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Chapter 14

Chapter 14. Networking and Internetworking. Objectives. To describe networks, the Internret and internetworks and explain why they are used To discuss briefly the TCP/IP protocol suite, IP addresses , protocol ports , and internet services and applications

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Chapter 14

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  1. Chapter 14 Networking and Internetworking

  2. Objectives • To describe networks, the Internret and internetworks and explain why they are used • To discuss briefly the TCP/IP protocol suite, IP addresses, protocol ports, and internet services and applications • To explain what the client-server software model is and how it works • To discuss various network software tools for electronic communication , • remote login, • file transfer, • remote command execution , and • status reporting • To describe briefly the secure shell • To cover the commands and primitives Fall 2005 expanded by Jozef Goetz

  3. Computer Networks and Internet works • When two or more computer hardware resources are connected they form a computer network • Local area Networks (LANs) • Metropolitan area networks (MANs) • Wide area networks (WANs) • An internetwork is a network of networks Fall 2005 expanded by Jozef Goetz

  4. A brief history of the Internet. • ARPANET (50s and 60s, some universities) • NSFNET (late 70s, all universities) • TCP/IP (invention ’74) became the official protocol in 1983. • When NSFNET and the ARPANET were connected, the growth became exponential • Many regional networks (Canada, Europe, the Pacific) joined up • In mid-80s people began viewing the collection of networks as the Internet • The glue that holds the Internet togetheris the TCP/IP reference model and TCP/IP protocol stack • ANS (Advanced Networks and Service) by MERIT, MCI, and IBM took over NSFNET in 1990 as ANSNET • ANSNET sold to American Online in 1995. Fall 2005 expanded by Jozef Goetz

  5. The ARPANET (2) • The original ARPANET design. Fall 2005 expanded by Jozef Goetz

  6. The ARPANET (3) • Growth of the ARPANET (a) December 1969. (b) July 1970. (c) March 1971. (d) April 1972. (e) September 1972. Fall 2005 expanded by Jozef Goetz

  7. NSFNET • The NSFNET backbone in 1988. Fall 2005 expanded by Jozef Goetz

  8. Internet Usage • Machine is on the Internet if • it runs the TCP/IP protocol stack, • has an IP address, and • can send IP packets to all the other machines on the Internet • Millions PC can call up an Internet service provider using a modem, be assigned a temporaryIP address, and send IP packets to all the other hosts Fall 2005 expanded by Jozef Goetz

  9. Internet Usage • Traditional applications (1970 – 1990) • E-mail • News • newsgroups devoted to different topics) • Remote login • Using telnet, rlogin, ssh programs • File transfer • Using FTP programs Fall 2005 expanded by Jozef Goetz

  10. Internet Usage • Early ’90s new application the WWW (World Wide Web) • invented by physicist Tim Berbers-Lee brought millions of nonacademic users • They started using the Mosaic browser (GUI) and then other browsers • The ch-r of the network was changed from an academic and military playground to a public utility Fall 2005 expanded by Jozef Goetz

  11. Architecture of the Internet. • A NAP (Network Access Point) is a room full of routers, at least one per backbone • A LAN in the room connects all the routers, • so packetscan be forwarded from any backboneto any other backbone • Overview of the Internet. • Signal is transferred to the ISP’s (Internet Service Provider) POP – Point of Present(located in the tel. switching office) and injected into the ISP’s regional network • from this point the system is fully digital and packet switched Fall 2005 expanded by Jozef Goetz

  12. Collection of Subnetworks The Internet is an interconnected collection of many networks. Fall 2005 expanded by Jozef Goetz

  13. X.25 Networks • Developed during 70's. 1st public data network interface between public packet-switched networks and customers. Data packet has a 3-byte header (a 12 bit connection #, a packet sequence #, an acknowledgment # etc.) and up to 126 bytes of data • Operate at 64 Kbps, so are very slow and becoming outdated. However there are still many of them in operation. • Connection oriented. Uses: • Switched Virtual Circuit - established when the first packet is sent. Circuit remains for duration of session providing in-order delivery, and flow control. • Permanent Virtual Circuit - established by agreement between the customer and the carrier. Like a leased line. Fall 2005 expanded by Jozef Goetz

  14. Frame Relay • Takes advantage of modern high-speed reliabledigital phone lines. Connection oriented. Property: In-order delivery, no error control, no flow control Akin to LAN • This allows simple protocolswith work done by user computers rather than by the network. Runs at 1.5 Mbps with few features. • Customer leases a permanent virtual circuit between two points. • This "virtual leased line" means that the wire is shared with other users at a great price reduction. Fall 2005 expanded by Jozef Goetz

