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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
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Services Provided by the Operating
System
Program development Editors and debuggers
Program execution
Access to I/O devices Controlled access to files
System access
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Services Provided by the Operating
System
Error detection and response Internal and external hardware errors
Memory error
Device failure
Software errors
Arithmetic overflow
Access forbidden memory locations
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Services Provided by the Operating
System
Accounting Collect usage statistics
Monitor performance
Used to anticipate future enhancements
Used for billing purposes
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Services Provided by the OperatingSystem
Responsible for managing resources Functions same way as ordinary
computer software
It is program that is executed
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Evolution of an Operating System
Hardware upgrades plus new types ofhardware
New services
Fixes
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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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Evolution of Operating Systems
Simple Batch Systems Monitors
Software that controls the sequence of events
Batch jobs together
Program branches back to monitor whenfinished
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Hardware Features
Memory protection Do not allow the memory area containing
the monitor to be altered
Timer
Prevents a job from monopolizing thesystem
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Hardware Features
Privileged instructions Certain machine level instructions can only
be executed by the monitor
Interrupts
Early computer models did not have thiscapability
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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
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Uniprogramming Processor must wait for I/O instruction to
complete before preceding
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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
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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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
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 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
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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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
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 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
Network Architectures and NetworkReference Models Other Terminologies
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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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Transportation Layer
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.
Transportation Layer
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Transportation Layer
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.
Transportation Layer
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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_protocol8/3/2019 OS and Networking Concepts
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Thank you !
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