Transcript Networking Standards and Models

FCN week 10
Network Standards and Models
The need for standards
Standards organisations
OSI model
TCP/IP model
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Standards
Processes or protocols that has been endorsed by
the networking industry
Ratified by a standards organization
Documented agreements containing
technical specifications or other precise criteria
that stipulate how a particular product or service
should be designed or performed
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Organisations responsible for standards
American National Standards Institute (ANSI)
Electronics Industry Alliance (EIA)
Institute of Electrical and Electronic Engineers (IEEE)
International Organization for Standardization (ISO)
International Telecommunication Union (ITU)
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IEEE Networking Specifications
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The Seven Layer OSI Model
At the top, the Application layer provides OS services for
application software
 The OSI model breaks the process of
communication down into several layers
Different stages data must/may go
through as it travels from one device
to another
Nmemonics –
Please do not throw sausage pizza away!
All PC’s seem to network data poorly
At the bottom, the Physical layer deals with wiring issues
Application
Presentation
Session
Transport
Network
Data link
Physical
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OSI model – Why bother?
Real-world network protocols don’t implement the
OSI seven layer protocol stack model
But nearly all network protocols are based on a
simplified layered model
The layered model helps us think about the many
processes involved in communicating over networks
A good model provides support for thinking
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OSI model – Why bother?
Benefits include
 assists in protocol design
 fosters competition
 changes in one layer do not affect other layers
 provides a common language
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The Application Layer
 Provides interface to the software enabling programs to use
network devices
 Definition of the way that network services use the network
 Defines how many services work, including
 File sharing, Network Printing, Message Services etc
 E.g Application Program Interface (API)
 Routine that allows a program to interact with the operating system
 Belongs to the Application layer of OSI Model
 Applications
 HTTP
 Email
 Etc...
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The Presentation Layer
This layer “presents” data, which is to say it does
some pre-processing, such as
data compression
encryption
character set conversion
Translates between the application and the network
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The Session Layer
A communications management layer
Defines how two computers synchronise, maintain
and close a communication session
This includes such things as
security authentication
acknowledgement of data transfer
establishing and relinquishing a connection
identity
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The Transport Layer
Data packet management
Ensures that chunks of data have been transferred
without error – does lots of error and flow control
Takes data and packs it into chunks or chops it up
into chunks suitable for transmission
Takes chunks and unpacks them or combines them
into data streams
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The Network Layer
This is Internet Protocol address layer for path
selection around the network
Routing of packets uses IP addresses
Network Layer Address
Resides at Network level of OSI Model
Follows hierarchical addressing scheme
Can be assigned through operating system
software
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The Data Link Layer
 Decodes packets into what are called frames which contain
Physical source and destination addressing
data validity / error checking
 The network technology being used will influence how this
layer works e.g. Ethernet, token ring …..
 To accommodate shared access for multiple network nodes,
the IEEE expanded the OSI Model by separating the Data Link
layer into two sublayers
Logical Link Control (LLC) sublayer
Media Access Control (MAC) sublayer
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The Physical Layer
This is the physical networking media layer which
includes the cabling technology
Defines the transmission technique and the
hardware definitions (connectors and so on)
Networking may take place over copper cables,
optical fibres, infra-red radiation, radio waves… and
this variation should be transparent to the user
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Communication Between Two Systems
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TCP/IP
 The problem with
the OSI model is a
‘concept’ not an
actual
implementation
 TCP/IP is a set of
protocols used.
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What is TCP/IP?
 TCP/IP stands for Transport Control Protocol / Internet
Protocol suite.
 TCP/IP was created in 1983 to replace NCP.
 TCP/IP can successfully switch packets from all shapes and
sizes and varieties of networks.
 Therfore TCP/IP has become the backbone of the Internet
and its composite LANs and WANs, due to it's ability to
switch packets from computer systems on any network to
another network, regardless of network peculiarities,
operating system differences and other packet differences
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What is TCP/IP?
 The higher layer, Transmission Control Protocol, manages
the assembling of a message or file into smaller packets that
are transmitted over the Internet and received by a TCP layer
that reassembles the packets into the original message.
 The lower layer, Internet Protocol, handles the address part
of each packet so that it gets to the right destination.
 Each gateway computer on the network checks this address
to see where to forward the message.
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What is TCP/IP?
 Even though some packets from the same message are
routed differently than others, they'll be reassembled at the
destination.
 Uses the client/server model of communication in which a
computer user (a client) requests and is provided a service
(such as sending a Web page) by another computer (a
server) in the network.
 TCP/IP communication is primarily point-to-point, meaning
each communication is from one point (or host computer) in
the network to another point or host computer.
 TCP/IP and the higher-level applications that use it are
collectively said to be "stateless" because each client request
is considered a new request unrelated to any previous one
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What is TCP/IP?
 Being stateless frees network paths so that everyone can use
them continuously.
 You will be familiar application protocols that use TCP/IP to
get to the Internet.
 These include the World Wide Web's Hypertext Transfer
Protocol (HTTP)
 File Transfer Protocol (FTP)
 Telnet (Telnet) which lets you logon to remote computers
 Simple Mail Transfer Protocol (SMTP).
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TCP/IP vs OSI
OSI Model
TCP/IP
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Layers with TCP/IP and OSI Model
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Conclusion
We have discussed:Organizations that set standards for networking
Standard “root concepts” of networking
Layered models of processes and layers in our
conceptual model of networking
Why protocols are required for interoperability
Details of the seven layers of the OSI model
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