Index

COMPUTER NETWORKING

  1. INTRO
    1. TCP/IP Five Layer Model
    2. NETWORKING DEVICES
    3. PHYSICAL LAYER
    4. DATALINK LAYER
  2. NETWORK LAYER
    1. IP
    2. SUBNET
    3. ROUTING
  3. TRANSPORT & APPLICATION LAYER
    1. TRANSPORT LAYER
    2. CONTROL FLAGS
    3. APPLICATION LAYER
    4. ALL TOGETHER
  4. NETWORK SERVICES
    1. DNS - NAMES RESOLUTION
    2. DHCP
    3. NAT
    4. VPN
  5. CONNECTING TO INTERNET
    1. BROADBAND
    2. WAN
    3. WIRELESS NETWORKING
  6. TROUBLESHOOTING
  7. MORE ABOUT
    1. DNS
    2. IPv6
    3. CLOUD

CONTROL FLAGS

TCP CONTROL FLAGS:
URG : (urgent) A value of one here indicates that the segment is considered urgent and the urgent pointer field has more data about this.
ACK : (acknowledge) A value of one in this field means that the acknowledgement number field should be examined.
PSH : (push) The transmitting device wants the recieving device to push currently-buffered data to the application on the recieving end as soon as possible.
RST : (reset) One of the sides in a TCP connection hasn't been able to properly recover from a series of missing or malformed segments.
SYN : (synchronise) It's used when first establishing a TCP connection and makes sure the recieving end knows to examine the sequence number field.
FIN : (finish) When this flag is set to a value 1, it means the transmitting computer doesn't have any more data to send and the connection can be closed.

THE THREE WAY HANDSHAKE :
images/9-1.png
Handshake : A way for two devices to ensure that they are speaking the same protocol .

FOUR WAY HANDSHAKE :
images/9-2.png

SOCKET :
The instantiation of an end-point in a potential TCP connection.
Socket state:
LISTEN - Ready and listening
SYN_SENT - Synchronisation has been sent but connection not established (client-side)
SYN_RECEIVED - A socket previously in listen state has received a synchronization req and sent back a SYN/ACK
ESTABLISHED - Connection UP
FIN_WAIT - FIN sent but ACK not received
CLOSE_WAIT - Application has been closed on TCP layer , but hasnt get relieved of that socket
CLOSE - Connection fully terminated


Connection-oriented Protocol:
Establishes a connection, and uses this to ensure that all data has been properly transmitted. like TCP

Connection-less protocol : ex: UDP

FIREWALL:
A device blocks traffic that meets certain criteria
Security
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