressing • Early vs. late binding • Server and networkload balancing • End-host network stackand socket API data centers . . . . servers Internet clients

29. Dumb management, smart network Network elements talk amongst themselves Adapting automatically Between Network and Management • Smart management, dumb network measure control

30. Between Administrative Domains Evolvable Protocols (under-specified, programmable) ? Global Properties (stability, scalability, reliability, security, managability, …) Autonomy (autonomous parties, with different economic objectives) Can we have all three? Under what conditions?

31. Conclusion • Networking is cool • Real, important problems • Opportunities for impact • Inherently interdisciplinary • But the field is immature • More of a “domain” than a “discipline” • Still searching for its intellectual center • Please help! • Master a discipline and apply it to networking • Define what the networking “discipline” really is

32. Random Advice on Being an Effective Graduate Student http://www.freedom-to-tinker.com/blog/jrex/advice-new-graduate-students