The Internet

1
The Internet

• Ideas formulated in the early 1960s.
• Fundamental work done around 1970.
• Some steps involved
• Creating the network idea.
• Creating the machines to run the network.
• Working with different kinds of computers.
• Designing generic protocols and interfaces.

2
Internet Foundations

• Packet switching instead of dedicated circuits.
• Distributed network for reliability.
• Machines to route traffic (IMPs).
• First network called ARPANET.
• Generic Protocols despite different end hosts.
• Remote Logins Telnet.
• Remote File Transfer FTP.
• Email and messaging.

3
Gateways

• Connect different kinds of networks.
• Data passed between networks is translated from
  one network type to another.
• Different Networks
• Cell Phones
• Wireless Computer Networks
• LANs

4
OSI Model

• Open System Interconnection Model
• Layer 7 Applications What you see.
• Layer 6 Presentation Encryption, data
  ordering.
• Layer 5 Session Connects applications.
• Layer 4 Transport Error correction.
• Layer 3 Network Routing/Switching.
• Layer 2 Data Link Convert data to bits.
• Layer 1 Physical Move the bits using energy.

5
Addresses

• Networked computers need names.
• On the Internet, domain names and IP numbers are
  used.
• IP is the Internet Protocol, the base protocol in
  use on the Internet.
• rac3.wam.umd.edu is a host name.
• rac3.wam.umd.edu also has an IP address
  128.8.10.143

6
Domain Names

• Consider rac3.wam.umd.edu.
• The top-level domain is .edu
• The domain name is umd.edu
• The subdomain is wam.
• The machine is rac3.
• Top-level domains include .com, .net, .org, etc
• Names can be assigned depending on access and
  permissions.
• Most domains represent many computers.

7
Domain lookup

• nslookup
• whois wam.umd.edu
• whois h whois.networksolutions.com wam.umd.edu
• Whois without the middle h whois.net argument
  will tell which domain server has the domain
  information.

8
IP Addresses

• Numbers that identify computers on the Internet.
• Many times assigned in blocks.
• They have 4 numbers.
• Each number is between 0 and 255 inclusive.
• 128.8.10.143 is an IP address.

9
Internet Protocol (IP)

• Breaks information into packets.
• IP is the network protocol.
• IP is unreliable, no guarantee of delivery.
• IP is connectionless packets can take different
  paths.
• Packets may arrive out of order.

10
TCP (Transmission Control Protocol)

• Controls the organization of the information.
• Provides reliability by ordering packets.
• It resends lost packets.
• Duplicates are ignored.
• Checks for transmission errors using a checksum.

11
Other Protocols

• Mail, telnet, ftp, newsgroups, and webpages all
  work with different protocols.
• They are protocols on top of TCP/IP.
• Their messages are reliable.
• They add extra data and rules.
• They send specific types of information.

12
Ports

• A single machine can listen for many different
  types of connections.
• Like different apartment numbers in a building.
• Telnet is on port 23, ftp on port 21, www on port
  80.
• You can use other ports above 1023 for special
  programs.

13
Class Cluster Accounts

• Unix Accounts.
• On machines called the detective cluster.
• WAM is at wam.umd.edu
• Detective machines are at dc.umd.edu
• Names holmes marlowe marple tracy wolfe

14
Login Names

• My account name on WAM is johna
• My account name on cs is jra
• My account name on dc is ja102001

15
Multiple Accounts

• Each account has similar features like email, but
  the addresses are different.
• Logging into different accounts means logging
  into different machines.
• Each client uses one of a few common protocols.

16
Logging in

• Its like using your WAM account for mail.
• The command to use to login is called telnet.
• On Windows click on the start button, then click
  on run, then type telnet.
• On a WAM lab UNIX machine type telnet on any
  command line.
• If you are on a MAC use NCSA telnet.

17
Class Cluster Accounts

• The name of your class account host the
  computer where the class accounts are stored is
  dc.umd.edu
• Type o dc.umd.edu
• o can be replaced with open.
• Type your login and password.

18
First steps

• Newsgroups will show up. You dont have to read
  this right now. Keep typing q and space until you
  exit the news program.
• Your prompt will look like
• Directories are like folders lists of files.
• Type ls -- lists the files in a
  directory.
• Try ls l Try ls la Try ls -F

19
Directories and files

• Directories organize files into a hierarchy.
• Files contain data and programs.
• Path where something is in the hierarchy.
• cd change directory
• cd name -- go to directory named name
• cd .. -- move up a directory
• cd -- change to home
  directory
• cd ja102001

20
Help and Logging out

• man -- gives help on commands.
• There is no help command, use man.
• logout -- lets you log off the machine.
• man k keyword -- gives you a list of commands
  that have information about the keyword, such as
  man k password.

21
Initial commands

• Type cd ja102001
• Type ls -l
• Type more Syllabus
• Type cp Syllabus
• Type mail
• Read new mail by hitting enter.
• Quit mail by typing quit.

22
Get project 1

• Type cd ja102001
• Type cd project1
• Type cp project1.description
• To print out project 1 for pickup at the AVW
  pickup window
• Type qpr q prl project1.description
• If you want to use your own printer or the WAM
  printers (10cents a page) you may.
• Use lpr project1.description for local printers.

23
Setting Up

• Type ja102001/setup
• Copy down the project code.
• If you forget your project code
• Type echo uid
• Type cd or type cd
• This will send you back to your home directory.

24
Using pico 1

• Simple text editor.
• Type pico syllabus
• The file is not there, so the file is blank.
• Type pico Syllabus
• The file IS there. UNIX is case sensitive.
• You can use arrow keys to move around.

25
Using pico 2

• The letter will represent control, as in x
  means hold down control and type x.
• Some important commands
• c (cancel) stops whatever you are doing
  and returns you to regular editing.
• x quit and save.
• o write out (save) the current file. It asks for
  a new name.

26
Using pico 3

• If you dont want to use the arrow keys to move
  around the screen, you can also use the following
  keys
• p move to previous line
• n move to next line
• b move left one space
• f move right one space

27
Using pico 4

• a move to the start of a line.
• e move to the end of a line.
• y move up a page.
• v move down a page.

28
Using pico 5

• Other Commands
• d delete current character.
• Backspace delete previous character.
• k delete current line.
• u pastes last deleted line to
  current position.
• k and u can be combined to copy text.

29
Using pico 6

• Some more commands
• w lets you search for
  text.
• m inserts a blank line
  above the current one.
• r read in (insert) an
  external file.
• t invoke the spell
  checker.