Networking Devices
Devices connected to this type of networking device will end up talking to all other devices at the same time.
What is a hub?
A hub is a physical layer device that allows for connections from many computers at once.
All the devices connected to a hub will end up talking to all other devices at the same time.
It's up to each system connected to the hub to determine if the incoming data was meant for them, or to ignore it if it isn't.
It's a device that contains many network ports. It's a container for the endpoints of many cables.
What is a patch panel?
Patch panels are network ports mounted on a wall or underneath your desk.
These ports are generally connected to the network via cables, run through the walls that eventually end at a patch panel.
A patch panel, is a device containing many network 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.
A globally unique identifier attached to an individual network interface. It's a 48-bit number normally represented by six groupings of two hexademical numbers.
What is a MAC address?
The two versions of IP addresses.
What are IPv4 and IPv6?
IPv4 are in decimal format - 12.30.56.78
IPv6 are in hexadecimal - 2001:0db8:85a3:0000:0000:8a2e:0370:7334
A device that blocks traffic that meets certain criteria.
What is a firewall?
Firewalls are a critical concept to keeping a network secure since they are the primary way you can stop traffic you don't want from entering a network.
Firewalls that operate at the transportation layer will generally have a configuration that enables them to block traffic to certain ports while allowing traffic to other ports.
This networking device can inspect the contents of the ethernet protocol data being sent around the network.
What is a switch?
a switch 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.
This reduces or even completely eliminates the size of collision domains on the network, which leads to fewer re-transmissions and higher overall throughput.
The most common plug for twisted pair network cables.
What are RJ45 plugs?
The most common plug is known as an RJ45, or Registered Jack 45.
It's one of many cable plugs specifications but by far, the most common in Computer Networking.
A network cable with an RJ45 plug can connect to an RJ45 network port.
It's a way to represent numbers using 16 digits.
What is hexadecimal?
Hexadecimal
0 1 2 3 4 5 6 7 8 9 A B C D E F
Decimal
0 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
A 32 bit long number that is made up of four octets and each octet is normally decimal numbers.
What is an IP address?
Example: 12.30.56.78 is a valid IP address
It's important to know that IP addresses belong to the networks, not the devices attached to those networks.
The most common connectionless protocol.
What is UDP?
UDP - User Datagram Protocol: UDP is used to for streaming audio and video.
The UDP protocol that is widely used for streaming audio and video, voice over IP (VoIP) and videoconferencing. UDP is considered an unreliable delivery protocol because it does not check for errors.
Routing tables contains the information necessary to forward a packet along the best path to the destination (server) and resides in this networking device.
What is a router?
This networking device has many network ports because their purpose is to connect many devices.
What is a switch?
Used to determine when the communications channels are clear and when the device is free to transmit data.
What is CSMA/CD?
CSMA/CD - Carrier-sense multiple access with collision detection.
The three primary types of address classes.
What are Class A, Class B and Class C?
The address class system is a way of defining how the global IP address space is split up.
Class A: Class A addresses are those where the first octet is used for the network ID and the last three are used for the host ID.
Class B: Class B addresses are where the first two octets are used for the network ID, and the second two are used for the host ID.
Class C: Class C addresses, are those where the first three octets are used for the network ID, and only the final octet is used for the host ID.
The order of the TCP flags that make up the Three-way Handshake.
What is SYN, SYN/ACK, ACK?
This networking device causes significant collision domains.
What is a hub?
A 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.
It really slows down network communications and is the primary reason hubs are fairly rare.
This illuminates when an electrical charge passes through it. They are commonly green, amber or red.
What is an LED?
LED: Light emitting diode.
Most network ports have two small LEDs.
One is the Link LED, and the other is the activity LED.
The link LED will be lit when a cable is properly connected to two devices that are both powered on.
The activity LED will flash when data is actively transmitted across the cable.
A mathematical calculation used to ensure that all data arrived intact.
What is a cyclical redundancy check?
The reason it's included in the Ethernet frame is so that the receiving network interface can infer if it received uncorrupted data.
The process of taking a single IP datagram and splitting it up into several smaller datagrams.
What is fragmentation?
While most networks operate with similar settings in terms of what size an IP datagram is allowed to be, sometimes, this could be configured differently.
If a datagram has to cross from a network allowing a larger datagram size to one with a smaller datagram size, the datagram would have to be fragmented into smaller ones.
The fragmentation offset field contains values used by the receiving end to take all the parts of a fragmented packet and put them back together in the correct order.
The TCP Socket State that represents a fully established connection; this is the normal state for the data transfer phase of the connection.
What is ESTABLISHED?
This networking device can inspect ethernet data to determine where to send things and can inspect IP data to determine where to send things.
What is a router?
Just like a switch can inspect Ethernet data to determine where to send things, a router can inspect IP data to determine where to send things.
Routers store internal tables containing information about how to route traffic between lots of different networks all over the world.
The most common type of router you'll see is one for a home network or a small office.
These devices generally don't have very detailed routing tables.
The purpose of these routers is mainly just to take traffic originating from inside the home or office LAN and to forward it along to the ISP, or Internet service provider.
These are attached to the devices that make up a computer network. Switches have many of these because their purpose is to connect many devices.
What are network ports?
Sometimes a network port isn't connected directly to a device.
Instead, there might be network ports mounted on a wall or underneath your desk.
A MAC address is split into two sections.
What are the unique identifier or OUI and Vendor assigned identifier?
OUI - Organizationally unique identifier. These are assigned to individual hardware manufacturers by the IEEE (Institute of Electrical and Electronics Engineers)
An example MAC address would be:
00:00:5e:00:53:af
The process by which a lower-layer protocol receives data from a higher-layer protocol and then places the data into the data portion of its frame.
What is encapsulation?
Example: When the entire contents of an IP datagram are encapsulated as the payload of an Ethernet frame.
A TCP connection progresses through a series of states during its lifetime.
What are TCP Socket States?
LISTEN represents waiting for a connection request from any remote TCP and port.
SYN-SENT represents waiting for a matching connection request after having sent a connection request.
SYN-RECEIVED represents waiting for a confirming connection request acknowledgment after having both received and sent a connection request.
ESTABLISHED represents an open connection, data received can be delivered to the user. The normal state for the data transfer phase of the connection.
FIN-WAIT-1 represents waiting for a connection termination request from the remote TCP, or an acknowledgment of the connection termination request previously sent.
FIN-WAIT-2 represents waiting for a connection termination request from the remote TCP. CLOSE-WAIT represents waiting for a connection termination request from the local user.
CLOSING represents waiting for a connection termination request acknowledgment from the remote TCP.
LAST-ACK represents waiting for an acknowledgment of the connection termination request previously sent to the remote TCP (which includes an acknowledgment of its connection termination request).
TIME-WAIT represents waiting for enough time to pass to be sure the remote TCP received the acknowledgment of its connection termination request.
CLOSED represents no connection state at all