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

DATALINK LAYER

ETHERNET :
Old technology .
CSMA/CD : Used to determine when the communications channels are clear, and when a devices is free to transmit data.

MAC : A globally unique identifier attached to an individual network interface.
Octet form.
First three octets of a MAC address - OUI - Organizationally Unique Identifier
Last three octects :unique
→ Ethernet uses MAC to ensure that tha data it sends has both an address for machine that sends and recieves.
This way traffic can be organized, avoiding collisions.

Unicast :
Transmission is always meant for just one recieving address.

If the least significant bit in ip address is set to 0 -> Only for one destination address
If the least significant bit in ip address is set to 1 -> Multicast frame

Ethernet broadcast :Sent to every single device on the LAN .

ETHERNET FRAME : Highly structured info
Data Packet : An all-encompassing term that represents any single set of binary data being sent across a network link.

• Preamble – informs the receiving system that a frame is starting and enables synchronisation.
• SFD (Start Frame Delimiter) – signifies that the Destination MAC Address field begins with the next byte.
• Destination MAC – identifies the receiving system.
• Source MAC – identifies the sending system.
• Type – defines the type of protocol inside the frame, for example IPv4 or IPv6.
• Data and Pad – contains the payload data. Padding data is added to meet the minimum length requirement for this field (46 bytes).
• FCS (Frame Check Sequence) – contains a 32-bit Cyclic Redundancy Check (CRC) which allows detection of corrupted data.
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