2. What is Protocol ? A protocol is a set of rules that make
communication on a network more efficient. Operational sequence to
carry our a specific task. Example : DNC, DHCP, HTTP.
3. Overview During the past two decades there has been a
tremendous increase in the numbers and sizes of networks. Many of
the networks, however, were built using different implementations
of hardware and software. As a result, many of the networks were
incompatible and it became difficult for networks using different
specifications to communicate with each other.
4. International Organization for Standards (ISO) To address
this problem, the International Organization for Standardization
(ISO) researched many network schemes. The ISO recognized that
there was a need to create a network model that would help network
builders implement networks that could communicate and work
together (interoperability) and therefore, released the OSI
reference model in 1984.
5. The Layered Model
6. Layered CommunicationLocation A I like Message rabbits L:
Dutch Information Ik hou for the Remote van Translator konijnen Fax
#:--- Information L: Dutch for the Ik hou Remote van Secretary
konijnen Source: Tanenbaum, 1996
7. Layered CommunicationLocation A Location B I like Jaime
Message rabbits les lapins L: Dutch Information L: Dutch Ik hou for
the Ik hou Remote van van Translator konijnen konijnen Fax #:---
Fax #:--- Information L: Dutch L: Dutch for the Ik hou Ik hou
Remote van Secretary van konijnen konijnen
8. Layered CommunicationLocation A Location B Layers I like
Jaime rabbits Message 3 les lapins L: Dutch Information L: Dutch Ik
hou van for the remote 2 Ik hou van translator konijnen konijnen
Fax #:--- Fax #:--- Information L: Dutch L: Dutch for the Ik hou Ik
hou remote van secretary 1 van konijnen konijnen
9. Why a Layered Network Model? 7 Application Reduces
complexity (one big problem to seven smaller 6 Presentation ones) 5
Session Standardizes interfaces 4 Transport Facilitates modular
engineering 3 Network Assures interoperable 2 Data Link technology
Accelerates evolution 1 Physical Simplifies teaching and
learning
10. Devices Function at Layers 7 Application 6 PresentationNIC
Card 5 Session 4 Transport 3 Network 2 Data Link 1 Physical
Hub
11. Host Layers }7 Application6 Presentation Host layers:
Provide accurate data delivery between5 Session computers4
Transport3 Network2 Data Link1 Physical
12. Media Layers }7 Application6 Presentation Host layers:
Provide5 Session accurate data delivery between computers4
Transport }3 Network2 Data Link Media layers: Control physical
delivery of messages1 Physical over the network
13. OSI Layers }7 Application6 Presentation Software layers5
Session4 Transport Heart of OSI }3 Network2 Data Link Hardware
layers1 Physical
14. Layer Functions7 Application Provides network services to
application processes (such as electronic mail, file transfer, and
terminal emulation) Closest to User & Data Integrity.
15. Layer Functions7 Application Network services to
applications6 Presentation Data representation Ensures data is
readable by receiving system Translates between multiple data
formats using a common data format. Encryption & Decryption
Compression & Decompress.
16. Layer Functions7 Application Network services to
applications6 Presentation Data representation5 Session Inter-host
communication Establishes, manages, and terminates sessions between
applications. Synchronizes Dialogue.
17. Layer Functions7 Application Network services to
applications6 Presentation Data representation5 Session Inter-host
communication4 Transport End-to-end connection reliability
Concerned with data transport issues between hosts Data transport
reliability Establishes, maintains, and terminates virtual circuits
Fault detection and recovery Flow control
18. Layer Functions7 Application Network services to
applications6 Presentation Data representation5 Session Inter-host
communication4 Transport End-to-end connection reliability3 Network
Addresses and best path Provides connectivity and path selection
between two end systems Domain of routing
19. Layer Functions7 Application Network services to
applications6 Presentation Data representation5 Session Inter-host
communication4 Transport End-to-end connection reliability3 Network
Addresses and best path2 Data Link Access to media Physical
addressing, network topology, Deliver of Frames. Error Detection
(No correction) FCS
20. Layer Functions7 Application Network services to
applications6 Presentation Data representation5 Session Inter-host
communication4 Transport End-to-end connection reliability3 Network
Addresses and best path2 Data Link Access to media1 Physical Binary
transmission Electrical & Mechanical Procedures. Wires,
Connectors, Voltage Level, Timing of Voltage, Maximum transmission
distance
21. Peer-to-Peer Communications Host A Host B7 Application
Application6 Presentation Presentation5 Session Session Segments4
Transport Transport Packets3 Network Network Frames2 Data Link Data
Link Bits1 Physical Physical
22. Data Encapsulation Host A Host B } {Application
ApplicationPresentation Data PresentationSession SessionTransport
TransportNetwork NetworkData Link Data LinkPhysical Physical
23. Data Encapsulation Host A Host B } {Application
ApplicationPresentation Data PresentationSession SessionTransport
Transport Network DataNetwork Header NetworkData Link Data
LinkPhysical Physical
24. Data Encapsulation Host A Host B } {Application
ApplicationPresentation Data PresentationSession SessionTransport
Transport Network DataNetwork Header Network Frame Network Data
FrameData Link Data Link Header Header TrailerPhysical
Physical
25. Data Encapsulation Host A Host B } {Application
ApplicationPresentation Data PresentationSession SessionTransport
Transport Network DataNetwork Header Network Frame Network Data
FrameData Link Data Link Header Header TrailerPhysical
0101101010110001 Physical
26. Layers 1 & 2:Physical & Data Link Layers
27. Physical and Logical Addressing0000.0c12.3456
28. MAC Address 24 bits 24 bits Vendor Code Serial Number
0000.0c12. 3456 ROM RAM MAC address is burned into ROM on a network
interface card
29. NIC - Addresses Two Addresses are associated with
NICPhysical Address Logical Address MAC IP (Media Access Control)
