fundamental of networking models LAN WAN MAN

NETWORK FUNDAMENTALS:
NETWORK FUNDAMENTALS:
INTRO TO NETWORK
INTRO TO NETWORK
STRUCTURE
STRUCTURE
AND PROTOCOL
AND PROTOCOL
LAN, WAN, TCP/IP
LAN, WAN, TCP/IP

OUTLINE
 Basic concepts in communications
 Understanding Networking.
 Understanding Transmission Medium (Network Cables)
 Understanding Network Hardware
 WAN and LAN
 Understanding Network Protocols

BASIC CONCEPTS
IN
COMMUNICATION

BASIC CONCEPTS
 Communications – activity associated with distributing
or exchanging information
 Telecommunications – technology of communications at
a distance that permits information to be created any
where and used everywhere with little delay
 Today it, involves
 Data: digital and analog
 Voice: spoken word
 Video: telelcommunication imaging

ESSENTIALS FOR COMMUNICATIONS
Must have a message
Message must have a transmitter
Message must have a medium
Message must be understood
Message must have some level of security
Source  Transmitter  Transmission  Receiver  Destination
Source System Destination System
Workstation/PC Workstation/PC
Medium
1 2 3 4 5 6

BIG PICTURE
What do you see here for a typical
network?

KEY NETWORK TERMINOLOGY
EXPLAINED (1)
 Networks needs to interconnect at a distance by a form
of point to point or point to multiple point connected
media
 A network is a group of computers connected together
in such a way as to allow
 Networks that are interconnected have proven to be low
cost, reliable, and efficient means of communicating at a
distance

KEY NETWORK TERMINOLOGY
EXPLAINED (2)
 Node: anything connected to the network, usually a
computer, but it could be a printer or a scanner
 Segment: any portion of a network that is separated by
a switch, bridge or a router from another part of a
network.
 Backbone: the main cabling of a network that all of the
segment connect to. Usually, the backbone is capable of
carrying more information than the individual
segments.
 Topology: The way each node is physically connected to
the network

COMMON TOPOLOGIES - BUS
 Bus: each node is daisy-chained (connected one right after the
other) along the same backbone. Information sent from a node
travels along the backbone until it reaches its destination node.
Each end of a bus network must be terminated with a resistor to
keep the

COMMON TOPOLOGIES - RING
 Ring: Similar to a bus network, rings
have nodes daisy chained, but the end
of the network in a ring topology
comes back around to the first node,
creating a complete circuit. Each node
takes a turn sending and receiving
information through the use of a
token. The token along with any data
is sent from the first node to the
second node which extracts the data
addressed to it and adds any data it
wishes to send. Then second node
passes the token and data to the third
node, etc. until it comes back around
to the first node again. Only the node
with the token is allowed to send
data . All other nodes must wait for
the token to come to them.

COMMON TOPOLOGIES - STAR
 In a star network, each node is connected to a central
device called a hub. The hub takes a signal that comes
from any node and passes it along to all the other nodes
in the network.

COMMON TOPOLOGIES – STAR BUS
 Prob. Most common topology used today. Combines
elements of the star and bus topologies to create a
versatile network environment.
 Nodes in particular areas are connected to hubs (and
create star topology), and hubs are connected together
along the network backbone (like a bus network).
 Often you have stars nested within stars.

OTHER NETWORK TOPOLOGIES
(ARCHITECTURE)
 Some basic network topologies not previously
mentioned:
 One-to-one
 Hierarchical
 Hybrid
 Client-server
 Multiple nodes

BASIC SIGNAL TERMINOLOGIES
 Bit: binary digit, either 0 or 1
 Baud (don’t really use anymore; not accurate)
= one electronic state change per second
 Bit rate – a method for measuring data
transmission speed – bits per second
 Mbps – millions of bits per second (data speed;
measure of bandwidth = total information flow
over a given time) on a telecommunication
medium
 8 bits = 1 byte
 Mb – million bits (quantity of data)
 MB – million bytes (quantity of data)
 Gbps – Billion bits per second (data speed)
 Teraflops – trillion operations per second
Kilo K 2^10
Mega M 2^20
Giga G 2^30
Tera T 2^40
Peta P 2^50
Exa E 2^60
Zetta Z 2^70
Yotta Y 2^80

DATA TRANSMISSION
 Successful transmission of data depends on:
 The quality of the signal being transmitted
 Characteristics of the transmission medium
 Data rate – bits per second in data communications
 Bandwidth – bandwidth or signal is constrained by the
transmitter and the nature of the transmission in cycles
per second or hertz
 Noise – Average level of noise over the communication
path.
 Error rate – rate at which errors occur where error in 1
or 0 bit occurs

UNDERSTANDING TRANSMISSION
MEDIUM

BASIC TRANSMISSION MEDIUM
CONCEPTS
 Medium is the physical path between transmitter and
receiver in a data transmission system
 Guided Medium: waves are guided along a solid
medium path (twisted pair, coaxial cable, and optical
fiber).
 Unguided medium: waves are propagated through the
atmosphere and inner/outerspace (satellite, laser, and
wireless transmissions).

