DCN - Lessons 1-3

ARPANET Meaning

Advanced Research Projects Agency Network

UCLA - SRI

ARPANET Purpose

ARPANET

was the first public packet-switched computer network. It was first used in 1969 and finally decommissioned in 1989. Its main use was for academic and research purposes.

Internet

is a global network of linked/interconnected computer networks that allows users to share information and communicate

Interconnected Networks, Network of networks, global network

Other terms of Internet

Intranet

is a private network within organization. The network is only accessible to its employees or members. Creates connections inside an organization.

Extranet

is an intranet that provides secured access to the authorized users outside the organization. Creates connections beyond an organization.

Local Area Network (LAN)

connects computers and devices within a limited area like home, office, or school

Personal Area Network (PAN)

is a network that connects a person's personal devices. It is mostly centered around a person

Metropolitan Area Network (MAN)

is a network that covers a larger geographic area than a LAN. This spans a city or a region.

Wide Area Network (WAN)

is a network that connects devices or smaller networks over large geographic distances. This may even span countries.

End Devices, Intermediary Network Devices, Cables and Connectors

Network Components

End Devices

are the devices that users interact with directly, such as computers, smartphones, and printers.

Network Interface Card (NIC)

is a piece of hardware that allows a computer to connect to a network.

Media Access Control address

The NIC contains the ____ of the device.

Intermediary Network Devices

These devices facilitate the flow of data between end devices.

Hub

is an old-fashioned device that connects multiple devices in a network.

Packet Sniffing

Hub Security Concern: is the practice of gathering, collecting, and logging some or all packets that pass through a computer network (ex.: Wireshark)

Man-in-the Middle

Hub Security Concern: Performing a man-in-the-middle (MITM) attack on a hub-based network involves intercepting and manipulating data packets as they pass through the network (ex.: Ettercap)

Switch

connects multiple devices and sends data directly to the intended recipient based on its unique address (called the MAC address)

Modem

connects a home network to the internet.

Router

It allows multiple devices to access the internet and sends data between networks based on their IP addresses

Wireless Access Point

extends the wireless network so that devices can connect even from a distance

Patch Panel

is used by companies to organize and connect ethernet cables

Cables and Connectors

are physical components that are used to connect devices in a network.

Coaxial

This is a type of cable that is commonly used for cable television and cable internet connections. Has foil shield, braided shield, outer jacket.

Twisted Pair

This is a type of cable that is commonly used for Ethernet connections.

Ethernet Extender

is used to extend ethernet cable beyond the maximum length allowed

Fiber optic cables

use pulses of light to transmit data

Simplex

one device can only send information to another device. It cannot receive the information back

Half Duplex

a device can both send and receive information, but not at the same time.

Full Duplex

devices can send and receive information at the same time.

Physical Topology

refers to the actual arrangement of devices

Logical Topology

refers to the logical connections and data flow patterns.

Bus

all devices connect to a single main cable, or backbone

Star

a central device (like a hub or switch) connects to all other devices.

Ring

each device connects to two others, forming a closed loop.

Mesh

every device connects to all others with multiple cables

Hybrid

combines different topologies, such as star, bus, ring, and mesh, to create a custom network solution

Interface Message Processor (IMP)

early predecessors of modern routers

was the packet switching node used to interconnect participant networks to the ARPANET from the late 1960s to 1989.

Network Control Protocol (NCP)

is a protocol that enables low-cost networking in home environments through peer-to-peer communication and a multi-master system.

the language used in communication on the early years of ARPANET

was initially used to manage and control the transmission of data between computers on the ARPANET

Lack of flexibility

point to point communications (NCP Limitations)

Scalability Issues

unable to accomodate the growing number of post networks on ARPANET (NCP Limitations)

Inefficient Error Handling

NCP’s error recovery mechanisms were limited (NCP Limitations)

Limited Addressing

NCP has restrictions in addressing, hindered the ability to route packets effectively across different networks (NCP Limitations)

Vint Cerf and Bob Kahn

Who developed the design and development of TCP/IP?

Transmission Control Protocol/Internet Protocol

TCP/IP Meaning

TCP/IP

provides a common set of protocols that could be used by all computers on the internet

protocol used by computer networks, consists of the rules that computers must follow

solved the limitations of NCP, became the foundation of the internet til today

Open Systems Interconnections (OSI)

Blueprint of how networks should work by dividing/breaks down communication process into different layers

framework of how communication should take place for each layer (7)

Application Presentation Session Transport

Upper layer of OSI (handles software applications and how they can communicate)

Network Data Link Physical

Lower layers of OSI (manages the data transmission across the network)

Physical Layer

transmitting data over the physical medium (cables, NIC, hubs) (physical media, topology, data encoding)

Data Link Layer

providing reliable data transmission between devices on the LAN (includes error detection) (switches and bridges) (physical addressing, ethernet, and Error Detection and Correction)

Network Layer

Determines the best path for data to

travel to the right network destination (ex.: routers)

Logical Addressing

Packet Fragmentation and

Reassembly

Routing

Packet Forwarding

Transport Layer

Provides reliable end-to-end

data transmission between

applications on different

devices.

