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www.nettech.inNettech Private Ltd.
Communication & Networking:An Overview
Prepared by :Swapan PurkaitDirectorNettech Private [email protected]+ 91 93315 90003
For Summer Training on Computer Networking visit www.nettech.in
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Organization
• Communication Systems• Networking Fundamentals• The INTERNET• Network Security
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Simple Communication Model
Source Destination
Transmission
media
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Example
client program server
communicationschannel
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Communication System
Source Modulator Demodulator Sink
Carrier
Noise
Transmissionmedia
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Data Communication Model
Modem
DCE
Modem
DCE
Computer
DTE
Computer
DTE
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Modes of Communication
Simplex
communications
Half-duplex (HDX)
communications
Full-duplex (FDX)
communications
or
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Communication Ports
9-pin D-typemale connector (COM1:)
9-pin or 25-pin D-typemale connector (COM2:)
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Transmission Media
• Wired– Twisted pair, Coaxial cable, FO
• Wireless– Short range
• Infrared– Long Range
• Microwave• Satellite
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Transmission Media
Metal sheath Innerconductor
Insulating outer conductor
Coaxialcable
Twisted-paircable
Inner cladding(glass)Inner fibre
(glass)
Outer cladding(PVC)
Fibre opticcable
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Telephone Network
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Cable TV Network
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Multiplexing
• Time-Division Multiplexing (TDM)• Frequency-Division Multiplexing (FDM)• Statistical Time-Division Multiplexing
(STDM)L1
L2
L3
R1
R2
R3Switch 1 Switch 2
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Networks
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Categories
• Communication Networks– PSTN
• Computer Networks– INTERNET
• Integrated Networks– Computer & Communication Networks
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Building Blocks
• Nodes: PC, special-purpose hardware…– hosts– switches
• Links: coax cable, optical fiber…– point-to-point
– multiple access
…
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Switched Networks
– two or more nodes connected by a link, or
– two or more networks connected by two or more nodes
• A network can be defined recursively as...
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Switching Strategies
• Circuit switching: carry bit streams– original telephone network
• Packet switching: store-and-forward messages– Internet
• See the schematic diagram next
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Ckt Vs. Pkt Switching
Circuit-switching
Packet-switching
possible routes
fixed routePSE
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Addressing and Routing
• Address: byte-string that identifies a node– usually unique
• Routing: process of forwarding messages to the destination node based on its address
• Types of addresses– unicast: node-specific– broadcast: all nodes on the network– multicast: some subset of nodes on the
network
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What Goes Wrong in the Network?
• Bit-level errors (electrical interference)• Packet-level errors (congestion)• Link and node failures
• Messages are delayed• Messages are deliver out-of-order• Third parties eavesdrop
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Layering
• Use abstractions to hide complexity• Abstraction naturally lead to layering• Alternative abstractions at each layer
Request/replychannel
Message streamchannel
Application programs
Hardware
Host-to-host connectivity
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Protocols
• Building blocks of a network architecture• Each protocol object has two different
interfaces– service interface: operations on this protocol– peer-to-peer interface: messages exchanged
with peer • Term “protocol” is overloaded
– specification of peer-to-peer interface– module that implements this interface
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Host 1
Protocol
Host 2
Protocol
High-levelobject
High-levelobject
Serviceinterface
Peer-to-peerinterface
Interfaces
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ISO-OSI 7 Layer Ref. Model
Application
Session
Transport
Network
Data Link
Physical
Presentation
Application
Session
Transport
Network
Data Link
Physical
Presentation
DATA