MEDIUM EXAMPLES BY TYPE
 Conductive: twisted pairs and coaxial cables
 Electromagnetic: microwave
 Light: lasers and optical fibers (need clear line of sight)
 Wireless – inner/outerspace; satellite (omnidirectional
 security issues)

COAXIAL CABLE (1)
 Widely installed for use in business and corporation
ethernet and other types of LANs.
 Consists of inter copper insulator covered by cladding
material, and then covered by an outer jacket
 Physical Descriptions:
 Covered by sheath material
 Outer conductor is braided shielded (ground)
 Separated by insulating material
 Inner conductor is solid copper metal

COAXIAL CABLE (2)
 Applications:
 TV distribution (cable tv); long distance telephone
transmission; short run computer system links
 Local area networks
 Transmission characteristics:
 Can transmit analog and digital signals
 Usable spectrum for analog signaling is about 400 Mhz
 Amplifier needed for analog signals for less than 1 Km and
less distance for higher frequency
 Repeater needed for digital signals every Km or less distance
for higher data rates
 Operation of 100’s Mb/s over 1 Km.

TWISTED PAIR CABLES
 Physical description:
 Each wire with copper conductor
 Separately insulated wires
 Twisted together to reduce cross talk
 Often bundled into cables of two or four twisted pairs
 If enclosed in a sheath then is shielded twisted pair (STP) otherwise
often for home usage unshielded twisted pair (UTP). Must be shield
from voltage lines
 Application:
 Common in building for digital signaling used at speed of 10’s Mb/s
(CAT3) and 100Mb/s (CAT5) over 100s meters.
 Common for telephone interconnection at home and office buildings
 Less expensive medium; limited in distance, bandwidth, and data rate.

CATEGORIES OF TWISTED PAIRS
CABLING SYSTEM
Category Maximum data
rate
Usual application
CAT 1 Less than 1
Mbps
analog voice (plain old
telephone service) Integrated
Services Digital Network Basic
Rate Interface in ISDN Doorbell
wiring
CAT 2 4 Mbps Mainly used in the IBM Cabling
System for token ring networks
CAT 3 16 Mbps Voice and data on 10BASE-T
Ethernet (certify 16Mhz signal)
CAT 4 20 Mbps Used in 16Mbps Token Ring
Otherwise not used much
CAT 5 100 Mbps 100 Mbps TPDDI
155 Mbps asynchronous
transfer mode (certify 100 Mhz
signal)
Specs describe cable
Material, type of
Connectors, and
Junction blocks to
Conform to a category

OPTICAL FIBERS (1)
 Physical Description:
 Glass or plastic core of optical fiber = 2to125 µm
 Cladding is an insulating material
 Jacket is a protective cover
 Laser or light emitting diode provides transmission light
source
 Applications:
 Long distance telecommunication
 Greater capacity; 2 Gb/s over 10’s of Km
 Smaller size and lighter weight
 Lower attenuation (reduction in strength of signal)
 Electromagnetic isolation – not effected by external
electromagnetic environment. Aka more privacy
 Greater repeater spacing – fewer repeaters, reduces line
regeneration cost
Repeaters 

OPTICAL FIBERS (2)
 multimode fiber is optical fiber that is designed to carry
multiple light rays or modes concurrently, each at a
slightly different reflection angle within the optical
fiber core. used for relatively short distances because
the modes tend to disperse over longer lengths (this is
called modal dispersion) .
 For longer distances, single mode fiber (sometimes
called monomode) fiber is used. In single mode fiber a
single ray or mode of light act as a carrier

WIRELESS TRANSMISSION (1)
 Frequency range (line of sight):
 26 GHz to 40 GHz: for microwave with highly directional
beam as possible
 30 MHz to 1 GHz: for omnidirectional applications
 300MHz to 20000 GHz: for infrared spectrum; used for point
to point and multiple point application (line of sight)
 Physical applications:
 Terrestrial microwave – long haul telecommunication service
(alternative to coaxial or optical fiber)
 Few amplifier and repeaters
 Propagation via towers located without blockage from trees,
etc (towers less than 60 miles apart)

WIRELESS TRANSMISSION (2)
 Satellite is a microwave relay station
 Geostationary orbit (22,000 miles) and low orbit (12000 miles)
 Satellite ground stations are aligned to the space satellite,
establishes a link, broadcast at a specified frequency. Ground
station normally operate at a number of frequencies – full duplex
 Satellite space antenna is aligned to the ground station establishes
a link and transmits at the specified frequency. Satellite are
capable of transmitting at multiple frequencies simultaneously,
full duplex.
 To avoid satellites from interfering with each other, a 4 degree
separation is required for 4/6 GHz band and 3 degree for 12/14
GHz band. Limited to 90 satellites.
 Disadv: not satellite repair capability; greater delay and
attenuation problems.

