COMS/CSEE 4140 Networking Laboratory Salman Abdul Baset Spring 2008 Agenda Administrivia Introduction to the lab equipment A simple TCP/IP example Overview of important networking.
Download ReportTranscript COMS/CSEE 4140 Networking Laboratory Salman Abdul Baset Spring 2008 Agenda Administrivia Introduction to the lab equipment A simple TCP/IP example Overview of important networking.
COMS/CSEE 4140 Networking Laboratory Salman Abdul Baset Spring 2008 Agenda Administrivia Introduction to the lab equipment A simple TCP/IP example Overview of important networking concepts 2 Course overview Goals Prerequisites Gain hands-on experience Apply and reinforce important networking concepts and techniques learned in CS4119 No socket programming CS4119, ELEN4710, ELEN6761 or equivalent Organization Weekly lectures review relevant materials Weekly labs 3 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 ) 4 Course staff Instructor: Salman Abdul Baset OHs: Tuesday 10am-12pm CEPSR 720/7LW2 Email: [email protected] TAs Jong-Yul Kim OHs: Friday 10:00am – 12pm CEPSR 721 Email: [email protected] Ankit Malhotra OHs: Thursday 10:30am-12:30pm INTEREST Lab Email: [email protected] 5 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 6 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 1st to the instructor 7 Structure of the labs Each lab has four parts: 1. 2. 3. 4. Prelab (individual) Lab session (group) Lab report (group) Feedback forms (individual – optional) 8 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 TCP/IP tutorial and technical overview (IBM Red Book) by A.Rodriguez, J. Gatrell, J. Karas, R.Peschke (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 9 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) 10 Other requirements CS account Swipe access through CRF MICE Facilities->Card Access->Request Access Level 6 Sponsor: Salman Baset End date: May 15, 2008 USB flash drive One per group 11 Website, discussion board Website http://www1.cs.columbia.edu/~salman/4140/ Discussion board, grades, prelab/lab report submissions http://courseworks.columbia.edu 12 Agenda Administrivia Introduction to the lab equipment A simple TCP/IP example Overview of important networking concepts 13 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 14 Internet Lab Equipment Router 1 Router 2 Router 3 Router 4 PC1 PC2 PC3 PC4 15 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 16 Linux PC 17 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 18 Ethernet Hubs Each hub has 4 or more RJ-45 ports Ports can operate at 10 Mbps or 100 Mbps 19 Connectors DB-9 (DE-9) connector (serial port) male PS2 Mini DIN 6 DB-25 connector DE-15/HD-15 (VGA connector) RJ-45 connector female 20 Ethernet Cables Category 5e cable (4 pairs) Straight cable Cross over cable Automatic roll over NICs 21 Lab Sequence Core Labs: Lab 1 Introduction to the Internet Lab Lab 2 - Single Segment IP Networks Lab 7 - NAT and DHCP Lab 3 - Static Routing Lab 4 Dynamic Routing Protocols Lab 5 Transport Protocols: UDP and TCP Lab 8 - Domain Name System Lab 9 - SNMP Lab 10 - IP Multicast Advanced Labs: Lab 6 - LAN switching 22 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. 23 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. 24 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. 25 In the Lab: 1. 2. 3. 4. 5. 6. 7. Submit Prelab through courseworks Bring USB drive, the lab manual Reboot Linux PCs Complete exercises as described in the lab manual Take measurements as instructed Save data to the USB drive Submit lab report through courseworks 26 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. 27 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? 28 Agenda Administrivia Introduction to the lab equipment A simple TCP/IP example Overview of important networking concepts 29 Topology Web request Web page Web client Web server 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? 30 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 31 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 32 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 <HTML> <BODY> <H1>Internet Lab</H1> Click <a href="http://www.netlab.net/index.html">here</a> for the Internet Lab webpage. </BODY> </HTML> • How does the HTTP request get from Argon to Neon ? 33 From HTTP to TCP Argon Neon HTTP client HTTP request / HTTP response HTTP server TCP client TCP connection TCP server 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 34 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. 