DATA
DATA
DATA
DATA
DATA
A
A
A
A
A
P
P
P
P
S
S
S
T
TN
DATAAPSTND D
DATA DATA
Actual Data Flow
Virtual Data Flow
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Data Flow in Layered Model
DATA DATA
Actual Data Flow
Virtual Data Flow User application. processand management functionsData interpretation, formatand control transformationAdministration and controlof session between two nodesNetwork transparent data transferand transmission controlRouting, switching and flowcontrol over a networkMaintain and release data:link, error and flow controlElectrical and mechanicalcharacteristics
Application
Session
Transport
Network
Data Link
Physical
Presentation
Application
Session
Transport
Network
Data Link
Physical
Presentation
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Logical View of Layers
N1
N7
Session
Transport
Network
Physical
Data Link
N2
N3
N4
N6
N8
N5
NETWORK A NETWORK B
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Types of Networks
• LAN– Local area
• MAN– Metropolitan area
• WAN– Wide area
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Ring, Star & Bus LAN
Ring network
Bus network
Star network
centralserver
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IEEE LAN Standards
Physical
MAC
LLC
Physical
MAC
LLC
LAN
Physical
Data link
Logical link control (LLC) IEEE 802.2
Media accesscontrol (MAC)IEEE 802.5 IEEE 802.3
Token ring CSMA/CDOSI model
Media accesscontrol (MAC)
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Campus Wide LAN
PRODUCTION_1
PRODUCTION_2
ADMIN_1
ADMIN_2
ELECT_1
INSTR_1MECH_1
Ethernet backbone
ELECT_1 can actas a stand-alonenetwork if required
Fan-outbox
Fan-outbox
Fan-outbox
Fan-outbox
Fan-outbox
Fan-outbox
Fan-outbox
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Internetworking
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Definition
• An internetwork is an interconnected collection of independent networks– Each independent network is often referred to
as an autonomous system (AS)• Internetwork is the generic name to any
kind of network interconnection • The INTERNET is a special internetwork
that uses TCP/IP protocol stack
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Difference with network?
• A network is a collection of interconnected computers
• An internetwork is a collection of interconnected networks (or AS’s)
R2
R1
H4
H5
H3H2H1
Network 2 (Ethernet)
Network 1 (Ethernet)
H6
Network 3 (FDDI)
Network 4(point-to-point)
H7 R3 H8
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Various Internetworking Cases
• LAN-LAN– EE LAN to CSE LAN in a campus network
• LAN-WAN– office LAN to the INTERNET
• WAN-WAN– ERNET to VSNL-net
• LAN-WAN-LAN– two offices connected via the INTERNET
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Practical Internetworking Scenario
• LAN for small domains of computers• LAN-LAN interconnection for a campus• LAN-WAN interconnection for INTERNET
connectivity• LAN-WAN-LAN interconnection for
connectivity between distant computers
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A common Example(LAN-LAN, LAN-WAN, LAN-WAN-LAN)
LAN A
LAN C
LAN D
Wide area
network
connection
Local network
backbone
Wide areanetwork
Gateway
or modem
LAN B
Bridge
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Internetworking Devices
• Repeater (layer 1) bit-level• Bridge (layer 2) frame-level• Router (layer 3) packet-level• Gateway (layer 4-7)
message-level– Transport layer gateway TPDU-level– Application layer gateway APDU-level
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The INTERNET
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Early History
• 1969, Dec – ARPANET went on air:: US DoD
• 1974 – TCP/IP discovered :: Cerf & Kahn• 1983, Jan 01 – TCP/IP became the official
protocol• MILNET is isolated from ARPANET• 1990 – the Internet takes over, ARPANET
dies• NSFNET is merged with ARPANET• 1992 – the Internet Society was set up
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The Internet Structure- Recent Past
NSFNET backboneStanford
BARRNET
regional
Berkeley
PARC
NCAR
UA
UNM
Westnet
regional
UNL KU
ISU
MidNet
regional
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The Internet Structure- Today
Backbone service provider
Peering
pointPeering
point
Large corporation
Large corporation
Small
corporation
“Consumer ” ISP
“Consumer ”ISP
“ Consumer ” ISP
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Traditional use of the Internet
• E-mail (SMTP)– Pine, outlook express, hotmail, yahoo, etc
• News (NNTP)– Usenet
• Remote login (Telnet)– Rlogin
• File transfer (FTP)– CuteFTP, download
• Browsing (HTTP)– WWW, Explorer, Netscape
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How to be on the Internet?
