OSI Model (TCP Model Ports/Protocol) Flashcards

1
Q

What does OSI stand for and name 2 facts, on witch mode do networks operate today?

A

open systems interconnect model
developed 1977 international organization for standardization
its a reference model (used to categorize the functions of a network, useful for troubleshooting)
under the TCP/IP mode

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2
Q

Name the acronym to list all OSI Layers in the correct order beginning with layer 1

A

Please Do Not Throw Sausauge Pizza Away
physical layer 1
data link layer 2
network layer 3
transport layer 4
session layer 5
presentation layer 6
application layer 7

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3
Q

What are networks designed to?

A

to make data flow across networks

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4
Q

Name the acronmy for data flows through the OSI model

A

Do Some People Fear Birthdays
Data 5 - 7
Segments Layer 4
Packets Layer 3
Frames Layer 2
Bits Layer 1

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5
Q

Name the Physical Layer Overview (2 points) and the Transition Modulation 1 point

A

first layer transmission of bits across the network occurs and includes physical and electrical network characteristics
Data type occurs as bits (binary bits represented as a serios of 1s and 0s)
transition moulation switching between levels to represent 1 or 0 (copper wire (cat 5/cat 6 - uses voltage 0V or +5/-5V, fiber optic cable - uses light on for 1 off for 0)

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6
Q

What are Layer 1 Connector Standards 4 points

A

RJ-45 connector - used in cat5/6 cables
wiring standards (TIA/EIA-568A, TIA/EIA-568B)
Crossover cables - TIA/EIA 568A on one end and B on the other end
Straight-through cables - TIA/EIA568B both sides

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7
Q

Name 6 different physical network toplogy layouts of layer 1

A

Bus, Ring, Star, Hub-and Spoke, Full Mesh, Partial Mesh
based on how cables are physically connected

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8
Q

Name and describe the two synchronization types of layer 1

A

Asychronous Communication (start and stop bits for out-of-sync data transmission
Synchronous Communication (real-time communication using a common time source)

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9
Q

Name 2 types of bandwitdth utilization of layer 1

A

Broadband (divides bandwith into spereate channels, cable TV
Baseband (uses all frequency of the cable all the time, telephone

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10
Q

What is multiplexing in layer 1 and name 3 types

A

involves taking some limited amount of resoucre and using it more efficiently (allows multiple people to use baseband connection same time)
Time Division Multiplexing (TDM) allocates dedicated time slots
Statistical Time Division Multiplexing (StatTDM) dynamically allocates time slots based on when people need it
Frequency Division Multiplexing(FDM) divides the medium into channels

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11
Q

Name 3 Layer 1 Devices and 2 layer 1 device characteristics

A

Cables - media (fiber optic, ethernet, coaxial)
Wireless Media (bluetooth,wifi, near field communication)
Inftrastructure Devices (hubs, access points, media converters)
simply repeat whatever they receive
no logic or decision-making at layer 1

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12
Q

What does layer 2 (Data Link Layer) do?

A

responsible for packaging bits from layer 1 into frames and transmitting them across the network
perform error detection and correction, identifies devices using MAC addresses and provides flow control

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13
Q

What does MAC (layer 2) stand for?

A

Media Access Control Address

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14
Q

Describe Mac (L2) in 3 points

A

a means for identifiying a device physically and allowing it to operate on a logical topology
a unique 48 bit physical addressing systsem is assigned to everey network interface card (NIC) produced (written in hexadecimal, first 24 bits - identify manufacturer, remaining 24 - identify the specific device
curcial for logical topology - identifying devices on the network

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15
Q

What is Logical Link Control (LLC) in Layer 2 3 points

A

provides connection services and acknowledges message receipt, ensuring controlled data flow
most basic form of flow control (limits data sent by a sender prevents receiver overwhelm
uses a cheksum to detect corrupted data frames

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16
Q

Name 3 Synchronization Methods at Layer 2

A

ischronous mode (common reference clock, time slots for transmissions, less overhead)
synchronous method (devices use the same clock, with beginning and ending frames, control characters for sync
asynchronous (devices reference own clock cycles, no strict control over communication timing

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17
Q

Name 3 Layer 2 devices and list operation to one of them

A

network interface cards (NICs)
bridges
switches (intelligent use of logic to learn and send data to specific devices based on mac addresses
switch operation (switches can use content addressable memory tables (CAM) with MAC addresses to identify physical ports connected to devices, enables selective data transmission to specific areas in network)

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18
Q

What is Network Layer 3 and Logical Addressing

A

concerned with routing and forwarding traffic using logical addresses
logical addressing (IP variants - common logical addressing schemes IPv4 - written in dotted octet notation which are four sets of numbers (172.16.254.1), IPv6
other protocols - replaced by ip (AppleTalk, IPX internetwork packet exchange)

