Lesson 4, 5, 6, 7

Standards Organization for Data Communications, Transmission Modes, and Two wire vs Four Wire Circuits and Types of Synchronization

Standards Organizations

An association of organizations, governments, manufacturers and users form the ____ and are responsible for developing, coordinating and maintaining the standards The purpose is that all data communications equipment manufacturers and users comply with these standards.

International Standard Organization (ISO)

the international organization for standardization on a wide range of subjects. It is comprised mainly of members from the standards committee of various governments throughout the world.

International Standard Organization (ISO)

It is even responsible for developing models which provide a high level of system compatibility, quality enhancement, improved productivity, and reduced costs. The ____ is also responsible for endorsing and coordinating the work of the other standards organizations.

International Telecommunications Union Telecommunication Sector (ITU-T)

is one of the four permanent parts of the International Telecommunications Union based in Geneva, Switzerland. It has developed three sets of specifications: the V series for modem interfacing and data transmission over telephone lines, the X series for data transmission over public digital networks, email, and directory services; the I and Q series for Integrated Services Digital Network (ISDN) and its extension Broadband ISDN.

International Telecommunications Union Telecommunication Sector (ITU-T)

Their membership consists of government authorities and representatives from many countries and it is the present standards organization for the United Nations.

Institute of Electrical and Electronics Engineers (IEEE)

____ is an international professional organization founded in United States and is compromised of electronics, computer and communications engineers. It is currently the world’s largest professional society with over 200,000 members.

Institute of Electrical and Electronics Engineers (IEEE)

It develops communication and information processing standards with the underlying goal of advancing theory, creativity, and product quality in any field related to electrical engineering.

American National Standards Institute (ANSI)

____ is the official standards agency for the United States and is the U.S. voting representative for the ISO. ____ is a completely private, nonprofit organization comprised of equipment manufacturers and users of data processing equipment and services. ____ membership is comprised of people form professional societies, industry associations, governmental and regulatory bodies, and consumer goods.

Electronics Industry Association (EIA

___ is a non profit U.S. trade association that establishes and recommends industrial standards ___ activities include standards development, increasing public awareness, and lobbying and it is responsible for developing the RS (recommended standard) series of standards for data and communications.

Telecommunications Industry Association (TIA)

is the leading trade association in the communications and information technology industry It facilitates business development opportunities through market development, trade promotion, trade shows, and standards development. It represents manufacturers of communications and information technology products and also facilitates the convergence of new communications networks.

Internet Architecture Board (IAB)

earlier known as Internet Activities Board is a committee created by ARPA (Advanced Research Projects Agency) so as to analyze the activities of ARPANET whose purpose is to accelerate the advancement of technologies useful for U.S military

Internet Architecture Board (IAB)

is a technical advisory group of the Internet Society and its responsibilities are;

I. Oversees the architecture protocols and procedures used by the Internet

II. Manages the processes used to create Internet Standards and also serves as an appeal board for complaints regarding improper execution of standardization process

III. Responsible for administration of the various Internet assigned numbers

IV. Acts as a representative for Internet Society interest in liaison relationships with other organizations. V. Acts as a source of advice and guidance to the board of trustees and officers of Internet Society concerning various aspects of internet and its technologies.

Internet Engineering Task Force (IETF)

It is a large international community of network designers, operators, vendors and researchers concerned with the evolution of the Internet architecture and smooth operation of the Internet.

Internet Research Task Force (IRTF)

It promotes research of importance to the evolution of the future Internet by creating focused, long term and small research groups working on topics related to Internet protocols, applications, architecture and technology.

The primary standards organizations for data
communication are:

Transmission mode

It means transferring of data between two devices. It is also known as communication mode.

Buses and networks

are designed to allow communication to occur between individual devices that are interconnected.

Simple Mode

Half Duplex Mode

Full Duplex Mode

Three Types of Transmission Mode

Simplex Model

In _____, the communication is unidirectional, as on a one way street. Only one of the two devices on a link can transmit, the other can only receive. The ____ can use the entire capacity of the channel to send data in one direction.

Simplex Mode

What mode of transition: Keyboard and traditional monitors. The keyboard can only introduce input, the monitor can only give the output.

Half Duplex Mode

In _____, each station can both transmit and receive, but not at the same time. When one device is sending, the other can only receive, and vice versa. The ____ is used in cases where there is no need for communication in both direction at the same time. The entire capacity of the channel can be utilized for each direction.

Half Duplex Mode

What mode of transition: Walkie talkie in which message is sent one at a time and messages are sent in both the directions.

Full Duplex Mode

In ____ mode, both stations can transmit and receive simultaneously. The capacity of the channel, however, must be divided between the two directions.

Full Duplex Mode

In ____, signals going in one direction share the capacity of the link with signals going in other direction, this sharing can occur in two ways

\
1\. Either the link must contain two physically separate transmission paths, one for sending and the other for receiving.

\
2\. Or the capacity is divided between signals traveling in both directions. It is used when communication in both directions is required all the time.