End-to-End Communication

Protocols: Transmission

Control Protocol and User

Datagram Protocol

Flow Control

Session Layer

Establishes, maintains, and ends communication between applications on different devices.

exchanges data in a structured way and provides synchronization and recovery mechanism

Presentation Layer

Handles data representation, encryption

and decryption, and compression.

converts data from one format to another

Application Layer

Provides services to applications and defines protocols for communication between them.

• Hypertext Transfer Protocol (HTTP)

• File Transfer Protocol (FTP)

• Simple Mail Transfer Protocol (SMTP)

Encapsulation

when you send data from one device to another over a network, the data goes through this process

is the process of adding headers and trailers (or both) to data as it moves through the layers of a network protocol stack, like the OSI model, to ensure proper routing and transmission.

is the process of wrapping data with protocol information at each layer of the OSI model, allowing for proper data transmission between network devices.

Decapsulation

unwrapping the data

is the process of removing headers and trailers from data as it moves up through the layers of a network protocol stack, allowing the original data to be accessed and understood by the receiving device.

Packet Fragmentation

is the process of breaking down packets into smaller pieces to fit into a network's maximum transmission unit (MTU), allowing for efficient data transmission over the network.

speed(UDP) and accuracy/reliability(TCP)

difference of TCP - Transmission Control Protocol and UDP - User Datagram Protocol (apps like gaming)

Digital to digital conversion

is the process of taking digital data and converting it into a digital signal that can be transmitted over a communication channel

Unipolar encoding

uses only high voltage to represent 1 and no or zero voltage to represent 0.

Polar Encoding

here, two voltage levels are used: One positive, and another is negative.

NRZ: NRZ-L & NRZ-I

_____ represents signal in either positive or negative. Two common methods are used: ____ & ____

NRZ-L

bit 1 is represented by a negative or low voltage while bit 0 is represented by

positive or high voltage.

NRZ-I

for every bit 1, there will be an inversion or change in voltage level either positive or negative. While for bit 0, no change in voltage level occurs.

Return Zero Encoding

have three values: positive, negative, and zero. Bit 1 is represented by positive ; bit 0 is represented by negative; and zero level has no representation. For every half duration the signal returns to zero level

Biphase encoding

changes the signal at the middle of the bit interval but does not return to zero.

Biphase: Manchester

for every half duration, there is transition voltage level from positive to

negative or negative to positive.

Bit 1 is represented by negative to positive transition

Bit 0 is represented by positive to negative transition

Biphase: Differential Manchester

for every half duration, there is transition voltage level from

positive to negative or negative to positive.

Bit 1 is represented by a transition in the half-duration only.

Bit 0 is represented by a transition in the first duration and transition in the half-duration

Bipolar encoding

represents three voltage levels: positive, negative and zero.

Alternate Mark Inversion (AMI)

0 is represented by zero voltage level. While 1 bit is represented by alternating positive and negative voltages.

Bipolar 8-Zero Substitution (B8ZS)

It provides a synchronization when there is 8 bits of zero or more. When 8 bits of zero occurs, it implements some changes in 0s string pattern based on the polarity of the previous 1 bit.

High-Density Bipolar 3 (HDB3)

It provides synchronization when there is 4 bits of zero. When 4 bits of zero occurs, it will look for the number of 1s bits that occurred since the last substitution. If the number of 1s bit is odd, then it will execute 000V. if the number of 1s bit is even, then it will execute B00V.

Pulse Code Modulation (PCM)

is a method used to convert analog to digital signals.

Sampling

is used to find the number of samples that represents continuous wave form completely.

Hertz

is used to measure the sample rate per second

Quantizing

involves assigning a numerical value to each sample.

bit depth

Quantizing use _: the number of bits in each sample.

Encoding

involves converting the values into a digital signal that can be transmitted over a communication channel

Transmission Media

is the physical medium used to transmit data from one point to another.

Total Internal Reflection

Fiber Optics has two parts: The core and the cladding. These two parts work together to create a phenomenon called

Single-mode Fiber

Used for long-distance transmissions

guided media

In ___, data is transmitted through the air or space.

Radio waves

are electromagnetic waves that transmit signals at all directions.

Terrestrial Microwave Transmission

is unidirectional. Data is transmitted

from one station to another.

Infrared Transmission

is a wireless technology used for short range communications. It cannot penetrate the walls.

Multiplexing

is a technique used to combine and send the multiple signals over a single medium.

Time Division Multiplexing

is a method that divides time into equal slots and assigns them to each device or user to transmit their data.

Synchronous Time Division Multiplexing

gives fixed time slots to each device.

Asynchronous Time Division Multiplexing

adjusts the slots according to the priority and need of each device.

Frequency Division Multiplexing

the available frequency band is divided into multiple sub-channels, each of which is assigned to a different signal or communication stream.

Wavelength Division Multiplexing

is a fiber-optic transmission technique that enables the use of multiple light wavelengths (or colors) to send data over the same medium.