Week 2 - Network TCP-IP Flashcards
Network
Two or more computers connected with a medium for the purpose of sharing resources
Network Protocol
An internationally accepted set of rules for connecting computers to the Internet and most other
networks
TCP/IP
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
TCP/IP Application Layer
– 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
TCP/IP Transport Layer
– 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
TCP/IP Internet Layer
– 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
TCP/IP Link Layer – Network Interface
– 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)
TCP/IP Link Layer – Physical layer
– 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)
Internet Layer
- 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
Protocols in the Internet Layer:
- Internet Protocol (IP)
– Contains addressing information that enables packets to be routed
– Two basic functions of IP are addressing and fragmentation - Internet Control Message Protocol (ICMP)
– Used to generate IP error messages
Transport Layer
Coordinates delivery of data from one location to
another on the network
* First need to Consider:
1. Connection Oriented
2. Connectionless
Connection-Oriented:
– 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
Connectionless
– 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!
2 main protocols in Transport layer
Responsible for delivering data from one location to another on the network
Two main protocols
– Transmission Control Protocol: Connection-Oriented
– User Datagram Protocol: Connectionless
Transmission Control Protocol (TCP)
– 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
Network Ports
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
User Datagram Protocol (UDP)
– Connectionless protocol
– Doesn’t perform error checking or acknowledge that messages were sent successfully
Application Layer
- 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
IP Address
– 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
Assigning IP Addresses
Every device on a network must have unique IP address
– Every device connected to your router at home must have unique IP.
Static IP
– 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)
Dynamic IP
– 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)
Decimal Numbering System
- 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
Binary Numbering System
– Uses only two digits (1 and 0)
– Used in computers
- Bit (also known as a binary digit)
Represents a single binary value
Network ID
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
Host ID
Identifies a computer or device on a network
Network Switch
Connects a device on a computer network
Communicates between devices on same network
Router
Used to connect networks and forward packets to their destinations
Communicate with computers having different network ID’s
Network Gateway
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
Subnet masks
- IP Address has two parts
1. Segment to determine which network you want to send message to (Network ID)
- 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
IP Address Classes
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
Class A networks
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
Class B networks
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
Class C Networks
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
Problem with class based IP addresses
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)
Variable Length Subnet Mask
Number of available host addresses = 2n - 2
n = number of 0’s
Telnet
Unsecure connection for remote command line
SSH
Establish secure tunnel over unsecure network
Remote commands can be sent through tunnel
Linux Text editor
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
Text editor
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.
Shell Script
text file containing a sequence of commands
vi command line text editor VIM
Included with most versions of UNIX and Linux
Learning curve
Knowing how to use it is crucial
Vim editor
Modular editor
Runs in different operational modes
1. Command mode
Use key combinations as commands instead of typing text
- Insert or Replace Mode
Typed text is displayed onscreen - Extended mode
Used for more advanced commands, such as saving
files, exiting vim, or searching and replacing text
Starting Vim
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
vim Command mode
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
vim Undo commands
Undo changes
type u
Keep typing u until you have reached your oldest change
Extended vim mode
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
