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dwallraff/mtu_overhead.md

Created March 9, 2017 18:09
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Encapsulation MTU overhead
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mtu_overhead.md

MTU Encapsulation overhead

  • TCP header adds 20 bytes
  • IPv4 header adds 20 bytes
  • IPv6 header adds 40 bytes

  • GRE (IP Protocol 47) (RFC 2784) adds 24 bytes (20 byte IPv4 header, 4 byte GRE header)
  • 6in4 encapsulation (IP Protocol 41, RFC 4213) adds 20 bytes
  • 4in6 encapsulation (e.g. DS-Lite RFC 6333) adds 40 bytes
  • Any time you add another outer IPv4 header adds 20 bytes
  • IPsec encryption performed by the DMVPN adds 73 bytes for ESP-AES-256 and ESP-SHA-HMAC overhead (overhead depends on transport or tunnel mode and the encryption/authentication algorithm and HMAC)
  • MPLS adds 4 bytes for each label in the stack
  • IEEE 802.1Q tag adds 4 bytes (Q-in-Q would add 8 bytes)
  • VXLAN adds 50 bytes
  • OTV adds 42 bytes
  • LISP adds 36 bytes for IPv4 and 56 bytes for IPv6 encapsulation
  • NVGRE adds 42 bytes
  • STT adds 54 bytes
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