Download The Infrastructure Technologies

The Infrastructure
Technologies
Communication
• All communications require:
– Transmitters/Senders and receivers
– Transmission medium
– Rules of communication
– A message
Transmitter
Medium
Receiver
Message
.
Computer Data Communication
• Transmitter/Receiver
– Combination of Hardware and software
• Physical Media Types
– Cable
 twisted pair
 coaxial cable
 fiber-optic cable
– Wireless media
 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
(Fig. 13.14)
Electromagnetic spectrum
• Signals transmitted in the context of a Carrier Signal
– Known frequency
– Known amplitude
Signal Incompatibility
• Inside the computer must have discrete/digital
1-bit
1-bit
0-bit
0-bit
• 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
As Signal Moves Over Line
• Signal degrades or loses strength.
– Called attenuation
• Signal picks up noise.
– EMI - Electromagmetic interference
– Static
– If not addressed, noise can overwhelm signal
• These limit the distance of some communications
Digital vs. Analog
• Analog
– contiguous signal
– amplify to boost
signal
 noise amplified, too
 noise accumulates
– filter known or
predictable noise
 tape hiss
• Digital
– discrete signal
 digits (0, 1)
– sample/retransmit
 boosts signal
 automatically filters
most noise
 errors function of
sampling rate
Both digital and analog data are transmitted in the
context of a carrier signal.
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
– common carrier
– boost and filter signal
• Enterprise networks
– Intranet
• Supply chain integration
– 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
Workstation
Server
• A bridge links
similar networks.
• A gateway links
dissimilar
networks.
Bridge
Server
Workstation
Workstation
Server
Gateway
Workstation
Workstation
Routers
Router
• accept messages at
one of several input
ports and forward
the message to the
appropriate output
port
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 (The server’s
operating system)
– Part of the NOS runs on each workstation
• Software that handles communication between the workstation and
the NOS
Server
Client
• Agent process on client
• client’s link to network
Network
Windows ME
– Examples
operating system
Network
• Novell NetWare
• Windows 2000 Server
• Windows NT
• Peer to Peer Networks
– NOS is installed on each attached workstation
– Runs on top of the local operating system
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
•
•
•
•
Circulating electronic token prevents collisions
Must possess the token to transmit a message
Random Access Control
Eliminates collisions
– CSMA/CD (collison detection)
• “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
Message A
• Most popular type
•
•
•
•
of message delivery
Break message into
packets
Transmit packets
independently
Multiple messages
share line
Reassemble
message at
receiving end
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
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 Open Systems Interconnect (OSI) Model
OSI layer
Responsibilities
The first four layers work with the user's message.
Application
Provides a logical link between an application program and
the lower-level protocols.
Presentation Performs necessary data representation and/or syntax
conversions; e.g., encryption/decryption.
Session
Establishes, maintains, and terminates a connection.
Transport
Breaks the message into packets. Ensures error free, end-toend delivery of the complete message.
The bottom three layers work with packets and control the network.
Network
Determines the best route for sending a packet from the
source node to the destination node.
Data-link
Formats a packet for transmission to the next node.
Physical
Interfaces with the physical communication medium.
Sending computer
Each level “talks to” the
equivalent level on the
other node.
Transmission errors call
for retransmission of
affected packet or
packets.
Message Flow
Receiving computer
Excel worksheet
created
Application
Display and
manipulate worksheet
Worksheet encrypted
and compressed
Presentation
Decrypt and
decompress
worksheet
Establish connection
Session
Drop connection
on completion
Divide into packets
and create messages
Transport
Reassemble packets
Verify delivery of
entire message
Determine packet
routing
Network
Reroute if necessary
Transmit one packet to
next node
Data link
Accept packets
Physical
Medium of
transmission
Medium of
transmission
Physical
Medium
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
– corresponds to OSI Application and Presentation layers
– protocols that directly support application programs
– protocols such as telnet, FTP, SMTP, DNS, POP, and
HTTP
• Transport layer
–
–
–
–
–
–
corresponds to OSI Session and Transport layers
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
• corresponds to OSI Network layer
• IP (Internet Protocol)
• routes and delivers individual packets
• Network access layer
– corresponds to OSI Data-link and Physical layer
– This is where Ethernet, Token ring and other network
access protocols reside
TCP/IP Layers (continued)
FTP request
Application program
FTP
header
Application layer
Transport layer
(each packet)
Internet layer
(each packet)
TCP
header
IP
header
TCP
header
FTP
header
FTP
header
FTP request
FTP request
FTP request
Network access
layer
Network
header
IP
header
TCP
header
FTP
header
FTP request
IP Address
• IP address
– 32 bit number
– dotted decimal format
– 134.53.40.2
• Standards
– IPV4 – current
– IPV6 – proposed
• 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 (ie. 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 History
• 1960s Started as ARPANET (Advanced Research Projects
Agency)
• 1986 NSFNET became internet Backbone (56Kbps)
• 1989 NSFNET upgraded to T1 1.44 (Mbps)
• 1991 NSFNET upgradet to T3 45 (Mbps)
• 1991 - First commercial traffic
• 1994 - First Web browser introduced
• 1995 NAPs Replaced NSFNET
• 1995 - Control turned over to independent governing bodies
Internet Terminology
• Interconnect Level
• Any means for bandwidth providers to interconnect
• Network Access Points (NAPS)
• MAEs, FIXs and CIX (pseudo NAPs)
• Network Service Providers NSPs (National Backbone
Providers)
• Replaced NSFNET (old backbone network)
• high-speed lines or series of connections that form the
major pathways of the internet
• Regional Networks
– connect up to one or more national backbone providers
• Local Internet Service Providers (ISPs)
• Consumers and Businesses
– Servers - Contain information and are located on
independently owned networks
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.