Networking and InternetworkingA client server presentation explain client server architecture.pptx

Networking and Internetworking
LANs,WANs, MANs, Switching, Protocols, Layered
architectures (OSI,TCP/IP), IP, IPAddressing,TCP and UDP,
Point to Point communication, Broadcast communication
Networking and Internetworking
1 Okemwa J - Dept of CS

Content
 This lecture is concerned with the characteristics of
protocols for communication between processes in a
distributed systems.
 We discuss protocols for the representation of collections of
data objects in messages and of references to remote objects.
 We discuss the construction of protocols to support the two
communication patterns that are most commonly used in
distributed programs

Networking
 A Network is a collection of computers and devices connected by
communications channels that facilitates communications among
users and allows users to share resources with other users.
Types of networks.
 LAN: Local Area Network
 MAN: Metropolitan Area Network
 WAN: Wide Area Network
 Network components can be grouped into four main categories:
• Hosts: are devices that send and receive messages directly across the
network.
• Shared peripherals: Shared peripherals are not directly connected to the
network, but instead are connected to hosts.
• Networking devices:
• Networking media
 The network devices, as well as networking media, are used to interconnect hosts.
3

Network components
A router is a networking device that connects a local
network to other local networks.
A switch connects multiple hosts to the network, but
unlike a hub, a switch can forward a message to a
specific host.

Communication Protocols
 A protocol is a set of rules that govern how computers
communicate.
 Encoding is the process of converting thoughts into the
language, symbols, or sounds, for transmission. Decoding
reverses this process in order to interpret the thought.
 All communication, both human and computer, is governed by
pre-established rules, or protocols.These protocols are
determined by the characteristics of the source, channel and
destination.
 Protocols are especially important on a local network. In a
wired environment, a local network is defined as an area where
all hosts must "speak the same language" or in computer terms
"share a common protocol".
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Okemwa J - Dept of CS

Communication Protocols
 Explain standard message patterns in relation to human
communication
 Unicast: A one-to-one message pattern is referred to as a unicast,
meaning that there is only a single destination for the message.
 Multicast: one-to-many pattern, is the delivery of the same message to
a group of host destinations simultaneously.
 Broadcast: a one-to-all message pattern.All the hosts get the
message.

Networking issues for distributed
systems
The subsequent development of distributed systems with
support for distributed application programs accessing shared
files and other resources set a higher standard of performance
to meet the needs of interactive applications.

Networking issues for distributed systems
1. Performance
 Performance parameters: Are those affecting the speed with which individual
messages can be transferred between two interconnected computers.
Latency: is the delay that occurs after a send operation is executed before data
starts to become available at the destination.
Point-to-Point data transfer rate: is the speed at which data can be
transferred between two computers in the network once transmission has
begun, usually quoted in bits per second.
 The time required for a network to transfer a message containing length bits
between two computers is:
Message transmission time = latency + length/data transfer rate
Total system bandwidth of a network: is a measure of throughput- the total
volume of traffic that can be transferred across the network in a given time.

 Reliability: Many applications are able to recover from communication
failures and hence do not require guaranteed error-free communication.
 The detection of communication errors and their correction is often best performed
by application-level software.
 Security: A firewall runs on a gateway, cryptographic techniques, with
end-to-end authentication, virtual private network (VPN).
 Scalability: The Internetworking technologies have to do well on the
internet but there are new development to make them cope up with the
increasing number of users.

 Mobility: Support continuous communication
 The addressing and routing schemes of the Internet and other networks
were developed before the advent of mobile devices.
 The expected future growth in the use of mobile devices will require further
extensions.
 Quality of service: The ability to ensure a certain service
level when transmitting and processing streams of real-time
multimedia data.
 Multicasting : many network technologies support the
simultaneous transmission of messages to several recipients.

TYPES OF NETWORKS
 LocalArea Network
 Wide Area Network
 MetropolitanArea Network
 Wireless Networks
 Internetworks
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Local Area Network
 Local area networks (LAN) - LANs carry messages at
relatively high speeds between computers connected to a
single communication medium such as twisted copper wire,
coaxial cable or optical fiber.
 A segment is a section of cable that serves a department or a
floor of a building and may have many computers attached.
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Wide Area Network
 WANs carry messages, at lower speeds between nodes.
 They are often in different organizations separated by large
distances
 They may be located in different cities, countries or
continents
13

Metropolitan Area Network
 This type of network is based on high bandwidth copper and
fiber optic cabling recently installed in some towns and cities
for the transmission of video, voice and other data over
distances of up to 50 kilometers.
14

Wireless Networks
 The convenient connection of portable and handheld devices
requires wireless communication.Wireless LAN, Infra Red
Links e. t. c
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Inter Network
 An internetwork is a communication subsystem in which
several networks are linked together to provide common data
communication facilities that conceal the technologies and
protocols of the individual component networks and the
methods used for their interconnection
16

