1. Network Standards
Standards are agreed published specifications or definitions which have been approved either by a standards body or have become established by common use
They are required to enable the interoperability of products
There are two main types:
De jure (by law)
De facto (by fact)
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2. De Jure and De Facto Standards
De jure standards
Produced or accepted by a recognised standards body
Communication and hardware standards are usually de jure (E.g V.90, EIA232C or RS232C)
De facto standards
Not produced or accepted by a recognised standards body but gain widespread use by market forces (E.g. Novell Netware, Microsoft’s NetBIOS)
Software standards are usually de facto (Windows)
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3. De Facto Standards De facto standards can be further divided into
Proprietary (or Closed)
Produced, owned and controlled by a commercial organisation (E.g. Microsoft Windows)
Non-proprietary (or Open)
Originally produced, owned and controlled by a commercial organisation but have been transferred to the public domain (E.g. Unix)
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4. International Standards Bodies
ISO (International Organization for Standardization)
Prefix = ISO
ITU-T (International Telecommunications Union – Telecommunications Sector) - previously called CCITT
Prefix = G. V. or X. or other letter followed by a dot
ETSI (European Technical Standards Institute)
Prefix = EN
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5. National Standards BodiesUS
ANSI (American National Standards Institute) - Prefix = ANSI
EIA (Electrical Industries Association) – Prefix = EIA
IEEE (Institute of Electrical and Electronic Engineers) - Prefix = IEEE UK
BSI (British Standards Institute) – Prefix = BS
Germany
DIN (Deutsches Institut für Normung) – Prefix = DIN
France
AFNOR (Association Française de Normalisation) - Prefix = NF
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6. Industry Groups IETF (Internet Engineering Task Force)
Prefix = RFC (Request for Comment)
Frame Relay Forum
Prefix = FRF
ATM (Asynchronous Transfer Mode) Forum
Prefix = AF
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7. Standards
ADVANTAGES
Products can be designed that will be interoperable with products from other vendors
Provide stability in the market-place for developers and consumers
Ensures a large market encouraging the development and mass production of chips and reducing costs
DISADVANTAGES
Tends to freeze the technology so that it doesn’t incorporate some of the latest ideas
Standardisation by consensus does not always produce the best solution and takes a long time
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8. Reference Models Open Systems Interconnection (OSI) Model
Department of Defense (DoD) Model
Hybrid Model
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9. OSI Reference Model
Open Systems Interconnection was an initiative of the International Organization for Standardization (ISO) in 1984
It was an attempt to develop a set of international standards to replace the existing proprietary standards and allow different manufacturers’ systems to interoperate
It defined a 7 Layer Reference Model
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10. OSI Reference Model OSI makes a clear distinction between:
Services
Interfaces
Protocols
OSI fits well with modern object-oriented programming
The OSI Model was devised before OSI protocols were specified which makes it very general
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11. OSI Reference Model
OSI protocols were defined for each layer, but with a very few exceptions lost ground to Internet protocols
Tanenbaum gives a good critique of OSI
Bad timing
Bad technology
Bad implementations
Bad politics
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12. OSI Reference Model
Despite its lack of successful implementations, the model does provide a useful framework with which to analyse and design communications protocols
It did also provide an impetus to the widespread adoption of open rather than proprietary standards
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13. OSI Layers Physical Layer Data Link Layer Network Layer
Transport Layer
Session Layer
Presentation Layer
Application Layer
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14. Layer 1 – The Physical Layer
Activates and maintains physical link between devices
Specifies physical characteristics (e.g. transmission distances, connectors, voltages)
Encodes and decodes data for transmission on physical media
Synchronises bits according to the transmission rate
Defines the transmission mode (simplex, half duplex or full duplex) and the line configuration (point-to-point or point-to-multipoint)
Includes wiring, repeaters and signals
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15. Layer 1 – The Physical Layer
Example Protocols
V.24 (Physical Interface for modems)
EIA 232 (Physical Interface for serial ports)
V.35 (Physical Interface for private circuits)
X.21 (Physical Interface for private circuits and public data networks)
G.703 (2 Mbit/s E1 Transmission standard)