  15. Broadband ISDN and ATM Connection oriented. • ISDN(Integrated Services Digital Network) • offers cable, video on demand, e-mail, etc. • ATM (Asynchronous Transfer Mode) early ’90s is underlying • Mechanism inside the tel. system. • Transmits in small fixed-size cells. Not synchronous. • Was supposed to merge voice, data, cable TV, telex, telegraph etc. into a single integrated system – it didn’t happen • Alive, used by carriers for internal transport Fall 2005 expanded by Jozef Goetz

  16. (a) Computer Networks and (b) Internetworks Fall 2005 expanded by Jozef Goetz

  17. Why Computer Networks and Internetworks? • Sharing of computer resources • computers, printers, plotters, scanners, files and software • Network as a communication medium • inexpensive, fast, reliable • Cost efficiency • large computing power available • Less performance degradation • if one computer crashes, the remining ones are still up Fall 2005 expanded by Jozef Goetz

  18. Network Models • International Standards Organization’s Open System InterconnectReference Model (ISO’s OSI 7-Layer Reference Model) • The TCP/IP 5-layer Model • Used in the Internet Fall 2005 expanded by Jozef Goetz

  19. Network Models Fall 2005 expanded by Jozef Goetz

  20. Reference Models • Protocols and networks in the TCP/IP model initially. • The Application layer contains all of the higher-level protocols • – telnet - virtual terminal protocol • – FTP – file transfer • – SMTP – e-mail • – DNS - Domain Name System • – NNTP - Network News Transfer Protocol • – HTTP - Hypertext Transfer Protocol Fall 2005 expanded by Jozef Goetz

  21. The TCP/IP Protocol Suite • As a user you can see the application layer in the from of applications and utilities • Web browsing, • file transfer, • remote login • etc. 1st -2nd layer is handled by the Network Interface Card -NIC card Fall 2005 expanded by Jozef Goetz

  22. Transport Layer:The TCP and UDP • The purpose of the transport layer is to transport application data from your machine to a remote machine and vice versa • User Datagram Protocol(UDP) offers the best effort delivery service • Transmission Control Protocol (TCP) is a connection-oriented protocol that establish a virtual connection with the destination before transmitting data, • thus the TCP leads • completelyreliable, • error free • in-sequence delivery of data Fall 2005 expanded by Jozef Goetz

  23. Routing of the Application Data-The Internet Protocol (IP) • The network layer is responsible for routing application data to the destination host • IP is responsible for transporting IP datagrams containing TCP segments or UDP datagrams to the destination host • The IP is a connectionless protocol, it simply sends the application data without establishing virtual connection with the destination before transmitting data, • thus the IP routing is best effort and doesn’t guarantee delivery of TCP segments or UDP datagrams Fall 2005 expanded by Jozef Goetz

  24. Routing of the Application Data-The Internet Protocol (IP) • In IPv4 the IP address (32 bits) is divided into three fields: • address class, • network ID and • host ID • In IPv6 the IP address is 128 bits and it covers the # of hosts 6 x 2^28 times the present world population • The address class field identifies the class of the address and dictates the number of bits used in the network ID and host ID fields • This scheme has 5 address classes : A,B,C,D,E Fall 2005 expanded by Jozef Goetz

  25. IPv4 Address Classes The sum of network IDs for class A, B, C = 1,113,664 networks The sum of hosts IDs for class A, B, C = 3,758,096,400 hosts Fall 2005 expanded by Jozef Goetz

  26. IPv4 Addresses in Dotted Decimal Notation • 32-bit binary numbers are difficult to remember • IPv4 addresses are given in dotted decimal notation (DDN) • In DDN all 4 bytes of an IPv4 address are written in their decimal equivalents and are separated by dots • Example: 192.102.10.21 Fall 2005 expanded by Jozef Goetz

  27. IP Addresses IP address formats. • 127.0.0.0. (or 127.x.x.x, where x is between 0-127) is known as localhost is used to send a data packet to itself. for testing purpose. • host ID = 1…1 is the broadcast address in order to send a data packet to all hosts on a network Fall 2005 expanded by Jozef Goetz

  28. IPv4 Address Classes Figure 14.5  An internetwork of four networks with one class A, one class B, and two class C networks connected via 4 routers class C class A class C class B Fall 2005 expanded by Jozef Goetz

