1. COMS/CSEE 4140 Networking Laboratory Salman Abdul Baset Spring 2008

2. 2 Agenda  Administrivia  Introduction to the lab equipment  A simple TCP/IP example  Overview of important networking concepts

3. 3 Course overview  Goals Gain hands-on experience Apply and reinforce important networking concepts and techniques learned in CS4119 No socket programming  Prerequisites CS4119, ELEN4710, ELEN6761 or equivalent  Organization Weekly lectures review relevant materials Weekly labs

4. 4 Materials covered (partial list)  Wide area networks Internetworking Static & dynamic routing  RIP, OSPF, BGP UDP & TCP  LAN switching & bridges  DHCP, NAT, DNS, SNMP (and various other 3 & 4 letter acronyms )

5. 5 Course staff  Instructor: Salman Abdul Baset OHs: Tuesday 10am-12pm CEPSR 720/7LW2 Email: salman@cs.columbia.edu salman@cs.columbia.edu  TAs  Jong-Yul Kim OHs: Friday 10:00am – 12pm CEPSR 721 Email: jyk@cs.columbia.edu jyk@cs.columbia.edu  Ankit Malhotra OHs: Thursday 10:30am-12:30pm INTEREST Lab Email: am2994@columbia.edu am2994@columbia.edu

6. 6 Lectures/labs: when and where?  Lectures When: Mondays: 5:40pm – 6:55pm Where: CLIC lab (486 CSB)  Labs When: Meeting times depend on groups Where: INTEREST lab Three slots (FCFS policy and/or time conflicts):  Mondays: 7pm-9:30pm  Tuesday: 7pm-9:30pm  Wednesday: 1pm-3:30pm

7. 7 Lab organization  Groups ( 3 people) One report per group Pre-labs and feedback form (optional) to be completed by each of the students individually  Group selection Find people that you can work with Random selection is also a choice Email group info by Feb 1 st to the instructor

8. 8 Structure of the labs  Each lab has four parts: 1. Prelab (individual) 2. Lab session (group) 3. Lab report (group) 4. Feedback forms (individual – optional)

9. 9 Bibliography & readings  TextBook Mastering Networks: An Internet Lab Manual by Jorg Liebeherr and Magda El Zarki ISBN: 0-201-78134-4. Publisher: Addison-Wesley. Copyright: 2004. Sample Chapters and more info at the authors' Web Site Sample Chapters and more info at the authors' Web Site TCP/IP tutorial and technical overview (IBM Red Book) by A.Rodriguez, J. Gatrell, J. Karas, R.Peschke (online)online  Reference books Computer networking: a top-down approach featuring the Internet by James Kurose and Keith Ross Cisco essentials book and Cisco web site Unix man pages & RFCs  Course web site will be populated with FAQ & links

10. 10 Grading scheme  Pre-lab questions: (20%) (individual)  Lab Reports (40%) (group)  Two exams, each 15% (30%) (individual) Final exam can be replaced by a group project  Class participation (5%) (individual) Lab participation (5%) (individual) (TAs may randomly ask a group member any question related to the lab)

11. 11 Other requirements  CS account through CRF  Swipe access MICE Facilities->Card Access->Request Access Level 6 Sponsor: Salman Baset End date: May 15, 2008  USB flash drive One per group

12. 12 Website, discussion board  Website http://www1.cs.columbia.edu/~salman/4140/  Discussion board, grades, prelab/lab report submissions http://courseworks.columbia.edu http://courseworks.columbia.edu

13. 13 Agenda  Administrivia  Introduction to the lab equipment  A simple TCP/IP example  Overview of important networking concepts

14. 14 Internet Lab Equipment  4 Cisco 2600 Routers  4 Linux PCs (Intel Celeron 2GHz, 256MB Ram, 40GB disk, cdrom, floppy, USB)  2 Ethernet hubs 2x 5-port Hub 3Com OfficeConnect Dual Speed (10/100) 2x 16-port NETGEAR hub  2 monitors, 2 keyboards, 2 mice  1 KVM switch  Cables