Full Duplex Mode

What mode of transition: Telephone Network in which there is communication between two persons by a telephone line, through which both can talk and listen at the same time.

full/full duplex mode

transmission is possible in both directions at the same time but not between the same two stations. It is possible only on multipoint circuits. Postal system can be given as a person can be sending a letter to one address and receive a letter from another address at the same time.

full/full duplex mode

What mode of transition: station 1 transmitting to station 2, while receiving from station 3

Circuit

is the physical path that runs between two or more points. It terminates on a port (that is, a point of electrical or optical interface), and that port can be in a host computer (that is, a switching device used to establish connections), on a multiplexer, or in another device.

Two-Wire Circuits & Four-wire Circuits

Two Types of Circuits

Two Wire Circuits

A _____ circuit has two insulated electrical conductors. One wire is used for transmission of the information. The other wire acts as the return path to complete the electrical circuit. These are circuits are generally deployed in the analog local loop, which is the last mile between the subscriber and the subscriber's first point of access into the network.

Two Wire Circuits

A telephone conversation inherently requires transmission in both directions. When both directions are carried on the same pair of wires, it is called ____

local switching center

The telephones in our homes and offices are connected to a _____ (exchange) by means of two wire circuits.

Two wire operation.

When oppositely directed portions of a single telephone conversation occur over the same electrical transmission channel or path.

hybrid coil

A ____ accomplishes the conversion for both two wire and four wire.

Modern Line Card

it is strictly an analog/digital interface to a system that has a completely digital and integrated signal path internally.

4ESS

Using actual wires to circuit switch a telephone call became obsolete when the crossbar switch (a mechanical system) was replaced by ___ electronic switches in the 1970s by the Bell System in the US.

Two pair and four pair

refer to the number of wires in the internal cabling plan.

Two wire and four wire

have to do with the number of electrical conductors associated with a transmission line.

Four Wire

A ____ circuit has two pairs of conductors. That is, it has two sets of one way transmission paths: one path for each direction and a complementary path to complete the electrical circuit.

Four Wire Circuits

wire circuits are used where there is distance between the termination points which requires that the signal be strengthened periodically.

Four Wire Circuits

A type of circuit that connects the various switches that make up the public switched telephone network (PSTN).

Four Wire Circuits

circuits are also used with leased lines, where a customer may be connecting locations of its own that are separated by distance. Also, all digital circuits are provisioned on this basis.

Four Wire Circuits

is a two-way circuit using two paths so arranged that the respective signals are transmitted in one direction only by one path and in the other direction by the other path.

Four Wire Circuits

gets its name from the fact that is uses four conductors to create two complete electrical circuits, one for each direction. The two separate circuits (channels) allow full duplex operation with low crosstalk.

Four Wire Circuits

was historically used to transport and switch baseband audio signals in the phone company telephone exchange before the advent of digital modulation and the electronic switching system eliminated baseband audio from the telco plant except for the local loop.

a. physical four wire

b. logical four wire

There are two types of four wire circuits:

physical four wire

In ___ you can actually count four wires.

logical four wire

wire, physically there are only two wires, but you derive the four individual paths by splitting the frequency. Half of the frequency band carries the transmit signal, and the other half carries the receive signal.

attenuated signals.

signals that have been losing power as they have traveled across the network, which are called ____.

amplifiers and repeaters

tools to augment signals that have been losing power as they have traveled across the network, which are called ___.

amplifier

An ___ boosts an attenuated signal back up to its original power level so it can continue to make its way across the network.

First generation amplifiers

were unidirectional. They could only amplify a signal moving in one direction, so any time you needed to provision a circuit that was going to be crossing a distance, you had to literally provision two circuits one to amplify the information in the transmit direction and a second to amplify the information in the receive direction.

local loop

is a two wire circuit for one reason only: to save copper. Using half the number of copper wire conductors per circuit means that the infrastructure cost for wiring each circuit is halved. Although a lower quality circuit, it allows full duplex operation by using a telephone hybrid to keep near and far voice levels equivalent.

Synchronization

means that the receiver must be able to determine, when to expect a new transmission and when to send acknowledgements. In other words transmitter and receiver should have an agreement on the nature as well as timing of the signals.

Synchronization

in the context of .NET, is a process that involves coordinating the execution of multiple threads to ensure a desired outcome without corrupting the shared data and preventing any occurrence of deadlocks and race conditions.

Synchronization

also occurs between network nodes to ensure that data streams are received and transmitted correctly, and to prevent data collision. It usually uses a clock signal transmitted in sequence with a data stream to maintain proper signal timing.

To synchronize

is to coordinate or time events so they happen all at the same time.

Timing

refers to the method used by the data communication system so that the destination station recognizes the start of a data stream and reliably reads the information sent.

1. Asynchronous Transmission
2. Synchronous Transmission.

Two major timing schemes are used:

Asynchronous communications or transmission

sends data from the source to the destination without synchronizing the two clock systems. The source and destination clocks are free running and not locked to each other. Short characters of 7 to 8 bit data are sent one at a time framed by a start bit and 1 or 2 stop bits.

Asynchronous communications

is used for low data transfer rates usually 128 kbps or less and short bursts of data. Faster data rates and longer data lengths cause the data errors at the receiver.

