Networking Flashcards
1
Q
Internet vs. Web
A
Internet is the physical system of computers and cables that connect them
Web is the information stored on the internet
2
Q
Server vs. Client
A
Client requests content; the server provides it
3
Q
ISP
Internet Service Provider
A
Company that runs a large network connected to other networks; connects individual users to the internet
4
Q
IP address
A
A computer’s location on the internet; it changes when you connect through different networks
5
Q
Ethernet cable
A
Physically connects computer to a network
6
Q
Router
A
Networking hardware; connects multiple devices and routes network traffic
7
Q
IP vs TCP
Internet protocol; transmission control protocol
A
Network protocols; they work together to get data to the right place
TCP delivers data from one network to another; IP gets it to the right computer
8
Q
HTML
Hypertext Markup Language
A
Coding language used by web browsers
9
Q
URL
Uniform Resource Locator
A
Web address in “human language”
Ex: www.google.com
10
Q
Domain name
A
Middle and end of a website’s URL
Ex: google.com
11
Q
ICANN
Internet Corporation for Assigned Names and Numbers
A
Registers domain names for web pages
12
Q
DNS
Domain Name System
A
Server software that takes the domain name a user enters, and finds the correct IP address for that web page
13
Q
NAT
Network address translation
A
Allows a company to have one public IP address, and use unroutable addresses for other devices in their network
Helps solve the problem of limited IP addresses
14
Q
Internet of Things
A
Refers to household items connected to the internet such as thermostats and refrigerators
15
Q
Coding vs. Scripting vs. Programming
A
Coding is the umbrella term; script languages usually handle very simple tasks, and programming languages are good for more complex tasks
16
Q
Open source software
A
Free for others to use, modify, and distribute
Ex: Linux, Firefox
17
Q
Application vs. system software
A
Apps are created to fill a specific need (ex: text editor); system software keeps the core system running
18
Q
Firmware
A
Software that’s permanently stored on a computer component (ex: BIOS)
19
Q
TCP/IP 5 layer model
A
Layers include: - Physical - Data link - Network - Transport - Application (See p. 1 in Course 2 notes for details)
20
Q
5 layer model - physical layer
A
Sets protocols for cables and other physical devices, to describe how signals are sent through these connections
Protocols: 10 Base T, 802.11
Data unit: bits
21
Q
5 layer model - data link layer
A
Defines how to interpret signals sent through physical layer, so different devices can communicate
Protocol: Ethernet, Wi-fi
Data unit: frames
Addresses: MAC address
22
Q
5 layer model - network layer
A
Allows different networks to communicate with each other through routers
Protocol: IP
Data unit: datagram
Addresses: IP address
23
Q
5 layer model - transport layer
A
Sorts out which client and server programs should get which data
Protocols: TCP, UDP
Data unit: segment
Addresses: port #
24
Q
5 layer model - application layer
A
The programs that receive data and decide what to do with it
Protocols: lots - depends on the app!
Data unit: message
25
TCP vs. UDP
Transmission control protocol vs. User datagram protocol
The two main protocols used at the transport layer
TCP provides mechanisms for reliable data delivery; UDP does not but can get things done with less traffic
26
OSI model
Open Systems Interconnection model
Similar to TCP/IP 5-layer model, but divides application layer into 3 layers - session, presentation, and application layers
27
Copper vs. fiber cables
Copper cables are most common, most durable, and much less expensive; fiber cables are faster and can transmit longer distances without data loss
28
Cat5 vs. Cat5e vs. Cat6
Types of copper cables; Cat5 is oldest and has the most problems with cross-talk
29
Cross-talk
When adjacent cables interfere with each other's data transmission; mostly a problem in older Cat5 cables
30
Hub
Device that connects computers on a LAN (local area network); it's a simple connection point that leaves the network very prone to collision domains
31
Switch
Network device that connects computers on a LAN (local area network) and sends data to the correct recipients
Improvement over the older hubs in that a switch reduces or even eliminates collision domains
32
Collision domain
Part of a network where only one device can communicate at once; increases network errors and reduces network speed
33
Router
Network device that can send data between different networks
34
Core router
ISP's sophisticated router that routes traffic to other ISPs
35
Gateway router
Router that serves as entry and exit for a network
36
Border Gateway Protocol
| BGP
Protocol used by routers to share data with other routers and learn the most efficient paths to forward traffic
37
Simplex vs. duplex communication
Simplex = data only goes one way (ex: baby monitor)
Full duplex = data can travel both directions at the same time (Cat6 cable; has 4 pairs and certain pairs are reserved for certain directions)
Half duplex = data can go both ways, but only one direction at a time (sometimes happens if there's a problem with a connection)
38
RJ45 port
Common "registered jack" port on the back of your computer
39
Patch panel
Network device that includes many ports; it's really just a place to connect cables
