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Networking | Security > Computer Networking & Security > Flashcards

Computer Networking & Security Flashcards

1
Q

What is the Physical Layer?

A

Represents the Physical devices that interconnect Computers. Copper, Fiber, and Wireless (Radio). Deals with the Cables, Connectors, and their respective Specifications.

Data Unit: Bits (The 1s, and 0s)

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2
Q

What is the Data Link Layer?

A

Responsible for defining a common way of interpreting these signals so network devices can communicate.

Protocol: Ethernet and/ or WiFi (wireless radio)
Data Unit: Frames
Addressing: MAC Address (00:07:5f:d5:2b:84)

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3
Q

What is the Network Layer?

A

Allows different networks to communicate with each other through devices known as routers.

Protocol: IP
Data Unit: Packets/ Datagram
Addressing: IP address (192.168.1.1)

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4
Q

What is the Transport Layer?

A

Sorts out which client and server programs are supposed to receive appropriate data.

Protocol: TCP/ UDP
Data Units: Segmets
Address: Port Numbers (443, 8080)

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5
Q

What is the Application Layer?

A

Home of applications - web browsers to Email clients.

Protocols: HTTP, SMTP
Data: Messages

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6
Q

What is Internet Protocol (IP)?

A

The Heart of the Internet and most smaller networks around the world.

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7
Q

Crosstalk

A

When an electrical pulse on one wire is accidentally detected on another wire.

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8
Q

Fiber Cables

A

Contain individual optical fibers, which are tine tubes made out of glass about the width of a human hair.

-transfer data faster than copper
-more expensive

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9
Q

Hub

A

A physical layer device that allows for connections from many computers at once.

-Layer 1 device

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10
Q

Collision Domain

A

A network segment where only one device can communicate at a time.

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11
Q

Switch

A

Primary device used to connect computers on a single network, referred to as a LAN, Local Area Network.

-Switching is the process of moving data within networks
-Layer 2 device
-inspects Ethernet Data
-Maintains MAC address Table

*Learn
*Flood
*Forward

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12
Q

Router

A

*A device that knows how to forward data between independent networks.
*A network device that forwards traffic depending on the destination address of that traffic.

-Layer 3 device
-Inspects IP Data

*Directly connected
*Static Route
*Dynamic Route

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13
Q

Border Gateway Protocol (BGP)

A

Routers share data with each other via this protocol, which lets them learn about the most optimal paths to forward traffic.

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14
Q

Bit

A

The smallest representation of data that a computer can understand: either a 1 or a 0.

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15
Q

Modulation

A

A way of varying the voltage of this charge moving across the cable

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16
Q

Duplex Communication

A

Concept that information can flow in both directions across the cable

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17
Q

Simplex communication

A

Data flows only one way - unidirectional.

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18
Q

Ethernet

A

The protocol most widely used to send data across individual links. (CAT5, CAT6, CAT7)

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19
Q

Carrier Sense Multiple Access / Collision Detection (CSMA/ CD)

A

Used to determine when the communications channels are clear, and when a device is free to transmit Data.

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20
Q

MAC Address

A

A Globally unique identifier attached to an individual network interface. It consists of a 48-bit number normally represented by 6 groupings of 2 hexadecimal numbers.

First 3 Octets of a MAC = Organizationally Unique Identifier (OUI)
Last 3 Octets of a MAC = Vendor assigned (NIC)

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21
Q

Binary

A

A representation of numbers using only 2-digits.

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22
Q

Hexadecimal

A

A representation of numbers using 16-digits.

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23
Q

Octet

A

In computer networking, any number that can be represented by 8 bits.

24
Q

Unicast

A

Transmission meant for just One receiving address

25
Q

Multicast

A

Transmission meant for a certain group (the meets criteria).

