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OSI Model & TCP/IP

Speaker: Junn-Keh Yeh

Date: 2010/04/21

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Out Line

Introduction OSI

OSI History

OSI Layers

Introduction TCP/IP

TCP/IP Layers

Layering Considered Harmful?

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Introduction OSI

The Open System Interconnection ReferenceModel (OSI Reference Model orOSI Model) is an

abstract description for layered communications

and computer network protocol design.

It divides network architecture into seven layerswhich, from top to bottom, are the Application,

Presentation, Session, Transport, Network, Data

Link, and Physical Layers. It is therefore often

referred to as the OSI Seven Layer Model.

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OSI History

In 1978, the International StandarsOrganization (ISO) began to develop

its OSI framework architecture.

OSI has two major components: anabstract model of networking, called

the Basic Reference Model or seven-

layer model, and a set of specificprotocols.

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OSI History

The concept of a 7 layer model wasprovided by the work of Charles

Bachman, then of Honeywell.

Various aspects of OSI designevolved from experiences with the

Advanced Research Projects Agency

Network (ARPANET) and the fledglingInternet.

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OSI LayersOSI Model

Data unit Layer Function

Host

layers

Data

7.Application Network process to application

6. PresentationData representation,

encryption and decryption

5. Session Interhost communicationSegment

s4. Transport

End-to-end connections and

reliability, Flow control

Media

layers

Packet 3. NetworkPath determination and logical

addressing

Frame 2. Data Link Physical addressing

Bit 1. PhysicalMedia, signal and binary

transmission

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Going from layer 1 to 7: Please Do Not Throw Sausage Pizza

Away

Going from layer 7 to 1: All People Seem To Need DataProcessing

http://en.wikipedia.org/wiki/Application_Layerhttp://en.wikipedia.org/wiki/Presentation_Layerhttp://en.wikipedia.org/wiki/Session_Layerhttp://en.wikipedia.org/wiki/Transport_Layerhttp://en.wikipedia.org/wiki/Network_Layerhttp://en.wikipedia.org/wiki/Logical_addresshttp://en.wikipedia.org/wiki/Logical_addresshttp://en.wikipedia.org/wiki/Data_Link_Layerhttp://en.wikipedia.org/wiki/Physical_Layerhttp://en.wikipedia.org/wiki/Physical_Layerhttp://en.wikipedia.org/wiki/Data_Link_Layerhttp://en.wikipedia.org/wiki/Logical_addresshttp://en.wikipedia.org/wiki/Logical_addresshttp://en.wikipedia.org/wiki/Network_Layerhttp://en.wikipedia.org/wiki/Transport_Layerhttp://en.wikipedia.org/wiki/Session_Layerhttp://en.wikipedia.org/wiki/Presentation_Layerhttp://en.wikipedia.org/wiki/Application_Layer

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Layer1: Physical Layer

The Physical Layer defines theelectrical and physical specifications

for devices. In particular, it defines the

relationship between a device and aphysical medium.

This includes the layout of pin,

voltages, cable specification, hubs,repeaters, network adapters, host bus

adapters, and more.

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Layer1: Physical Layer

The major functions and servicesperformed by the Physical Layer are: Establishment and termination of a

connection to a communication medium.

Participation in the process whereby thecommunication resources are effectivelyshared among multiple users. Forexample, flow control.

Modulation, or conversion between the

representation of digital data in userequipment and the corresponding signalstransmitted over a communications channel.These are signals operating over the physicalcabling (such as copper and optical fiber) or

over a radio link. 8

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Layer1: Physical Layer con.

The same applies to local-area networks, suchas Ethernet, token ring ,

FDDI(Fiber Distributed Data Interface),

ITU-T( International Telecommunication UnionTelecommunication Standardization Sector)

G.hn and IEEE802.1I.

Personal area networks such as

Bluetooth and IEEE 802.15.4.

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Layer 2: Data Link Layer

The Data Link Layer provides thefunctional and procedural means totransfer data between network entitiesand to detect and possibly correct errors

that may occur in the Physical Layer.

Originally, this layer was intended forpoint-to-point and point-to-multipoint

media, characteristic of wide area mediain the telephone system.

The data link layer is divided into twosub-layers by IEEE.

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Layer 2: Data Link Layer

One is Media Access Control (MAC)and another is Logical Link Control(LLC).

Mac is lower sub-layer, and it definesthe way about the media accesstransfer, such asCSMA/CD/CA(Carrier Sense Multiple

Access/Collision Detection/CollisionAvoidance)

LLC provides data transmission

method in different network. It will re-acka e date and add a new header. 11

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Layer 3: Network Layer

The Network Layer provides thefunctional and procedural means of

transferring variable

length data sequences from a sourceto a destination via one or more

networks, while maintaining the quality

of service requested by the TransportLayer.