40
Ethernet protocol
Protocol for the data link layer; allows different kinds of devices to communicate
41
MAC address
Unique identifier assigned to a device when it's manufactured
48-bit number (6 groups of 2 hexadecimal digits each)
42
Organizationally Unique Identifier
OUI
First 3 octets of a MAC address that are assigned to a particular hardware manufacturer
(The manufacturer can make up the last 3 octets)
43
Broadcast
Transmission meant for all devices on your local network
MAC address of recipient is always FF:FF:FF:FF:FF:FF
44
Ethernet frame
A data packet at the data link level
45
Checksum
A field in many data transmissions that allows the receiving device to confirm that it got the whole message
Also called "cyclical redundancy checks"
46
IPv4
Uses 32-bit IP address
Ex: 172.16.254.1
47
Static vs. dynamic IP addresses
Dynamic IP - assigned through DHCP; common for clients
Static IP - best for servers and network devices
48
IP datagram
Data packet at the network level
49
TTL
Time to live
One of many fields in an IP datagram header; tells how many router hops the datagram can travel before it's discarded
50
IP address classes (A,B,C,D,E)
A: First octet is network ID and last 3 octets are host ID (there are only a small number of these, but they're good for really large networks)
B: 2 octets for network ID and 2 for host ID
C: 3 octets for network ID and 1 for host ID (this class has lots of small networks)
D: used for multicasting (first octet is 224-239)
E: unassigned; used for testing (first octet is 240-255)
51
CIDR
Classless interdomain routing
Replaces the older IP address classes (A through E); in CIDR, the address can be broken up into network ID and host ID at any point
52
ARP table
Address resolution protocol
List of IP addresses in a local network, and the MAC addresses connected with them
53
Subnetting
Taking a large network and splitting it up into smaller ones; each subnet will have its own gateway router
54
Routing table
Each router stores IP address for each network it knows, along with total hops to get there and a few other details
55
Interior gateway protocols
Distance-vector protocols vs. link state routing protocols
Ways for routers in a large network to share info with each other
Distance vector is the older version; link state routing is newer and faster, but takes more memory and processing power
56
Exterior gateway protocols
Used by routers to share info between different networks
57
Non-routable address space
Defined by RFC 1918; helps solve the problem of limited IP addresses because many networks can be using the same non-routable address
58
Multiplexing / demultiplexing
Gathering data from multiple sources and sending it as a whole / taking data delivered to the same node and delivering it to the correct recipients
In the 5-layer model, only the transport layer can do this
59
Port
16-bit number (0-65,535) used to direct traffic to specific services running on a computer
60
Port 0
Not used for network traffic, but sometimes for traffic between different services on the same computer
61
Ports 1-1,023
System or well-known ports; used for common network services
62
Ports 1,024-49,151
Registered ports; used for network services that aren't the most common ones
63
Ports 49,152-65,535
Private or ephemeral ports; temporary and used for establishing outbound connections
64
TCP control flags
Optional part of a TCP header
Flags include ACK (acknowledged) and SYN (synchronize) used in establishing a TCP connection, and FIN (finish) used to close the connection
65
3-way handshake
Nickname for the TCP communication that opens a network connection between 2 computers
Computer A: SYN
Computer B: SYN/ACK
Computer A: ACK
66
4-way handshake
Nickname for the TCP communication that closes a network connection between 2 computers
Computer A: FIN
Computer B: ACK
Computer B: FIN
Computer A: ACK
67
Socket states
Refers to TCP communication; you can send a data request to any port you want, but you'll only get a response if a program has opened a socket on that port
States can include LISTEN, SYN_SENT, SYN_RECEIVED, ESTABLISHED, FIN_WAIT, CLOSE_WAIT, and CLOSED
(details in Course 2 notes p 14)
68
Firewall
Network device or program that blocks traffic that meets certain criteria
(Ex: If a server hosts a company's web page and internal file storage, the firewall would be set to allow public access to Port 80, but to block all external IP addresses from the file server port)
69
Microsoft IIS, Apache, nginx
Examples of popular web servers
70
HTTP
Hypertext transfer protocol
Protocol used by web servers and web browsers
71
DNS
Domain Name System
Global network service that converts a domain name (ex: www.google.com) into the correct IP address
72
DHCP
Dynamic Host Configuration Protocol
Application layer protocol that automatically assigns IP addresses when devices connect to a network
73
NAT
Network Address Translation
Technology that allows a gateway (usually a router or firewall) to use it's own IP address for outgoing traffic, and send replies back to the correct hosts
74
VPN
Virtual Private Network
Creates a private "tunnel" through the internet, so that a remote device can connect to a local network
Requires a router and VPN server in the network that's allowing access
Ex: I might use VPN technology to connect my laptop to my work network when I'm working from home