26
Q

Broadcast

A

Transmission sent to every single device on the LAN (Network). Ethernet broadcast address is all “Fs”

FF:FF:FF:FF:FF:FF

27
Q

Start Frame Delimiter (SFD)

A

Part of the Preamble (the last byte). Signals to a receiving device that the preamble is over and that the actual frame contents will now follow.

28
Q

Ethernet Frame

A

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

Consists of the following:

1 - Preamble
2 - Destination MAC
3 - Source MAC
4 - Payload

29
Q

Ether-type field

A

16 bits long - used to describe the protocol of the contents of the frame

30
Q

Preamble

A

8 or 64 bits long, split into 2 sections. First part is used to regulate speed at which data is sent.

31
Q

VLAN Header

A

Indicates that the frame itself is what’s called a VLAN frame

32
Q

Payload

A

In Networking terms, it is the actual data being transported, which is everything that isn’t a Header.

33
Q

Frame Check Sequence

A

A 4-byte (32-bit) number that represents a checksum value for the entire frame

34
Q

Checksum value

A

Is calculated by performing what is known as a cyclical redundancy check against the frame

35
Q

Cyclical Redundancy Check (CRC)

A

An important concept for data integrity, and is used all over computing, not just network transmissions.

36
Q

IP Datagram

A

Highly structured series of fields that are strictly defined.

37
Q

IP Header

A

Consists of:

1 - Version. IPv4 vs IPv6
2 - Header Length. Almost always 20 bytes in length
3 - Service Type. 8 bits used to specify details about Quality of Service (QoS). Determines which IP Datagram has priority.
4 - Total Length. Indicates the total length of the IP datagram it’s attached to.
5 - Identification - 16 bit number used to group messages together.
6 - Flag - use to indicate if a datagram is allowed to be fragmented, or to indicate that the datagram has already been fragmented.
7 - Fragmentation - The process of taking a single IP datagram and splitting it up into several smaller datagrams.
8 - Time to Live (TTL) - 8 bit field that indicates how many router hops a datagram can traverse before it is thrown away “expires.”
9 - Protocol. 8 bit field that contains data about what transport layer protocol is being used (TCP or UDP).
10 - Header Checksum. A checksum of the contents of the entire IP datagram header
11 - Source IP
12 - Destination IP
13 - IP Options. An optional field and is used to set special characteristics for datagrams primarily used for testing purposes
14 - Padding. A series of Zeros used to ensure the header is correct total size.

38
Q

Address Resolution Protocol (ARP)

A

A protocol used to discover the hardware address of a node with a certain IP address.

39
Q

ARP Table

A

A list of IP addresses and the MAC addresses associated with them. Entries expire after a short amount of time to ensure changes in the network are accounted for.

40
Q

Subnetting

A

The process of taking a large network and splitting it up into many individual and smaller subnetworks, or Subnets.

41
Q

IP Address Classes

A

Class A: 0-127 Range, 16 million hosts
Class B: 128-191 Range, 64,000 hosts
Class C: 192-223 Range, 254
Class D: 224-239 Range, N/A hosts
Class E: 240-255 Range, N/A hosts

42
Q

Subnet Masks

A

32-bit numbers that are normally written out as four octets in decimal.

43
Q

CIDR

A

Classless Inter Domain Routing.

Address classes are no longer relevant. Network masks now determines the Network ID. This gives flexibility to Networks and allows Networks to be different sizes.

44
Q

Demarcation Point

A

Describes where one network or system ends and another one begins

45
Q

Routing Table (Basic)

A

Destination Network - This column contain a row for each network that the router knows about.

Next Hop - The IP address of the next router that should receive data intended for the destination networking question

Total Hop - a collection of “hops” that Routers maintain to ensure they know the shortest path.

Interface - a collection of IP address (Network) that is assigned to each of the Router’s interface

46
Q

Subnetting

A

Taking a network and dividing it into SUB-NETWORKS

*Network ID
*Broadcast IP
*First Host IP
*Last Host IP
*Next Network
*Total # of IP Addresses
*CIDR/ Subnet

47
Q

VLAN

A

Virtual Local Area Network.

