1. CSEE W4140 Networking Laboratory Opening Lecture Jong Yul Kim 01.25.2010

2. Computer Science in one word Abstraction “a mechanism and practice to reduce and factor out details so that one can focus on a few concepts at a time” - wikipedia

3. Figure from Computer Networking: a top down approach

6. INTERNET

7. Details Figure from “Google: A Behind-the-Scenes Tour” by Jeff Dean

8. Reality Figure from “Google: A Behind-the-Scenes Tour” by Jeff Dean

9. Real Network Protocols “RIP is a distance-vector protocol that operates in a manner very close to the idealized DV protocol we examined” -Computer Networking: A Top-Down Approach 4/e

10. Course Objectives  The main idea: learning by doing Build a network using PCs, routers, cables Configure them properly Run the experiment Observe real network protocol behavior Gather data Analyze and evaluate  Explore how abstract concepts are designed to work in real life and to observe how they really behave

11. Course Objectives  Reinforce your knowledge of networks  Gain first-hand experience and skills  Learn how to use Linux for networks  Pre-requisite Computer Networks or equivalent

12. Required Textbook Mastering Networks: An Internet Lab Manual (= The Manual) You must have The Manual! One reserved copy in the Engineering library.

13. Lab sequence

14. Lab Organization  Each lab has three parts Prelab HW - individually Lab session Lab report  You need to bring Your Lab Manual A USB drive to store your data in groups of two

15. Lab Times  Tuesdays 10 am ~ 12 pm  Tuesdays 4:10 ~ 6:40 pm  Wednesdays 10 am ~ 12 pm This one might be changed.  10 students in each lab time  Please sign up!

16. Lab Equipment

17. Lectures  Mondays 2:30 ~ 4:00 pm at 327 Mudd  Go over topics in the upcoming lab  Discussions on reading assignments  Review of relevant Computer Networks material

18. Grading Prelab HW10% Lab performance & Lab reports60% Midterm10% Final10% In-class quiz & Participation10% Open-book, open-notes, open to quiet discussions

19. Homework Policy  Prelab HW Individual work Due every Friday at 11:59 pm Don’t copy and paste from other sources  Lab reports Team work Due before next lab Don’t turn in 100 page reports! Avg. 5~20

20. Academic Honesty Policy  Summary: Do your own work.  Do not copy other’s homework (past or current students).  Do not copy and paste from wikipedia or any other source including textbooks, web sites, etc.  If you cannot think of another way to explain your answer, you should give proper credit to the source. http://www.cs.columbia.edu/education/honesty

21. Homework Policy  Late submission 20 points deducted per day But you can use 3 late days  At most 1 week for reconsideration after grades are announced

22. Contact and Office Hours  Instructor Jong Yul Kim (jyk@cs) TBA after lab sessions are fixed.  TAs Kyung Wha Kim (kk2515) Varun Mahendra (vum2001) Third TA (???)

23. How to fail this class quickly #1 Connect any lab machine to the Internet. ALWAYS be careful and ask yourself before you plug it in: “Where is the other end of the cable?”

24. How to fail this class quickly #2 Leave the door to CRF open. ALWAYS keep CRF entrance closed. Lab doors can be open while you’re in the lab.

25. To get the most out of this course  Prepare for labs in advance Read the lab manual beforehand If you’re not familiar with something in the lab, consult textbook, ask me or TAs during office hours or by email Submit your prelab HW on time  Come to class

26. Review of Important Concepts The following slides are from the texbook’s authors. Some content have been modified to fit this class.

27. Layers  The complexity of the communication task is reduced by using multiple protocol layers:  Each protocol is implemented independently  Each protocol is responsible for a specific subtask  Protocols are grouped in a hierarchy  A structured set of protocols is called a communications architecture or protocol suite

28. TCP/IP Protocol Suite  The TCP/IP protocol suite is the protocol architecture of the Internet  The TCP/IP suite has four layers: Application, Transport, Network, and Data Link Layer  End systems (hosts) implement all four layers. Gateways (Routers) only have the bottom two layers.

29. Functions of the Layers  Data Link Layer: Service: Reliable transfer of frames over a link Media Access Control on a LAN Functions: Framing, media access control, error checking  Network Layer: Service: Move packets from source host to destination host Functions: Routing, addressing  Transport Layer: Service: Delivery of data between hosts Functions: Connection establishment/termination, error control, flow control  Application Layer: Service: Application specific (delivery of email, retrieval of HTML documents, reliable transfer of file) Functions: Application specific

30. TCP/IP Suite and OSI Reference Model The TCP/IP protocol stack does not define the lower layers of a complete protocol stack

31. Assignment of Protocols to Layers

32. Layered Communications

33. Service Primitives N+1 Layer Entity N Layer Entity N+1 Layer Peer Protocol Request Delivery Indicate Delivery Communication services are invoked via function calls. The functions are called service primitives

34. Service Primitives Recall: A layer N+1 entity sees the lower layers only as a service provider Service Provider N+1 Layer Entity N+1 Layer Peer Protocol Request Delivery Indicate Delivery

35. Service Access Points  A service user accesses services of the service provider at Service Access Points (SAPs)  A SAP has an address that uniquely identifies where the service can be accessed

36. Layers in the Example

37. Layers and Services  Service provided by TCP to HTTP: reliable transmission of data over a logical connection  Service provided by IP to TCP: unreliable transmission of IP datagrams across an IP network  Service provided by Ethernet to IP: transmission of a frame across an Ethernet segment  Other services: DNS: translation between domain names and IP addresses ARP: Translation between IP addresses and MAC addresses

38. Encapsulation and Demultiplexing  As data is moving down the protocol stack, each protocol is adding layer-specific control information

39. Encapsulation and Demultiplexing in our Example  Let us look in detail at the Ethernet frame between Argon and the Router, which contains the TCP connection request to Neon.  This is the frame in hexadecimal notation. 00e0 f923 a820 00a0 2471 e444 0800 4500 002c 9d08 4000 8006 8bff 808f 8990 808f 4715 065b 0050 0009 465b 0000 0000 6002 2000 598e 0000 0204 05b4

40. Encapsulation and Demultiplexing

41. Encapsulation and Demultiplexing: Ethernet Header

42. Encapsulation and Demultiplexing: IP Header

44. Encapsulation and Demultiplexing: TCP Header Option: maximum segment size

45. Encapsulation and Demultiplexing: TCP Header

46. Encapsulation and Demultiplexing: Application data No Application Data in this frame

47. Main Points of Lab 1  Getting acquainted Hardware setup Linux Network tools (ping, tcpdump, wireshark)  Lab reports How to capture data What to include / exclude in lab reports

48. Homework  Prelab 1 & 2 due on Friday (01.29.2010)  Lab report 1 due by next week  Read RFC 826 by next class