os and networking concepts

8/3/2019 OS and Networking Concepts

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Vaishali Kamat1O/S and N/Wconcepts

Operating Systems andNetworking concepts


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Operating System Concepts

Definition Objectives

Services

Evolution


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Operating System

A program that controls the execution ofapplication programs

An interface between applications and

hardware The purpose of an operating system is

to provide an environment in which auser can execute programs in aconvenientand efficientmanner.


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Layers of Computer System


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Kernel

Portion of operating system that is inmain memory

Contains most frequently used functions

Also called the nucleus


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Operating System Objectives

Convenience Makes the computer more convenient to

use

Efficiency

Allows computer system resources to beused in an efficient manner

Ability to evolve

Permit effective development, testing, andintroduction of new system functionswithout interfering with service


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Operating System Objectives Accuracy

Ensures the correct operation of thecomputer system



Services Provided by the Operating

System

Program development Editors and debuggers

Program execution

Access to I/O devices Controlled access to files

System access




System

Error detection and response Internal and external hardware errors

Memory error

Device failure

Software errors

Arithmetic overflow

Access forbidden memory locations




System

Accounting Collect usage statistics

Monitor performance

Used to anticipate future enhancements

Used for billing purposes



Services Provided by the OperatingSystem

Responsible for managing resources Functions same way as ordinary

computer software

It is program that is executed



Evolution of an Operating System

Hardware upgrades plus new types ofhardware

New services

Fixes



Evolution of Operating Systems

Serial Processing No operating system

Machines run from a console with displaylights, toggle switches, input device, and

printer

Schedule time

Setup included loading the compiler,

source program, saving compiled program,and loading and linking


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O/S and N/Wconcepts

Evolution of Operating Systems

Simple Batch Systems Monitors

Software that controls the sequence of events

Batch jobs together

Program branches back to monitor whenfinished



O/S and N/Wconcepts

Hardware Features

Memory protection Do not allow the memory area containing

the monitor to be altered

Timer

Prevents a job from monopolizing thesystem



O/S and N/Wconcepts

Hardware Features

Privileged instructions Certain machine level instructions can only

be executed by the monitor

Interrupts

Early computer models did not have thiscapability



O/S and N/Wconcepts

Memory Protection

User program executes in user mode Certain instructions may not be executed

Monitor executes in system mode

Kernel mode Privileged instructions are executed

Protected areas of memory may beaccessed



O/S and N/Wconcepts

Uniprogramming Processor must wait for I/O instruction to

complete before preceding



O/S and N/Wconcepts

Multiprogramming When one job needs to wait for I/O, the

processor can switch to the other job


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Multiprogramming


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Time Sharing

Using multiprogramming to handlemultiple interactive jobs

Processors time is shared among

multiple users

Multiple users simultaneously accessthe system through terminals


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Major Achievements

Processes Memory Management

Information protection and security

Scheduling and resource management System structure


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Processes A program in execution

An instance of a program running on acomputer

The entity that can be assigned to and

executed on a processor A unit of activity characterized by a

single sequential thread of execution, a

current state, and an associated set ofsystem resources


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Process

Consists of three components An executable program

Associated data needed by the program

Execution context of the program

All information the operating system needs tomanage the process


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Memory Management

Process isolation Automatic allocation and management

Support of modular programming

Protection and access control Long-term storage


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Virtual Memory

Allows programmers to addressmemory from a logical point of view

No gap between the execution ofsuccessive processes while oneprocess was written out to secondarystore and the successor process wasread in


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Virtual Memory and File System

Implements long-term store Information stored in named objects

called files


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Paging Allows process to be comprised of a

number of fixed-size blocks, calledpages

Virtual address is a page number and

an offset within the page Each page may be located any where in

main memory

Real address or physical address inmain memory


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Virtual Memory Addressing


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Information Protection and Security

Availability Concerned with protecting the system

against interruption

Confidentiality

Assuring that users cannot read data forwhich access is unauthorized


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Information Protection and Security

Data integrity Protection of data from unauthorized

modification

Authenticity

Concerned with the proper verification ofthe identity of users and the validity ofmessages or data

Scheduling and Resource


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Scheduling and Resource

Management

Fairness

Give equal and fair access to resources

Differential responsiveness

Discriminate among different classes ofjobs

Efficiency

Maximize throughput, minimizeresponse time, and accommodate asmany uses as possible