WIRELESS LAN
 Wireless LAN
 HiperLAN (European standard; allow communication at
up to 20 Mbps in 5 GHz range of the radio frquency
(RF) spectrum.
 HiperLAN/2 operate at about 54 Mbps in the same RF
band.

HUBS
 A hub is the place where data converges from one or
more directions and is forwarded out in one or more
directions.
 Seen in local area networks
Reference to
equipment

GATEWAYS
 A gateway is a network point that acts as an entrance to
another network. On the internet, in terms of routing, the
network consists of gateway nodes and host nodes.
 Host nodes are computer of network users and the
computers that serve contents (such as Web pages).
 Gateway nodes are computers that control traffic within
your company’s network or at your local internet service
provider (ISP)

ROUTERS
 A router is a device or a software in a computer that
determines the next network point to which a packet should
be forwarded toward its destination.
 Allow different networks to communicate with each other
 A router creates and maintain a table of the available routes
and their conditions and uses this information along with
distance and cost algorithms to determine the best route for
a given packet.
 A packet will travel through a number of network points
with routers before arriving at its destination.

BRIDGE
 a bridge is a product that connects a local area network
(LAN) to another local area network that uses the same
protocol (for example, Ethernet or token ring).
 A bridge examines each message on a LAN, "passing"
those known to be within the same LAN, and
forwarding those known to be on the other
interconnected LAN (or LANs).

WHAT IS THE DIFFERENCE BETWEEN?
 Bridge: device to interconnect two LANs that use the
SAME logical link control protocol but may use different
medium access control protocols.
 Router: device to interconnect SIMILAR networks, e.g.
similar protocols and workstations and servers
 Gateway: device to interconnect DISSIMILAR protocols
and servers, and Macintosh and IBM LANs and
equipment

SWITCHES
 Allow different nodes of a network to communicate
directly with each other.
 Allow several users to send information over a network
at the same time without slowing each other down.

MAJOR CATEGORIES OF NETWORKS
 Local Area Networks (LAN)
 A network of computers that are in the same general
physical location, within a building or a campus.
 Metropolitan Area Networks (MAN)
 Wide Area Networks (WAN)
Issues of size and breadth.

LOCAL AREA NETWORK
 Small interconnected of personal computers or workstations and
printers within a building or small area up to 10 Kms.
 Small group of workers that share common application programs and
communication needs.
 LANs are capable of very high transmission rates (100s Mb/s to G
b/s).
 LAN equipment usually owned by organization. Medium may be
owned or leased from telephone company provider or common carrier.
 PC or Workstation interconnected to medium (twisted pair; fiber
optics; etc) through concentrators to servers. LAN is interconnected
with other networks via switches and router/gateways.
 Advanced LANs using circuit switching are available. ATM LANs,
fibre channel baseband, and broadband LANs are being used. Etc.
1. Ethernet
2. Token Ring

WHAT IS ETHERNET?
 A group of standards for defining a local area network
that includes standards in cabling and the structure of
the data sent over those cables as well as the hardware
that connects those cables.
 Independent of the network architecture
 Flavors of ethernet
 IEEE 802.3 Ethernet Specification
 Great detail specifying cable types, data formats, and
procedures for transferring that data through those cables
 IEEE 802.5 Token Ring Specification

NETWORK INTERFACE CARD (NIC)
 Every computer and most devices (e.g. a network
printer) is connected to network through an NIC. In
most desktop computers, this is an Ethernet card (10 or
100 Mbps) that is plugged into a slot on the computer
motherboard.

HOW DOES ETHERNET WORK?
 Using MAC addresses to distinguish between machines,
Ethernet transmits frames of data across baseband
cables using CSMA/CD (IEEE 802.3)

WHAT IS A MAC ADDRESS?
 Media Access Control (MAC) Address – are the physical
address of any device, e.g. a NIC in a computer on the
network. The MAC address has two parts of 3 bytes
long. The first 3 bytes specify the company that made
the NIC and the second 3 bytes are the serial number of
the NIC.

WHAT IS A TOKEN RING?
 All computers are connected in a ring or star topology
and a binary digit or token passing scheme is used in
order to prevent the collision of data between two
computers that want to send messages at the same
time.