  29. Symbolic Names • Symbolic names are easier to remember • remain the same even if the numeric address changes • must be unique for a host on the Internet • Format: hostname.domain_name where: domain_name = organization_name.top-level_domain • organization_nameis assigned by the Network Information Center • Attaching the name of a host to a domain name with a period between them yields the fully qualified domain name (FQDN) for the host • e.g. egr.up.edu – egr is a host name at the University of Portland • e.g. faculty.ulv.edu – faculty is a host name at the University of La Verne Fall 2005 expanded by Jozef Goetz

  30. Top-Level Internet Domains Fall 2005 expanded by Jozef Goetz

  31. Fall 2005 expanded by Jozef Goetz

  32. The Domain Name System • Domain Name System (DNS) service translates symbolic names to equivalent IP addresses • DNS implements a distributed database of name-to-address mappings • A set of dedicated hosts run name serversthat take requests from the application software • and work together to map domain names to the corresponding IP addresses • every organization runs at least 1 name server • app uses gethostbyname() to get its IP address Fall 2005 expanded by Jozef Goetz

  33. The Domain Name System #a static hosts file contains the domain names and their IP addresses configureed by the system admin $ cat /etc/hosts # Internet host table # 127.0.0.1 localhost 203.128.0.6 yamsrv1.ece.gatech.edu loghost 203.128.0.1 shahalami 192.168.1.1 suraj-ge0 $ $ /sbinifconfig -a lo0: flags=849<UP,LOOPBACK,RUNNING,MULTICAST> mtu 8232 inet 127.0.0.1 netmask ff000000 le0: flags=863<UP,BROADCAST,NOTRAILERS,RUNNING,MULTICAST> mtu 1500 inet 192.102.10.89 netmask ffffff00 broadcast 192.102.10.255 $ Fall 2005 expanded by Jozef Goetz

  34. The Domain Name System • [jgoetz@raq4 ~]$ nslookup faculty.ulv.edu • Server: NS.ULV.EDU # this a name server • Address: 64.69.149.200 • Name: faculty.ulv.edu • Address: 192.231.179.91 • [jgoetz@raq4 ~]$ host 192.231.179.91 • 91.179.231.192.IN-ADDR.ARPA domain name pointer FACULTY.ULV.EDU Fall 2005 expanded by Jozef Goetz

  35. The Domain Name System Fall 2005 expanded by Jozef Goetz

  36. The Domain Name System • nslookup uses file /etc/resolv.conf to find the host that runs the name server and passes the request over it. titan/jozefg > cat /etc/resolv.conf domain ecs.fullerton.edu search ecs.fullerton.edu fullerton.edu nameserver 127.0.0.1 nameserver 137.151.27.1 nameserver 137.151.1.1 titan/jozefg > Fall 2005 expanded by Jozef Goetz

  37. The Domain Name System • nslookup uses file /etc/resolv.conf to find the host that runs the name server and passes the request over it. • dig interacts with name servers specified in /etc/resolv.conf and display their responses Fall 2005 expanded by Jozef Goetz

  38. The Domain Name System [jgoetz@raq4 ~]$ dig faculty.ulv.edu ; <<>> DiG 8.3 <<>> faculty.ulv.edu ;; res options: init recurs defnam dnsrch ;; got answer: ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 4 ;; flags: qr aa rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 2, ADDITIONAL: 2 ;; QUERY SECTION: ;; faculty.ulv.edu, type = A, class = IN ;; ANSWER SECTION: faculty.ulv.edu. 1D IN A 192.231.179.91 ;; AUTHORITY SECTION: ulv.edu. 1D IN NS ns.ulv.edu. ulv.edu. 1D IN NS ns2.ulv.edu. ;; ADDITIONAL SECTION: ns.ulv.edu. 1D IN A 64.69.149.200 ns2.ulv.edu. 1D IN A 64.69.154.123 ;; Total query time: 25 msec ;; FROM: raq4.ulv.edu to SERVER: default -- 64.69.149.200 ;; WHEN: Wed Nov 16 22:25:25 2005 ;; MSG SIZE sent: 33 rcvd: 116 Fall 2005 expanded by Jozef Goetz

