Week 1 Flashcards
Intro to networking
Protocol
Defined set of standards that computers must follow in order to communicate properly.
Computer Networking
The name given to the full scope of how computers communicate with each other
What are the five layers in the five layer network model from lowest to highest?
- Physical
- data link
- network
- transport
- application
What’re the five network layers’ protocols, protocol data units, and addressing?
Physical - 10 base T, 802.11 - Bits - n/a
data link - Ethernet, Wi-Fi - frames - MAC address
network - IP - datagram - IP address
transport - TCP/UDP - segment - port #’s
application - HTTP, SMTP, etc… - messages - n/a
Physical layer
Represents the physical devices that interconnect computers.
Data link layer
Responsible for defining a common way of interpreting signals sent by the physical layer, so network devices can communicate
A.k.A - network interface or network access layer
Network layer
A.k.a the internet layer
Allows different networks to communicate with each other through devices known as routers
Internetwork
A collection of networks connected together through routers, the most famous of these being the internet
Transport layer
Sorts out which client and server programs are supposed to get that data
UDP
User datagram protocol
What is the difference between TCP and UDP?
TCP provides mechanisms to ensure that data are reliably delivered, while UDP does not!
Application layer
A lot of programs such as browsers and email have their own protocols
The actual programs the user interacts with.
What is the difference between the five layer model and the OSI networking model?
The OSI model abstracts the application model into three layers to make a total of 7 layers
What are the most common forms of copper twisted-pair cables used in networking?
Cat5, Cat5e, and Cat6
Crosstalk
When an electrical pulse on one wire is accidentally detected on another wire
Fiber cables
Contain individual optical fibers, which are tiny tubes made out of glass about the width of a human hair
Hub
A physical layer device that allows for connections from many computers at once
Collision domain
A network segment where only one device can communicate at a time.
Difference between a network switch and a hub
Network switches are s lot more common than hubs
A switch is a data link layer device whereas a hub is a physical layer device, because a switch can detect the contents of the data being sent whereas a hub cannot
LAN
Local Area Network
A single network that utilizes hubs and switches to connect its computers
Router
A device that knows how to forward data between independent networks
Operates in the network layer
What devices are considered the backbone of the internet?
Core routers at internet service provider networks
Border Gateway Protocol
BGP
Routers share data with each other via this protocol, which lets them learn about the most optimal paths to forward traffic
Modulation (Line Coding when referring to network cables)
A way of varying voltage of the charge moving across a cable
How many twisted pairs in a network cable jacket?
4 pairs of twisted cables so 8 copper wires total
Duplex communication
The concept that information can flow in both directions across the cable
Simplex communication
The concept that information flows in one direction only.
Full duplex vs half duplex
Full is when the client and the server can communicate with each other at the same time due to 1 or 2 twisted pair cables being reserved to send data one way and 1 or 2 twisted pair cables sending data the other way
Half is when they have to take turns
What is the most common plug type for network cables?
RJ45
What are the two lights on network port?
Link light - lit when the cable is properly connected to two devices that are powered on
Activity light - flashes when data is actively being transmitted across the cable.
Patch panel
A device with a lot of cable ports. Serves no other purpose than being an endpoint for devices. Typically the patch panel is also connected to a switch or hub.
Data link layer
Abstracts the physical layer for the layers high up in the stack so the data can be read the same no matter what hardware is being used.
CSMA/CD
Used to determine when the communications channels are clear, and when a device is free to transmit data
MAC address
Media access control address
A globally unique identifier attached to an individual network interface
48-bit number normally represented by six groupings or two hexadecimal numbers
Ethernet frame
A data packet at the Ethernet level
Highly structured collection of information presented in a specific order
Preamble
8 bytes long, and can be split into two sections
Start Frame Delimiter
SFD
Signals to a receiving device that the preamble is over and the actual frame contents will now follow. Its the last byte of the preamble.
Destination MAC Address
The hardware address of the intended recipient
Comes immediately after the preamble
EtherType field
16 bits long and used to describe the protocol of the contents of the frame
VLAN Header
Indicates that the frame itself is what’s called a VLAN frame
If this is present then the EtherType field follows it
Virtual LAN
VLAN
A technique that lets you have multiple logical LANs operating on the same physical equipment
Used to separate different forms of traffics
Allows one physical network to have multiple LANS
Payload
In networking terms, is the actual data being transported, which is everything that isn’t a header
Can be up to about 1500 bytes long
Frame Check Sequence
FCS
A 4 byte number that represents a checksum value for the entire frame
How is the checksum value calculated?
Calculated by performing what’s known as a cyclical redundancy check against the frame
Cyclical Redundancy Check
CRC
A data integrity concept used in data computing
A math transformation that uses polynomial division to get a number (checksum) representing the data. That value should always be the same. Lets the receiving end know the data was not corrupted.
