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Midterm

ITM 301 Study Guide - Midterm Guide: Simple Mail Transfer Protocol, Optical Fiber Cable, Statistical Time-Division Multiplexing


Department
Information Technology Management
Course Code
ITM 301
Professor
Franklyn Prescod
Study Guide
Midterm

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Page 1 of 31
Chapter 1
Server (Host Computer) stores data or software that can be accessed by the clients
Client the input-output hardware device at the user’s end of a communication circuit
Circuit the pathway through which the messages travel
Telecommunications - Transmission of voice, video, and/or data
Data Communications - Movement of computer information by means of electrical or optical
transmission systems
Local Area Networks (LAN) - room, building
a group of PCs that share a circuit.
Backbone Networks (BN) - less than few kms
a high speed backbone linking together organizational LANs at various locations.
Metropolitan Area Networks (MAN) - (more than a few kms)
connects LANs and BNs across different locations
Often uses leased lines or other services used to transmit data.
Wide Area Networks (WANs) - (far greater than 10 kms)
Same as MAN except wider scale
Intranet
A LAN that uses the Internet technologies within an organization
Open only those inside the organization
Example: insurance related information provided to employees over an intranet
Extranet
A LAN that uses the Internet technologies across an organization including some
external constituents
Open only those invited users outside the organization
Accessible through the Internet
Example: Suppliers and customers accessing inventory information in a company over
an extranet

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Page 2 of 31
2 Important Multi-layer network models
Open Systems Interconnection Model
Created by International Standards Organization (ISO) as a framework for computer
network standards in 1984
Based on 7 layers
1. Application Layer - set of utilities used by application programs
2. Presentation Layer - formats data for presentation to the user
provides data interfaces, data compression and translation between different data
formats
3. Session Layer - initiates, maintains and terminates each logical session between sender and
receiver
4. Transport Layer - deals with end-to-end issues such as segmenting the message for network
transport, and maintaining the logical connections between sender and receiver
5. Network Layer - responsible for making routing decisions
6. Data Link Layer - deals with message delineation, error control and network medium access
control
7. Physical Layer - defines how individual bits are formatted to be transmitted through the
network
Internet Model
Created by DARPA originally in early 70’s
Developed to solve to the problem of internetworking
Layers allow simplicity of networking in some ways
Easy to develop new software that fits each layer
Relatively simple to change the software at any level
Matching layers communicate between different computers and computer platforms
Accomplished by standards that we all agree on
e.g., Physical layer at the sending computer must match up with the same layer in the
receiving computer
Somewhat inefficient
Involves many software packages and packets
Packet overhead (slower transmission, processing time)
Interoperability (ability to exchange and use information) achieved at the expense of
perfectly streamlined communication
Based on 5 layers - Based on Transmission Control Protocol/ Internet Protocol (TCP/IP) suite
1. Application Layer - used by application program
2. Transport Layer - responsible for establishing end-to-end connections, translates domain names
into numeric addresses and segments messages
3. Network Layer - responsible for making routing decisions (Chooses computer) and find address
of that computer
4. Data Link Layer responsible for moving a message from one computer to the next computer in
the network path from the sender to the receiver. Performs 3 functions:
Controls the physical layer by deciding when to transmit messages over the media
Formats messages by indicating where they start and end
Detects and corrects errors that have occurred during transmission
5. Physical Layer physical connection between the sender and receiver (Hardware, circuits)

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Page 3 of 31
Protocols - Sets of standardized rules to define how to communicate at each layer and how to interface
with adjacent layers
Used by Network model layers
Standards (Importance) - Provide a “fixed” way for hardware and/or software systems (different
companies) to communicate
Help promote competition and decrease the price
Types of Standards
Formal standards
o Developed by an industry or government standards-making body
De-facto standards
o Emerge in the marketplace and widely used
o Lack official backing by a standards-making body
Standardization Process
o Specification - Developing the nomenclature and identifying the problems to be
addressed
o Identification of choices - Identifying solutions to the problems and choose the
“optimum” solution
o Acceptance - Defining the solution, getting it recognized by industry so that a uniform
solution is accepted
Major Standard Bodies
o ISO (International Organization for Standardization)
Technical recommendations for data communication interfaces
Composed of each country’s national standards orgs.
Based in Geneva, Switzerland (www.iso.ch)
o ITU-T (International Telecommunications Union Telecom Group
Technical recommendations about telephone, telegraph and data
communications interfaces
Composed of representatives from each country in UN
Based in Geneva, Switzerland (www.itu.int)
o ANSI (American National Standards Institute)
Coordinating organization for US (not a standards- making body)
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