Basic concepts of Network and design

1. Snehal Kulthe
Department of Management Science

2.  Data communication refers to the
transmission of the digital data between two
or more computers The physical connection
between networked computing devices is
established using either cable media or
wireless media. The best-known computer
network is the Interne

3.  A workstation (WS) is a computer dedicated
to a user or group of users engaged in
business or professional work. It includes
one or more high resolution displays and a
faster processor than a personal computer
(PC). A workstation also has greater
multitasking capability because of
additional random access memory (RAM),
drives and drive capacity. A workstation may
also have a higher-speed graphics adapters
and more connected peripherals.
 The term workstation also has been used to
reference a PC or mainframe terminal on a
local area network (LAN). These
workstations may share network resources
with one or more large client computers and
network servers.

4.  In Computer science, client-server is a software
architecture model consisting of two parts, client systems
and server systems, both communicating over a computer
network or on the same computer. A client-server
application is a distributed systemmade up of both client
and server software. Client server application provide a
better way to share the workload.The
client process always initiates a connection to the server,
while the server process always waits for requests from
any client. When both the client process and
server process are running on the same computer, this is
called a single seat setup.
 Another type of related software architecture is known
as peer-to-peer, because each host
or application instance can simultaneously act as both a
client and a server (unlike centralized servers of
the client-server model) and because each has equivalent
responsibilities and status. Peer-to-peer architectures are
often abbreviatedusing the acronym P2P.

6.  The client-server relationship describes the relation
between the client and how it makes a service request to the
server, and how the server can accept these requests, process
them, and return the requested information to the client. The
interaction between client and server is often described
using sequence diagrams. Sequence diagrams are
standardized in the Unified Modeling Language.
 Both client-server and P2P architectures are in wide usage
today.
 The basic type of client-server software architecture employs
only two types of hosts: clients and servers. This type of
architecture is sometimes referred to as two-tier. The two-
tier architecture means that the client acts as one tier
and server process acts as the other tier.
 The client-server software architecture has become one of
the basic models of network computing. Many types of
applications have been written using the client-server model.
Standard networked functions such as E-
mail exchange, webaccess and database access, are based on
the client-server model. For example, a web browser is a
client program at the user computer that may access
information at any web server in the world.

7.  A computer network is a set
of computers connected
together for the purpose of
sharing resources. The most
common resource shared
today is connection to the
Internet. Other shared
resources can include a
printer or a file server. The
Internet itself can be
considered a computer
network.

8.  A network protocol defines rules and conventions for
communication between network devices. Network
protocols include mechanisms for devices to identify and
make connections with each other, as well as formatting
rules that specify how data is packaged into messages
sent and received. Some protocols also support
message acknowledgment and data compression designed
for reliable and/or high-performance network
communication.
 Modern protocols for computer networking all generally
use packet switching techniques to send and receive
messages in the form of packets —messages subdivided
into pieces that are collected and re-assembled at their
destination. Hundreds of different computer network
protocols have been developed each designed for
specific purposes and environments

9.  Internet Protocols
The Internet Protocol family contains a set of related (and among
the most widely used) network protocols. Beside Internet Protocol
(IP) itself, higher-level protocols like TCP, UDP, HTTP, and FTP all
integrate with IP to provide additional capabilities. Similarly, lower-
level Internet Protocols like ARP and ICMP also co-exist with IP. In
general, higher level protocols in the IP family interact more closely
with applications like Web browsers while lower-level protocols
interact with network adapters and other computer hardware.
 Wireless Network Protocols
Thanks to Wi-Fi, Bluetooth and LTE, wireless networks have become
commonplace. Network protocols designed for use on wireless
networks must support roaming mobile devices and deal with issues
such as variable data rates and network security.
 Network Routing Protocols
Routing protocols are special-purpose protocols designed
specifically for use by network routers on the internet. A routing
protocol can identify other routers, manage the pathways
(called routes) between sources and destinations of network
messages, and make dynamic routing decisions. Common routing
protocols include EIGRP, OSPF, and BGP.

10.  TCP/IP, or the Transmission Control
Protocol/Internet Protocol, is a suite of
communication protocols used to
interconnect network devices on the internet.
TCP/IP can also be used as a communications
protocol in a private network (an intranet or
an extranet).
 Short for transmission control protocol/Internet
protocol, TCP/IP is a set of rules (protocols)
governing communications among all computers on
the Internet. More specifically, TCP/IP dictates how
information should be packaged (turned into
bundles of information called packets), sent, and
received, as well as how to get to its destination.
TCP/IP was developed in 1978 and driven by Bob
Kahn and Vint Cerf.

11. LAN MAN WAN
A LAN (local area network)
is a group of computers
and network devices
connected together,
usually within the same
building. By definition, the
connections must be high
speed and relatively
inexpensive (e.g., token
ring or Ethernet). Most
Indiana University
Bloomington departments
are on LANs.
A LAN connection is a
high-speed connection to a
LAN. On the IUB campus,
most connections are
either Ethernet (10 Mbps)
or Fast Ethernet (100
Mbps), and a few locations
have Gigabit Ethernet
(1000 Mbps) connections.
A MAN (metropolitan area
network) is a larger
network that usually spans
several buildings in the
same city or town. The IUB
network is an example of a
MAN.
A WAN (wide area
network), in comparison to
a MAN, is not restricted to
a geographical location,
although it might be
confined within the
bounds of a state or
country. A WAN connects
several LANs, and may be
limited to an enterprise (a
corporation or an
organization) or accessible
to the public. The
technology is high speed
and relatively expensive.
The Internet is an example
of a worldwide public
WAN.

