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Chapter 14 Networking and Internetworking. Credits: Parts of the slides are based on slides created by UNIX textbook authors, Syed M. Sarwar, Robert Koretsky, Syed A. Sarwar, 2005 Addison Wesley. expanded by Jozef Goetz, 2012. Objectives.
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Chapter 14 Networking and Internetworking Credits: Parts of the slides are based on slides created by UNIX textbook authors, Syed M. Sarwar, Robert Koretsky, Syed A. Sarwar, 2005 Addison Wesley expanded by Jozef Goetz, 2012
Objectives • You may ignore all slides with commands started with r* • To describe networks, the Internet 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
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
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 overNSFNET in 1990 as ANSNET • ANSNET sold to American Online in 1995.
The ARPANET • The original ARPANET design. IMP - Interface Message Processor
The ARPANET • Growth of the ARPANET (a) December 1969. (b) July 1970. (c) March 1971. (d) April 1972. (e) September 1972.
NSFNET • The NSFNET backbone in 1988.
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 atemporary (dynamic) IP address, and send IP packets to all the other hosts
Internet Usage • Traditional applications (1970 – 1990) • E-mail • News • newsgroups devoted to different topics) • Remote login • Using telnet, WinSCP, rlogin, ssh programs • File transfer • Using FTP programs
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
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
Collection of Subnetworks The Internet is an interconnected collection of many networks. SNA: Systems Network Architecture -IBM's mainframe network standards
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 • circuitremains 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
Frame Relay • Takes advantage of modern high-speed reliabledigital phonelines. Connection oriented. Property: In-order delivery, no error control, no flow control, akin to LAN • This allows simple protocolswith work done by user computersrather than by the network. • Runs at 1.5 Mbps with few features. • Customer leasesapermanent virtual circuit between two points. • this "virtual leased line" means that the wire is shared with other users at a great price reduction.
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
(a) Computer Networks and (b) Internetworks R - routers
Why Computer Networks and Internetworks? • Sharing of computer resources • computers, printers, plotters, scanners, files and software • Network as a communicationmedium • inexpensive, fast, reliable • Cost efficiency • large computing power available • Less performance degradation • if one computer crashes, the remaining ones are still up
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
Network Models with approximate mapping between the two • The first 4 layers deal with the communication between hosts. • The 5th layer deals with the Internet services provided by various applications. • Most of the 1st layer is handled by hardware (communication medium used, attachments of hosts to the medium). • The rest of the 1st layerand all the 2nd layer is handled by the (Network Interface Card) NICcard in a host. • Layers 3 and 4 are fully implemented in the operating systems kernelon most existing systems. • The first 2 layers are network hardware specific, the others are work independently of the physical layer
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
The TCP/IP Protocol Suite • As a user you can see the application layer in the form of applications and utilities • Web browsing, • file transfer, • remote login • etc. 1st -2nd layer is handled by the Network Interface Card -NIC card
The TCP/IP Protocol Suite • IGMP - Internet Group Management Protocol • handlesmulticasting • ICMP - Internet Control Message Protocol • Handles errorsandcontrol messages. • Protocol is used to forward information, primarily error messages. • To see if a computer is running, the `ping' program sends an echo request, which is part of ICMP. • ARP -Address Resolution Protocol is a protocol for mapping an Internet Protocol IP address to a physical machine address (MAC) that is recognized in the local network. • For example, in IP Version 4, the most common level of IP in use today, an address is 32 bits long. • In an EthernetLAN, however, addresses for attached devices are 48 bits • RARP - Reverse Address Resolution Protocol is a protocol by which a physical machine in a LAN can request to learn its IP addressfrom a gatewayserver's Address Resolution Protocol (ARP) table or cache. • A network administrator creates a table in a LAN’s gateway router that maps the physical machine (MAC addresses) into IP addresses. 1st -2nd layer is handled by the Network Interface Card -NIC card
Transport Layer: The TCP and UDP • The purpose of the transport layer is to transport applicationdata from your machine to a remote machine and vice versa • User Datagram Protocol(UDP) is a connectionless protocol, offers the best effortdelivery service • Transmission Control Protocol (TCP) is a connection-oriented protocol that establish a virtualconnection with the destination before transmitting data, • thus the TCP leads • completelyreliable, • error free • in-sequence delivery of data
Routing of the Application DataThe 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 the best effortand doesn’t guarantee delivery of TCP segments or UDP datagrams
Routing of the Application DataThe Internet Protocol (IP) • In IPv4 the IP address (32 bits) is divided into three fields: • address class, • network ID and • host ID • The address classfield 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
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
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. • hostID = 1…1 is the broadcast address in order to send a data packet to all hosts on a network
IPv4 Address Classes The sum of network IDs for class A, B, C = 2^7 + 2^14 + 2^21 = 1,113,664 networks The sum of hosts IDs for class A, B, C = 2^24 + 2^16 + 2^ 8 = 3,758,096,400 hosts
IPv4 Address Classes Prove all ranges!!!
