Networking: Physical and Data Link Layers Flashcards
Bit
The smallest representation of data that a computer can understand
Border Gateway Protocol (BGP)
A protocol by which routers share data with each other
Broadcast
A type of Ethernet transmission, sent to every single device on a LAN
Broadcast address
A special destination used by an Ethernet broadcast composed by all Fs
Cable categories
Groups of cables that are made with the same material. Most network cables used today can be split into two categories, copper and fiber
Cables
Insulated wires that connect different devices to each other allowing data to be transmitted over them
Carrier-Sense Multiple Access with Collision Detection (CSMA/CD)
CSMA/CD is used to determine when the communications channels are clear and when the device is free to transmit data
Collision domain
A network segment where only one device can communicate at a time
Computer networking
The full scope of how computers communicate with each other
Copper cable categories
These categories have different physical characteristics like the number of twists in the pair of copper wires. These are defined as names like category (or cat) 5, 5e, or 6, and how quickly data can be sent across them and how resistant they are to outside interference are all related to the way the twisted pairs inside are arranged
Crosstalk
Crosstalk is when an electrical pulse on one wire is accidentally detected on another wire
Cyclical Redundancy Check (CRC)
A mathematical transformation that uses polynomial division to create a number that represents a larger set of data. It is an important concept for data integrity and is used all over computing, not just network transmissions
Data packet
An all-encompassing term that represents any single set of binary data being sent across a network link
Datalink layer
The layer in which the first protocols are introduced. This layer is responsible for defining a common way of interpreting signals, so network devices can communicate
Destination MAC address
The hardware address of the intended recipient that immediately follows the start frame delimiter
Duplex communication
A form of communication where information can flow in both directions across a cable
Ethernet
The protocol most widely used to send data across individual links
Ethernet frame
A highly structured collection of information presented in a specific order
EtherType field
It follows the Source MAC Address in a dataframe. It’s 16 bits long and used to describe the protocol of the contents of the frame
Fiber cable
Fiber optic cables contain individual optical fibers which are tiny tubes made of glass about the width of a human hair. Unlike copper, which uses electrical voltages, fiber cables use pulses of light to represent the ones and zeros of the underlying data
Five layer model
A model used to explain how network devices communicate. This model has five layers that stack on top of each other: Physical, Data Link, Network, Transport, and Application
Frame check sequence
It is a 4-byte or 32-bit number that represents a checksum value for the entire frame
Full duplex
The capacity of devices on either side of a networking link to communicate with each other at the exact same time
Half-duplex
It means that, while communication is possible in each direction, only one device can be communicating at a time
Hexadecimal
A way to represent numbers using a numerical base of 16
Hub
It is a physical layer device that broadcasts data to every computer connected to it
Internet Protocol (IP)
The most common protocol used in the network layer
Internet Service Provider (ISP)
A company that provides a consumer an internet connection
Internetwork
A collection of networks connected together through routers - the most famous of these being the Internet
Line coding
Modulation used for computer networks
Local Area Network (LAN)
A single network in which multiple devices are connected
Modulation
A way of varying the voltage of a constant electrical charge moving across a standard copper network cable
Multicast frame
If the least significant bit in the first octet of a destination address is set to one, it means you’re dealing with a multicast frame. A multicast frame is similarly set to all devices on the local network signal, and it will be accepted or discarded by each device depending on criteria aside from their own hardware MAC address
Network layer
It’s the layer that allows different networks to communicate with each other through devices known as routers. It is responsible for getting data delivered across a collection of networks
Network port
The physical connector to be able to connect a device to the network. This may be attached directly to a device on a computer network, or could also be located on a wall or on a patch panel
Network switch
It is a level 2 or data link device that can connect to many devices so they can communicate. It can 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
Node
Any device connected to a network. On most networks, each node will typically act as a server or a client
Octet
Any number that can be represented by 8 bits
Organizationally Unique Identifier (OUI)
The first three octets of a MAC address
OSI model
A model used to define how network devices communicate. This model has seven layers that stack on top of each other: Physical, Data Link, Network, Transport, Session, Presentation, and Application
Patch panel
A device containing many physical network ports
Payload
The actual data being transported, which is everything that isn’t a header
Physical layer
It represents the physical devices that interconnect computers
Preamble
The first part of an Ethernet frame, it is 8 bytes or 64 bits long and can itself be split into two sections
Protocol
A defined set of standards that computers must follow in order to communicate properly
Simplex communication
A form of data communication that only goes in one direction across a cable
Source MAC address
The hardware address of the device that sent the ethernet frame or data packet. In the data packet it follows the destination MAC address
Start Frame Delimiter (SFD)
The last byte in the preamble, that signals to a receiving device that the preamble is over and that the actual frame contents will now follow
Transmission Control Protocol (TCP)
The data transfer protocol most commonly used in the fourth layer. This protocol requires an established connection between the client and server
Transport layer
The network layer that sorts out which client and server programs are supposed to get the data
Twisted pair cable
The most common type of cabling used for connecting computing devices. It features pairs of copper wires that are twisted together
Unicast transmission
A unicast transmission is always meant for just one receiving address
User Datagram Protocol (UDP)
A transfer protocol that does not rely on connections. This protocol does not support the concept of an acknowledgement. With UDP, you just set a destination port and send the data packet
Virtual LAN (VLAN)
It is a technique that lets you have multiple logical LANs operating on the same physical equipment
VLAN header
A piece of data that indicates what the frame itself is. In a data packet it is followed by the EtherType