  39. A portion of the Internet domainname hierarchy Fall 2005 expanded by Jozef Goetz

  40. Request For Comments (RFCs) • The TCP/IP standards are described in a series of documents, known as the Request for Comments • RFCs are first published as the Internet Drafts and are made available to all Internet users for reviewer and feedback by placing them in known RFC repositories • After the review process is complete, a draft can become a standard • Some RFCs are for information only others are experimental Fall 2005 expanded by Jozef Goetz

  41. Well-known Internet Services Fall 2005 expanded by Jozef Goetz

  42. The Client-Server Software Model • Internet services are implemented by using a paradigm in which the software for a service is partitioned into 2 parts • The part that runs on the host on which the user running the application is logged on to is called the client software • The part that’s usually starts running when a host boots is called the server software • Connection-oriented client server models: • client sends a connection request to the server and • the server either rejects or accepts the request. • If server accepts the request, the client and server are said to be connected through a virtual connection Fall 2005 expanded by Jozef Goetz

  43. The Client-Server Software Model http://faculty.ulv.edu/~jgoetz/ Fall 2005 expanded by Jozef Goetz

  44. Displaying the Names uname [OPTION]... DESCRIPTION Print certain system information. With no OPTION, same as -s. -a, --all print all information -m, --machine print the machine (hardware) type -n, --nodename print the machine's network node hostname -r, --release print the operating system release -s, --sysname print the operating system name -p, --processor print the host processor type -v print the operating system version --help display this help and exit --version output version information and exit [jgoetz jgoetz]$ uname Linux [jgoetz jgoetz]$ uname -n raq4.ulv.edu [jgoetz jgoetz]$ uname -a [jgoetz jgoetzLinux raq4.ulv.edu 2.2.16C37_V #1 Sat Apr 12 15:06:43 PDT 2003 i686 unknown Fall 2005 expanded by Jozef Goetz

  45. Displaying the Host Name $ uname -n yamsrv1.ece.gatech.edu $ uname -a SunOS yamsrv1.ece.gatech.edu 5.8 Generic_108528-22 sun4u sparc SUNW,Ultra-250 $ hostname– name of the host you are logged on to yamsrv1.ece.gatech.edu [jgoetz jgoetz]$ hostname raq4.ulv.edu Fall 2005 expanded by Jozef Goetz

  46. Displaying Users on a Network $ rwho | more - remote who displays info about the usercurrently using machines on your network: log name, computer:terminal, date and time the user logged in Bobk upibm7:ttyC4 Jul 26 12:03 Dfrakes upibm47:ttyp2 Jul 26 11:49 Lulay upsun17:pts/0 Jul 26 10:17 Oster upsun17:pts/2 Jul 26 12:28 Sarwar upibm7:ttyp2 Jul 26 11:15 $ rwho -a | more Bobk upibm7:ttyC4 Jul 26 12:03 dfrakes upibm47:ttyp2 Jul 26 11:49 kent upibm48:ttyp0 Jul 26 03:41 8:49 kittyt upibm9:ttyp0 Jul 26 07:36 1:28 kuhn upsun29:console Jul 16 13:11 99:59 lulay upsun17:pts/0 Jul 26 10:17 oster upsun17:pts/2 Jul 26 12:28 pioster upsun20:pts/0 Jul 26 09:53 2:41 sarwar upibm7:ttyp2 Jul 26 11:15 sarwar upsun29:pts/0 Jul 26 11:24 1:00 $ Fall 2005 expanded by Jozef Goetz

  47. Displaying Users on a Network rusers [options] [host_list] Purpose: Display the login names of the remote userslogged on to all the machines on ourlocal network Output: Information about the users logged on to the hosts on your local network in one line per machine format Commonly used options/features: -a Display allhost names even if no user is using it -l Display the user information in a long format similar to that displayed by the who command Fall 2005 expanded by Jozef Goetz

  48. Displaying Users on a Network for particular machine Fall 2005 expanded by Jozef Goetz

  49. Displaying the Status of Hosts on a Network ruptime [options] – remote uptime Purpose:Show status of all connected machines on the local area network Output: Status of machines including machine name, up/down status, time a machine has been up (or down) for-called machine uptime, and the number of users logged on to the machine Commonly used options/features after sorting: -l Display output after sorting it with load average -t Display output after sorting it by machine uptime -u Display output after sorting it by the number of users Fall 2005 expanded by Jozef Goetz

  50. Displaying the Status of Hosts on a Network Commonly used options/features after sorting: -l Display output after sorting it with load average -t Display output after sorting it by machine uptime -u Display output after sorting it by the number of users Fall 2005 expanded by Jozef Goetz

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