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Network Layer#

Control Plane#

  • Per-router control plane
  • Logically centralized control plane

IP - Internet Protocol#

IP Datagram Format#

  • 5 x 32-bit fixed-length headers
    • 4 bits protocol version
    • 4 bits header length (number of words)
    • 8 bits type of service
    • 16 bits total length (total datagram length in bytes)
    • 16 bits identification (identifier for fragmentation)
    • 3 bits flags (set to 1 if this is not the last fragment)
    • 13 bits fragment offset (for reassembly)
    • 8 bits time to live (maximum number of remaining hops)
    • 8 bits protocol (specifies the encapsulated protocol in data)
    • 16 bits header checksum
    • 32 bits source IP address
    • 32 bits destination IP address
  • options (variable length)
  • variable-length payload

IP Addressing#

  • IPV4: 32-bit address
  • IPV6: 128-bit address

What is an interface?

What is a subnet?

References#