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COM581 Network Operating Systems > Week 2 - Network TCP-IP > Flashcards

Week 2 - Network TCP-IP Flashcards

1
Q

Network

A

Two or more computers connected with a medium for the purpose of sharing resources

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2
Q

Network Protocol

A

An internationally accepted set of rules for connecting computers to the Internet and most other
networks

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3
Q

TCP/IP

A

A suit of networking protocols that Encapsulates a number of different protocols for different network communication tasks
* Two core protocols:
1. Transmission Control Protocol
2. Internet Protocol

3 layers, Application, Transport and Internet

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4
Q

TCP/IP Application Layer

A

– Programs talk to Application layer
– Application protocols
(e.g. email, file transfer, web browsing)
– Programs use different protocols depending on required task
– Sends Data Transport Layer
– Receives Data Transport Layer
– Application protocols: FTP, HTTP

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5
Q

TCP/IP Transport Layer

A

– Coordinates delivery of data from one location to another on the network
– Sending
* Break message up into packets
* Add correction info
– Receiving
* Re-assemble packets into original message
* Carries out error checking
* Identify proper application to deliver message to
– Protocols used: TCP and UDP

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6
Q

TCP/IP Internet Layer

A

– Implements rules of internet addressing
* Adds address to packets (IP Address)
* IP Address: 32 bit (4 octets)

Routers Implement Internet Layer
* Receive packets and then route them to the correct destination

Send
* Select the next-hop (gateway/network node) host and
transmit packet by passing to Link Layer

Destination Receive
* Pass packets to appropriate transport layer protocol

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7
Q

TCP/IP Link Layer – Network Interface

A

– Network Interface
* Defined by type of physical network the device is connected to (Ethernet)

Receiving:
– Delivers to appropriate Internet Layer Protocol

Sending:
– Specifies Internet Layer Protocol

Assemble final frame that will be sent over network
– Add source and destination MAC address
– MAC address (physical address of network card)

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8
Q

TCP/IP Link Layer – Physical layer

A

– Physical layer
* Consists of cables or other connection media
* Deals with data as bits traveling across a network
medium
* Convert packets to electricity (cable network) or
electromagnetic waves (wireless network)

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9
Q

Internet Layer

A
  • Sends packets to their specified destinations
  • Adds an IP-specific header to the packet
  • Header contains information such as:
    – Source
    – Destination
    – Version
    – Internet header length
    – Protocol
    – Other information about the data
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10
Q

Protocols in the Internet Layer:

A
  1. Internet Protocol (IP)
    – Contains addressing information that enables packets to be routed
    – Two basic functions of IP are addressing and fragmentation
  2. Internet Control Message Protocol (ICMP)
    – Used to generate IP error messages
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11
Q

Transport Layer

A

Coordinates delivery of data from one location to
another on the network
* First need to Consider:
1. Connection Oriented
2. Connectionless

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12
Q

Connection-Oriented:

A

– Protocol that requires that a logical connection be
established between two devices before transferring
data
– Devices Perform Handshaking
* Source requests connection
* Destination accepts connection
* Source confirms connections
– Bi-Directional
* Both sides must be able to communicate with each
other

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13
Q

Connectionless

A

– No Logical Connection made between devices
– No handshaking required
– One Direction
* Source to destination
* Source does not check if destination is still there, or if
it is prepared to receive information…it just sends it!

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14
Q

2 main protocols in Transport layer

A

Responsible for delivering data from one location to another on the network

Two main protocols
– Transmission Control Protocol: Connection-Oriented
– User Datagram Protocol: Connectionless

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15
Q

Transmission Control Protocol (TCP)

A

– Connection-oriented protocol
– When sending: keeps track of packets sent
– When receiving: confirms receipt of packets and
reassembles them into a single file after they’ve all
arrived
– Controls the flow of messages

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16
Q

Network Ports

A

Application specific construct serving as a communication endpoint

  • Packets are delivered to specific computer on a network.
    – May be multiple processes running on that computer
    interested in send/receiving network packets
  • Port Numbers are used to address packets to specific processes
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17
Q

User Datagram Protocol (UDP)

A

– Connectionless protocol
– Doesn’t perform error checking or acknowledge that messages were sent successfully

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18
Q

Application Layer

A
  • Sits at the top of the TCP/IP model
  • Contains the higher-level protocols used for network communication in the Transport layer
  • Provides services for user applications to employ
    – E.g. Web Browser using HTTP protocol
    – E.g. Email Client using SMTP protocol
  • Application Layer Standardizes Communication
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19
Q

IP Address

A

– A unique number that identifies a computer or device on a TCP/IP network
– Format
* Four numbers (Octets) separated by periods
* Example: 192.168.75.136

20
Q

Assigning IP Addresses

A

Every device on a network must have unique IP address
– Every device connected to your router at home must have unique IP.

