jozef goetz, 2012 1 expanded by jozef goetz, 2012 credits: parts of the slides are based on slides...

Jozef Goetz, 2012

1

expanded by Jozef Goetz, 2012

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

Jozef Goetz, 2012

2Objectives 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 ,

1. remote login, 2. file transfer, 3. remote command execution , and 4. status reporting

To describe briefly the secure shell

To cover the commands and primitives

Jozef Goetz, 2012

3Computer Networks and Internet works

When two or more computer hardware resources are connected they form a computer network

1. Local area Networks (LANs)2. Metropolitan area networks (MANs)3. Wide area networks (WANs)

An internetwork is a network of networks

Jozef Goetz, 2012

4A 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 together is 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.

Jozef Goetz, 2012

5The ARPANET The original ARPANET design.

IMP - Interface Message Processor

Jozef Goetz, 2012

6The ARPANET

Growth of the ARPANET (a) December 1969. (b) July 1970. (c) March 1971. (d) April 1972. (e) September 1972.

Jozef Goetz, 2012

7

NSFNET The NSFNET backbone in 1988.

Jozef Goetz, 2012

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 temporary (dynamic) IP address, and send IP packets to all the other hosts

Jozef Goetz, 2012

9

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

Jozef Goetz, 2012

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

Jozef Goetz, 2012

11Architecture of the Internet.

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

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 packets can be forwarded from any backbone to any other backbone

Jozef Goetz, 2012

12Collection of Subnetworks

The Internet is an interconnected collection of many networks.

SNA: Systems Network Architecture

-IBM's mainframe network standards

Jozef Goetz, 2012

13X.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

Jozef Goetz, 2012

14Frame Relay• Takes advantage of modern high-speed reliable

digital phone lines.

Connection oriented.Property:

In-order delivery, no error control, no flow control,

akin to LAN

• This allows simple protocols with 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.

Jozef Goetz, 2012

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

Jozef Goetz, 2012

16

(a) Computer Networks and (b) Internetworks

R - routers

Jozef Goetz, 2012

17Why 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 remaining ones

are still up

Jozef Goetz, 2012

18Network Models

International Standards Organization’s Open System Interconnect Reference Model (ISO’s OSI 7-Layer Reference Model)

The TCP/IP 5-layer Model Used in the Internet

Jozef Goetz, 2012

19

Network Modelswith 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 layer and all the 2nd layer is handled by the (Network Interface Card) NIC card in a host.

•Layers 3 and 4 are fully implemented in the operating systems kernel on most existing systems.

•The first 2 layers are network hardware specific, the others are work independently of the physical layer

Jozef Goetz, 2012

20Reference 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

Jozef Goetz, 2012

21The TCP/IP Protocol Suite

As a user you can see the application layer in the form of applications and utilities

1. Web browsing,

2. file transfer, 3. remote login4. etc.

1st -2nd layer is handled by the Network Interface Card -NIC card

Jozef Goetz, 2012

22The TCP/IP Protocol Suite IGMP - Internet Group

Management Protocol handles multicasting

ICMP - Internet Control Message Protocol

Handles errors and control 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 Ethernet LAN, however, addresses for attached devices are 48 bits

1st -2nd layer is handled by the Network Interface Card -NIC card

RARP - Reverse Address Resolution Protocol is a protocol by which a physical machine in a LAN can request to learn its IP address from a gateway server'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.

Jozef Goetz, 2012

23Transport 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) is a connectionless protocol, 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

completely reliable, error free in-sequence delivery of data

Jozef Goetz, 2012

24Routing 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 effort and

doesn’t guarantee delivery of TCP segments or UDP datagrams

Jozef Goetz, 2012

25Routing of the Application DataThe Internet Protocol (IP)

In IPv4 the IP address (32 bits) is divided into three fields:

1. address class, 2. network ID and 3. host ID

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

Jozef Goetz, 2012

26IPv4 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

Jozef Goetz, 2012

27IP 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

Jozef Goetz, 2012

28

IPv4 Address Classes

The sum of network IDs for class A, B, C = 2^7 + 2^14 + 2^21 = 1,113,664 networksThe sum of hosts IDs for class A, B, C = 2^24 + 2^16 + 2^ 8 = 3,758,096,400 hosts

Jozef Goetz, 2012

29


Prove all ranges!!!

Jozef Goetz, 2012

30


•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 2^28 times the present world population

Jozef Goetz, 2012

31


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 A

class C

class C

class B

Jozef Goetz, 2012

32Symbolic 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_name is 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

Jozef Goetz, 2012

33

A portion of the Internet domain name hierarchy

Jozef Goetz, 2012

34

Top-Level Internet Domains

Jozef Goetz, 2012

35

Jozef Goetz, 2012

36The 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 servers that 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

Jozef Goetz, 2012

37

Inverse domain The servers that handle the

inverse domain are also hierarchical.

