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Getting Connected
CECS 5030
with Cathie Norris, Jennifer Smolka
& Gerald Knezek
The Internet Today
 Worldwide network of networks
 Government agencies,
educational institutions,
hospitals, and commercial
organizations
The Internet Today
 Phenomenal growth - 1
million/month
 End of 2001 – 500 million
users
 Largest connection of
networks in the world
How the Internet Works
 Local connection via modem, leased-line,
ISDN, etc.
 Router at provider’s point-of-presence
How the Internet Works
 Small providers buy from big providers
 NorthwestNet
 NorthwestNexus
 Big providers interconnect with each other
 MCI
MCI
AT&T
 Sprint
 AT&T
NWNET
NWNEXUS
The Internet uses TCP/IP
 Share common protocol TCP/IP
 Transmission Control Protocol/Internet
Protocol
 “/” means it operates at two levels
TCP
IP
The Internet uses TCP/IP
 Created more than thirty years ago by
the Department of Defense Advanced
Research Projects Agency (DARPA)
 TCP/IP is the still the basis for the
Internet
The Internet uses TCP/IP
 IP Address – unique identifier
 IP resides in the Network Layer
 TCP resides in the Transport Layer
TCP/IP
 Network Protocols
 Internet Protocol (IP)
• Every computer on the Internet has a
unique number which is the destination
point
• Where you are and how I get there
 Transmission Control Protocol (TCP)
• How is my data getting between you
and me
TCP/IP
 Application Protocols
 Terminal Emulation (Telnet)
 HyperText Transfer Protocol (HTTP)
 File Transfer Protocol (FTP)
 Simple Mail Transfer Protocol (SMTP)
 Simple Network Management Protocol
(SNMP)
 Domain Name Service (DNS)
TCP/IP in the OSI Model
Seven Layer Open System Interconnect Model
Application
Presentation
Session
Transport
Network
Logical Link
Physical
FTP, Telnet
SNMP
TFTP
NFS
TCP
UDP
ARP
IP
LLC
Ethernet, WAN, Token Ring, FDDI
TCP/IP in the OSI Model
Application
Presentation
Session
Transport
Network
Logical Link
Physical
FTP, Telnet
SNMP
TFTP
NFS
TCP
UDP
ARP
IP
LLC
Ethernet, WAN, Token Ring, FDDI
Internet Protocol (IP)
 IP is a connectionless
service that provides basic
datagram delivery services.
 IP takes care of addressing,
or making sure the routers
know what to do with your
data when it arrives.
Internet Protocol (IP)
 Not everything is sent over
the Internet is not sent as a
BATCH – or complete file
 Sent over as packet of
smaller pieces
 256 characters or 512
characters (maybe longer)
Internet Protocol
 Every computer on the Internet has a
unique address.
 Information sent across IP networks is
broken up into bite-sized pieces, called
packets.
 The information within a packet is
usually between 1 and about 1500
characters long.
IP Envelopes
DATA
From: 192.112.36.5
To: 128.174.5.6
IP Packet
Internet Protocol
 Some addressing information goes at the
beginning of your message; this
information gives your network enough
information to deliver the packet of data.
 Internet addresses consist of four
numbers each less than 256.
 192.112.36.5
 128.174.5.6
Internet Protocol
IP Addresses
 Class A Networks: 128.x.x.x
 Class B Networks: 146.79.x.x
 Class C Networks: 192.100.10.x
IP addresses are running out - Extensions
to the current IP address protocol will be
required - IPng
Transmission Control
Protocol
 Reliable
 TCP takes the information you want to
transmit and breaks it into pieces.
 TCP numbers each piece so receipt can
be verified and the data can be put back
in the proper order.
