ICT 390 {quiz 2}

What are the Rules of communication?

• Simplex: Communication take One direction only

• Half-duplex: Communication can take place in either direction but only one at a time

• Full-duplex: Communication in Both direction and simulationally

Message Sequence Vs. Byte System Orinted:

Message orientated: Message Boundaries are preserved. Two messages each sent as same file size (e.g: 2KB. they will be received as the same file size (e.g: 2KB)

Bye system: Stream of bytes; No message boundaries are preserved

On Internet: TCP-Bytes- stream oriented

Connectionless vs. Connection-orientated

• Connection  Orientated:  eg. Modeled after the telephone

  system

1. Set up Connection

2. Use connection

3. Tear down connection

Connectionless: eg. Modeled after the postal system

• Each packet carries destination address

⇒Determines how to route it to destination

Unreliable connectionless

⇒Datagram service

What is interoperablity?

Different Networks, technologies, protocol TCP can handle anything behind the scene

Standards: what is ISO, and the two IAB

ISO: Organization for International Standards:

  ⇒ USA represented as ANSI

Internet Standards:

• 1980: Internet Activities Board (IAB)

• 1986: Internet Architecture Board (IAB)

What are the two task forces under IAB, and what are their main responsibilities?

What does IAB stand for

IAB
IETF: Internet Engineering Task Force	IRTF: Internet Research Task force
Focuses on Short term issues	Focuses on long term engineering research issue
Congestion ControlSecurity Web and internet Transparent	Research groups: network management Internet congestion Measurement & Analysis Quantum Internet Thiy to Thiy, Crypto Forum

IAB stands for: Internet Architecture Board

Steps to develop Internet Standard:

1. Describe idea in a technical report

⇒Request for Comment (RFC)

2. report is distributed

3. If it generates sufficient interest

⇒Draft the standard

4. Working implementation at 2 sites working for ~4 months

5. If IAB is Convinced: Internet Standard

2 reason for Standards:

• Large scale production reducing cost

• reduce chaos

How are networks organized?

Networks are organized as a series of layers or levels. Each layer provides Services to the upper layer, but the implementation details at the lower layer are not visible to the upper layer

What is a interface?

• Interface: Set of Primitives the lower layer offers to the upper layer . We want a clean Interface

⇒ A collection of well-understood functions

What is a protocol and what does it define?

• Protocol:  is an agreement between communication on how  communication must proceed

  • Protocol Defines

    • 1. The format of message that will be exchanged

    • 2. Defines set of actions to be taken upon the receipt of the message

What is a Protocol Stack?

Protocol stack: A set of protocols, one protocol layer per layer

What is a Network Architecture?

Network Architecture: A set of protocols  and services

What is a Layering Principle?

• Layering principle: whatever transformation @ Layer N at sender has done, it will be reversed at layer N at receiver side

  • E.g: Transformation T at sender, receiver will perform T^-1

  • changing the implementation of a service is different from changing the service itself

What are the two benefits and draw backs of Layering? Describe two for benefits and one for drawbacks.

Benefits: Know 2	Drawbacks: Know 1
Each layer can be designed, implemented and tested independent of each other	May have a duplicate functions in layer
changes in one layer does not propagate to another layer	2) Increase in delay
Enables a specific component of a complex system to be described with ease
Layers can implement a specific function ⇒enables a modular design
Layering is a powerful concept: it simplifies protocol design and testing

What is the OSI refrence model?
Who developed it?
How many layers are there?
Why was it developed?

OSI Reference Model: Open system Interconnection
ISO Developed it
7 Layer model
Developed with a view to standardized communication protocol

What are the principle Used to arrive at 7 layer mode: {list 2}

1. each layer is created when a different level of abstraction is needed

2. each layer should perform a well-defined function

3. layer boundaries should be chosen with a view to limit information flow across layers

4. Layers should be chosen with an eye toward standardization of protocol

Is the OSI model a Network Architecure?

Not a Network Architecture, it does not specify the exact services and protocol

What are the seven layers of the OSI model, and what is the Protocol Data Unit (PDU) associated with each layer?

What is the difference between packets and frames?

7. Application Layer	APDU: Application protocol Data Unit
6. Presentation Layer	PPDU: Presentation protocol Data Unit
5. Session Layer	SPDU: Session protocol Data unit
4. Transportation Layer	TPDU
3. Network Layer	Packet
2. Data Link	Frame
1. Physical Layer	Bits
Packets: Independent of underlying networking technology	Frame: Dependent on networking technology

In the OSI model what is a packet and Frame? which one is independent and which one is dependent?

Packet: Encapsulated in fame; Independent
Frame: Specific to Networking technology

What is the physical layer?