Conventional representation

has asynchronous data flowing left to right and synchronous data flowing right to left.

Stop bits

The purpose of the ____ is to indicate the end of data. There could be 1 or 2 stop bits with 1 being the typical number of stop bits used today.

Asynchronous transmission

the characters are sent individually with a quiet period in between (quiet meaning 0 bit level). It requires the transmitting station and the receiving station to have individual internal free running clocks operating at the same frequency.

Free running

means that the clocks are not locked together.

\

Start bit

The receive station starts checking for data after the ____ is received (It is a wakeup call).

Synchronous transmission

it is a method of data communication that requires the source and destination to synchronize their clocks together.

1. Externally clocked synchronous transmission
2. Internally encoded synchronous transmission

There are two types of synchronous data transmission:

Asynchronous Transmission

there are 3 to 4 bits of overhead (start, stop, parity bits) sent with each character of data (7 to 8 bits). The start and stop bits were used to identify the beginning and end of transmission.

\

Synchronous transmission

blocks of data up to 64Kbytes in size can be sent without loss or corruption of data. A start field and end field indicate the beginning and end of transmission. Smaller overhead results in a more efficient delivery of data.

Externally clocked synchronous transmission

has separate lines from the data lines for synchronizing the clock. For example. in addition to the normal handshaking control lines, the V.35 physical layer standard has two pairs of wires used for synchronizing the source and destination clocks.

Transmit, Receive

The ____ Timing balanced pair is used to send out a timing clock to the destination, the _____ Timing balanced pair is a separate clock timing received from the destination.

99\.9%

how many percent does the time the transmit and receive data rates are the same.

Fields

Special sequence of bits called ___ are required at the beginning and end of the block of data to inform the destination that new data is arriving.

Start Field, End Fields

Synchronous Transmission sends blocks of characters at a time. Each block of data is preceded by a ____ which is used to tell the receiving station that a new packet of characters is arriving. The blocks of data also have ___ to indicate the end of the data block.

4 bytes

Synchronous transmission is more efficient than asynchronous (character transmission) as little as only ____ (2 Start Framing Bytes and 2 Stop Framing bytes) are required to transmit up to 8K bytes.

Overhead

Extra bytes, like the Start and Stop Frame, that are not part of the data are called ____. It consists of control information used to control the communication.

Efficiency

Generic Packet X

is used as an introduction to Synchronous Data Transmission.

Different frame types

(Ethernet, Token Ring, SDLC, HDLC, Frame Relay, ATM, Cell Relay, etc...)

Basic Frame Structure

Preamble

Starting Delimiter/Alert Burst/Start of Header. At the beginning of each frame (packet), there will be a sequence of bytes (8 bit words), called the _____

Preamble

It informs the receiving station that a new packet is arriving Synchronize the receive clock with the transmitted clock The ___ is a series of bytes with a specific bit pattern that is used only by the Preamble.

Names used by other protocols for the Preamble are:

Starting Delimiter, Alert Burst and Start of Header.

Address Field(s):
Source and/or Destination

The ___ consists of a Source Address and/or a Destination Address. The Source and Destination Addresses are hexadecimal numbers that identify the sender Source and receiver Destination. The Network Addresses reside in either the Network Interface Card's firmware or can be either assigned during the initialization of the NIC. The purpose of the Source Address is to identify to the network who is sending data. The purpose of the Destination Address is to identify to the network who should be receiving the data. Under some protocols, there may not be both Source and Destination Addresses. Only one address may be present.

Control Field

The ____ is used to indicate the Type of Information being sent as Data. The Type of Information can be Control information used when establishing a connection (handshaking) or it can be Data such as file transfers between clients and servers. Its purpose is to identify what the purpose of the packet or frame is: Control or Data. It can also be used to indicate the size of the packet and Data.

Data/Message Field

The ____ or Message is the actual information that is being transmitted. The Control Field would indicate the Data Field size. The ___ is also called the Info field by some protocols.

Optional Pad The Data

The ____ is used to pad the data field when the protocol has a fixed Data Field size. If the Data Field size is fixed at 1200 bytes and only 300 bytes of information is available then the Pad will fill in the remaining 900 bytes with characters (e.g. 900 bytes of 00h). The protocol may also use the Pad to ensure a minimum Data field size.

CRC/ Frame Check Sequence

The ____ contains an error checking number that the Destination can use to verify that the packet is okay and error free.

End Frame Delimiter

is a series of bytes that have a specific bit pattern that identifies the end of the packet to the Destination. Not all protocols have these fields, protocols with fixed packet size may not need the field as the Destination may simply count the number of bytes it has received.

Comparison between asynchronous and synchronous data transmission:

1. Data synchronization
2. Process synchronization:

Types of Synchronization

Lock, mutex , and semaphores

Examples of process synchronization

Locks

are one synchronization technique. A___ is an abstraction that allows at most one thread to own it at a time. If a thread tries to acquire a lock currently owned by another thread, it blocks until the other thread releases the lock.

Semaphore

is typically an integer variable, it allows multiple program threads to access the finite instance of resources.

mutex

is an object. It allows multiple program threads to access a single shared resource but one at a time.