This means the netid part 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 bottom to 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.

Jozef Goetz, 2012

38DNS lookup utility: host

[jgoetz jgoetz]$ host ulv.eduulv.edu has address 192.231.179.66ulv.edu mail is handled (pri=5) by mxg1.ulv.eduulv.edu mail is handled (pri=5) by mxg2.ulv.edu

[jgoetz jgoetz]$ host 192.231.179.6666.179.231.192.IN-ADDR.ARPA domain name pointer www.ulv.edu

[cs253u@shell cs253u]$ host ecs.fullerton.eduecs.fullerton.edu has address 137.151.27.1

[cs253u@shell cs253u]$ host 137.151.27.11.27.151.137.in-addr.arpa domain name pointer ecs.fullerton.edu.[cs253u@shell cs253u]$

Jozef Goetz, 2012

39The Domain Name System #DNS service is to use a static host file /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/hosts127.0.0.1 localhost192.231.179.91 raq4.ulv.edu # Cobalt automated entry for eth0192.231.179.81 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 -aeth0 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:Ethernet HWaddr 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 $

Jozef Goetz, 2012

40The 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 shell192.168.3.25 ldap.int.ecs.fullerton.edu ldap192.168.3.29 ecsmysql.ecs.fullerton.edu ecsmysql192.168.3.30 mail.ecs.fullerton.edu mail137.151.28.223 lupus.ecs.fullerton.edu lupus192.168.3.200 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

Jozef Goetz, 2012

41The Domain Name System#lookup for the IP address of a host name:[cs253u@shell cs253u]$ nslookup ecs.fullerton.edu

Server: 192.168.3.26 # name serverAddress: 192.168.3.26#53

Name: ecs.fullerton.eduAddress: 137.151.27.1

[jgoetz jgoetz]$ nslookup ulv.eduServer: ns.ulv.eduAddress: 64.69.149.200Name: ulv.eduAddress: 192.231.179.66

[jgoetz@raq4 ~]$ nslookup faculty.ulv.eduServer: ns.ulv.edu # this a name server Address: 64.69.149.200Name: faculty.ulv.eduAddress: 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.confdomain ulv.edusearch ulv.edunameserver 64.69.149.200nameserver 64.69.154.123[jgoetz jgoetz]$

Jozef Goetz, 2012

42The 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

dig interacts with name servers specified in /etc/resolv.conf and display their responses – gives more info than nslookup

Jozef Goetz, 2012

43The 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 64.69.149.200ns2.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

[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 64.69.149.200ns2.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

Jozef Goetz, 2012

44The 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 64.69.149.200ns2.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

Jozef Goetz, 2012

45

Well-known Internet Services

Jozef Goetz, 2012

46The 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

Jozef Goetz, 2012

47

The Client-Server Software Model

http://faculty.ulv.edu/

Jozef Goetz, 2012

48Displaying 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]$ unameLinux

[jgoetz jgoetz]$ uname -nraq4.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

Jozef Goetz, 2012

49Displaying the Host Name$ uname -nyamsrv1.ece.gatech.edu

$ uname -aSunOS 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]$ hostnameraq4.ulv.edu

-a, --all print all information -m, --machine print the machine (hardware) type -n, --nodename print the machine's network node

hostname --help

Jozef Goetz, 2012

50cpu info.[jgoetz jgoetz]$ less /proc/cpuinfo

[cs253u@shell cs253u]$ less /proc/cpuinfoprocessor : 1vendor_id : AuthenticAMDcpu family : 15model : 35model name : Dual Core AMD Opteron(tm) Processor 175stepping : 2cpu MHz : 2211.280cache size : 1024 KBfdiv_bug : nohlt_bug : nof00f_bug : nocoma_bug : nofpu : yesfpu_exception : yescpuid level : 1flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca

cmovpat pse36 clflush mmx fxsr sse sse2 ht syscall nx mmxext lm

3dnowext 3dnow lahf_lm pni

/proc/cpuinfo (END)

Jozef Goetz, 2012

51Displaying Users on a Network

$ rwho | more - remote who displays info about the user currently using machines on your network: log name, computer:terminal, date and time the user logged in

Bobk upibm7:ttyC4 Jul 26 12:03Dfrakes upibm47:ttyp2 Jul 26 11:49Lulay upsun17:pts/0 Jul 26 10:17Oster upsun17:pts/2 Jul 26 12:28Sarwar upibm7:ttyp2 Jul 26 11:15$ rwho -a | moreBobk upibm7:ttyC4 Jul 26 12:03dfrakes upibm47:ttyp2 Jul 26 11:49kent upibm48:ttyp0 Jul 26 03:41 8:49kittyt upibm9:ttyp0 Jul 26 07:36 1:28kuhn upsun29:console Jul 16 13:11 99:59lulay upsun17:pts/0 Jul 26 10:17oster upsun17:pts/2 Jul 26 12:28pioster upsun20:pts/0 Jul 26 09:53 2:41sarwar upibm7:ttyp2 Jul 26 11:15sarwar upsun29:pts/0 Jul 26 11:24 1:00$

