week 1

8P8C

A common connector or plug used on the end of the network cable. Also known as RJ-45.

Internet Service Provider (ISP)

A company that connects computers to the internet for a fee. Abbreviated to ISP.

Server

A computer that awaits and responds to requests for data.

Client

A computer that requests data stored on a server.

bit

A contraction of "Binary Digit". A bit is the single unit of information in a computer, typically represented as a 0 or 1.

data packet

A data packet is an all-encompassing term that represents any single set of binary data being sent across a network link.

Open Systems Interconnection model (OSI model)

A description of all communication on a network expressed as seven layers.

multicast frame

A frame intended for a preselected number of computers, such as a specific workgroup. that it will be accepted or discarded by each device depending on criteria aside from their own hardware MAC address. Network interfaces can be configured to accept lists of configured multicast addresses for these sort of communication.

unicast frame (transmission)

A method for data transfer from a source address to a destination address. If the least significant bit in the first octet of a destination address is set to zero, it means that Ethernet frame is intended for only the destination address

Address Resolution Protocol (ARP)

A protocol in the TCP/IP suite used with the command-line utility of the same name to determine the MAC address that corresponds to a particular IP address.

Frame Check Sequence (FCS)

A sequence of bits placed in a frame that is used to check the primary data for errors. a 4-byte (32-bit) long number that represents the checksum value for the entire frame

broadcast frame

An Ethernet frame sent to destination address FFFF.FFFF.FFFF, meaning that the frame should be delivered to all hosts on that LAN.

User Datagram Protocol (UDP)

An alternative to TCP that achieves higher transmission speeds at the cost of reliability is an alternative communications protocol to Transmission Control Protocol (TCP) used primarily for establishing low-latency and loss-tolerating connections between applications on the internet.

VLAN tag

Any frame with a ___ will only be delivered out of a switch interface configured to relay that specific tag.

Half Duplex

Communication between two devices whereby transmission takes place in only one direction at a time.

Full Duplex

Communication that happens in two directions at the same time.

Local Area Network (LAN)

Connects a group of computers in close proximity, such as in an office building, school, or home

Application Layer

The seventh layer of the OSI model. This layer's protocols enable software programs to negotiate formatting, procedural, security, synchronization, and other requirements with the network.

Protocol

a defined set of standards that computers must follow in order to communicate properly.

Simplex Communication

-communication that occurs in one direction only -Examples: radio, TV, baby monitors, garage door opener, pager, etc

OSI Model Layers

7. Application 6. Presentation 5. Session 4. Transport 3. Network 2. Data Link 1. Physical

SFD (start-of-frame delimiter)

A 1-byte field that indicates where the data field begins in an Ethernet frame.

hexadecimal

A base-16 number system that uses sixteen distinct symbols 0-9 and A-F to represent numbers from 0 to 15.

twisted-pair cable

Cables made of copper wires that are twisted around each other and are surrounded by a plastic jacket (such as traditional home phone wire). eight pairs

Copper cables

Cat5 cat5e Cat6 (category)

RJ45

Ethernet connector, RJ stands for "registered jack"

Ethernet Broadcast Address

FF-FF-FF-FF-FF-FF (all nodes receive the package)

EtherType Field

It's 16 bits long and used to describe the protocol of the contents of the frame

Virtual LAN (VLAN)

It's a technique that lets you have multiple logical LANs operating on the same physical equipment

Border Gateway Protocol (BGP)

Routers share data between each other via this protocol, which lets them learn about the most optimal paths to forward traffic A core routing protocol that bases routing decisions on the network path and rules.

Duplex Communication

The concept that information can flow in both directions across the cable.

Preamble

The first part of an Ethernet frame. It is 8 bytes or 64 bits long and can itself be split into two sections. The first seven bytes are a series of alternating ones and zeros. These act partially as a buffer between frames and can also be used by the network interfaces to synchronize internal clocks they use, to regulate the speed at which they send data. This last byte in the preamble is known as the SFD or start frame delimiter.

OUI (Organizationally Unique Identifier)

The first three bytes of a MAC address that uniquely identify a network device manufacturer. These are assigned to individual hardware manufacturers by the IEEE or the Institute of Electrical and Electronics Engineers.

Transport Layer

The layer sorts out which client and server programs are supposed to get that data. The fourth layer of the OSI model. In this layer protocols ensure that data are transferred from point A to point B reliably and without errors. this layer services include flow control, acknowledgment, error correction, segmentation, reassembly, and sequencing.

physical layer

The lowest, or first, layer of the OSI model. Protocols in the Physical layer generate and detect signals so as to transmit and receive data over a network medium. These protocols also set the data transmission rate and monitor data error rates, but do not provide error correction. It represents the physical devices that interconnect computers. This includes the specifications for the networking cables and the connectors that join devices together along with specifications describing how signals are sent over these connections.

