Download The Infrastructure Technologies

The Infrastructure
Technologies
Communication
All communications require:
 Transmitters/Senders and receivers
 Transmission medium
 Rules of communication
 A message
Transmitter
Medium
Message
Receiver
Computer Data Communication

Transmitter/Receiver

Combination of Hardware
and software

Physical Media Types

Cable




twisted pair
coaxial cable
fiber-optic cable
Wireless media



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
radio
microwave
cellular telephone
satellite
infrared
Data Communication Media
■
Bandwidth


■
Measure of a medium’s
carrying capacity
Measured in bits (bps)
Two categories


Baseband
 one line, one channel
 most local
communication
Broadband
 one line, simultaneous
channels
 DSL, cable
Connection Type Bandwidth
Local telephone line
56 Kbps
Wireless
2G digital cellular
2.5G digital cellular
3G digital cellular
Bluetooth
Wi-Fi (802.11b)
19.2 Kbps
144 Kbps
2 Mbps
1 Mbps
Up to 11 Mbps
Home satellite service
400 Kbps
DSL
1.44 Mbps
Cable service
2 to 10 Mbps
Leased line (T-1, T-3)
1.5 to 43 Mbps
Fiber optic cable
Up to 10 Gbps
The Message
Message
Header



Body
Trailer
Messages have header and trailer carry information
for delivering and ensuring the integrity of the
message
These are used by application and communication
protocols
The electronic form of a message is a signal
Protocols


A precise set of rules for communicating
A communication protocol defines:





message format (header/trailer)
communication speed
How the message is encoded (e.g., ASCII,
EBCDIC)
filtering/error correction rules
An implementation of standard rules for
passing parameters between adjacent layers
Signal Transmission
Time
+
0
Amplitude
Cycle
Cycle
Frequency = cycles per unit of time


Signals transmitted in the context of a Carrier
Signal
Known frequency
Known amplitude
Signal Incompatibility
1-bit
1-bit
0-bit
0-bit
■
Inside the computer must have discrete/digital
■
Many existing communication lines are
continuous/analog (especially in the last mile)
■
Signal must be converted between digital/discrete
and analog/continuous through
modulation/demodulation.
■
The function of a modem
Networks

A network consists of two or more computers
linked by communication lines.

Connectivity – the ability of a device or
software to work with other devices and/or
software over a network connection

Each connected device is called a node
Local Area Network - LAN

Small geographic scope

Computers in close proximity

Local communications


no boosting or filtering
Workstations
Wide Area Network - WAN



Network of networks
Computers geographically disbursed
Long-distance communication



Enterprise networks


Intranet
Supply chain integration


common carrier
boost and filter signal
Extranet
Global networks
Internetworking Hardware

Use to connect multiple LANs or WANs

Have intelligence to filter, route and do protocol
conversion

Examples

Bridges - Similar Networks

Gateways - Dissimilar networks

Routers

Switches
Bridges and Gateways
Workstation
Workstation
Workstation
Workstation
Workstation
Server
■
A bridge links
similar networks.
■
A gateway links
dissimilar
networks.
Workstation
Bridge
Server
Workstation
Workstation
Server
Gateway
Workstation
Workstation
Routers

accept messages
at one of several
input ports and
forward the
message to the
appropriate output
port
Router
Out
In
Common Network Topologies
Bus
Ring
Star
Clients/Server Networks
Client
Client
Server
Printer
Client
File system
Client
Peer to Peer Networks
Peer computer
Peer computer
File
system
File
system
Peer
computer
File
system
Peer computer
File
system
Network Operating Systems
■
■
Client/server architecture LANs
 The system software runs on the server
 Part of the NOS runs on each workstation
 Software that handles communication between the
workstation and the NOS
Server
 Agent process on client
Network
 client’s link to network
operating system
Network
 Examples
 Novell NetWare
 Windows Server 2000,
2003, NT Server
Peer to Peer Networks
 NOS is installed on each attached workstation
 Runs on top of the local operating system
Client
Windows ME
Communication
software
Message Delivery
■
■
Each computer or terminal is a node
Messages (signals) are either


■
Broadcast to all nodes
Or move from node to node (point to point)
 Topology or routing determines the route
Protocols define the precise rules to follow for LAN
access and message delivery (Many different protocol
exist)
■
Popular LAN Access control methods