15. 15 Internet Lab Equipment PC1 PC2 PC3 PC4 Router 1 Router 2 Router 3 Router 4

16. 16 Linux PCs  PCs and routers are labeled as: PC1, PC2, etc, Router1, Router2, etc.  PCs run Linux Fedora Core 5  Each PC has: a floppy drive, a cdrom drive, a serial port, 5x 10/100 Mbps Ethernet interface cards (NICs) named eth0 – eth4. 2x USB ports

17. 17 Linux PC

18. 18 Cisco Routers  Routers are labeled: Router1, Router2, Router3, Router4.  Routers run Cisco IOS 12.0 or a later version  Each router has: a console port an auxiliary port two 10/100 Mbps Fast Ethernet interfaces

19. 19 Ethernet Hubs  Each hub has 4 or more RJ-45 ports  Ports can operate at 10 Mbps or 100 Mbps

20. 20 Connectors  DB-9 (DE-9) connector (serial port)  PS2 Mini DIN 6  DB-25 connector  DE-15/HD-15 (VGA connector)  RJ-45 connector malefemale

21. 21 Ethernet Cables  Category 5e cable (4 pairs)  Straight cable  Cross over cable  Automatic roll over NICs

22. 22 Lab Sequence

23. 23 Core Labs  Lab 1 – Introduction to the Internet Lab Overview of the Internet Lab equipment; introduction to ethereal and tcpdump.  Lab 2 – Single Segment IP Networks Configuring a network interface for IP networking; address resolution with ARP; security problems of common Internet applications.

24. 24 Core Labs (cont.)  Lab 3 – Static routing IP forwarding and routing between IP networks; setup a Linux PC and a Cisco router as an IP router; manual configuration of routing tables.  Lab 4 – Dynamic Routing Protocols Routing protocols RIP, OSPF and BGP.  Lab 5 – Transport Protocols: UDP and TCP Data transmissions with TCP and UDP; TCP connection management; TCP flow control; retransmissions in TCP; TCP congestion control.

25. 25 Advanced Labs  Lab 6 - LAN switching LAN switching in Ethernet networks; forwarding of Ethernet frames between LAN switches/bridges; spanning tree protocol for loop free routing between interconnected LANs.  Lab 7 - NAT and DHCP Setup of a private network; dynamic assignment of IP addresses with DHCP.  Lab 8 – Domain Name System Domain name resolution with DNS; name server hierarchy; setup of a DNS root server.  Lab 10 – IP Multicast Multicast group management with IGMP; IP multicast forwarding; Multicast routing protocols PIM-SM and PIM-DM.

26. 26 In the Lab: 1. Submit Prelab through courseworks 2. Bring USB drive, the lab manual 3. Reboot Linux PCs 4. Complete exercises as described in the lab manual 5. Take measurements as instructed 6. Save data to the USB drive 7. Submit lab report through courseworks

27. 27 Additional notes  The equipment of the Internet Lab is not connected to the Internet. Warning: Do not connect the lab equipment to the Internet.  Each lab has an anonymous feedback sheet. The feedback is used to improve the setup and organization of the labs.  Since you have administrative (root) privileges on the Internet Lab equipment, exercise caution when modifying the configuration of the Internet Lab equipment.  No eating or drinking in the lab.  Bring your laptops to the lab.

28. 28 Tips for the lab  Ethereal is your best friend in 4140!  Each lab session comprises of several [sometimes independent] exercises. Discuss with your group members if you can do the exercise in parallel.  Traffic does not flow! the power is on? connected to the correct interface? interface LED? ethernet wire is behaving correctly? ARP and routing tables? are you observing traffic on the correct interface?