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16. Layer 2 – The Data Link Layer
Manages data transmission using physical addresses across a single physical link
Activates and deactivates the physical link
Controls the framing of data
Manages physical addresses and bridging
Detects and notifies errors
Controls data flow
Controls access to shared media
Two sub-layers
LLC (Logical Link Control)
MAC (Media Access Control)
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17. Layer 2 – The Data Link Layer
Example Protocols
Ethernet II
IEEE (Ethernet)
IEEE (Token Ring)
HDLC (High-level Data Link Control)
SLIP (Serial Link Internet Protocol)
PPP (Point to Point Protocol)
ISDN (Integrated Services Digital Network)
Frame Relay
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18. Layer 3 – The Network Layer
Sends data from source network to destination network
Creates and maintains network map
Determines paths through internetwork
Routes packets
Manages network addresses
Manages routing tables
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19. Layer 3 – The Network Layer
Example Protocols
IP (Internet Protocol)
ICMP (Internet Control Message Protocol
IPX (Internetwork Packet Exchange) - Novell
BootP (Boot Protocol)
ARP (Address Resolution Protocol)
RARP (Reverse Address Resolution Protocol)
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20. Layer 4 – The Transport Layer
Provides end-to-end data transmission
Controls end-to-end connections 
Multiplexes data from different applications into a data stream
Segments and reassembles data
Hides detailed network dependent information from upper layers
Guaranties integrity (flow control) for connection-oriented services
Guaranties reliability (right order without loss or duplication) for connection-oriented services
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21. Layer 4 – The Transport Layer
Example Protocols
TCP – Transmission Control Protocol (connection-oriented)
UDP – User Datagram Protocol (connectionless)
SPX – Sequenced Packet Exchange (connection oriented Novell protocol)
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22. Layer 5 – The Session Layer
Controls all communication sessions and dialog between applications by coordinating services
Controls dialog
Groups and checkpoints data transfers for recovery purposes
 Three Modes
Simplex / Half duplex / Full duplex 
Three Stages
Connection establishment
Data transfer
Connection release
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23. Layer 5 – The Session Layer
Example Protocols
SQL (Structured Query Language)
RPC (Remote Procedure Call) - Sun but standardised by IETF
NFS (Network File System) - Sun
ASP (Apple Session Protocol)
DNA SCP (Digital Network Architecture Session Control Protocol)
X Window – Unix based graphical interface to remote systems (MIT)
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24. Layer 6 – The Presentation Layer
Ensures Application Layer will be able to read data 
Determines syntax of data transfer
Data handling (encryption/compression)
Converts data formats - E.g. EBCDIC (IBM) to ASCII
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25. Layer 6 – The Presentation Layer
Example Protocols
HTML (Hyper-Text Mark-up Language)
PICT (Picture Format) – Apple
TIFF (Tagged Image File Format)
JPEG (Joint Photographic Expert Group) - compression format
GIF (Graphics Interchange Format) – CompuServe
MIDI (Musical Instrument Digital Interface)
MPEG – Moving Picture Expert Group compression format
QuickTime –Audio and video compression format (Apple)
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26. Layer 7 – The Application Layer
Provides network services to applications
Organises resources
Synchronises applications
Controls data integrity (error correction)
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27. Layer 7 – The Application Layer
Example Protocols
SMTP (Simple Mail Transfer Protocol)
POP3 (Post Office Protocol 3)
IMAP (Internet Message Access Protocol)
FTP (File Transfer Protocol)
TFTP (Trivial File Transfer Protocol)
HTTP (Hyper-Text Transfer Protocol)
Telnet (virtual terminal protocol)
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28. OSI Protocol Encapsulation
Data
APPL
Data A
PRES
Data A P
SESS
Data A P S
TRANS
Data A P S T
NET
Data A P S T N
DLINK
Data A P S T N D
PHYS
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29. Types of OSI Service Primitives
Request
Issued by a service user to invoke a service and pass parameters
Indication
Issued by a service provider to indicate that a procedure has been invoked by the peer service user and to provide associated parameters or for to notify the service user of a provider-initiated action
Response
Issued by a service user to acknowledge or complete some procedure previously invoked by an indication to that user
Confirmation
Issued by a service provider to acknowledge or complete some procedure previously invoked by a request by the service user
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30. Example of an OSI Service Primitive
Service user
(Layer N+1)
Service provider
(Layer N)
Connection
Request
Connection
Indication
Connection
Response
Connection
Confirmation
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