CMSI 182
Intro to Computer Science
Week 13
Tuesday B.J. Johnson Doolan 222 09:25 – 10:40
Where We Are:
I/O Peripherals History Lesson Algorithms Abstractions Programs Languages Architecture RAM/ROM Applications O/S HD Router Internet We’re here!This Week’s Agenda
Homework questions
Networking Fundamentals
Thanksgiving
Network Terms
LAN: Local Area Network
WAN: Wide Area Network
CLAN/CWAN: Classified LAN/WAN
AP: Access Point
TCP: Transfer Control Protocol
IP: Internet Protocol
TCP/IP: you figure it out…
Open network: public domain
Network Types
Bus
Star
Ring
Token Ring Network
Network Parts
Hub
Basically just a miniature bus Plug in cables from computers They can all talk to each other
All messages go to all computers MINIMAL networking
Switch
Smarter hub
Can send messages only to specific
computers
Network Parts
Router
Used to join multiple networks together Example is joining home network to the
internet
• Fed from DSL modem, Cable modem, or FiOS
• Distributes signals to computers, printers, etc.
• Frequently have 4, 6, or more ports
• Have an input connection and fan-out outputs
• Frequently include wireless connectivity
Network Parts
Repeater
A smaller version of a hub
Only has two ports; connects two buses All traffic is passed
Bridge
More complex repeater
Two ports; connects two buses
Network Parts
Gateway
Point at which a LAN connects to the
internet
Provides a passage between the LAN and
the “outside world” of the internet
May be simply a router
Network Parts
Ethernet
Both hardware and protocol technologies IEEE 802 family
• IEEE 802 - basic standards descriptions
• IEEE 802.11 wireless version
• 802.11 B – 11 Mbps, 2.4 GHz band
• 802.11 G – 54 Mbps, 2.4 GHz band
• 802.11 N – 54 Mbps, either 2.4 or 5 GHz
• Includes multiple input/multiple output
antennas
• “Channelized” transmit bands
Typical Home Network
Internet connects
to DSL modem
Modem connects
to router
Router connects to
home computers
Wired (cabled) connections Wireless over 802.11 b/gNetwork Parts
Security
Can be set up in your router
Router login from connected computer Usually address 192.168.1.1
Usually factory login • User name “admin”
• No password
• First thing to do is change those!!
Router can be set to “secure” mode • WAP and WEP
• WAP is more secure; requires a “key”
7 Deadly Network Layers
Application – file Xfer, email, etc.
Presentation – protocol conversion,
encryption/decryption, etc.
Session – process-to-process comm.;
setup/ending sessions
Transport – msg. delivery btw. hosts
Network – address translation
Data Link – transfer of data using…
Physical – transmit data over cable
The Internet
Generic name
Multiple networks
All connected together
Specific name “THE Internet”
Started by DARPA and several academic
institutions (UC Berkeley, UCLA, etc.)
Linked world wide
Multiple versions of LANs, WANs,
corporate networks, etc. all connected together
Internet Composition
“Tiered” architecture
You and me and our computers
Addressing for Access
Each computer has a network interface card
or “NIC”
Each card has a specific Media Access
Control (MAC) address
A set of six hex values
E.g., “00-13-A9-08-07-49” Hard-wired onto the NIC
This is how the computer is identified
DSL connections are made using this
May need to set up DSL with one “main”
Addressing for Access
Each computer is assigned an “IP”
address
Static IP: assigned for the LAN and set
“forever” in the computer settings
Dynamic IP: assigned every time the
computer connects to the LAN
IP address is how the computer is
identified for message traffic
Consists of four “octets”
xxx.xxx.xxx.xxx like 192.168.1.1 Each octet is a byte; total is 32 bits
Domains, Names, Addresses
People can’t remember numbers, so we
translate the octets to words
First we get a top-level domain (TLD), like
.com, .edu, .org, .gov; also country codes like .uk, .au, or .ru
Then we get “registered domains” which
must be approved by “ICANN”
Usually assigned to ISPs like AOL, etc These two make up the “domain” like
google.com or dmv.gov or lmu.edu
ISPs can then allocated “sub-domains”
which is where the left end comes from; like mail.google.com
Domain Name Lookup
Names are stored in a Domain Name
Server in the Domain Name System
(DNS)
When a browser points to an “address”
the computer looks up the names on
the DNS server for which it is
configured
You can find all this information for
your computer from a terminal window
Windows: “ipconfig /all” Mac: “ifconfig”
Internet Applications: email
Many types of protocols
Three most common
SMTP – Simple Mail Transfer Protocol • Oldest
• Primarily text transfer
POP3 – Post Office Protocol V.3
• User downloads messages to her own host
• User manages message storage locally
IMAP – Internet Mail Access Protocol • Messages stay on the mail server
• User can manage them on the server
Internet Applications: ftp
FTP – File Transfer Protocol
Application program Client/server protocol
• Must be an ftp server program on remote
• User starts ftp client on local host
File transfer in ascii/binary mode
Also a number of GUI-based clients • fireFTP firefox plugin
• Filezilla
• ftp commander
Internet Applications: telnet
Not an acronym
Provides a command line interface to
the remote computer
Start from terminal window by typing
“telnet <IP address>”
Often uses “secure shell” or SSH
Putty – free download secure program SSH itself can be used
Internet Applications: streams
VoIP – voice over internet protocol
Radio – pandora, grooveshark
Video – youtube, etc.
Unicasting
N-unicast – one computer sends a stream
to many other computers
Multicast – one computer sends messages
The World Wide Web
Hypertext
Hyperlinks
HyperText Markup Language
HyperText Transfer Protocol
Web page
Web site
Browser / Web Server
URL/URI
URL Parts
Uniform Resource Locator (URL) Uniform Resource Identifier (URI) Uniform Resource Name (URN)
For internet stuff, we only care about the
URL
Comprises:
Protocol like “http://”
Mnemonic name like “www.lmu.edu”
The directory path to the file of interest The file name of the web page file
Example:
For Thursday ~
HAPPY TURKEY DAY!
