RFC 6751, "Native IPv6 behind IPv4-to-IPv4 NAT Customer Premises Equipment (6a44)", October 2012

Errata ID: 3390
Status: Held for Document Update
Type: Technical
Publication Format(s) : TEXT
Reported By: Andreas Cudok
Date Reported: 2012-10-19
Held for Document Update by: Nevil Brownlee
Date Held: 2014-01-20

Section 6.6.2 says:

RR4-2 IPv6 PACKET FROM A 6a44 CLIENT TO ANOTHER 6a44 CLIENT

  (IPv4, N1, B, UDP(Z1, W, [IPv6, <C.N1.Z1...>, <C.N2.Z2...>, ...]))
  <figure omitted>

If ALL the following conditions are satisfied, the 6a44 relay MUST
return back via its downstream IPv4 interface an IPv6/ UDP/IPv4
packet containing the same encapsulated packet, having its UDP/IPv4
destination set to the UDP/IPv4 address found in the 6a44 destination
address, and having its UDP/IPv4 source set to the 6a44-relay
UDP/IPv4 address: (1) the IPv4 packet contains a complete UDP
datagram (protocol = 17, offset = 0, more-fragment bit = 0); (2) the
UDP payload is an IPv6 packet (length of at least 40 octets, version
= 6); (3) the IPv6 source address starts with the 6a44-network IPv6
prefix followed by the UDP/IPv4 source address of the received
packet; (4) the IPv6 destination address starts with the 6a44-network
IPv6 prefix.

It should say:

RR4-2 IPv6 PACKET FROM A 6a44 CLIENT TO ANOTHER 6a44 CLIENT

  (IPv4, N1, B, UDP(Z1, W, [IPv6, <C.N1.Z1...>, <C.N2 != B .Z2...>,
   ...]))
  <figure omitted>

If ALL the following conditions are satisfied, the 6a44 relay MUST
return back via its downstream IPv4 interface an IPv6/UDP/IPv4
packet containing the same encapsulated packet, having its UDP/IPv4
destination set to the UDP/IPv4 address found in the 6a44 destination
address, and having its UDP/IPv4 source set to the 6a44-relay
UDP/IPv4 address: (1) the IPv4 packet contains a complete UDP
datagram (protocol = 17, offset = 0, more-fragment bit = 0); (2) the
UDP payload is an IPv6 packet (length of at least 40 octets, version
= 6); (3) the IPv6 source address starts with the 6a44-network IPv6
prefix followed by the UDP/IPv4 source address of the received
packet; (4) the IPv6 destination address starts with the 6a44-network
IPv6 prefix and the embedded IPv4 address (bits 48-79) MUST be
different from the 6a44-relay anycast address.

Notes:

Requesting N2 != B prevents unwanted packets sent from the 6a44 relay to itself and makes the system more robust against DOS attacks.

This is really an enhancement, not an error, so it's Held (rather than Verified)

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