What is it ?

• It is a connectionless protocol (when packets travel there is no connection)
• It is a datagram service (can connect to destination through different ways)
• technically packets follow any route
• Header talks about how the packet moves and its characteristics ( more like destination address)

Header Diagram

Explanation :

1. VER(Version):

• 4 bit (0100)
  1. HLEN(Header Length):

• 4 bit

• Talks about the length of the head and its significance

• Header size from 20-60 bytes
  1. Type of Service (DSCP) :

• 8 bit, first 3 defines the precedence, DTRC(Delay, Throughput, Reliability, Cost) defines the next 4 bits, last bit is reserved for future purpose

• For less Delay make it 1

• Rate of transfer (Throughput) should be more than 1 otherwise 0

• Reliability(Packets should be transferred properly), high ->1, otherwise 0

• Cost

• using the shortest path so 1, otherwise 0

• Differentiated Services Code Point
• 6 bits reserved, rest 2 bits for ECN (Explicit Congestion Notification)
  1. Datagram Length (Total Length): 16 bit (header + payload)
  2. Fragmentation:
• Identification

• identifies datagram originating from source

• Flags

• 3 bit, defines 3 flags

• Fragmentation offset

• 13 bit, defines the relative position of fragment w.r.t datagram

• Dividing the entire network into small fragments
  1. TTL (Time To Live):

• 8 bit

• We use this when data is in a loop
  1. Protocol : 8 bit, usage of different protocols will be mentioned
  2. Header Checksum : 16 bit, checksum is used for error detection
  3. Source IP Address : 32 bit
  4. Destination IP Address : 32 bit
  5. Options + Padding :

• To add extra data only when its not in 32 bit multiplication

• 40 bytes

Class Ranges

• Class A (0-127 bytes)
• Class B (128-191 bytes)
• Class C (192-223 bytes)
• Class D (224-239 bytes)

• Class E (240-255 bytes)