Jozef Goetz, 2012

52Displaying Users on a Network.

rusers [options] [host_list]

Purpose: Display the login names of the remote users logged on to all the machines on our local networkOutput: 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 all host 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

Jozef Goetz, 2012

53Displaying Users on a Network

for particular machine

Jozef Goetz, 2012

54Displaying 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

Jozef Goetz, 2012

55Displaying 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

Jozef Goetz, 2012

56Testing a Network Connection

ping [options] hostname

Purpose: Send an IP datagram to ‘hostname’ to test whether it is on the network (or Internet); if the host is alive it simply echoes the received datagramOutput: Message(s) indicating whether

the machine is alive

Commonly used options/features:-c count Send and receive ‘count’ (e.g. 3) packets-f Send 100 packets per second or as many as can be handled by the network; only the superuser can use this option-s packetsize Send ‘packetsize’ packets; the default is

56 bytes (plus an 8 byte header)

Jozef Goetz, 2012

57Testing a Network Connection

ping -c count Send and receive ‘count’ packetsping -s packetsize Send ‘packetsize’ packets; the default is

56 bytes (plus an 8 byte header); Test yahoo.com

Jozef Goetz, 2012

58Displaying Information About Users

finger [options] [user_list]

Purpose: Display information about the users in the ‘user_list’;

without a ‘user_list’, the command displays

a short status report about all the users currently logged on to the specified

hosts

Output: User info extracted from the ~/.project and ~/.plan files

Commonly used options/features:-m Match ‘user_list’ to login names only-s Display output in a short format

[jgoetz@raq4 ~]$ finger JozefLogin: jgoetz Name: Jozef GoetzDirectory: /home/sites/site7/users/jgoetz Shell: /bin/bashOn since Wed Nov 30 21:05 (PST) on pts/1 from 64.69.147.181No mail.No Plan.

Jozef Goetz, 2012


[jgoetz@raq4 ~]$ finger -s JozefLogin Name Tty Idle Login Time Office Office Phonejgoetz Jozef Goetz pts/1 Nov 30 21:05 (64.69.147.181)

[jgoetz@raq4 ~]$

[jgoetz@raq4 ~]$ finger -m jgoetzLogin: jgoetz Name: Jozef Goetz

Directory: /home/sites/site7/users/jgoetz Shell: /bin/bashOn since Wed Nov 30 21:05 (PST) on pts/1 from 64.69.147.184No mail.No Plan.

-m Match ‘user_list’ to login names only-s Display output in a short format

Jozef Goetz, 2012


-m Match ‘user_list’ to login names only-s Display output in a short format

Jozef Goetz, 2012


// if the finger server is running

[jgoetz jgoetz]$ finger [email protected][ulv.edu]finger: connect: No route to host[jgoetz jgoetz]$ [email protected]

Jozef Goetz, 2012

62Remote Login. The telnet protocol is designed to allow you to connect to a

remote computer over a network

telnet [options] [host[port]]

Purpose: To connect to a remote system ‘host’ via a network; the ‘host’ can

be specified by its name or IP address in dotted decimal notation

Commonly used options/features:-a Attempt automatic login-l Specify a user for login

usage: telnet [-l user] [-a] host-name [port]e.g.titan/bin > telnet -l jgoetz -a faculty.ulv.edu

Trying 192.231.179.91...Connected to FACULTY.ULV.EDU (192.231.179.91).Escape character is '^]'.Password:Last login: Wed Nov 29 13:00:01 from cpe-66-74- …

telnet help //ortelnet --help // to get available cmds

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63Remote Login (contd.)

$ telnet upsun29

Trying 192.102.10.89...Connected to upsun29.egr.up.edu.Escape character is ‘^]’.UNIX(r) System V Release 4.0 (upsun29.egr.up.edu)login: sarwarPassword: **********Last login: Sat Dec 27 05:05:37 from upYou have mail.DISPLAY = (‘)TERM = (vt100)$

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64

Remote Login (contd.)

[jgoetz jgoetz]$ telnet -?telnet: invalid option -- ?Usage: telnet [-8] [-E] [-L] [-S tos] [-a] [-c] [-d] [-e char] [-l user][-n tracefile] [-b hostalias ][-r] [host-name [port]]

Ctrl + D close the session

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65Remote Login (contd.)