29. 29 Agenda  Administrivia  Introduction to the lab equipment  A simple TCP/IP example  Overview of important networking concepts

30. 30 Topology Web request Web page  A user on host argon.netlab.edu (“Argon”) makes web access to URL http://neon.netlab.edu/index.html.  What actually happens in the network? Web clientWeb server

31. 31 HTTP Request and HTTP response  Web server runs an HTTP server program  HTTP client Web browser runs an HTTP client program  sends an HTTP request to HTTP server  HTTP server responds with HTTP response

32. 32 HTTP Request GET /example.html HTTP/1.1 Accept: image/gif, */* Accept-Language: en-us Accept-Encoding: gzip, deflate User-Agent: Mozilla/4.0 Host: 192.168.123.144 Connection: Keep-Alive

33. 33 HTTP Response HTTP/1.1 200 OK Date: Sat, 25 May 2002 21:10:32 GMT Server: Apache/1.3.19 (Unix) Last-Modified: Sat, 25 May 2002 20:51:33 GMT ETag: "56497-51-3ceff955" Accept-Ranges: bytes Content-Length: 81 Keep-Alive: timeout=15, max=100 Connection: Keep-Alive Content-Type: text/html Internet Lab Click here for the Internet Lab webpage. How does the HTTP request get from Argon to Neon ?

34. 34 From HTTP to TCP  To send request, HTTP client program establishes an TCP connection to the HTTP server Neon.  The HTTP server at Neon has a TCP server running

35. 35 Resolving hostnames and port numbers  Since TCP does not work with hostnames and also would not know how to find the HTTP server program at Neon, two things must happen: 1. The name “neon.netlab.edu” must be translated into a 32-bit IP address. 2. The HTTP server at Neon must be identified by a 16-bit port number.

36. 36 Translating a hostname into an IP address  The translation of the hostname neon.netlab.edu into an IP address is done via a database lookup  The distributed database used is called the Domain Name System (DNS)  All machines on the Internet have an IP address: argon.netlab.edu 128.143.137.144 neon.netlab.edu 128.143.71.21

37. 37 Finding the port number  Note: Most services on the Internet are reachable via well-known ports. E.g. HTTP servers on the Internet can be reached at port number “80”.  So: Argon simply knows the port number of the HTTP server at a remote machine.  On most Unix systems, the well-known ports are listed in a file with name /etc/services. The well-known port numbers of some of the most popular services are: ftp21finger79 telnet23http80 smtp 25nntp 119 tftp69ssh23 ntp123

38. 38 Requesting a TCP Connection  The HTTP client at argon.netlab.edu requests the TCP client to establish a connection to port 80 of the machine with address 128.141.71.21

39. 39 Invoking the IP Protocol  The TCP client at Argon sends a request to establish a connection to port 80 at Neon  This is done by asking its local IP module to send an IP datagram to 128.143.71.21  (The data portion of the IP datagram contains the request to open a connection)

40. 40 Sending the IP datagram to an IP router  Argon (128.143.137.144) can deliver the IP datagram directly to Neon (128.143.71.21), only if it is on the same local network (“subnet”)  But Argon and Neon are not on the same local network (Q: How does Argon know this?)  So, Argon sends the IP datagram to its default gateway  The default gateway is an IP router  The default gateway for Argon is Router137.netlab.edu (128.143.137.1).

41. 41 The route from Argon to Neon  Note that the gateway has a different name for each of its interfaces.

42. 42 Finding the MAC address of the gateway  To send an IP datagram to Router137, Argon puts the IP datagram in an Ethernet frame, and transmits the frame.  However, Ethernet uses different addresses, so-called Media Access Control (MAC) addresses (also called: physical address, hardware address).  Therefore, Argon must first translate the IP address 128.143.137.1 into a MAC address.  The translation of addressed is performed via the Address Resolution Protocol (ARP)

43. 43 Address resolution with ARP

44. 44 Invoking the device driver  The IP module at Argon, tells its Ethernet device driver to send an Ethernet frame to address 00:e0:f9:23:a8:20

45. 45 Sending an Ethernet frame  The Ethernet device driver of Argon sends the Ethernet frame to the Ethernet network interface card (NIC)  The NIC sends the frame onto the wire

46. 46 Forwarding the IP datagram  The IP router receives the Ethernet frame at interface 128.143.137.1, recovers the IP datagram and determines that the IP datagram should be forwarded to the interface with name 128.143.71.1  The IP router determines that it can deliver the IP datagram directly

47. 47 Another lookup of a MAC address  The router needs to find the MAC address of Neon.  Again, ARP is invoked, to translate the IP address of Neon ( 128.143.71.21) into the MAC address of neon (00:20:af:03:98:28).