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Layer 3: Network Layer

The Network Layer performs network routing functions,

perform fragmentation and reassembly,

report delivery errors.

Routers operate at this layersending

data throughout the extended network

and making the Internet possible.

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Layer 4: Transport Layer

The Transport Layer providestransparent transfer of data between

end users, providing reliable data

transfer services to the upper layers. The Transport Layer controls the

reliability of a given link through flow

control, segmentation/desegmentation,and error control.

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Layer 4: Transport Layer

Feature Name TP0 TP1 TP2 TP3 TP4

Connection oriented network Yes Yes Yes Yes Yes

Connectionless network No No No No Yes

Concatenation and separation No Yes Yes Yes Yes

Segmentation and reassembly Yes Yes Yes Yes Yes

Error Recovery No Yes No Yes Yes

Reinitiate connection (if an

excessive number ofPDUs are

unacknowledged)

No Yes No Yes No

multiplexing and demultiplexing

over a single virtual circuitNo No Yes Yes Yes

Explicit flow control No No Yes Yes Yes

Retransmission on timeout No No No No Yes

Reliable Transport Service No Yes No Yes Yes15

http://en.wikipedia.org/wiki/Protocol_data_unithttp://en.wikipedia.org/wiki/Virtual_circuithttp://en.wikipedia.org/wiki/Virtual_circuithttp://en.wikipedia.org/wiki/Protocol_data_unit

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Layer 5: Session Layer

The Session Layer controls thedialogues (connections) between

computers.

It establishes, manages andterminates the connections between

the local and remote application.

It provides for full-duplex, half-duplex,or simplex operation, and establishes

checkpointing, adjournment,

termination, and restart procedures. 16

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Layer 5: Session Layer

The OSI model made this layerresponsible for graceful close ofsessions, which is a property of

the Transmission Control Protocol,and also for session check pointingand recovery, which is not usuallyused in the Internet Protocol Suite.

The Session Layer is commonlyimplemented explicitly in applicationenvironments that use remoteprocedure calls.

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Layer 6: Presentation Layer

The Presentation Layer establishes a contextbetween Application Layer entities, in whichthe higher-layer entities can use differentsyntax and semantics, as long as thepresentation service understands both and

the mapping between them. This layer provides independence from

differences in data representation (e.g.,encryption) by translating from application to

network format, and vice versa. This layer formats and encrypts data to be

sent across a network, providing freedomfrom compatibility problems.

It is sometimes called the syntax layer.

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Layer 7: Application Layer

The application layer is the OSI layerclosest to the end user, which meansthat both the OSI application layer andthe user interact directly with thesoftware application.

Application layer functions typicallyinclude: identifying communication partners, determining resource availability,

synchronizing communication.

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Layer 7: Application Layer

Identifying communication partners Determines the identity and availability of

communication partners for an applicationwith data to transmit.

Determining resource availability Decide whether sufficient network or the

requested communication exist.

Synchronizing communication

All communication between applicationsrequires cooperation that is managed by theapplication layer.

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Layer 7:Application Layer

Some examples of application layerimplementations include

Hypertext Transfer Protocol (HTTP)

File Transfer Protocol (FTP) Simple Mail Transfer Protocol (SMTP)

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http://en.wikipedia.org/wiki/OSI_modelhttp://en.wikipedia.org/wiki/OSI_model

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OSI Feature

Open system standards over the world

Rigorously defined structured,

hierarchical network model

Complete description of the function

Provide standard test procedures

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Introduction TCP/IP

The Internet Protocol Suite (commonlyknown as TCP/IP) is the set

of communications protocols used for

the Internet and other similar networks. It is named from two of the most

important protocols in it:

the Transmission Control Protocol (TCP) and

the Internet Protocol (IP), which were the first

two networking protocols defined in this

standard.

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TCP/IP Layers

OSI TCP/IP

Application LayerApplication Layer

TELNET, FTP, SMTP, POP3, SNMP,

NNTP, DNS,NIS, NFS, HTTP, ...

Presentation Layer

Session Layer

Transport Layer Transport LayerTCP , UDP , ...

Network Layer Internet LayerIP , ICMP, ARP, RARP, ...

Data Link LayerLink Layer

FDDI, Ethernet, ISDN, X.25,...

Physical Layer

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TCP/IP Stack

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TCP/IP Encapsulation

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TCP/IP Some Protocol

Layer Protocol

Applicatio

n

DNS, TFTP, TLS/SSL, FTP, Gopher, HTTP, IMAP, IRC, NN

TP, POP3, SIP, SMTP, SMPP, SNMP, SSH, Telnet, Echo, R

TP, PNRP, rlogin, ENRP

Routing protocols like BGP and RIP which run over

TCP/UDP, may also be considered part of the InternetLayer.