21
Q

Static IP

A

– Manually assigned IP by user
– User must enter IP, Subnet Mask, Default Gateway
and DNS Server IP
– Could potentially give 2 devices same IP (IP
Conflict)

22
Q

Dynamic IP

A

– DHCP: Dynamic Host Configuration Protocol
– Computer Connects to network, it requests IP information from the DHCP server.
– DHCP assigns IP, Subnet, Gateway, DNS
– Keeps record of assigned IP addresses (no duplicate IP)

23
Q

Decimal Numbering System

A
  • Decimal numbers
    – Used in IP addresses
    – Have 10 possible digits (0 to 9)
  • Computers convert decimal IP addresses into binary numbers
  • Decimal numbers divided into four octets
    – Each octet is 8 bits
    – An IP address has 32 bits
24
Q

Binary Numbering System

A

– Uses only two digits (1 and 0)
– Used in computers
- Bit (also known as a binary digit)
Represents a single binary value

25
Q

Network ID

A

Identifies the network where the host is located
Computers can communicate only with other computers on the same network
– They must have the same network ID to exchange
information

26
Q

Host ID

A

Identifies a computer or device on a network

27
Q

Network Switch

A

Connects a device on a computer network
Communicates between devices on same network

28
Q

Router

A

Used to connect networks and forward packets to their destinations
Communicate with computers having different network ID’s

29
Q

Network Gateway

A

Node in a network that connects two networks with different transmission protocols together
* Commonly referred to as a router, with key role of enabling traffic flow in and out of a network

30
Q

Subnet masks

A
  • IP Address has two parts
    1. Segment to determine which network you want to send message to (Network ID)
  1. Segment to determine which computer on that network you want to send message to (Host ID)
  • Subnet mask
    – Used to determine which part of an IP address is the network ID and which part is the host ID
  • A subnet mask is 32 bits

When computer reads subnet mask, it converts decimal to binary.

1 means that the corresponding part of the IP address is a NETWORK address

0 means that the corresponding part of the IP address is a
HOST address

31
Q

IP Address Classes

A

IP addresses are divided into five classes to accommodate varying network sizes
– Class A, Class B, and Class C: most common classes

– Class D and E networks are for multicasting and
experimentation

32
Q

Class A networks

A

Subnet mask is 255.0.0.0
* The first bit of IP Address is always 0
* There can be only 127 Class A networks on the entire Internet
– Allows 16,777,214 hosts per network
* Assigned to regional internet registries and Dept of
Defence in US
– Several companies have a Class A network including;
* Apple, Ford

33
Q

Class B networks

A

Subnet mask is 255.255.0.0
* The first two bits of IP Address are always 10
* Assigned to large organizations
– Such as government agencies, universities, and typical companies

34
Q

Class C Networks

A

Subnet mask is 255.255.255.0
* The first three bits of IP Address are always 110
* More than 2 million Class C networks are possible
– Each network can have only 254 hosts
* Assigned to small organizations

35
Q

Problem with class based IP addresses

A

If we had 2000 hosts, we would have to choose class B, but then we would hae 63,000+ unused host addressed which would be a waste of 1000’s of potential network addresses.

Solution - Use classless IP addressing
Classless Interdomain Routing (CIDR)

36
Q

Variable Length Subnet Mask

A

Number of available host addresses = 2n - 2
n = number of 0’s

37
Q

Telnet

A

Unsecure connection for remote command line

38
Q

SSH

A

Establish secure tunnel over unsecure network
Remote commands can be sent through tunnel

39
Q

Linux Text editor

A

2 types
GUI Editor and Command Line Editor

GUI
- Intuitive and easy to use
- Select and edit text quickly with mouse

Command Line Editor
- GUI are not always available, particularly on servers
- More difficult to use
- Powerful when you know how to use

40
Q

Text editor

A

Program sued to create and edit plain text files
Not same as a word processor
Main purpose is to create a file to be used by another program e.g., HTML for a web browser.

41
Q

Shell Script

A

text file containing a sequence of commands

42
Q

vi command line text editor VIM

A

Included with most versions of UNIX and Linux

Learning curve

Knowing how to use it is crucial

43
Q

Vim editor

A

Modular editor

Runs in different operational modes
1. Command mode
Use key combinations as commands instead of typing text

  1. Insert or Replace Mode
    Typed text is displayed onscreen
  2. Extended mode
    Used for more advanced commands, such as saving
    files, exiting vim, or searching and replacing text
44
Q

Starting Vim

A

Type
vim followed by a filename and press enter

If the filename doesn’t exist, vim creates an empty
file with this filename

If the filename does exist, vim opens up that file for
editing

45
Q

vim Command mode

A

Chosen automatically when starting vim

Allows you to issue different commands for
navigation and changing modes

Examples:
i
Enter insert mode
H
Move cursor to top of screen
G
Move cursor to bottom of file

46
Q

vim Undo commands

A

Undo changes
type u
Keep typing u until you have reached your oldest change

47
Q

Extended vim mode

A

Offers advanced features

Save and quit

Search and replace

Customization options

Enter extended mode
Type the : symbol

Example:
:q quits vim
:wq saves and quits vim

COM581 Network Operating Systems (11 decks)

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