2.0 Networking Flashcards
A series of moving vans
Efficiently move large amounts of data • Use a shipping truck • The network topology is the road • Ethernet, DSL, cable system • The truck is the Internet Protocol (IP) • We’ve designed the roads for this truck • The boxes hold your data • Boxes of TCP and UDP • Inside the boxes are more things • Application information
TCP and UDP
Transported inside of IP
-Encapsulated by the IP protocol
Two ways to move data from place to place
-Different features for different applications
OSI Layer 4
-The transport layer
Multiplexing
-Use many different applications at the same time
-TCP and UDP
TCP - Transmission Control Protocol
Connection-oriented -A formal connection setup and close "Reliable" delivery -Recovery from errors -Can manage out-of-order messages or retransmissions Flow control -The receiver can manage how much data is sent
UDP-User Datagram Protocol
Connectionless
-No formal open or close to the connection
“Unreliable” delivery
-No error recovery
-No reordering of data or retransmissions
No flow control
-Sender determines the amount of data transmitted
Speedy delivery
The IP delivery truck delivers from one (IP) address to another (IP) address
-Every house has an address, every computer has an IP address
Boxes arrive at the house/IP address
-Where do the boxes go?
-Each box has a room name
Port is written on the outside of the box
-Drop the box into the right room
Lots of ports
IPv4 sockets - Server IP address, protocol, server application port number
-Client IP address, protocol, client port number
Non-epthemeral ports - permanent port numbers
-Ports 0 through 1,023
-Usually on a server or service
Ephemeral ports - temporary port numbers
-port 1,024 through 65,545
-Determined in real-time by the client
Port numbers
TCP and UDP ports can be any number between 0 and 65,535
Most servers (services) use non-ephemeral (not-temporary) port numbers
-This isn’t always the case
-It’s just a number
Port numbers are for communication, not security
Service port numbers need to be “well known”
TCP port numbers aren’t the same as UDP port numbers.
FTP - File Transfer Protocol
tcp/20 (active mode data), tcp/21 (control)
-Transfers files between systems
Authenticates with a username and password
-some systems use a generic/anonymouse login
Full-featured functionality
-List, add, delete, etc.
SSH - Secure Shell
Encrypted communication link - tcp/22
-looks and acts the same as Telnet
Telnet
Telnet - Telecommunication Network-tcp/23
Login to devices remotely
Console access
In-the-clear communication
Not the best choice for production systems
SMTP - Simple Mail Transfer Protocol
Server to server email transfer -tcp/25
Also used to send mail from a device to a mail server
-commonly configured on mobile devices
and email clients
Other protocols are used for clients to recieve email
-IMAP, POP3
DNS - Domain Name System
Converts a names to IP addresses - udp/53
www.professormesser.com= 162.159.246.164
These are very critical resources
-usually multiple DNS servers are in production
HTTP and HTTPS
Hypertext Transfer Protocol - tcp/80
-communication in the browser
-and by other applications
In the clear or encryped - HTTPS - tcp/443
-supported by nearly all web servers and clients
POP / IMAP
Receive emails from an email server
-authenticate and transfer
POP - Post office Protocol version 3 - tcp/110
-basic mail transfer functionality
IMAP4
-Internet Message Access Protocol v4 - tcp/143
-includes management of email inbox from multiple clients
RDP - Remote Desktop Protocol
Share a desktop from a remote location over tcp/3389
• Remote Desktop Services on many Windows versions
• Can connect to an entire desktop
or just an application
• Clients for Windows, macOS, Linux, Unix,
iPhone, Android, and others