75
Proxy server
Server that acts on behalf of a client to access another server
Includes gateway routers, web proxy (used to limit employee access to non-business sites), reverse proxy (distributes heavy web traffic to multiple web servers)
76
Dial-up internet
Also called PSTN (Public Switched Telephone Network) or POTS (Plain Old Telephone Network)
Uses a modem to convert digital data to analog, and back
77
Modem (Modulator/Demodulator)
Used in dial-up internet connections; converts digital data to analog (which can be transferred via phone lines) and back to digital
78
Baud rate
Measurement of dial-up internet connection speed; how many bits can be passed across a phone line in a second
79
Broadband
Any connection that isn't dial-up; connection is always on
Includes T-carriers, DSL, cable broadband, and fiber connections
80
T-carrier internet connection
Uses dedicated cables, originally for phone calls but evolved to transmit broadband data
Reliable but expensive
T3 includes 28 T1 lines for one connection, with total speed of 44.7 mbps
81
DSL (digital subscriber lines)
Uses same cables as phone/T-carrier connections, but uses frequencies that transmit data faster and don't interfere with phone calls
82
DSLAM (digital subscriber line access multiplexer)
The "modem" for a DSL connection; establishes a connection and keeps it running as long as the DSLAM is turned on
83
ADSL (asymmetric DSL) vs SDSL (symmetric DSL)
ADSL has different speeds for outbound and inbound data; good for home use, where you usually don't need to do much uploading
SDSL uses the same high speed for upload and download; good for business and becoming more popular for home use
Usually max speed of 1.544 mbps (same as T1 line)
84
HDSL (high bit-rate DSL)
DSL connection that provides speeds over 1.655 mbps
85
Cable broadband
Uses TV cables, but on a different frequency
Bandwidth is shared within a network, so it might slow down during periods of heavy use
86
Cable modem
Modem for a cable broadband connection; one modem connects a consumer network with an ISP (instead of each customer having a modem, such as in point-to-point technologies)
87
Fiber internet connections
Used for the core of the internet, such as between ISPs
Fiber uses light for signals; can transmit data faster and for longer distances without degradation
88
FTTX
Fiber to the X
Can include FTTN (fiber to the neighborhood), FTTB (to the building or business), FTTH (to the home) or FTTP (to the premises)
89
WAN
Wide Area Network
Combines networks at multiple physical locations into one network
Usually requires that you contract a link across the internet with your ISP; fast but expensive, so good for large companies with lots of data transfer between sites
90
WAN (wide area network) vs. point-to-point VPN (virtual private network)
WAN is very fast but expensive; good for large companies with lots of data transfer between different office locations
Point-to-point VPN uses cloud services to host your data, so there's no need for an expensive high-speed line connecting your offices; each host connects to its gateway router as usual
91
IEEE 802.11
Set of standards that define how WiFi devices should communicate (specifically at physical and data link layers)
92
802.11b (or 802.11a, 802.11g, n, ac, ...)
Each is a standard in the 802.11 "family"
They use the same protocols but operate on different frequencies (different at physical layer and same at data link layer)
93
2.4 Ghz vs. 5 Ghz WiFi bands
5 Ghz (Gigahertz) networks are usually faster and less susceptible to interference, but have less range
94
Wireless access point
Device that bridges the wireless and wired parts of a network
95
Wireless networks - ad-hoc vs. wireless LAN
WLANs are most common; access points form bridge between wired and wireless parts of the network
In ad-hoc network, nodes all speak directly to each other (ex: smartphones connecting to nearby phones for photo exchange)
Mesh network is a hybrid of the two - includes wired and wireless devices, and various devices communicate directly with each other
96
Wireless frequency band vs. channel
Frequency band is a range of frequencies set aside for a particular type of communication
Channels are smaller sections of a frequency band; a wireless network uses multiple channels to avoid collision domains (each wireless access point selects a channel with the least possible overlap with its neighbors, or you can manually set a channel)
97
WEP vs. WPA
| Wired equivalent privacy vs. WiFi protected access
WEP is an old encryption technology for wireless networks, which really no one should be using anymore
WPA replaced it and uses 128-bit encryption key; today we're mostly using WPA2 with 256-bit key
98
MAC filtering
A way of securing a wireless network, by only allowing connections from MAC addresses that you trust
Doesn't protect your data as it's being transmitted wirelessly, but stops unauthorized devices from connecting to the network itself
99
Cellular networking (or mobile networking
Not WiFi, but works in a similar way, with its own set of specs similar to the 802.11 family
Each cell tower serves as an access point, and uses a frequency that minimizes overlap with its neighbors
Cellular frequency bands are good for long-distance transmission (miles rather than meters)