-Allows you to break up one Physical Switch into multiple Virtual Switches
-Allows to extend Virtual Switches to other Physical Switches
-Cost effective
-Increase Security
-Each VLAN is its own Broadcast Domain
-Enables Logical Topology to be unconstrained by your Physical Topology
-802.1Q is the open standard for Tagging Layer 2 Frames
-Native VLAN can traverse a Trunk (tagged) link without a VLAN Tag

48
Q

Route Precedence

A

Routers compare 3 items to determine a best patch:

1 - Route Specificity (More Specific is Best)
2 - Admin Distance (lower is better)
3 - Metric (lower is better)

*If all 3 are identical, Routers will load balance across multiple paths (ECMP - Equal Cost Multi Path)

49
Q

NAT

A

Network Address Translation.

-translates private IP addresses to public IP addresses and vice versa
-used to also conserve Public IP addresses
-masks (hides) internal network infrastructure (private local)

*Inside vs Outside
*Local vs Global

50
Q

HTML & HTTP

A

Hyper Text Markup Language - how websites are written
Hyper Text Transfer Protocol - how websites are transferred / translated

51
Q

SSL & TLS

A

Secure Socket Layer & Transport Layer Security - builds a secure, protected Tunnel (conceptual illustration) across the Internet.

Cryptographic protocols used to secure communication over a network. They provide encryption (C), data integrity (I), and authentication (AAA) between client and server.

SSL VPN - can also protect other Data Transfer

*VPN Providers allows for anonymity over the Internet (hides IP Address)

52
Q

Hashing

A

Used to provide Integrity. Creates what is called a Digest (aka Checksum, Fingerprint, Hash, CRC).

Algorithm which takes as input a message of arbitrary length and produces as output a “fingerprint” of the original message.

hello = (8+5+12+12+15) = 52 Digest

*Infeasible to produce a given digest
*Impossible to extract original message
*Slight changes produce drastic difference
*Resulting digest is fixed width (length)

53
Q

Encryption

A

Is used to provide Confidentiality (only intended recipient can interpret the data).

Simple Encryption
hello —> Encryption —> lohel
Plain Text (Data before Encryption) —– Cipher Text (Data while/ after Encrypted)

Key Based Encryption
*Symmetric (same Key)
*Asymmetric (Public & Private Keys)
*Algorithm created by Experts
*Secret Keys can be randomly generated
*Scalable

hello —> Encryption + [KEY] —> xH8q9

54
Q

Key Based Encryption

A

Symmetric Encryption: Encrypt/ Decrypt using SAME keys
*Faster (lower CPU cost
*Cipher is same size as Plain Text
*Secret key must be shared (less secure)
*used for Bulk Data

Asymmetric Encryption: Encrypt / Decrypt using DIFFERENT keys
*2 different keys are mathematically related
*What one Key Encrypts, only the other can Decrypt (Public & Private Keys)
*Slower - requires larger Key sizes
*Private Key is never shared (more secure)
*Restricted to Limited Data

55
Q

Asymmetric vs Symmetric Types

A

Asymmetric algorithms:
*DSA
*RSA (2048 bits key)
*Diffie-Hellman
*ECDSA
*ECDH

Symmetric algorithms:
*DES (56 bit key)
*RC4 (128 bit key)
*3DES (168 bit key)
*AES (128, 192, 256 bit keys)
*ChaCha20 (128 or 256 bit keys)

56
Q

Public & Private Keys

A

Each User has a Public Key and a Private Key.

*Encryption - provides Confidentiality
*Signature - provides Integrity & Authentication (Pair of Asymmetric Keys)

Hybrid Encryption - concept of using both Asymmetric and Symmetric Encryption. Best of both worlds.
*How SSH / IPSec protect bulk data
*SSL/ TLS protect bulk data

57
Q
A

Networking | Security (1 decks)

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