• A machine is capable to be on the Internet, if it has – An IP address– TCP/IP support – Ability to send IP packets– Physical connectivity
• Today TCP/IP is built into most OS’s
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Connecting from Home
• Windows/Linux has TCP/IP inbuilt• Configure TCP/IP for your ISP & modem• Configure dial-up connection• Connect modem to your PC (connectivity) • Dial ISP’s # using PPP• Login and get temporary IP• Start browser or e-mail client
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Connecting to ISP via Modem
Modem
Modem
Modemstack
Modem
Modem33.6 Kbps
Modem56 Kbps
Public switchedtelecommunicationnetwork
ISP Server
INTERNET
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TCP/IP Stack
• Unlike OSI, it is a 5 layer architecture– Session & presentation layers are merged into
application layer• Lower 2 layers are not specified
– Any LAN can fit into IP– This is a prime reason for its popularity
• Has its origin in UNIX OS
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TCP/IP Architecture
Computer onnetwork A Physical medium
FTP/TELNETApplication
TCP
IP
Application
TCP
IP
Networkcontrollersoftware
Networkcontrollersoftware
Computer onnetwork B
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Internet Routing
• Overview– Forwarding vs. routing
• 2-level routing– IGP and EGP
• Distance vector• Link state• Route calculation
– Dijkstra’s algorithm
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INTERNET PROTOCOL(IP)
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Versions
• Two versions are there:– Version 4 (IPv4)
• 32 bit address– Version 6 (IPv6)
• 128 bit address
• Mobility support– Mobile IP
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Global IP Addresses
• Properties– globally unique– hierarchical: network + host– 32/128 bit
• Dotted Decimal Notation– 10.3.2.4– 128.96.33.81– 192.12.69.77
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Subnetting
• Add another level to address/routing hierarchy: subnet
• Subnet masks define variable partition of host part• Subnets visible only within site
Network number Host number
Class B address
Subnet mask (255.255.255.0)
Subnetted address
111111111111111111111111 00000000
Network number Host IDSubnet ID
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How are subnet masks specified?
Subnetid HostidNetwork ID = 128.138
16 bits 8 bits 8 bits
Subnetid (241) Hostid (78)Network ID = 128.138
16 bits 10 bits 6 bits
11111111 11111111 11111111 00000000 255.255.255.0
11111111 11111111 11111111 11 000000 255.255.255.192
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IPv6
• Though CIDR has given IPv4 some breathing space, its days are numbered.
• In 1990, IETF started work on a new version of IP which will never run out of addresses
• In 19993, it is decided as IPv6 – Since IPv5 was already in use for an
experimental real-time streaming protocol
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INTERNET Domain Names
edu gov com mil usa uk fr
ac
ed bath napier man
eece cs mmseeece.napier.ac.uk
intel sony nec
wwwwww.eece.napier.ac.uk
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Examples
• Hostsnettech.in [domain name] 202.144.75.66 [IP address] --> 80:23:A8:33:5B:9F [ethernet MAC address]
• Files/usr/llp/tmp/foo (server, fileid)
• Users Swapan Purkait [email protected]
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Network Security
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Common Security Risks
Hacker To test out someone's security system; steal data
Businessman To discover a competitor's marketing strategy
Accountant To embezzle money from a company
Stockbroker To deny a promise made via e-mail
Con man To steal credit card numbers for sale
Student To have fun snooping on peoples' e-mail
Terrorist To destroy data (say by virus attack)
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Security Measures
• Physical Layer: covert channel, spread-spectrum• Data Link Layer: link encryption• Network Layer: packet-filter• Application Layer: firewall, cryptography
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Secret Key System
Alice Bob
D ES K ey DES K ey
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SSL
• It is stream-based consisting of three phases
• In initial handshake phase, secure communications are established
• In intermediate data transfer phase, application-to-application dialog (with data encryption) occurs
• In closing handshake phase, connection is terminated
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Looking Forward
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The Power of “O”
YOUR BUSINESS
High data rate ~ Tbps
High reliability of fibre ~ 30 years
Low error rate < 10 (̂-6)
Un-repeatered over longer distances
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The Power of “M”
YOUR BUSINESS
Handy devices Consumer oriented
Freedom for movement
Anywhere, anytime
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Future = Optical + Mobile
• Wireless mobile communication has already attracted global attraction
• DWDM optical technology is maturing at a very high speed
• Future global trends show-Wide-spread adoption of wireless mobile
access to optical backbones
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