IPv4 Address Classes • A: Very large organizations and government agencies • B: Large organizations: AT&T, IBM, MIT, large universities etc. • C: Small to medium sized organizations: ISP, small consulting companies, • community colleges, universities • In IPv4 the IP address (32 bits) • In IPv6 the IP address is 128 bits and it covers the # of hosts 6 x 2^28times the present world population
IPv4 Address Classes Figure 14.5 An internetwork of 4 networks with one class A, one class B, and 2 class C networks connected via 4 routers class C class A class C class B
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 e.g.students.up.edu where: domain_name = organization_name.top-level_domain • organization_nameis assigned by the Network Information Center e.g. laverne.edu • 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
The Domain Name System • Domain Name System (DNS)servicetranslatessymbolicnamesto 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 tothe corresponding IP addresses • every organization runs at least 1 name server • app uses gethostbyname() to get its IP address
Inverse domain • The servers that handle the inverse domain are also hierarchical. • This means the netidpart of the address should be at a higher level than the subnetid part, and the subnetid part higher than the hosted part. • In this way, a server serving the whole site is at a higher level than the servers serving each subnet. • To follow the convention of reading the domain labels from the bottomto the top, an IP address such as 132.34.45.121 (a class 13: address with netid 132.34) is read as 121.45.34.132.in-addr. area. • This configuration makes the domain look inverted when compared to a generic or country domain.
DNS lookup utility: host [cs253u@shell cs253u]$ host ecs.fullerton.edu ecs.fullerton.edu has address 137.151.27.1 [cs253u@shell cs253u]$ host 137.151.27.1 1.27.151.137.in-addr.arpa domain name pointer ecs.fullerton.edu. [cs253u@shell cs253u]$ [jgoetz jgoetz]$ host ulv.edu ulv.edu has address 192.231.179.66 ulv.edu mail is handled (pri=5) by mxg1.ulv.edu ulv.edu mail is handled (pri=5) by mxg2.ulv.edu [jgoetz jgoetz]$ host 192.231.179.66 66.179.231.192.IN-ADDR.ARPA domain name pointer www.ulv.edu
The Domain Name System #DNS service is to use a statichostfile /etc/hosts #a static hosts file contains the domain names and their IP addresses configured by the system admin $ cat /etc/hosts [jgoetz jgoetz]$ cat /etc/hosts 127.0.0.1 localhost 192.231.179.91 raq4.ulv.edu # Cobalt automated entry for eth0 192.231.179.81 loki.ulv.edu loki #Veritas Backup Server #to view IP address and other info about host’s interface to the network $ /sbin/ifconfig –a # faculty.ulv.edu has 192.231.179.91 [jgoetz jgoetz]$ /sbin/ifconfig -a eth0 Link encap:Ethernet HWaddr 00:10:E0:05:A8:F4 inet addr:192.231.179.91 Bcast:192.231.179.95 Mask:255.255.255.224 UP BROADCAST RUNNING MULTICAST MTU:1500 Metric:1 RX packets:212947098 errors:0 dropped:0 overruns:0 frame:0 TX packets:318162567 errors:3 dropped:0 overruns:0 carrier:3 collisions:0 txqueuelen:100 Interrupt:5 Base address:0x8000 eth1 Link encap:EthernetHWaddr 00:10:E0:05:A8:F3 BROADCAST MULTICAST MTU:1500 Metric:1 RX packets:0 errors:0 dropped:0 overruns:0 frame:0 TX packets:0 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:100 Interrupt:9 Base address:0x8100 lo Link encap:Local Loopback inet addr:127.0.0.1 Mask:255.0.0.0 UP LOOPBACK RUNNING MTU:3924 Metric:1 RX packets:1749416 errors:0 dropped:0 overruns:0 frame:0 TX packets:1749416 errors:0 dropped:0 overruns:0 carrier:0 collisions:0 txqueuelen:0 $
The Domain Name System [cs253u@shell cs253u]$ cat /etc/hosts # Do not remove the following line, or various programs # that require network functionality will fail. 127.0.0.1 localhost.localdomain localhost shell 192.168.3.25 ldap.int.ecs.fullerton.edu ldap 192.168.3.29 ecsmysql.ecs.fullerton.edu ecsmysql 192.168.3.30 mail.ecs.fullerton.edu mail 137.151.28.223 lupus.ecs.fullerton.edu lupus 192.168.3.200 lupus2.ecs.fullerton.edu lupus2 • [jgoetz@raq4 ~]$ host 192.231.179.91 • 91.179.231.192.IN-ADDR.ARPA domain name pointer FACULTY.ULV.EDU