13.  A network topology is the arrangement of a
network, including its nodes and connecting
lines. There are two ways of defining
network geometry: the physical topology and
the logical (or signal) topology.
 The physical topology of a network is the
actual geometric layout of workstations.
There are several common physical
topologies, as described below and as shown
in the illustration.

15. 1. In the bus network topology, every workstation is
connected to a main cable called the bus.
Therefore, in effect, each workstation is directly
connected to every other workstation in the
network.
2. In the star network topology, there is a central
computer or server to which all the workstations
are directly connected. Every workstation is
indirectly connected to every other through the
central computer.
3. In the ring network topology, the workstations are
connected in a closed loop configuration. Adjacent
pairs of workstations are directly connected. Other
pairs of workstations are indirectly connected, the
data passing through one or more intermediate
nodes.

16. 4. If a Token Ring protocol is used in a star or ring
topology, the signal travels in only one direction,
carried by a so-called token from node to node.
5. The mesh network topology employs either of two
schemes, called full mesh and partial mesh. In the full
mesh topology, each workstation is connected directly
to each of the others. In the partial mesh topology,
some workstations are connected to all the others,
and some are connected only to those other nodes
with which they exchange the most data.
6. The tree network topology uses two or more star
networks connected together. The central computers
of the star networks are connected to a main bus.
Thus, a tree network is a bus network of star
networks.
7. Logical (or signal) topology refers to the nature of
the paths the signals follow from node to node. In
many instances, the logical topology is the same as
the physical topology. But this is not always the case.
For example, some networks are physically laid out in
a star configuration, but they operate logically as bus
or ring networks.

17.  The Open Systems Interconnection model (OSI model) is
a conceptual model that characterizes and standardizes
the communication functions of a telecommunication or
computing system without regard to its underlying internal
structure and technology. Its goal is the interoperability of
diverse communication systems with standard protocols.
The model partitions a communication system
into abstraction layers. The original version of the model
defined seven layers.
 A layer serves the layer above it and is served by the layer
below it. For example, a layer that provides error-free
communications across a network provides the path
needed by applications above it, while it calls the next
lower layer to send and receive packets that comprise the
contents of that path. Two instances at the same layer are
visualized as connected by a horizontalconnection in that
layer.

20.  Application (Layer 7)
OSI Model, Layer 7, supports application and end-user processes.
Communication partners are identified, quality of service is identified,
user authentication and privacy are considered, and any constraints on
data syntax are identified. Everything at this layer is application-specific.
This layer provides application services for file transfers, e-mail, and
other network software services. Telnet and FTP are applications that
exist entirely in the application level. Tiered application architectures
are part of this layer.
Layer 7 Application examples include WWW browsers, NFS, SNMP,
Telnet, HTTP, FTP
 Presentation (Layer 6)
This layer provides independence from differences in data
representation (e.g., encryption) by translating from application to
network format, and vice versa. The presentation layer works to
transform data into the form that the application layer can accept. This
layer formats and encrypts data to be sent across a network, providing
freedom from compatibility problems. It is sometimes called the syntax
layer.
Layer 6 Presentation examples include encryption, ASCII, EBCDIC,
TIFF, GIF, PICT, JPEG, MPEG, MIDI.

21.  Session (Layer 5)
This layer establishes, manages and terminates
connections between applications. The session layer
sets up, coordinates, and terminates conversations,
exchanges, and dialogues between the applications
at each end. It deals with session and connection
coordination.
Layer 5 Session examples include NFS, NetBios
names, RPC, SQL.
are protocols with physical layer components.
 Transport (Layer 4)
OSI Model, Layer 4, provides transparent transfer
of data between end systems, or hosts, and is
responsible for end-to-end error recovery and flow
control. It ensures complete data transfer.
Layer 4 Transport examples include SPX, TCP, UDP.

22.  Network (Layer 3)
Layer 3 provides switching and routing technologies, creating logical
paths, known as virtual circuits, for transmitting data from node to node.
Routing and forwarding are functions of this layer, as well
as addressing, internetworking, error handling, congestion control and packet
sequencing.
Layer 3 Network examples include AppleTalk DDP, IP, IPX.
 Data Link (Layer 2)
At OSI Model, Layer 2, data packets are encoded and decoded into bits. It
furnishes transmission protocolknowledge and management and handles
errors in the physical layer, flow control and frame synchronization. The data
link layer is divided into two sub layers: The Media Access Control (MAC) layer
and the Logical Link Control(LLC) layer. The MAC sub layer controls how a
computer on the network gains access to the data and permission to transmit
it. The LLC layer controls frame synchronization, flow control and error
checking.
Layer 2 Data Link examples include PPP, FDDI, ATM, IEEE 802.5/ 802.2, IEEE
802.3/802.2, HDLC, Frame Relay.
 Physical (Layer 1)
OSI Model, Layer 1 conveys the bit stream - electrical impulse, light or
radio signal — through the network at the electrical and mechanical level. It
provides the hardware means of sending and receiving data on a carrier,
including defining cables, cards and physical aspects. Fast Ethernet, RS232,
and ATM