Collision detection
Token passing
Network Access Control Methods
■
Distributed Access Control

Token passing

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CSMA/CD (collision detection)



■
Circulating electronic token prevents collisions
Must possess the token to transmit a message
Random Access Control
Eliminates collisions
“Listen” for quiet line (carrier signal); then send message
Collision occurs with simultaneous messages
Must wait and resend
Three major standard protocols for LANs



Ethernet - (CSMA/CD, Star or Bus)
Token-Ring - (Token passing, Ring)
ARCnet - (Token passing, Star or bus)
Packet Switching
■
■
■
■
■
Most popular type of
message delivery
Message A
Packet A1
Packet A2
Packet A3
Packet A3
Packet B2
Packet X3
Packet A1
Packet Y1
Open
Packet Z2
Packet A2
Packet Z1
Packet Y2
Packet X2
Open
Open
Packet Y3
Packet B1
Packet
Packet
Packet X1
Break message into
packets
Transmit packets
independently
Multiple messages
share line
Reassemble message
at receiving end
Packet A1
Packet A2
Message A
Packet A3
Packet Switching
■
■
Packets can follow different routes to reach
destination
Error handling is important


■
Packets can arrive out of order
Individual packets may be lost
Objectives



Deliver the message accurately
Efficient utilization of available bandwidth
Efficient error recovery
The TCP/IP Model
Application layer
TCP/IP is the
standard packet
switching protocol
for the Internet
Transport layer
Internet layer
Network access layer
TCP/IP Layers
■
■
Application layer
 protocols that directly support application
programs
 protocols such as telnet, FTP, SMTP, DNS, POP,
and HTTP
Transport layer
 TCP (Transmission Control Protocol)
 creates packets and reassembles messages
 guarantees delivery
 Receiving end acknowledges each packet
 Sending end re-sends unacknowledged packets
TCP/IP Layers (continued)
■
■
Internet layer
•
IP (Internet Protocol)
•
routes and delivers individual packets
Network access layer

This is where Ethernet, Token ring and other
network access protocols reside
IP Address
■
IP address
 32 bit number
 dotted decimal format
 134.53.40.2
■
Standards
 IPv4 – current: IPv4 addresses are 32 bits


supports 232 (about 4.3 billion) addresses
IPv6 – proposed: a 64-bit (sub-)network prefix and a 64bit host part

■
supports 2128 addresses
Internet protocol communication requires IP address
Assigning an IP Address
■
■
■
All computers attached to the Internet must have an
IP address.
Static allocation
 IP address established at installation
 linked to specific computer’s Media Access
Control (MAC) address (i.e. Ethernet address)
Dynamic allocation
 IP address allocated dynamically at login time
 Must use a protocol such as Dynamic Host
Configuration Protocol (DHCP)
Domains
Domain
aero
biz
com
coop
edu
info
gov
mil
museum
name
net
org
pro
Signifies
Air-transport industry
Business organization
US commercial
Coooeratives
US educational
Unrestricted
US government
US military
Museums
Individuals
US network
US non-profit
Professionals
Domain
au
br
ca
cn
de
fi
fr
gb
in
it
jp
ru
za
Signifies
Australia
Brazil
Canada
China
Germany
Finland
France
Great Britian
India
Italy
Japan
Russia
South Africa
Domain Name System (DNS)
•
Accepts domain name
•
Converts to IP address
•
Network operating system routine on

each host

each server

each Internet service provider (ISP)

each network service provider (NSP )
Caching
■
Domain name and IP address cached by
all participating Domain Name Systems.
■
Subsequent references use cached IP
address.

Business student uses cob
Internet Architecture
Network Service Provider (NSP)
Network
Access Point
(NAP)
Network
Access Point
(NAP)
Network Service Provider (NSP)
Regional Internet
Service Provider
Local ISP
Regional Internet
Service Provider
Local ISP
Regional Internet
Service Provider
Local ISP
Internet Access
■
■
■
■
■
Access via local point of presence (POPs)
 by local call
 broadband access into the home
ISPs provide access (the “on-ramp”)
POPs connect up the network hierarchy to an
interconnect point
Phone is most common for individuals
Broadband (Cable and ADSL) are coming fast...and
competing for market share.