The Domain Name System • #lookupfor the IP address of a host name: • [cs253u@shell cs253u]$ nslookup ecs.fullerton.edu • Server: 192.168.3.26 # name server • Address: 192.168.3.26#53 • Name: ecs.fullerton.edu • Address: 137.151.27.1 • [jgoetz jgoetz]$ nslookup ulv.edu • Server: ns.ulv.edu • Address: 64.69.149.200 • Name: ulv.edu • Address: 192.231.179.66 • [jgoetz@raq4 ~]$ nslookup faculty.ulv.edu • Server: ns.ulv.edu # this a nameserver • Address: 64.69.149.200 • Name: faculty.ulv.edu • Address: 192.231.179.91 #nslookup uses file /etc/resolv.conf to find the host that runs the name server and passes the request over it. [jgoetz jgoetz]$ cat /etc/resolv.conf domain ulv.edu search ulv.edu nameserver 64.69.149.200 nameserver 64.69.154.123 [jgoetz jgoetz]$
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. • [cs253u@shell cs253u]$ cat/etc/resolv.conf nameserver 192.168.3.26 • diginteracts with name servers specified in /etc/resolv.conf and display their responses – gives more infothan nslookup
The Domain Name System • [jgoetz jgoetz]$ dig ulv.edu • ; <<>> DiG 8.3 <<>> 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: • ;; ulv.edu, type = A, class = IN • ;; ANSWER SECTION: • ulv.edu. 12H IN A 192.231.179.66 • ;; AUTHORITY SECTION: • ulv.edu. 12H IN NS ns2.ulv.edu. • ulv.edu. 12H IN NS ns.ulv.edu. • ;; ADDITIONAL SECTION: • ns.ulv.edu. 12H IN A 64.69.149.200 • ns2.ulv.edu. 12H IN A 64.69.154.123 • ;; Total query time: 11 msec • ;; FROM: raq4.ulv.edu to SERVER: default -- 64.69.149.200 • ;; WHEN: Thu Nov 15 16:21:26 2007 • ;; MSG SIZE sent: 25 rcvd: 108 [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
The Domain Name System • [jgoetz jgoetz]$ dig ulv.edu • ; <<>> DiG 8.3 <<>> 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: • ;; ulv.edu, type = A, class = IN • ;; ANSWER SECTION: • ulv.edu. 12H IN A 192.231.179.66 • ;; AUTHORITY SECTION: • ulv.edu. 12H IN NS ns2.ulv.edu. • ulv.edu. 12H IN NS ns.ulv.edu. • ;; ADDITIONAL SECTION: • ns.ulv.edu. 12H IN A 64.69.149.200 • ns2.ulv.edu. 12H IN A 64.69.154.123 • ;; Total query time: 11 msec • ;; FROM: raq4.ulv.edu to SERVER: default -- 64.69.149.200 • ;; WHEN: Thu Nov 15 16:21:26 2007 • ;; MSG SIZE sent: 25 rcvd: 108 dig ecs.fullerton.edu ; <<>> DiG 9.2.4 <<>> ecs.fullerton.edu ;; global options: printcmd ;; Got answer: ;; ->>HEADER<<- opcode: QUERY, status: NOERROR, id: 29854 ;; flags: qr aa rd ra; QUERY: 1, ANSWER: 1, AUTHORITY: 1, ADDITIONAL: 0 ;; QUESTION SECTION: ;ecs.fullerton.edu. IN A ;; ANSWER SECTION: ecs.fullerton.edu. 86400 IN A 137.151.27.1 ;; AUTHORITY SECTION: ecs.fullerton.edu. 86400 IN NS ecs.fullerton.edu. ;; Query time: 22 msec ;; SERVER: 192.168.3.26#53(192.168.3.26) ;; WHEN: Fri Mar 14 23:54:21 2008 ;; MSG SIZE rcvd: 65
The Client-Server Software Model • Internet servicesare 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
The Client-Server Software Model http://faculty.ulv.edu/
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
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 -a, --all print all information -m, --machine print the machine (hardware) type -n, --nodename print the machine's network node hostname --help
cpu info. [jgoetz jgoetz]$ less /proc/cpuinfo [cs253u@shell cs253u]$ less /proc/cpuinfo processor : 1 vendor_id : AuthenticAMD cpu family : 15 model : 35 model name : Dual Core AMD Opteron(tm) Processor 175 stepping : 2 cpu MHz : 2211.280 cache size : 1024 KB fdiv_bug : no hlt_bug : no f00f_bug : no coma_bug : no fpu : yes fpu_exception : yes cpuid level : 1 flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 ht syscall nx mmxext lm 3dnowext 3dnow lahf_ lm pni /proc/cpuinfo (END)