Network Standards and Models

Network Communication

• Recognize data• Divide data into manageable chunk• Add information to each chunk to:

– Determine where the data is coming from– Identify where the data is going to

• Add timing and error checking information• Put the data on the network and send it on its

way

Why Networking Standards are needed?

• Standards provide a fixed way for hardware and/or software systems to communicate.

• Need for standard protocols so that software/hardware from different vendors could communicate

• Network operating systems follow strict rules (protocols) to control how each of the previous tasks are accomplished.

• For example, USB enables two pieces of equipment to interface even though they are manufactured by different companies.

• By allowing hardware and software from different companies to interconnect, standards help promote competition.

Types of Standards

There are two main types of standards:• Formal: a standard developed by an industry

or government standards-making body• De facto: standards that emerge in the

marketplace and are widely used, but lack official backing by a standards-making body

The Standardization Processes:Three Steps

• Specification: developing the classification and identifying the problems to be addressed.

• Identification of choices: identify solutions to the problems and choose the “optimum” solution.

• Acceptance: defining the solution, getting it recognized by industry so that a uniform solution is accepted.

Networking Standards Organizations

1. ANSI2. EIA3. IEEE4. ISO5. ITU

American National Standards Institute (ANSI)

• ANSI is an organization composed of more than 1000 representatives from industry in addition to other fields, such as chemical and nuclear engineering, health and safety, and construction.

• ANSI also represents the United States in setting international standards.

Electronic Industries Alliance (EIA)

• EIA is a trade organization composed of representatives from electronics manufacturing firms across the United States.

• EIA began as the Radio Manufacturers Association (RMA) in 1924; over time it evolved to include manufacturers of televisions, semiconductors, computers and networking devices.

Institute of Electrical and Electronic Engineers (IEEE)

• The IEEE is an international society composed of engineering professionals.

• Its goals are to promote development and education in the electrical engineering and computer science fields.

International Organization for Standardization (ISO)

• ISO is a collection of standards organizations representing 130 countries.

• ISO’s goal is to establish international technological standards to facilitate global exchange of information and barrier-free trade.

International Telecommunication Union (ITU)

• The ITU is a specialized United Nations agency that regulates international telecommunications, including radio and TV frequencies, satellite and telephony specifications, networking infrastructure, and tariffs applied to global communications.

• It also provides developing countries with technical expertise and equipment to advance those nations’ technological bases.

IEEE Networking Specifications

• 802.1 – Internetworking – Covers routing, bridging, and internetwork communications.

• 802.2 – Logical Link Control – Relates to error and flow control over data frames.

• 802.3 – Ethernet LAN – Covers all forms of Ethernet media and interfaces.

• 802.4 – Token Bus LAN – Covers all forms of Token Bus media and interfaces.

• 802.5 – Token Ring LAN – Covers all forms of Token Ring media and interfaces.

• 802.6 – Metropolitan Area Network (MAN) – Covers MAN technologies, addressing, and services.

IEEE Networking Specifications

• 802.7 – Broadband Technical Advisory Group – Covers broadband networking media, interfaces, and other equipment.

• 802.8 – Fiber Optic Technical Advisory Group – Covers use of fiber-optic media and technologies for various networking types.

• 802.9 – Integrated Voice/Data Networks – Covers integration of voice and data traffic over a single network medium.

• 802.10 – Network Security – Covers network access controls, encryption, certification, and other security topics.

• 802.11 – Wireless Networks – Standards for wireless networking for many different broadcast frequencies and usage techniques.

• 802.12 – High Speed Networking – Covers a variety of 100Mbps plus technologies, including 100BASEVG-AnyLAN.

LAYERED TASKS

• Use of the concept of layers in our daily life. • As an example, let us consider two friends who

communicate through postal mail. • The process of sending a letter to a friend would be

complex if there were no services available from the post office.

Sender, Receiver, and CarrierHierarchy

Tasks involved in sending a letter

THE OSI MODEL

• Established in 1947, the International Standards Organization (ISO) is a multinational body dedicated to worldwide agreement on international standards.

• An ISO standard that covers all aspects of network communications is the Open Systems Interconnection (OSI) model. It was first introduced in the late 1970s.

ISO is the organization.OSI is the model.