Data Link Layer

The network interface/the network access layer the layer is responsible for defining a common way of interpreting physical layer's signals, so network devices can communicate The second layer in the OSI model. The Data Link layer bridges the networking media with the Network layer. Its primary function is to divide the data it receives from the Network layer into frames that can then be transmitted by the Physical layer.

Internet Protocol (IP)

The network protocol that deals with the routing of packets through interconnected networks to the final destination

checksum value

This is calculated by performing what's known as a cyclical redundancy check against the frame. This number is calculated by added all the bytes in a file. If this number changes, it will cause an antivirus program to be alerted that the file has changed in size.

Patch Panel

a device containing many net ports but it does no other work. It's just a container for the endpoints of many runs of cable. Additional cables are then generally ran from a patch panel to switches or routers to provide network access to the computers at the other end of those links.

Fiber cable

a glass tube and allows photons of light to be shot through cable. The fastest form of wired cabling

Modulation

a way of varying the voltage of this charge moving across the cable modulation is the process of varying one or more properties of a periodic waveform

Octet

any number that can be represented by 8 bits восьмибитовый байт

TCP/IP Model

application, transport, internet, data link, physical

Payload

in networking terms is the actual data being transported, which is everything that isn't a header. The data ____ of a traditional Ethernet frame can be anywhere from 46 to 1500 bytes long. This contains all of the data from higher layers such as the IP, transport and application layers that's actually being transmitted

Router

is a device that knows how to forward data between independent networks. A device that transfers data from one network to another in an intelligent way

Ethernet frame

is a highly structured collection of information presented in a specific order.

Collision Domain

is a network segment where only one device can communicate at a time. If multiple systems try sending data at the same time, the electrical pulses sent across the cable can interfere with each other. This causes these systems to have to wait for a quiet period before they try sending their data again. On an Ethernet network, a(n) ____ is the portion of a network in which collisions occur if two nodes transmit data at the same time.

Hub

is a physical layer device that allows for connections from many computers at once. A device that uses its ports to connect devices (computers, printers, etc.) together Physical layer device

Transmission Control Protocol (TCP)

is a standard protocol that defines how to establish and maintain a network conversation via which application programs can exchange data provides reliable, ordered, and error-checked delivery of a stream of packets on the internet. TCP is tightly linked with IP and usually seen as TCP/IP in writing.

Cyclical Redundancy Check (CRC)

is an important concept for data integrity and is used all over computing, not just network transmissions. A CRC is basically a mathematical transformation that uses polynomial division to create a number that represents a larger set of data. Anytime you perform a CRC against a set of data, you should end up with the same checksum number. error checking method in which The message is treated as one long binary number. That number is divided by some preset number. The remainder is appended to the message as the error-checking hash code.

switch

it can actually inspect the contents of the Ethernet protocol data being sent around the network, determine which system the data is intended for and then only send that data to that one system. A computer networking device that connects network segments Data link layer device

Media Access Control (MAC) address

it is a globally unique identifier attached to an individual network interface. It's a 48-bit number normally represented by six groupings of two hexadecimal numbers. A unique identifier assigned to network adapters by the manufacturer. This address is six octets in length and is written in hexadecimal.

Ethernet

its standards also define a protocol responsible for getting data to nodes on the same network or link.

Destination MAC address

the hardware address of the intended recipient. Ethernet frame

Source MAC Address

the hardware address of the source in ethernet frame

Line Coding

the process of converting digital data to digital signals. It allows devices on either end of a link to understand that an electrical charge in a certain state is a zero, and in another state is a one. Through this seemingly simple techniques, modern networks are capable of moving 10 billion ones and zeros across a single network cable every second.

Network layer

this layer allows different networks to communicate with each other through devices known as routers. A collection of networks connected together through routers is an internetwork, the most famous of these being the Internet The third layer in the OSI model. Protocols in the Network layer translate network addresses into their physical counterparts and decide how to route data from the sender to the receiver.

computer networking

to the full scope of how computers communicate with each other.

CSMA/CD

used to determine when the communications channels are clear and when the device is free to transmit data. Short for carrier sense multiple access with collision detection. It is the method for multiple hosts to communicate on a Ethernet.

модуляция

процесс изменения одного или нескольких параметров модулируемого несущего сигнала при помощи модулирующего сигнала.