 Acknowledgments
TCP Packet
Encapsulation
DATA
Bytes 1 to 500
To: 128.174.5.6
TCP Packet
From: 192.112.36.5
To: 128.174.5.6
IP Packet
SLIP and PPP
 Extensions of IP over voice-grade
modem lines:
 Serial Internet Protocol (SLIP)
 Point-to-Point Protocol (PPP)
 Allow internet access from the PC in
your home by dialing up over modems
to an Internet host.
TCP/IP
Applications/Services
 Terminal Emulation (Telnet)
 File Transfer Protocol (FTP)
 HyperText Transfer Protocol (HTTP)
 Simple Mail Transfer Protocol (SMTP)
 Simple Network Management Protocol (SNMP)
 Domain Name Service (DNS)
Terminal Emulation
(Telnet)
 Telnet is the login
and terminal
emulation program
for TCP/IP
environments
 Primary function is
to allow users to log
into remote host
systems
 Requires username
and password
How to Telnet
 Open your DOS prompt
 Type telnet
 Your telnet window opens...
Uses for Telnet Today
 Use of Telnet has diminished
in recent years
 Still being used to:
 Connect to routers
 Remote management of
servers
 Access to home system
while traveling
File Transfer Protocol
(FTP)
 Important for building web pages
 Primary mode of moving complete file
from one computer to another
 FTP is a program for transferring files in
TCP/IP environments (ASCII or Binary)
File Transfer Protocol
(FTP)
 Client – when you want information
 Server – when you have the information
 Typically, a user at a client computer
downloads files from a remote server
FTP Terms: DOS
 GET (MGET): You are
downloading a file (or files)
from another computer to
your desktop
 PUT (MPUT): You are
uploading a file (or files)
from your desktop to
another computer
File Transfer Protocol
(FTP)
 Must logon to server
 Requires username and password to
access normal file system
 Anonymous FTP allows access to anyone
to a special file system (e.g.
ftp.microsoft.com)
FTP Terms: DOS
 CD: Change Directory
 Move up or down the directory structure
 MD: Make Directory
 New storage space
FTP Transparent
Often FTP commands are transparent
through your browser or through a FTP
program like WS FTP.
HyperText Transfer
Protocol
 Primary application protocol that
underlies the world wide web
 Provides user access to the files that
make up the web
 Anywhere – anyplace – anytime
HyperText Transfer
Protocol
 Defines HOW they get there, not what
they look like
 Files can be in many different formats
(text, graphics, audio, video, etc.)
 Hypertext markup language (HTML) is the
standardized language for creating web
pages
Simple Mail Transfer
Protocol
 SMTP is the electronic mail transfer
protocol used in TCP/IP environments
 Provides a store-and-forward mail
capability between host computer mail
systems on the network
 MIME (Multimedia Internet Mail Exchange)
has become the standard for document
attachments
Domain Name Service
 DNS is a TCP/IP service that maps network
address numbers, for example,
123.456.789, to an easy to remember name,
such as: www.microsoft.com
 Internet and TCP/IP applications such as
telnet, FTP and SMTP access DNS to locate
names you’ve specified and resolves them
to a numeric address and inserts it into a
message for transport.
Domain Name Service
 The address information is stored at many
locations in a hierarchical structure, not at
one central depository
 Each site has a domain server that maintains
information about the local nodes
Node
Node
Central Hub
Node
Node
Client/Server
Architectures
 Two-tier
 “Fat” Client: User Interface + Application
 Database Server
 Example: File servers, SQL Servers
Client/Server
Architectures
 Three-tier
 “Thin” Client: User Interface only
 Application Server
 Database Server
 Examples: Mail servers, Business
applications
Client/Server
Architectures
 Application Programming Interfaces
 SQL, ODBC
 APPC
 TP Monitors
 RPC
 Interface Definition Languages
 DCE
 CORBA
 Microsoft OLE
References
From Networking 101
Jim Cabral, Puget Technology Group, Inc. &
Tammy Ruth, Children’s Hospital and Medical Center
www.pugettech.com
cabralje@pugettech.com
truth@chmc.org