Transport TCP, UDP, DCCP, SCTP, IL, RUDP, RSVP

Internet

IP (IPv4, IPv6), ICMP, IGMP, and ICMPv6

OSPF for IPv4 was initially considered IP layer protocol

since it runs per IP-subnet, but has been placed on the Linksince RFC 2740.

Link ARP, RARP, OSPF (IPv4/IPv6), IS-IS, NDP

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http://en.wikipedia.org/wiki/Application_layerhttp://en.wikipedia.org/wiki/Application_layerhttp://en.wikipedia.org/wiki/Domain_Name_Systemhttp://en.wikipedia.org/wiki/Trivial_File_Transfer_Protocolhttp://en.wikipedia.org/wiki/Transport_Layer_Securityhttp://en.wikipedia.org/wiki/File_Transfer_Protocolhttp://en.wikipedia.org/wiki/Gopher_(protocol)http://en.wikipedia.org/wiki/HyperText_Transfer_Protocolhttp://en.wikipedia.org/wiki/Internet_Message_Access_Protocolhttp://en.wikipedia.org/wiki/Internet_Relay_Chathttp://en.wikipedia.org/wiki/Network_News_Transfer_Protocolhttp://en.wikipedia.org/wiki/Network_News_Transfer_Protocolhttp://en.wikipedia.org/wiki/Post_Office_Protocolhttp://en.wikipedia.org/wiki/Session_Initiation_Protocolhttp://en.wikipedia.org/wiki/Simple_Mail_Transfer_Protocolhttp://en.wikipedia.org/wiki/Short_message_peer-to-peer_protocolhttp://en.wikipedia.org/wiki/Simple_Network_Management_Protocolhttp://en.wikipedia.org/wiki/Secure_Shellhttp://en.wikipedia.org/wiki/Telnethttp://en.wikipedia.org/wiki/Echo_protocolhttp://en.wikipedia.org/wiki/Real-time_Transport_Protocolhttp://en.wikipedia.org/wiki/Real-time_Transport_Protocolhttp://en.wikipedia.org/wiki/Peer_Name_Resolution_Protocolhttp://en.wikipedia.org/wiki/Rloginhttp://en.wikipedia.org/w/index.php?title=Endpoint_Handle_space_Redundancy_Protocol&action=edit&redlink=1http://en.wikipedia.org/wiki/Border_Gateway_Protocolhttp://en.wikipedia.org/wiki/Routing_Information_Protocolhttp://en.wikipedia.org/wiki/Transport_layerhttp://en.wikipedia.org/wiki/Transmission_Control_Protocolhttp://en.wikipedia.org/wiki/User_Datagram_Protocolhttp://en.wikipedia.org/wiki/Datagram_Congestion_Control_Protocolhttp://en.wikipedia.org/wiki/Stream_Control_Transmission_Protocolhttp://en.wikipedia.org/wiki/IL_Protocolhttp://en.wikipedia.org/wiki/Reliable_User_Datagram_Protocolhttp://en.wikipedia.org/wiki/Resource_reservation_protocolhttp://en.wikipedia.org/wiki/Internet_Layerhttp://en.wikipedia.org/wiki/Internet_Protocolhttp://en.wikipedia.org/wiki/IPv4http://en.wikipedia.org/wiki/IPv6http://en.wikipedia.org/wiki/Internet_Control_Message_Protocolhttp://en.wikipedia.org/wiki/Internet_Group_Management_Protocolhttp://en.wikipedia.org/wiki/ICMPv6http://en.wikipedia.org/wiki/Open_shortest_path_firsthttp://tools.ietf.org/html/rfc2740http://en.wikipedia.org/wiki/Link_Layerhttp://en.wikipedia.org/wiki/Address_Resolution_Protocolhttp://en.wikipedia.org/wiki/Reverse_Address_Resolution_Protocolhttp://en.wikipedia.org/wiki/Open_shortest_path_firsthttp://en.wikipedia.org/wiki/IS-IShttp://en.wikipedia.org/wiki/Neighbor_Discovery_Protocolhttp://en.wikipedia.org/wiki/Neighbor_Discovery_Protocolhttp://en.wikipedia.org/wiki/IS-IShttp://en.wikipedia.org/wiki/IS-IShttp://en.wikipedia.org/wiki/IS-IShttp://en.wikipedia.org/wiki/Open_shortest_path_firsthttp://en.wikipedia.org/wiki/Reverse_Address_Resolution_Protocolhttp://en.wikipedia.org/wiki/Address_Resolution_Protocolhttp://en.wikipedia.org/wiki/Link_Layerhttp://tools.ietf.org/html/rfc2740http://en.wikipedia.org/wiki/Open_shortest_path_firsthttp://en.wikipedia.org/wiki/ICMPv6http://en.wikipedia.org/wiki/Internet_Group_Management_Protocolhttp://en.wikipedia.org/wiki/Internet_Control_Message_Protocolhttp://en.wikipedia.org/wiki/IPv6http://en.wikipedia.org/wiki/IPv4http://en.wikipedia.org/wiki/Internet_Protocolhttp://en.wikipedia.org/wiki/Internet_Layerhttp://en.wikipedia.org/wiki/Resource_reservation_protocolhttp://en.wikipedia.org/wiki/Reliable_User_Datagram_Protocolhttp://en.wikipedia.org/wiki/IL_Protocolhttp://en.wikipedia.org/wiki/Stream_Control_Transmission_Protocolhttp://en.wikipedia.org/wiki/Datagram_Congestion_Control_Protocolhttp://en.wikipedia.org/wiki/User_Datagram_Protocolhttp://en.wikipedia.org/wiki/Transmission_Control_Protocolhttp://en.wikipedia.org/wiki/Transport_layerhttp://en.wikipedia.org/wiki/Routing_Information_Protocolhttp://en.wikipedia.org/wiki/Border_Gateway_Protocolhttp://en.wikipedia.org/w/index.php?title=Endpoint_Handle_space_Redundancy_Protocol&action=edit&redlink=1http://en.wikipedia.org/wiki/Rloginhttp://en.wikipedia.org/wiki/Peer_Name_Resolution_Protocolhttp://en.wikipedia.org/wiki/Real-time_Transport_Protocolhttp://en.wikipedia.org/wiki/Real-time_Transport_Protocolhttp://en.wikipedia.org/wiki/Echo_protocolhttp://en.wikipedia.org/wiki/Telnethttp://en.wikipedia.org/wiki/Secure_Shellhttp://en.wikipedia.org/wiki/Simple_Network_Management_Protocolhttp://en.wikipedia.org/wiki/Short_message_peer-to-peer_protocolhttp://en.wikipedia.org/wiki/Simple_Mail_Transfer_Protocolhttp://en.wikipedia.org/wiki/Session_Initiation_Protocolhttp://en.wikipedia.org/wiki/Post_Office_Protocolhttp://en.wikipedia.org/wiki/Network_News_Transfer_Protocolhttp://en.wikipedia.org/wiki/Network_News_Transfer_Protocolhttp://en.wikipedia.org/wiki/Internet_Relay_Chathttp://en.wikipedia.org/wiki/Internet_Message_Access_Protocolhttp://en.wikipedia.org/wiki/HyperText_Transfer_Protocolhttp://en.wikipedia.org/wiki/Gopher_(protocol)http://en.wikipedia.org/wiki/File_Transfer_Protocolhttp://en.wikipedia.org/wiki/Transport_Layer_Securityhttp://en.wikipedia.org/wiki/Trivial_File_Transfer_Protocolhttp://en.wikipedia.org/wiki/Domain_Name_Systemhttp://en.wikipedia.org/wiki/Application_layerhttp://en.wikipedia.org/wiki/Application_layer