(Internet Protocol) L2 Address L3 Address Permanent Logical (Can be
Changed) 48 Bit 32 Bit Hexadecimal Notation Dotted Decimal Notation
Ex : 01-5C-D9-6B-03-2E Ex : 192.168.6.1
30. Layer 3:Network Layer
31. Network Layer: Path Determination Which Path? Which Path?
Layer 3 functions to find the best path through the
internetwork
32. Network Layer Protocol OperationsX Y C C A A Each router
provides its services to support upper layer functions
33. Network Layer Protocol Operations X Y C C A A B B Host X
Host YApplication ApplicationPresentation PresentationSession
Router A Router B Router C SessionTransport TransportNetwork
Network Network Network NetworkData Link Data Link Data Link Data
Link Data LinkPhysical Physical Physical Physical Physical Each
router provides its services to support upper layer functions
35. Transport Layer Segments upper-layer applications
Establishes an end-to-end connection Optionally, ensures data
reliability
36. Transport LayerSegments Upper-Layer ApplicationsApplication
Electronic File TerminalPresentation Mail Transfer SessionSession
Transport Application Application Data Data Port Port Segments
37. Transport Layer Establishes ConnectionSender Receiver
Synchronize Negotiate Connection Synchronize Acknowledge Connection
Established Data Transfer (Send Segments)
38. Transport LayerSends Segments with Flow Control Transmit
Sender Receiver Buffer Full Not Ready Stop Process Segments Go
Ready Buffer OK Resume Transmission
41. Transport to Network Layer End-to-End Segments Routed
Packets
42. Session Layer Network File System (NFS) Structured Query
Language (SQL) Remote-Procedure Call (RPC) X Window System
AppleTalk Session Protocol (ASP) DEC Session Control Protocol (SCP)
Service Request Service Reply Coordinates applications as they
interact on different hosts
43. Session Layer In networking a session is a semi-permanent
interactive information interchanges, a communication or a meeting
between two or more communicating devices, or between a computer
and a user (Login Session). A session begins when an application
wants to make connection to a remote server, the session layer
opens a temporary channel between the two. A session is established
at a certain point in time and torn down at a later point in time.
There could be more than one session at the same time. The session
layer can time stamp data. So that it knows where to re-start the
transfer.
44. Presentation Layer Text Graphics Data Visual images ASCII
PICTlogin: EBCDIC TIFF Encrypted JPEG Sound GIF MIDI Video MPEG
QuickTime Provides code formatting and conversion for
applications
45. Presentation Layer ASCII : American Standard Code for
Information Interchange. EBCDIC: Extended Binary Coded Decimal
Interchange Code. JPEG : Joint Picture Expert Group. TIFF : Tagged
Image File Format. GIF : Graphical Image Format. BMP : Bitmap
Image. MPEG : Motion Picture Expert Group. AVI : Audio Video
Interleave. WAV : Windows Audio Video
46. Application Layer COMPUTER APPLICATIONS NETWORK Word
Processor APPLICATIONS INTERNETWORK Presentation Graphics
Electronic Mail APPLICATIONS File Transfer Electronic Data
Interchange Spreadsheet Remote Access World Wide Web Database
Client-Server Process E-Mail Gateways Design/Manufacturing
Information Location Special-Interest Bulletin Boards Project
Planning Network Management Financial Transaction Services Others
Others Internet Navigation Utilities Conferencing (Voice, Video,
Data) Internetwork applications Others can extend beyond the
enterprise (i.e., to suppliers, etc.)
47. Summary OSI reference model describes building blocks of
functions for program-to- program communications between similar or
dissimilar hosts Layers 47 (host layers) provide accurate data
delivery between computers Layers 13 (media layers) control
physical delivery of data over the network