HOW DO TOKEN RINGS WORK?
1. Empty information frames are continuously circulated on the ring.
2. When a computer has a message to send, it inserts a token in an
empty frame (this may consist of simply changing a 0 to a 1 in the
token bit part of the frame) and inserts a message and a
destination identifier in the frame.
3. The frame is then examined by each successive workstation. If the
workstation sees that it is the destination for the message, it
copies the message from the frame and changes the token back to
0.
4. When the frame gets back to the originator, it sees that the token
has been changed to 0 and that the message has been copied and
received. It removes the message from the frame.
5. The frame continues to circulate as an "empty" frame, ready to be
taken by a workstation when it has a message to send.

UNDERSTANDING NETWORK
PROTOCOLS

PROTOCOLS OF COMPUTER
COMMUNICATIONS AND NETWORKS
 Protocol are used for communication between computers in
different computer networks. Protocol achieves:
 What is communicated between computers?
 How it is communicated?
 When it is communicated?
 What conformance (bit sequence) between computers?
 Key elements of a protocol are:
 SYNTAC: Data format and signal levels
 SEMANTICS: Control information for coordination and error handling
 TIMING: Synchronization, speed matching, and sequencing
 Examples of protocols:
 WAN Protocol: TCP/IP
 LAN Protocol: Media Access Control; Contention; Token Passing

PROTOCOL ARCHITECTURE
 Architecture provides high degree of cooperation
between two computers.
 Example:

ISO/OSI REFERENCE MODEL (1)
 Open Systems Interconnection
 No one really uses this in the real world.
 A reference model so others can develop detailed
interfaces.
 Value: The reference model defines 7 layers of functions
that take place at each end of communication and with
each layer adding its own set of special related
functions.
 Flow of data through each layer at one

ISO/OSI REFERENCE MODEL (2)
How to transmit signal; coding
Hardware means of sending and 
receiving data on a carrier
Two party communication: Ethernet 
Routing and Forwarding Address: IP 
End-to-end control & error checking
(ensure complete data transfer): TCP 
Establish/manage connection 
ASCII Text, Sound (syntax layer) 
File Transfer, Email, Remote Login 

WHAT IS TCP/IP?
 Transmission Control Protocol (TCP) – uses a set of rules to
exchange messages with other Internet points at the information
packet level
 Internet Protocol (IP) – uses a set of rules to send and receive
messages at the Internet address level
 Is the predominate network protocol in use today (Other includes
OSI Model) for interoperable architecture and the internet.
 TCP/IP is a result of protocol research and development conducted
on experimental packet switched network by ARPANET funded by
the defense advanced research projects agency (DARPA). TCP/IP
used as internet standards by the internet architecture board
(IAB).

TCP/IP FIVE INDEPENDENT LEVELS
 Application Layer: contains the logic needed to support the various
user applications. Separate module are required for each application.
 Host-to-host or transport Layer: collection of mechanisms in a single
and common layer
 Internet Layer: IP provides the routing functions across the multiple
networks
 Network access layer: concerned with access to and routing data
across a network for two end systems attached to the same network.
 Physical Layer: covers physical interface between PC or workstation
and a transmission medium or network
HTTP / FTP / Telnet /
SMTP / SLIP / PPP 
TCP keep track of the
individual packets 
And reassemble
IP handles actual 
delivery of packets

TCP (EXAMPLE)
 Web Server: serves HTML pages
 TCP layer in the server divides the file into one or more
packets, numbers the packet, then forward packets
individually to IP.
 Note: each packet has the same destination IP address,
it may get routed differently through the network.
 TCP (on the client) reassembles the individual packets
and waits until they have arrived to forward them as a
single file.
 Connection-oriented protocol

ASSOCIATED TCP/IP PROTOCOLS &
SERVICES
HTTP This protocol, the core of the World Wide Web, facilitates
retrieval and transfer of hypertext (mixed media) documents.
Stands for the HyperText Transfer protocol
Telnet A remote terminal emulation protocol that enables clients to log
on to remote hosts on the network.
SNMP Used to remotely manage network devices. Stands for the
Simple Network Management Protocol.
DNS Provides meaningful names like achilles.mycorp.com for
computers to replace numerical addresses like 123.45.67.89.
Stands for the Domain Name System.
SLIP/
PPP
SLIP (Serial Line Internet Protocol) and PPP (Point to Point
Protocol) encapsulate the IP packets so that they can be sent
over a dial up phone connection to an access provider’s modem.

FURTHER READINGS
 Basics: Complete Idiots Guide to Networking, 3rd
Edition (Wagner and Negus)
 Practical Network Cabling (Freed and Derfler)
 Networking books by William Stallings:
 Business Data Communications
 Operating Systems: Internals and Design Principles
 Data & Computer Communications
 Local and Metropolitan Area Networks
 High-speed networks TCP/IP and ATM Design Principles
 Online Audio/Video Recording of Networking Class:
 http://www.cis.ohio-state.edu/~jain/videos.htm

fundamental of networking models LAN WAN MAN

fundamental of networking models LAN WAN MAN

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