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19
Q

Name 3 layer 3 switching/routing methods

A

packet switching (routing) (data is divided into packets and then forwarded, most commonly used method)
circuit switching (a dedicated communicationn link is established between two devices
message switching (data is divided into messages which may be stored and then forwarded)

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20
Q

2 points of route discorvery and selection on layer 3

A

routers maintain routing tables for determining the best path (dynamic protocols (RIP Routing Information Protocol, OSPF Open Shortest Path First) enable routers to share and update route information
routing protocols help decide how data is going to flow across the network and how routers are going to communicate that information)

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21
Q

Name 3 Connection Services at Layer 3

A

augments layer 2 services
involves flow control (prevents sender from overwhelming receiver)
packt reordering (ensures data packets arrive and are reassambled in the correct order)

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22
Q

What is ICMP name 2 examples L3

A

sending error messages and operational information to an IP destination
ping (most commonly used ICMP, help troubleshoot nw issues by testint connectivity and response times
traceroute (traces route of packet through the network

23
Q

Name Devices and Protocols of Layer 3, what devices are commonly encounterd L3 devices in the exam

A

Routers
Mulit-layer switches (combine l2 and l3 router features, switch is always l2 unless specifically mentioned multi-layer which makes it l3)
protocols (IPV4, IPV6, ICMP)
IP and routers

24
Q

Transport Layer 4 and what so called upper layers

A

dividing line between the upper layers and the lower layers of the OSI model
upper layers (Transport, Session, Presentation, Application)

25
Q

What are segments in layer 4?

A

data type in transport layer

26
Q

Describe TCP of layer 4

A

Transmission Control Protocol (TCP) (connection-orientated protocol that is a reliable way to transport segments across the network, with acknowledgement, uses three-way handshake (SYN- synchronization, SYN-ACK- synchronization - acknowledgement, ACK - acknowledgement)
Windowing for flow control
used for all network data that needs to be assured to get to its final destination

27
Q

Describe UDP of layer 4

A

User Datagram Protocol (UDP) (connectionless protocol unreliable way to transport segements (datagram), used for audio and visual streaming, no three-way handshake and less overhead, no acknowledgement or retransmissions

28
Q

What data types are to remember for the exam L4

A

Segment - data type for TCP
Datagram - data type for UDP

29
Q

TCP 5 points vs UDP 5 points

A

TCP (reliable - three-way handshake, connection-oriented, segment retransmission and flow control trhough windowing, sequencing, ack of segements
UDP (unreliable - no three-way handshake, connectionless, no retransmission and no windowing, no secquencing, no ack of datagrams)

30
Q

TCP vs UDP what is Windowing 3 points layer 4

A

allows clients to adjust the amount of data in each segments during transmission
optimize throughput and bandwidth
open or close window based on retransmissions

31
Q

TCP vs UDP what is Buffering 3 points layer 4

A

occurs when devices allocate memory to store segements if bandwidth is not readily available
Buffer (temporary storage for segments)
prevents overflow by clearing segments

32
Q

Name 3 Layer 4 Devices and Protocols

A

TCP and UDP
WAN accelerators
load balancers
firewalls

33
Q

Describe the Session Layer (L5)

A

Manage sessions, ensuring seperate conversations to prevent data intermingling

34
Q

Name and Describe 3 Modes of the Session Layer l5

A

setting up a session (checking of user credentials and assigning numbers to sessions to help identify)
maintaining session (continuous data transfer between parties, if connection breaks will require re-establishment, includes acknoledgement of data
tearing down a session (ending session once communication goals are achived, mutual agreement or one party disconnects

35
Q

Name Layer 5 devices and protocols

A

H.323 (used for setting up, maintaining and tearing down voice and vide connections, operates over the real-time transport protocol (RTP)
NetBIOS (utilized by computers for file sharing over a network, commonly associated with Windows file sharing
Layer 5 issues involve protocols and software rather than specific devices

36
Q

What is presentation layer 6?

A

responsible for formatting data for exchange and securing it through encryption

37
Q

What is layer 6 data formatting and name 4 formats

A

formatting data by a computer to have compatibility between different devices
formats (American Standard Code for Information Interchange (ASCII - text-based language to use, esnures data is readable by receiving system, provides proper data structures, negotiates data transfer syntax for the application layer 7)
GIFs - motion pictures
JPEG - photographs
PNG - internet images
formates enable compability between different devices

38
Q

What is Encryption in Layer 6?

A

used to scramble data in transit to keep it secure and provide data confidentiality
Transport Layer Security (TLS) (esnures secure data transfer, creates an encrypted tunnel, protecting sensitive information)

39
Q

What do scripting languages in layer 6 do?