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Why Layering Considered

Harmful? In the data networking context

structured layering implies that thefunctions of each layer are carried outcompletely before the protocol dataunit is passed to the next layer.

This means that the optimization ofeach layer has to be done separately.

Such ordering constraints are inconflict with efficient implementation ofdata manipulation functions.

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Why Layering Considered

Harmful?As a result of inter-layer dependencies,

increased layering can quickly lead toviolation of the Simplicity Principle.

Industry experience has taught us that

increased layering frequently increasescomplexity and hence leads to increasesin OPEX(Operating Expense),as is predicted by the Simplicity Principle.

It is always possible to agglutinatemultiple separate problems into a singlecomplex interdependent solution. In mostcases this is a bad idea.

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References

http://en.wikipedia.org/wiki/OSI_model

http://en.wikipedia.org/wiki/Internet_Pr

otocol_Suite

http://lips.lis.ntu.edu.tw/YTCHIANG/STUDY/others/tcpiposi.htm

RFC 3439

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http://en.wikipedia.org/wiki/OSI_modelhttp://en.wikipedia.org/wiki/Internet_Protocol_Suitehttp://en.wikipedia.org/wiki/Internet_Protocol_Suitehttp://lips.lis.ntu.edu.tw/YTCHIANG/STUDY/others/tcpiposi.htmhttp://lips.lis.ntu.edu.tw/YTCHIANG/STUDY/others/tcpiposi.htmhttp://lips.lis.ntu.edu.tw/YTCHIANG/STUDY/others/tcpiposi.htmhttp://lips.lis.ntu.edu.tw/YTCHIANG/STUDY/others/tcpiposi.htmhttp://en.wikipedia.org/wiki/Internet_Protocol_Suitehttp://en.wikipedia.org/wiki/Internet_Protocol_Suitehttp://en.wikipedia.org/wiki/OSI_model