Network Protocols: Design and Analysis

1. Network Protocols: Design and Analysis Polly Huang EE NTU http://cc.ee.ntu.edu.tw/~phuang phuang@cc.ee.ntu.edu.tw

2. Introduction [Hanson99a] [Jamin97b] [Levin83a] Internet Overview

3. What you’re up against • 40 papers • about 3 per class (!) • plus supplementary if you want :-) • Written for experts • Written for the time (not now) • All having to show how cool they are • as opposed to a completely objective overview • Some good, some not

4. What’s on your side • Some overview in lectures • Discussion with peers • Reading groups are good! • Use context • Related papers, reference textbook, own background • Hinds in the first 3 papers • [Hanson99a], [Jamin97b], [Levin83a]

5. [Hanson99a]

6. Hints: In the Reading • Skim first, then read in depth • Abstract • Introduction • Conclusion • While going through the paper, takes notes • Highlight key-words/phrases/sentences • Numerate points • Summarize sections/paragraphs • Scribble thoughts

7. Hints: After Reading • Write a 1-2 paragraph summary • Keep a database (bibilography) of all your papers • Authors, paper title, publisher, date, location • List of keywords • Your summary/assessment of the papers • Location of your on-line copy • Good for a research-oriented career • Will save lots of time when you write a paper • Will save lots of hair when you want to know something

8. [Jamin97b]

9. Telling Good from Bad • New idea • Really new? how do you know? • Related work & context • The problem • Clearly stated? • Evaluation • Do their experiments back up their claims? • Are their experiments statistically sound?

10. On the Review Forms • Novelty • New idea • Clarity • The problem • Reality (practicality) • Evaluation • Importance, significance, relevance • How much impact? • Would things change?

11. OK for Beginners • Clarity • Easiest • Judging the writing • Evaluation • Easy • Judging the experiments and technical content

12. Challenging for the Advanced • Novelty • Hard • Need to follow/read enough papers in the area • Importance • Hardest • Need to have breadth and know enough development in the area

13. [Levin83a]

14. Kinds of Papers • Idea papers • Better have good insight into something! implementable? • Systems papers • Is their system really new? solid? insight? lessons? alternatives? • Analysis papers • Are their models clean? relevant? • Evaluation papers • Traces or experiments of existing systems • Do they show insight into something new?

15. Context • SOSP is a top OS conference • SIGCOMM, SIGMETRICS, MOBILCOM • Give guidance to writers about systems papers • From the reviewer’s perspective

16. Trying to Address 2 Questions • What makes a paper important? • What makes a paper clear? • This should not over-shadow the technical merit • It, however, may influence (sometimes critically) the reviewer’s impression on the paper • Just keep in mind that the reviewers are busy!

17. About Importance • Novelty • Idea new and original • Practicality • Applicable, implementable, deployable • For system papers, yes • Not necessary true for general papers

18. And Impact Factor • Lessons learned • New problems identified • Previous results contradicted • Things changed • For a lot of people • A lot but for few people

19. About Clarity • Clearly states lessons learned • Reasoning (why, not just what) • Puts results in context • Related work, premise • Avoids extra baggage • Irrelevant technical details • Less critical analytical elaboration

20. The Communication Interface • Clear presentation • Organization, good abstract • Good writing • Readability

21. If you are writing… • Think the criteria • Novelty, reality, impact, and clarity • My advise to this class • Start from Clarity • English is the bottleneck for most of you • Practice makes perfect • Without this, the organization, sometimes even the work could well be effort in vain • When this is done reasonably well, your advisor will be able to help you with the rest

22. Theory vs. Implementation • Theory is incredibly important • Can predict general results • Help understand systems • Implementation is incredibly important • Explore real-world constraints (sometimes abstracted away in theory)

23. Embrace Them Both • Best papers tend to have both • Neither is sufficient • (some) assumptions in the theory are not all that realistic • Ex. Ethernet cannot reach more than 36% utilization [but it fails to consider higher levels] • (some) systems work is just trees, no forest • Ex. distributed.net broke the RC5-64 challenge in 1757 [but what does that say about security in general]

24. This’s Why Teamwork is Good • Some are • good at grasp symbols, abstract notations • keen in detecting patterns in random phenomena • experienced in implementations • This team can be great