A

control how ASCII text is displayed on the screen (HTML Hypertext Markup Language, XML extensible markup language, PHP Hypertext Preprocessor, JavaScript

40
Q

What are standard text formats for and name 3 of them in layer 6

A

different ways of displaying text using ones and zeros
ASCII, Unicode EBCDIC (Extended Binary Coded Decimal Interchange Code)

41
Q

What are image formats and name 5 of them l6

A

different graphical represntations of 1s and 0s (GIFs Graphics Interchange Format, JPEGs Joint Photographic Experts Group, TIFFs Tagged Image File Format, Scalable Vector Graphics, PNGs Portable Network Graphics)

42
Q

What are movie file formats in layer 6 3 points

A

1s and 0s formatted to create watchable videos (MP4s MPEG-4 Part 14, WPEGs Moving Picture Experts Group, MOV movie quick time player)

43
Q

What are encryption algorithms? name 2 l6

A

scrambles data to provide confidentiality and security during transit and storage
TLS
SSL (Secure Socket Layer - deprecated and replaced by TLS)

44
Q

What is application layer 7

A

provides application-level services where users communicate with the computer
focus on lower-level applications (file transfer, network transfer

45
Q

What are Application services 6 points l7

A

unites components for more than one network application (file transfer, file sharing, email (low-level protocols - POP3 (Post Office Protocol), IMAP (Internet Message Access Protocol), SMTP (Simple Mail Transfer Protocol)
remote access
network management
client-server processes

46
Q

What is Service Advertisement 2 points l7

A

applications send announcements to other devices on the network
devices advertise the services they offer (printers and file servers managed by Active Directory (AD), self-advertising devices like wireless printers

47
Q

Name all types of protocols l7 5 points

A

Email (POP3, IMAP, SMTP)
Web Browsing (HTTP Hypertext Transfer Protocol, HTTPS)
Domain Name Service (DNS)
File Transfer Protocols (FTP, FTPS FTP over TLS, SFTP Simple File Transfer Protocol, ein veraltetes Netzwerkprotokoll ohne Verschlüsselung & Signatur)
Remote Access (Telnet, SSH Secure Shell, SNMP Simple Network Management Protocol)

48
Q

Encapsulation and Decapsulation, describe each and make a layer example for both

A

encapsulation (process of putting headers and sometimes trailers around data)
decapsulation (removing the applied encapsulation to access original data)
OSI Model Layers (moving down from l7 to 1 - encapsulation, moving up from l1 to 7 decapsulation)

49
Q

What does PDU stand for, what is it and name examples for each layer

A

Packet Data Unit (a single unit of informations transmitted in a computer network (terminology used for each layer is written as L(layer number) PDU, Example - L7 PDU
There are special names for the PDUs for layers 1, 2, 3 and 4
l1 Bits
l2 Frames
l3 Packets
l4 Segements (TCP), Datagrams (UDP)

50
Q

TCP Headers describe 10 mandatory fields, how many bytes of information?

A

10 mandatory fields, totalling 20 bytes of information: source port
destination port
sequence number
ack numbers
TCP data offset
Reserved data - always set to zero
Control flags (SYN - synchronize connection in three-way handshake, ACK acknowledgment of the successful receipt of data, FIN finished - tears down connections created by three-way handshake, RST reset - used when an unexpected packet is received, PSH push - ensures data is given priority, URG urgent identifies incoming data as urgent
window size
TCP checksum
Urgent pointer
mTCP optional

51
Q

UDP Header 4 fields, how many bytes?

A

8 byte header
Source port
Destination port
length - indicates total packet bytes
checksum - not mandatory

52
Q

IP Header Layer 3 13 fields

A

versions
length of IP header
type of service
total length of packet and header
identifier
flags
fragmented offset
time to live
protocol
header checksum
source IP address
destination ip address
options and padding

53
Q

Ethernet Header L2 4 points

A

destination MAC address
source MAC address (physical address used to identify a network card on a local area network, processed by switches)
EtherType field (used to indicate which protcol is encapsulated in the payload of a frame IPV4 or 6)
VLAN Tag - optional (IEEE 802.1Q, IEEE802.1AD)
a frame being sent at l2 will also contain a payload (data being sent across the network, 42 bytes - using VLANs, 46 bytes - no VLANs, maximum transmission unit (MTU) (max size for payload 1500 bytes for ethernet), Jumbo frames (9000 MTU) frames larger than 1500 bytes, require reconfiguring MTU

54
Q

Data Transmission what used for 3 points

A

encapsulation of data adding header at each layer
(L4 - source/destination ports, L3 source/desination IP address, L2 source/destination MAC addresses, L1 data transmitted as 1s and 0s)
decapsulation at each intermediate device until the device until the final host is reached
final host decapsulates to layer 7 for application understanding