1.1

• OSI model


  A model for learning purposes only.
• TCP/IP model


  Actual collection of internet protocols
• PDU


  Data used at the layer.
• MAC Address

  
  

  Important Fields: Source and Destination
• Physical layer


  Layer 1 of the OSI model
• Bits


  PDU used in Layer 1
• Frames


  PDU used in Layer 2
• Mac Addresses

  Important fields in Layer 2
• Switches

  Devices relevant to Layer 2
• Layer 3

  Finding locations
• Layer 4

  Ensuring the delivery
• Layers 5,6,7

  Condensed into the application layer
• Encapsulation and decapsulation


  The process of encasing several PDUs as they move from one device to the other for transmitting data
• Encapsulation


  Process of enclosing data in a header and footer for transmission
• Switch


  Device that forwards data packets based on MAC addresses
• Header


  Information at the beginning of a data packet that includes control data
• Footer


  Information at the end of a data packet used for error checking
• Internet Protocol


  Protocol responsible for addressing and routing packets across networks
• TCP

  A connection-oriented protocol for reliable data delivery
• UDP

  User Datagram Protocol, a connectionless protocol for faster data delivery
• Connection-oriented


  Type of communication that requires a dedicated connection for data transfer
• Connectionless


  Type of communication that does not establish a dedicated connection before data transfer
• TCP Flags


  Guarantees the receiver gets the data.
• 1. TCP 3-way handshake

  1. SYN flag

  2. SYN/ACK flag

  3. ACK flag
• TCP 3-way handshake

  
  

  Data transfer begins after the ACK packet
• Payload


  Relative to the header of the data sent to the network
• L3 Header


  Contains L4 Header + Application Data
• L2 Header/Footer


  Contains L3 Header + L4 Header + Application Data
• Headers merge with the payload as they go down the layers
• Bigger MTU


  Results in faster performance
• Fragmentation


  Chopping a packet's size into smaller pieces
• MTU settings must match on all devices between 2 points
• The slowest MTU determines the MTU of all packets
• MTU is used in specialised networks like datacentres with MTU of 9000 bytes or more