Key Elements of


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Key Elements of

Operating System


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System Structure

View the system as a series of levels Each level performs a related subset of

functions

Each level relies on the next lower levelto perform more primitive functions

This decomposes a problem into a

number of more manageablesubproblems


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Process Hardware Levels Level 1

Electronic circuits

Objects are registers, memory cells, andlogic gates

Operations are clearing a register orreading a memory location

Level 2 Processors instruction set

Operations such as add, subtract, load,and store


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Process Hardware Levels Level 3

Adds the concept of a procedure orsubroutine, plus call/return operations

Level 4

Interrupts


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Concepts with Multiprogramming Level 5

Process as a program in execution

Suspend and resume processes

Level 6 Secondary storage devices Transfer of blocks of data

Level 7

Creates logical address space forprocesses

Organizes virtual address space intoblocks


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Deal with External Objects Level 8

Communication of information andmessages between processes

Level 9

Supports long-term storage of named files

Level 10

Provides access to external devices usingstandardized interfaces


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Deal with External Objects Level 11

Provides an interface to the operatingsystem for the user


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Modern Operating Systems Microkernel architecture

Assigns only a few essential functions tothe kernel

Address spaces

Interprocess communication (IPC) Basic scheduling


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Modern Operating Systems Multithreading

Process is divided into threads that can runconcurrently

Thread

Dispatchable unit of work executes sequentially and is interruptable

Process is a collection of one or more threads


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Modern Operating Systems Symmetric multiprocessing (SMP)

There are multiple processors

These processors share same mainmemory and I/O facilities

All processors can perform the samefunctions


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Modern Operating Systems Distributed operating systems

Provides the illusion of a single mainmemory space and single secondarymemory space


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Modern Operating Systems Object-oriented design

Used for adding modular extensions to asmall kernel

Enables programmers to customize an

operating system without disrupting systemintegrity


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Windows Architecture Modular structure for flexibility

Executes on a variety of hardwareplatforms

Supports application written for otheroperating system


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Threads and SMP Operating system routines can run on any

available processor

Different routines can execute simultaneouslyon different processors

Multiple threads of execution within a singleprocess may execute on different processorssimultaneously

Server processes may use multiple threads

Share data and resources between process


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UNIX Hardware is surrounded by the

operating system software

Operating system is called the systemkernel

Comes with a number of user servicesand interfaces

Shell

Components of the C compiler


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UNIX


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Modern UNIX Systems System V Release 4 (SVR4)

Solaris 9

4.4BSD

Linux


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Types of Operating System

Real Time

Multi-user / Single-User

Multi-tasking / Single-tasking Distributed

Embedded system


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Tasks of Operating System

Process Management

Memory Management

System Calls

User Interface command-line/GUI

Buffering and spooling

Interrupt Handling

File Management

Secondary Storage Management

Scheduling

Computer Security

Computer Networking


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Networking Concepts

Definition Parts of a Network Network Channels LANs, MANS, WANs, Backbone Networking Protocols Network Topologies

Network Architectures and NetworkReference Models Other Terminologies


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Networking DefinitionTwo or more computers are connected To Communicate with each other To Share resources and files


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Networking Concepts




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Parts of a Network Servers Host Computer Clients Channels Network Circuit Interface Devices Modems / Network

Interface Cards Operating System


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Networking Concepts




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Networking Channels Classification dimensions:

Transmission Medium wired line,wireless

Transmission rate or bandwidthmeasured as bps

Transmission directional capabilitysimplex, half-duplex, full-duplex

Signal Type analog, digital


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Networking Concepts




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LANs, MANs, WANs, Backbone LANs limited geographical area MANs/WANs Larger geographical

area Backbones High-bandwidthed

channels connecting LANs


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Networking Concepts




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Networking Protocols The OSI Model supports two general types of

protocols. Both are common:

Connection-Oriented

Sender and receiver first establish a connection,possibly negotiate on a protocol. (virtual circuit)

Transmit the stream of data. Release the connection when done.

E.g. Telephone connection.

Connectionless

No advance setup is needed. Transmit the message (datagrams) when sender is

ready.

E.g. surface mail.