48. 48  The IP protocol at Router71, tells its Ethernet device driver to send an Ethernet frame to address 00:20:af:03:98:28 Invoking the Device Driver at the Router

49. 49 Sending another Ethernet frame  The Ethernet device driver of Router71 sends the Ethernet frame to the Ethernet NIC, which transmits the frame onto the wire.

50. 50 Data has arrived at Neon  Neon receives the Ethernet frame  The payload of the Ethernet frame is an IP datagram which is passed to the IP protocol.  The payload of the IP datagram is a TCP segment, which is passed to the TCP server

51. 51 Wrapping up the example  Data traverses a sequence of layers  Each layer has protocols to handle the packets

52. 52 Agenda  Administrivia  Introduction to the lab equipment  A simple TCP/IP example  Overview of important networking concepts

53. 53 TCP/IP Suite and OSI Reference Model The TCP/IP protocol stack does not define the lower layers of a complete protocol stack

54. 54 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

55. 55 Assignment of Protocols to Layers

56. 56 Layered Communications  An entity of a particular layer can only communicate with: 1. a peer layer entity using a common protocol (Peer Protocol) 2. adjacent layers to provide services and to receive services

57. 57 Layered Communications 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

58. 58 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

59. 59 Exchange of Data  The unit of data send between peer entities is called a Protocol Data Unit (PDU)  For now, let us think of a PDU as a single packet  Scenario: Layer-N at A sends a layer-N PDU to layer-N at B  What actually happens: A’s layer-N passes the PDU to one the SAPs at layer-N-1 Layer-N-1 entity at A constructs its own (layer-N-1) PDU which it sends to the layer-N-1 entity at B PDU at layer-N-1 = layer-N-1 Header + layer –N PDU AB

60. 60 Exchange of Data AB

61. 61 Layers in the Example

62. 62 Layers in the Example Send HTTP Request to neon Establish a connection to 128.143.71.21 at port 80 Open TCP connection to 128.143.71.21 port 80 Send a datagram (which contains a connection request) to 128.143.71.21 Send IP datagram to 128.143.71.21 Send the datagram to 128.143.137.1 Send Ethernet frame to 00:e0:f9:23:a8:20 Send Ethernet frame to 00:20:af:03:98:28 Send IP data-gram to 128.143.71.21 Send the datagram to 128.143.7.21 Frame is an IP datagram IP datagram is a TCP segment for port 80

63. 63 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

64. 64 Encapsulation and Demultiplexing  As data is moving down the protocol stack, each protocol is adding layer-specific control information

65. 65 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

66. 66 Ethereal

67. 67 Parsing the information in the frame

68. 68 Encapsulation and Demultiplexing

69. 69 Encapsulation and Demultiplexing: Ethernet Header

70. 70 Encapsulation and Demultiplexing: IP Header

71. 71 Encapsulation and Demultiplexing: IP Header

72. 72 Encapsulation and Demultiplexing: TCP Header Option: maximum segment size

73. 73 Encapsulation and Demultiplexing: TCP Header

74. 74 Encapsulation and Demultiplexing: Application data No Application Data in this frame

75. 75 Different Views of Networking  Different Layers of the protocol stack have a different view of the network. This is HTTP’s and TCP’s view of the network.

76. 76 Network View of IP Protocol

77. 77 Network View of Ethernet  Ethernet’s view of the network

78. 78 What a router chassis looks like Cisco CRS-1Juniper M320 6ft 19 ” 2ft Capacity: 1.2 Tb/s Power: 10.92 KWh Weight: 0.5 Ton Cost: $500K 3ft 2ft 17 ” Capacity: 320 Gb/s Power: 3.1 kWh

79. 79 Cisco CRS-1

80. 80 Next week  Lab 1 & 2  Submit prelab 1 & 2 through courseworks  Apply for swipe access  Form a group  Bring a USB drive  Reading Chapter 0, p1-25, 45-71 Optional: IBM red book, chapter 1.