# reverts to the telnet client – place in the foreground

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66Using Telnet to Invoke Other Well-known Services

invokes a daytime service running at port 13

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67The rlogin Command The rlogin command allows you to log on to a host on your

local network (or remote)

rlogin [options] hosts

Purpose: To connect to a remote LINUX or UNIX ‘host’ via a network ; the ‘host’ can be specified

by its name or IP address in the dotted decimal notation

Commonly used options/features:-ec Set the escape character to ‘c’( the default is ‘~’)-l user User ‘user’ as the login name on the remote host

slogin [options] hosts - secure version uses strong cryptography for transmitting data

e.g.[jgoetz jgoetz]$ rlogin -l jozefg ecs.fullerton.edu ecs.fullerton.edu: Connection refused // it is not a local network

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68The rlogin Command

$ rlogin upsun -l performPassword:Last login: Mon Dec 18 12:08:12 from upsun21.up.eduSunOS Release 4.1.3 (UPSUN_SERVER) #5: Mon Nov 14

17:31:44 PST 1994DISPLAY 5 (upx46:0.0)TERM 5 (vt100)$ whoamiperform$ hostnameupsun.egr.up.edu$

-ec Set the escape character to ‘c’( the default is ‘~’)-l user User ‘user’ as the login name on the remote host

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69Remote Command Execution

rsh – remote shellrsh [options] host [command]

Purpose: To execute a command on a remote machine

, ‘host’, on the same network; the rlogin command is executed if no

‘command’ is specified

Commonly used options/features:-l user Use ‘user’ as the login name

on the remote host

ssh [options] host [command] -secure version uses strong cryptography for transmitting data

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70Figure 14.8 The semantics of the rsh upsun29 ps command

The same network

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71Figure 14.9 The semantics of the rsh upsun29 sort students > sorted_students command

students and sorted_students are files

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Jozef Goetz, 2012


•input from local file students and store the sorted result in a sorted_students file on the remote machine

•the sort cmd takes input from the students file on the local machine, (upibm7) and the output is sent to the sorted_students file on the local machine

When used without arguments, the rsh reverts to the rlogin command.it is executed if no ‘arguments’ is specified

//to log on a different network on the Internet

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74File Transfer

ftp [options] [host]Purpose:

To transfer files from or to a remote ‘host’

Commonly used options/features -d Enable debugging-i Disable prompting during

transfers of multiple files-v Show all remote responses

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75File Transfertitan/jozefg > ftp -v faculty.ulv.edu // -v Show all remote responses

Connected to faculty.ulv.edu.220 ProFTPD 1.2.9 Server (ProFTPD) [192.231.179.91]500 AUTH not understood500 AUTH not understoodKERBEROS_V4 rejected as an authentication typeName (faculty.ulv.edu:jozefg): jgoetz331 Password required for jgoetz.Password:230 User jgoetz logged in.Remote system type is UNIX.Using binary mode to transfer files.

ftp> ls -l200 PORT command successful150 Opening ASCII mode data connection for file list-rw-r--r-- 1 jgoetz site7 123392 Nov 28 21:01 Assig.doc-rwxrwxrwx 1 jgoetz site7 13 Oct 31 07:22 mdrwxrwsr-x 4 jgoetz site7 4096 Jun 1 2006 web226 Transfer complete.

ftp>

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76File Transfer

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77

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78Remote Copy

rcp[options] [host:]sfile [host:]dfilercp[options] [host:]sfile [host:]dir

Purpose: To copy ‘sfile’ to ‘dfile’ source file – sfile destination file - dfile

Commonly used options/features-p

Attempt to preserve file modify and access times; without this option the command uses the current value

of unmask to create file permissions

-r Recursively copy files at ‘sfiles’ to ‘dir’

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79Remote Copy (contd.)

$ rcp ~/myweb/*.html upsun29:webmirror

$ rcp ~/unixbook/Chapter[1-9].doc upsun29:unixbook.backup

$ rcp upsun29:ece446/projects/*.[c,C] ~/swprojects.backup

$ rcp -rp www1:* www2:

$

Secure version of the rcp command

$ scp prog4.c upsun29:~/courses/cs213/programs/$ scp -r upsun21.egr.up.edu:courses.$ scp -rp www1:* www2:$

-p Attempt to preserve file modify and access times; -r Recursively copy files at ‘sfiles’ to ‘dir’

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80Interactive Chat

talk user [tty]Purpose: to initiate interactive

chat with ‘use’ who is logged in on a ‘tty’ terminal

$ talk bob

[Waiting for your party to respond]Message from [email protected] at 13:36 ...talk: connection requested by [email protected]: respond with: talk [email protected]

$ talk sarwar@upibm7

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81Tracing the Route from One Site to Another Site

traceroute www.yahoo.com

#some administrators disable this cmd for security

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82

Important Internet

Organizations

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83

Web Resources

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84

Web Resources

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85Request For Comments (RFCs) – omit it

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

jozef goetz, 2012 1 expanded by jozef goetz, 2012 credits: parts of the slides are based on slides...

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