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Networking Layer Protocols Layer 3 Protocols

Tasks Packetizing

Addressing

Routing

Steps Binary representation at senders machine

Senders binary representation broken into packets

Packets sent to receiver computer

Packets received at receiver computer

Packets assembled at receiver computer Binary representation at receiver computer

Egs TCP/IP, IPX/SPX


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Data-Link Layer Protocols

Layer 2 Protocols Tasks

Delineation

Error Control Channel Access

Egs Ethernet, Token-ring, Slip, PPP

Every Network has one NetworkLayer and one Data-link Layerprotocol


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Networking Concepts

Definition Parts of a Network Network Channels

LANs, MANS, WANs, Backbone Networking Protocols Network Topologies



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Networking Topologies

Basic geometric layout for connectingthe computers to the Networkchannel

Determines the method of channelaccess

Topologies :

Bus

Ring

Star


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Bus Topology

Clients, servers, resources areconnected directly to a single channel

Bus = single channel

Runs from one end of the network tothe other

Networks using Ethernet, use Bus

Topology

Ri T l


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Ring Topology

All computers in the LAN connectedto a close loop circuit

Each computer linked to the next

Networks using token ring use RingTopology

S T l


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Star Topology

All clients connected individually tothe server

Each client uses a direct channel

Was common in the Mainframe era Not commonly used in LANs

Used in some WANs now

N ki C


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Networking Concepts

Definition Parts of a Network Network Channels

LANs, MANS, WANs, Backbone Networking Protocols Network Topologies

Network Architectures andNetwork Reference Models Other Terminologies

Network Architectures and Network Reference


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et o c tectu es a d et o e e e ceModels

Architecture versus Reference Model:

Architecture : It may be seen as a detailedgeneric blueprint with unambiguous definitionsof services, interfaces, organization anddefined protocols that helps in design and

implementation of a set of relevant protocolstack / suite based network / internet work

Reference Model : It is the same as thearchitecture minus the specifically defined

readily usable protocols.


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ISO OSI Reference Model

Application LayerPresentation Layer

Session Layer

Transport Layer

Network Layer

Data Link Layer

Physical Layer

ApplicationSubsystem

CommunicationSubsystem

Ph i l L


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Physical Layer Media used for device connection

(copper cables, fiber optics,wireless, etc.)

Supporting hardware (repeaters,

hubs and network interface cards). Also includes:

connector design

definition of electrical signaling andencoding

time or synchronization methods.

Ph i l L


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Physical Layer

The Physical Layer translates theoutgoing bits received from the DataLink Layer into signals, places thesignal on the media

At the receiving station convertsincoming signals into bits for handoffto the Data Link Layer.

The Physical Layer deals only withbits on the wire and makes NOADDRESSING DECISIONS

D t li k L


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Data-link Layer The Data Link Layer relies on the

services of the Physical Layer. It receivesand interprets the bit stream as a FRAMEof data.

The header includes physical orhardware (MAC) addresses of thedestination and source hosts.

The DLL is responsible for the error and

flow control between devices.

CRC (cycle redundancy check) ensuresthat the bits sent are the bits received.

D t li k L


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Data-link Layer Flow control ensures that data

transmission is not performed until thereceiving device is ready to receive.

Ethernet and IEEEs 802.3 are examples

of data link services. In Ethernet, the DLL is one layer

facilitating both the hardware address,media access, payload identification.

With 802.3 the DLL is divided into sublayers.

D t li k L


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Data-link Layer The Logical Link Control (LLC) sub layer

provides protocol (payload) and controlinformation.

The Media Access Control (MAC)implements the access method and

hardware address. Hardware that operates at layer 2

includes bridges and switches. Thesedevices make decisions based on thedestination hardware address contained

in the frame. The NIC also provides layer 2 service at

the host.

N t k L


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Network Layer

The Network Layer can be used toroute datafrom network to network ingeographically separate areas.

Logical addressing is used to enableprotocols operating at the NetworkLayer to deliver the data.

When data is passed to the NetworkLayer it is called a packet.

N t k L


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Network Layer The packet is wrapped in a header

specific to the protocol (IP and IPXare examples) in use.

Each protocol differentiates its

address scheme. Some protocol addresses are

regulated

Some schemes allow the administrator

total flexibility.

The logical address is divided into aNetwork ID and a Host ID.

Net ork La er


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Network Layer

Routers:

Devices that operate at the NetworkLayer.