35 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 36 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: ftp 21 finger 79 telnet 23 http 80 smtp 25 nntp 119 tftp 69 ssh 23 ntp 123 37 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 38 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 39 connection) 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). 40 The route from Argon to Neon Note that the gateway has a different name for each of its interfaces. 41 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) 42 Address resolution with ARP 43 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 44 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 45 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 46 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). 47 Invoking the Device Driver at the Router The IP protocol at Router71, tells its Ethernet device driver to send an Ethernet frame to address 00:20:af:03:98:28 48 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. 49 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 50 Wrapping up the example Data traverses a sequence of layers Each layer has protocols to handle the packets 51 Agenda Administrivia Introduction to the lab equipment A simple TCP/IP example Overview of important networking concepts 52 TCP/IP Suite and OSI Reference Model Application Layer The TCP/IP protocol stack does not define the lower layers of a complete protocol stack Application Layer Transport Layer Network Layer (Data) Link Layer Presentation Layer Session Layer Transport Layer Network Layer (Data) Link Layer Physical Layer TCP/IP Suite OSI Reference Model 53 Functions of the Layers Data Link Layer: Service: Functions: Network Layer: Service: Functions: Move packets from source host to destination host Routing, addressing Service: Functions: Delivery of data between hosts Connection establishment/termination, error control, flow control Transport Layer: Reliable transfer of frames over a link Media Access Control on a LAN Framing, media access control, error checking Application Layer: Service: HTML Functions: Application specific (delivery of email, retrieval of documents, reliable transfer of file) Application specific 54 Assignment of Protocols to Layers ping application HTTP Telnet FTP TCP DNS SNMP Application Layer Transport Layer UDP Routing Protocols ICMP RIP IP IGMP PIM Network Layer OSPF DHCP ARP Ethernet Data Link Layer 55 Network Interface 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 N+1 Layer Protocol N+1 Layer N+1 Layer services N+1 Layer Entity Entity layer N+1/N interface N Layer N Layer Entity N Layer Protocol N Layer Entity N-1 Layer Entity N-1 Layer Protocol N-1 Layer Entity layer N/N-1 interface N-1 Layer 56 Layered Communications A layer N+1 entity sees the lower layers only as a service provider N+1 Layer Entity N+1 Layer Peer Protocol N+1 Layer Entity Indicate Delivery Request Delivery Service Provider 57 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 N Layer Layer-N Entity Layer N-1 SAP layer N/N-1 service interface N-1 Layer Layer- N-1 Entity 58 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 A N Layer Entity PDU (at layer N) N Layer Entity B 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 59 PDU at layer-N-1 = layer-N-1 Header + layer –N PDU Exchange of Data A B Layer-N Entity control Layer-N PDU and control data is sent to SAP of Layer-N-1 Layer-N Entity N PDU SAPs Layer- N-1 Entity Layer- N-1 Entity Header control N PDU (of layer N-1) N PDU PDU of Layer-N-1 60 Layers in the Example HTTP HTTP protocol HTTP TCP TCP protocol TCP IP Ethernet IP IP protocol Ethernet argon.tcpiplab.edu 128.143.137.144 Ethernet IP protocol Ethernet Ethernet router71.tcpip- router137.tcpiplab.edu lab.edu 128.143.137.1 128.143.71.1 00:e0:f9:23:a8:20 IP Ethernet neon.tcpip-lab.edu 128.143.71.21 61 Layers in the Example HTTP TCP IP Frame is an IP datagram Ethernet Send HTTP Request to neon Establish a connection to 128.143.71.21 at port 80Open TCP connection to 128.143.71.21 port 80 IP datagram is a TCP segment for port 80 Send IP data-gram to Send a datagram (which contains a connection Send IP datagram to IP 128.143.71.21 request) to 128.143.71.21 128.143.71.21 Frame is an IP datagram Send the datagram to 128.143.137.1 Ethernet Ethernet HTTP