1. Deals with the transmission of unstructured bit stream

2. It deals with mechanical, electrical, procedural, characteristic to access physical medium

What is the Data Link layer responsible for?

• Data Link: Have message Boundaries

  • Provide reliable transfers of information across physical link

    • sends block of data with the necessary synchronization error-control  and Flow control information

  • Flow control: technique that prevents a fast sender from overrunning a slow receiver

    • between a pair of hosts.

  • conjection control: Deals with the overall network (global)

    • Implement this by implementing flow control between hosts

What is the network layer responsible for?

• Network Layer: Responsible for establishing and maintaining connections

  • Determines how packets are routed from source to destination

What is the transport layer responsible for?

• Transport Layer: Provides reliable transparent transfer of data between end-prints. It also provides error control and flow control

What is the session Layer responsible for?

• Session Layer: establishes and Maintain session

1. Manages dialogue control. keeps track of whose turn it is

2. Token management - only the side holding the token can perform critical operations

3. perform synchronization, insert checkpoints in the data stream.

What is the presentation layer responsible for?

• Presentation: Functions requested frequently enough ⇒ warrant a solution

  • Deals with the syntax and semantics of information

how are information stored in memory? List two example of each architectures

Big endian: stores by most significant byte first	ex: Motorola 6800 series, Ibm power
Little endian: Least significant byte first	ex. Intel, macOS

TCP/IP reference Model:
What does TCP stand for?
what does IP stand for?
list an example of what uses TCP/IP reference model.
what is the goal?

• TCP: Transmission Control Protocol

• IP:  Internet Protocol

• GOAL: connect any pair of host (regardless of their hardware differences) to communicate with each other

How many layers does the TCP/IP reference model have?
what are each of the layer?

• 4 layered model

---

Application

Transport

Internet

Host to network: data link and Physical

What is the Internet Layers?

• Internet layer: holds the architecture together ⇒ defines official packet format which is the Internet protocol (IP) format

  ⇒ routes packets to their destination, performs routing of packets

how does TCP ensure reliable data delivery?

TCP: A reliable, connection-oriented protocol that allows a byte-stream to be delivered without error to its destination. It implement flow control

Is tcp refrence model a network architecture?

 It is a network architecture because it defines the exact protocol and Services

What led to the failure of the OSI reference model:

1. bad timing

2. bad implementation

3. bad politics

4. bad technology

How is data transmitted through a communication medium, and why is copper commonly used for wired transmission

• All forms of data communication involve encoding energy in some form 

⇒ transmit energy across some medium

• wired transmission - use a good conductor of electricity 

• ⇒ copper (also cheap)

What is used to carry data in wired and wireless transmission

• Electric current → carry data through wires

• wireless transmission → carry data through the air

What is a twisted-pair cable, and what are the two main reasons its wires are twisted together?

• Twisted pair: Each copper wire is covered with an insulation materials (plastic) and a pair of such wires twisted together

• reasons for twist:

1. Limits the amount of electromagnetic energy emitted by the wire

2. They protect the wire from electromagnetic energy emitted by other sources

What changes as the category (Cat) of twisted-pair cables increases?

• As the number of cat increases: (cat 5 → cat6 →cat 7….)

1. Uses better insulating material ⇒ teflon

2. More twist

3. Longer distant

4. higher speed

What are the two types of coaxial cables, and what are they used for?
How does the shielding in a coaxial cable reduce electromagnetic interference?
What do UTP and STP stand for?

Coaxial cable

• 2 Versions

  • 75 ohm = broadband cable (home)

  • 50 ohm = Baseband (lan)

• Inner wire surround by heavy material

  • limits amount of electromagnetic energy emitted by inner wire

  • protects em energy from other sources

• UTP: Unshielded Twisted Pair

• STP: Shielded Twisted Pair

What is optical fiber, and how does it transmit data?
What are the three main components of an optical transmission system?
What are the advantages and disadvantages of using optical fiber for data transmission?

• Allow the use of flexible glass fibers to carry data

  • known as optical fiber

  • uses light to transport data

• Miniature glass enclosed in a plastic jacket

• Optical transmission system has 3 components: know all 3

1. Transmitter at one end of the fiber transmits pulses of light

2. transmission medium

3. Receiver ⇒ uses light sensitive transistor to receive pulse of light

• benefits: Fast, more stable, high speed, not subjective to interference

• drawbacks: Have to replace whole fiber line if it breaks, too expensive to repair broken fiber, hard to locate when it broke

LED (Light emitting diode) vs. Laser

LED	LASER
Short distance	longer distance
Cheaper	more expensive
Lower bandwidth	Higher bandwidth
light beam wider	Light beam narrow