Use routing protocols to pass network

connectivity information and routableprotocols to pass the data.

A network wishing to communicate

with another network requires agateway device.

The router serves as the gateway.

Communication System


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Communication System

Layers 1 through 3 make up thecommunication subsystem.

They are implemented in hardwareand supported by software.

Each layer is independent.

Transportation Layer


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The Transport Layer provides end toend data transport with a logicalconnection between the sender andthe receiving hosts.

It ensures data integrity through flowcontrol and reliable data transport.

Additionally the multiplexing of

upper layer applications and sessionmanagement provides fortransparent data transfer.



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Windowing or flow control is criticalin the prevention of lost data.

(The window is the amount of dataeach side is "willing" to accept.)

Preventing the sending station fromoverflowing the receiver buffers,congestion and data loss is reduced

and reliable data transport can beachieved.



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Transportation Layer Reliable transport includes:

The acknowledge of segments

Retransmission of lost segments

Reordering of segments into correct

sequence. For reliable transport operation, a

connection between peers must beestablished. Handshaking between peers is used

to establish the connection (virtualcircuit).

Session Layer


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Session Layer The Session Layer sets checkpoints

at specified intervals duringapplication execution.

These checkpoints break the data

into grouping for error detection. In the event of a failure, both

participating nodes/applications will,upon establishment ofcommunication, use the synchpoints to restart and continue theapplication from the point of failure.

Presentation Layer


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Presentation Layer

Presentation Layer services include:

translation between code sets

encryption of data

data compression/decompression.

Through these translation servicesthe Presentation Layer ensures thatapplication data is readable between

participating hosts.

Application Layer


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Application Layer Network applications interface to the

network through the Application Layer.

Support is provided for:

file transfers

messaging services data access

Layer 7 protocols examples include FTP,TELNET and HTTP.

Layer 7 ensures availability of thecommunicating entities and resources forcommunication.

Application Subsystem


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Application Subsystem

Layers 4 thru 7 comprise theapplication subsystem.

They are implemented in software.

Networking Concepts


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Networking Concepts

Definition

Parts of a Network

Network Channels

LANs, MANS, WANs, Backbone Networking Protocols

Network Topologies

Network Architectures and NetworkReference Models

Other Terminologies

Other Terminologies


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Other Terminologies

Bridges :A network bridge connectsmultiple network segments.

Hubs :A common connection pointfor devices in a network. Hubs arecommonly used to connect segmentsof a LAN.

NIC : Network Interface Card. Board

that provides network communicationcapabilities to and from a computersystem. Also called an adapter.s

Other Terminologies


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Other Terminologies Switches :A network switch is a

small hardware device that joinsmultiple computers together withinone local area network (LAN).

Technically, network switchesoperate at layer two (Data Link Layer)of the OSI model.

Repeaters :Its a two-ports electronic

device that just repeats what receivesfrom one port to the other. A multi-port repeater is called hub.

Other Terminologies


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Other Terminologies Gateways :In a communications network,

a network node equipped for interfacingwith another network that uses differentprotocols - translating capability. Whenused for network security, it is called

Firewall. Routers :is an electronic device used to

connect two or more computers or otherelectronic devices to each other, and

usually to the Internet, by wire or radiosignals. This allows several computers tocommunicate with each other and to theInternet at the same time.

Other Terminologies


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Other Terminologies Clouds :abstraction of node

connectivity in the networkingcontext

Services :Functionalities

provided by a layer / protocol/Entity Service Access Points:

defined addresses / portsthrough which data /parameters are passed

Other Terminologies


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Other Terminologies Interfaces: Peer-to-Peer / Layer-to-Layer / entity-

to-entity Interoperability - Applies to different

implementations of the same specification. Eachparticipating device must have the identicallayering for interoperability.

Compatibility - applies to independentimplementations of the different specifications Tunneling - tunneling protocol when one

network protocol (the delivery protocol)encapsulates a different payload protocol. Byusing tunneling one can (for example) carry apayload over an incompatible delivery-network, orprovide a secure path through an untrustednetwork.
http://en.wikipedia.org/wiki/Network_protocolhttp://en.wikipedia.org/wiki/Encapsulation_(networking)http://en.wikipedia.org/wiki/Encapsulation_(networking)http://en.wikipedia.org/wiki/Network_protocol


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Thank you !

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