TCP IP Send the datagram Ethernet to 128.143.7.21 argon.tcpipneon.tcpip-lab.edu router71.tcpip- router137.tcpipSend Ethernet frame Send Ethernet frame lab.edu 128.143.71.21 lab.edu to 00:20:af:03:98:28 to 00:e0:f9:23:a8:20 lab.edu 128.143.137.144 128.143.137.1 128.143.71.1 00:e0:f9:23:a8:20 62 Layers and Services Service provided by TCP to HTTP: Service provided by IP to TCP: unreliable transmission of IP datagrams across an IP network Service provided by Ethernet to IP: reliable transmission of data over a logical connection 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 63 Encapsulation and Demultiplexing As data is moving down the protocol stack, each protocol is adding layer-specific control information User data HTTP HTTP Header User data HTTP Header User data TCP TCP Header IP TCP segment IP Header Ethernet TCP Header HTTP Header User data IP datagram Ethernet Header IP Header TCP Header HTTP Header Ethernet frame User data Ethernet Trailer 64 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 4500 8990 0000 05b4 f923 002c 808f 0000 a820 9d08 4715 6002 00a0 4000 065b 2000 2471 8006 0050 598e e444 8bff 0009 0000 0800 808f 465b 0204 65 Ethereal View 1: Summary of packets View2: Details of packet headers View 3: Packet content in hexadecimal and ASCII representation 66 Parsing the information in the frame 4 bytes destination address 00:e0:f9:23:a8:20 Ethernet header (14 bytes) source address 0:a0:24:71:e4:44 type 0x0800 version 0x4 IP Header (20 bytes) Type of Service/TOS 0x5 0x00 Identification flags 0x9d08 0102 time-to;ive protocol 0x80 0x06 cource IP address 128.143.137.144 destination IP address 128.143.71.21 header length source port number 162710 TCP Header (24 bytes) 0x6 Ethernet trailer (4 bytes) destination port number 8010 sequence number 0x0009465b acknowledgement number 0x00000000 flags 0000102 unused 0000002 TCP checksum 0x598e option type option length 0x02 0x04 header length total length (in bytes) 0x002c fragment offset 00000000000002 header checksum 0x8bff window size 819210 urgent pointer 0x0000 maximum segment size 146010 CRC 67 Encapsulation and Demultiplexing 6 bytes destination address 4 bytes source address type Ethernet Header CRC IP Header TCP Header Application data Ethernet Trailer Ethernet frame 68 Encapsulation and Demultiplexing: Ethernet Header 6 bytes 00:e0:f9:23:a8:20 4 bytes 0:a0:24:71:e4:44 0x0800 Ethernet Header CRC IP Header TCP Header Application data Ethernet Trailer Ethernet frame 69 Encapsulation and Demultiplexing: IP Header 32 bits version (4 bits) header length DS flags (3 bits) Identification (16 bits) TTL Time-to-Live (8 bits) Total Length (in bytes) (16 bits) ECN Protocol (8 bits) Fragment Offset (13 bits) Header Checksum (16 bits) Source IP address (32 bits) Destination IP address (32 bits) Ethernet Header IP Header TCP Header Application data Ethernet Trailer Ethernet frame 70 Encapsulation and Demultiplexing: IP Header 32 bits 0x4 0x5 0x0 0x0 9d08 12810 4410 0102 00000000000002 0x06 8bff 128.143.137.144 128.143.71.21 Ethernet Header IP Header TCP Header Application data Ethernet Trailer Ethernet frame 71 Encapsulation and Demultiplexing: TCP Header 32 bits Source Port Number Destination Port Number Sequence number (32 bits) Acknowledgement number (32 bits) header length 0 Flags TCP checksum option type length window size urgent pointer Max. segment size Option: maximum segment size Ethernet Header IP Header TCP Header Application data Ethernet Trailer Ethernet frame 72 Encapsulation and Demultiplexing: TCP Header 32 bits 162710 8010 60783510 010 610 0000002 0000102 0x598e 210 Ethernet Header IP Header 819210 00002 410 TCP Header 146010 Application data Ethernet Trailer Ethernet frame 73 Encapsulation and Demultiplexing: Application data No Application Data in this frame Ethernet Header IP Header TCP Header Application data Ethernet Trailer Ethernet frame 74 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. Argon 128.143.137.144 Neon 128.143.71.21 HTTP client HTTP server HTTP server TCP client TCP server TCP server IP Network 75 Network View of IP Protocol 76 Network View of Ethernet Ethernet’s view of the network 77 What a router chassis looks like Cisco CRS-1 Juniper M320 19” 17” Capacity: 1.2 Tb/s Power: 10.92 KWh Weight: 0.5 Ton Cost: $500K 6ft Capacity: 320 Gb/s Power: 3.1 kWh 3ft 2ft 2ft 78 Cisco CRS-1 79 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. 80