25. Science vs. Engineering • The roles of science and engineering in networking and systems • Huge amount of engineering (“construction”) • What can we reallybuild? • Ex. Napster or WWW were engineering triumphs • Really important science (“discovery”) • The Internet is a complex system with many interactions we don’t understand • There are principals that affect all possible systems

26. Questions?

27. The Overview

28. The Internet Now and Beyond

29. The Internet, Circa 1969

30. A 1999 Internet ISP Map [data courtesy of Ramesh Govindan and ISI’s SCAN project]

31. The Internet, Posterized, Circa 2000 [data courtesy of UCSD’s caida]

32. Internet Development Mantra “We reject kings, presidents and voting. We believe in rough consensus and running code.” - Dave Clark Quote from a T-shirt commonly worn at IETF meetings

33. Glimpses of the Future? USC Robo- Mote home entertainment: Onkyo’s network-enabled stereo receiver cell-phones: millions of IP-enabled handsets today [Rahimi, Sukhatme, et al., 2002] PC/104 UCB mote: an 8-bit sensor node with non-IP based networking http://www.picoweb.net/ (an 8-bit web server with Ethernet) a sensor network (tracking the truck)

34. Some Definitions • Host: computer, desktop, PDA, light switch, etc. (also a node) • Link: path followed by bits. • Wire or wireless • Broadcast, point-to-point, and in-between • Switch: moves bits between alternate links • Packet switching: stateless, store and forward • Circuit switching: stateful, cut through • other terms: hub, router, base-station

35. … Networks Point-to-Point wired or wireless Multiple Access …

36. Internetworks • A network can be defined recursively as... • Two or more nodes connected by a link, or • Two or more networks connected by two or more nodes

37. The Global Network • Structure • Getting started • What and where? • Getting data there • Metrics

38. Getting started: A Host • Host configuration needs: • a physical network cable (Ethernet, etc.) • an IP address • a network mask • a gateway • a DNS server (and other servers) • 2003: a mail server • Automated with DHCP (and better still in IPv6)

39. Getting started: A Network • Network configuration needs: • a wire (from the phone or cable company) • a router • a firewall, a IP sharing or NAT machine? • an ISP to connect you to the Internet • network addresses (192.168.1.xxx)—a subnet • plus whatever servers you want (DHCP, DNS, Email) • Automated in IPv6

40. Getting started: An ISP • ISP needs: • a big block of addresses • connections to one or more other ISPs, peerings • multiple routers, probably at exchange point (a POP or MAE) • servers for your users: mail, web, etc. • servers for you: monitoring, etc. • an AUP (Acceptable Use Policy) • a lawyer

41. Idealized Network Structure Backbones Regionals Campus LANs

42. The Global Network • Structure • Getting started • What and where? • Getting data there • Metrics

43. Internet How Do Computers Find Each Other? Computer1 Computer 2

44. Different Kinds of Addresses • Will talk about names, addresses, binding in [Saltzer81a] • For now, what are names and addresses in the Internet? • URL/URNs: http://www.isi.edu • Domain names www.isi.edu • IP address / port numbers: 128.125.1.1 • MAC address: 12:34:45:67:ae:0a

45. Finding IP Address:Domain Naming System (DNS) Local DNS server Computer 1 What’s the IP address for www.usc.edu? It is 128.125.19.146 How does computer 1 know its address? either hard-coded, or gets it at boot time w/DHCP How does the server know computer 1’s address? usually hard-coded, or via DNS updates, and requests

46. Finding Ether Address:Address Resolution (ARP) Broadcast: who knows the Ethernet address for 128.125.51.41? Ethernet Broadcast: Yes, I am 08-00-2c-19-dc-45 Ethernet

47. Finding Things: The USER’s Perspective • http://cc.ee.ntu.edu.tw/~phuang/teach/net-protocol-fall-03/ • http a protocol • cc.ee.ntu.edu.tw a web server name • ~phuang/…fall-03/ a path on that server • Beware: • names vs. addresses at multiple layers • Alternatively, using a search engine • Network Protocols Polly Teaching

48. The Global Network • Structure • Getting started • What and where? • Getting data there • Metrics

49. Packet Traveling Through the Internet Routers send packet to next closest hop H R H R H H R R R R H: Hosts R: Routers R H R H

50. How do the routers know where to send data? • Forwarding tables at each router populated by routing protocols. • Routing tables optimize distance • Subject also to policies • Will talk more about this in routing weeks.