Importance of standardization
 The most common set of protocols used on local wired
networks is Ethernet.
 In the early days of networking, each vendor used their own,
proprietary methods of interconnecting network devices and
networking protocols. Equipment from one vendor could not
communicate with equipment from another.
 Standards are beneficial to networking in many ways:
– Facilitate design
– Simplify product development
– Promote competition
– Provide consistent interconnections
– Facilitate training
– Provide more vendor choices for customers
17

Protocols
 Protocols Refer to a well-known set of rules and formats to be used for
communication between processes in order to perform a given task.The
definition of a protocol has two important parts to it:
 A protocol is implemented by a pair of software modules located in the
sending and receiving computers.
 A process wishing to transmit a message to another process issues a call to
a transport protocol module, passing it a message in the specified format.
 Each layer of network software communicates by local procedure calls
with the layers above and below it.

Layered architectures
Basic networking model
 Use the layers of the OSI model as a guide for understanding
how Computers communicate on the Network.
 The OSI Model specifies Protocols used in the network.

Using the OSI Model
 Using a layered approach requires that the network technician be
familiar with the various functions that occur as messages are
created, delivered, and interpreted by the network devices and hosts
on the network.
 The process of moving data across a network is highly structured. It
is best visualized using the seven layers of the Open Systems
Interconnection (OSI) model, commonly referred to as the OSI
model.The OSI model breaks network communications down into
multiple processes.
 Each process is a small part of the larger task.

Using the OSI Model

Read about OSI Model
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Using the OSI Model
 The seven layers of the OSI model can be divided into two parts:
upper layers and lower layers.
The upper layer is sometimes used to refer to any layer
above the transport layer of the OSI model.
The upper layers of the OSI model deal with application
functionality and generally are implemented only in software.
The lower layers of the OSI model handle data transport
functions.The physical and data link layer are implemented in
both hardware and software.The physical layer is closest to the
physical network medium, or network cabling.

OSI Model Protocols and
Technologies
 Protocols
 Technologies
 Network components

Technologies
 It is important to understand which functions are performed at
each layer, and what network information is available to the
devices or software programs performing these functions.
 Looking at how the OSI model breaks the common task of
sending and receiving email into separate and distinct steps.
 Step 1: Upper layers create the data.
When a user sends an email message, the alphanumeric
characters within the message are converted to data that can
travel across the network.This process is called encoding

Upper-level layers
 Layer 7:The application layer :This is the layer at which communication
partners are identified, quality of service is identified, user authentication and
privacy are considered, and any constraints on data syntax are identified. (This
layer is not the application itself, although some applications may perform
application layer functions.) Protocols: FTP,DNS,HTTP,SMTP,POP3
 Layer 6:The presentation layer :This is a layer, usually part of an operating
system, that converts incoming and outgoing data from one presentation format
to another (for example, from a text stream into a popup window with the
newly arrived text). Sometimes called the syntax layer.
 Layer 5:The session layer :This layer sets up, coordinates, and terminates
conversations, exchanges, and dialogs between the applications at each end. It
deals with session and connection coordination. CommonApplication Program
Interfaces include NetBIOS,TCP/IP Sockets and Remote Procedure
Calls (RPCs).

Technologies
 Step 2: Layer 4 packages the data for end-to-end
transport.
The data that comprises the email message is packaged for
network transport at Layer 4. Layer 4 breaks the message down
into smaller segments.
Functions in the transport layer indicate the type of delivery
service.
Layer 4 functions are implemented in software that runs on
the source and destination hosts.

Transport Layer
Important
 The transport layer provides the actual communication facilities for
most distributed systems.
Standard Internet protocols
 TCP: connection-oriented, reliable, stream-oriented communication
 UDP: unreliable (best-effort) datagram communication.
Note
 IP multicasting is often considered a standard available service

Technologies
 Step 3: Layer 3 adds the network IP address information.
The email data received from the transport layer is put into a packet
that contains a header with the source and destination logical IP
addresses.
 Step 4: Layer 2 adds the data link layer header and trailer.
Each network device in the path from the source to the destination,
including the sending host, encapsulates the packet into a frame.
The frame contains the physical address of the next directly-
connected network device on the link.

Technologies
 Step 5: Layer 1 converts the data to bits for transmission.
The frame is converted into a pattern of 1s and 0s (bits) for
transmission on the medium.
 At the receiving host, the process described in steps 1 through 5
are reversed, with the message traveling back up the layers to the
appropriate application.

Low-level layers
 Network layer: describes how packets in a network of computers
are to be routed.
 Data link layer: prescribes the transmission of a series of bits into a
frame to allow for error and flow control
 Physical layer: contains the specification and implementation of
bits, and their transmission between sender and receiver
Observation
 For many distributed systems, the lowest-level interface is that of the
network layer.

OSI MODEL
Drawbacks
 Focus on message-passing only
 Often unneeded or unwanted functionality
 Violates access transparency

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