Relationship of OSI Layers

• Each layer of the OSI model must communicate with the layer above and below it– For example, the Presentation layer must communicate

with the Application layer (one above) and the Session layer (one below)

• As data passes down through the OSI layers, each layer (except Physical) adds some information to the data

• When data reaches the receiving computer, the information added by each layer of the OSI model is read and processed by the corresponding layer on the receiving computer

• This is referred to as peer-layer communications

Relationships among Seven layers of the OSI model

Computer A Computer B

VirtualCommunication

Application

Presentation

Session

Transport

Network

Data Link

Physical

Application

Presentation

Session

Transport

Network

Data Link

Physical

The interaction between layers in the OSI model

An exchange using the OSI model

Physical layer

The physical layer is responsible for movements ofindividual bits from one hop (node) to the next.

Data link layer

The data link layer is responsible for moving frames from one hop (node) to the next.

Hop-to-hop delivery

Network layer

The network layer is responsible for the delivery of individual packets from

the source host to the destination host.

Source-to-destination delivery

Transport layer

The transport layer is responsible for the delivery of a message from one process to another.

Reliable process-to-process delivery of a message

Session layer

The session layer is responsible for dialog control and synchronization.

Presentation layer

The presentation layer is responsible for translation, compression, and encryption.

Application layer

The application layer is responsible for providing services to the user.

Summary of layers

TCP/IP PROTOCOL SUITE

• The layers in the TCP/IP protocol suite do not exactly match those in the OSI model.

• The original TCP/IP protocol suite was defined as having four layers: host-to-network, internet, transport, and application.

• However, when TCP/IP is compared to OSI, we can say that the TCP/IP protocol suite is made of five layers: physical, data link, network, transport, and application.

TCP/IP and OSI model

ADDRESSINGFour levels of addresses are used in an internet employing the TCP/IP protocols: physical, logical, port, and specific.

Relationship of layers and addresses in TCP/IP

Applying the OSI Model

OSI Process

Physica l LayerP laces bits on to the network m edia

Data Link LayerPackages data into fram es

Adds FC S; adds physical addressespasses to Physical layer

Network layerAdd network addresses

passes da ta to Data Link Layer

Transport layerSubdivides data

adds sequencing infopasses data to N e twork layer

Session layerAdds a con trol fram e to data tha t

indica tes that you have the right to transm it datapasses data to T ransport laye r

Presentation layerencyrpts reques t (if necessary )

adds any codes required to im plem ent form attingpasses request to S ession layer

Application leve lform ulates requestfor data and sends

request to Presenta tion layer

Request for e -m ail is received by Physical laye ron rece iving com puter

Request is passed up the layers of the OSI m odelEach layer read, processes and rem oves in fo added by coorespond ing layer on sending com puter

User Requests M ail

In Next Figure a node with physical address 10 sends a frame to a node with physical address 87. The two nodes are connected by a link (bus topology LAN). As the figure shows, the computer with physical address 10 is the sender, and the computer with physical address 87 is the receiver.

Example 1

Physical addresses

Most local-area networks use a 48-bit (6-byte) physical address written as 12 hexadecimal digits; every byte (2 hexadecimal digits) is separated by a colon, as shown below:

Example2

07:01:02:01:2C:4B

A 6-byte (12 hexadecimal digits) physical address.

Next Figure shows a part of an internet with two routers connecting three LANs. Each device (computer or router) has a pair of addresses (logical and physical) for each connection. In this case, each computer is connected to only one link and therefore has only one pair of addresses. Each router, however, is connected to three networks (only two are shown in the figure). So each router has three pairs of addresses, one for each connection.

Example 3

IP addresses

Next Figure shows two computers communicating via the Internet. The sending computer is running three processes at this time with port addresses a, b, and c. The receiving computer is running two processes at this time with port addresses j and k. Process a in the sending computer needs to communicate with process j in the receiving computer. Note that although physical addresses change from hop to hop, logical and port addresses remain the same from the source to destination.

Example 4

Port addresses

Communication Functions according to the OSI Model

User applications ..

Encryption/decryption

compression/expansion

Choice of syntax

Sessioncontrol

Session to transportmapping

Session management

Sessionsynch.

Layer and flowcontrol

Error recovery

Multiplexing

Connection control

Routing Addressing

Errorcontrol

Flowcontrol

Data link establishment

Synch Framing

Access to transm. media

Physical and electrical interface

Activation/ deactivation of con.

Application layer

Presentation layer

Session layer

Transport layer

Network layer

Link layer

Physical layer

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