Folks, The following is an OPS-DIR review of draft-ietf-6man-ug. SUMMARY: The draft points out a real problem in RFC 4291 and corrects the problem. I encourage the OPS AD's to ballot YES. Details: RFC 4291 says: "For all unicast addresses, except those that start with the binary value 000, Interface IDs are required to be 64 bits long and to be constructed in Modified EUI-64 format." As a consequence, the bits 6 and 7 of the IID (known as the u and g bits) are understood as described in IEEE802. Subsequent to the publication of RFC 4271, the IETF has published many documents in which the IID is not constructed in Modified EUI-64 format. Therefore, the u and g bits are relatively meaningless. draft-ietf-6man-ug corrects the problem by modifying RFC 4271 as follows: OLD> "For all unicast addresses, except those that start with the binary value 000, Interface IDs are required to be 64 bits long and to be constructed in Modified EUI-64 format." "For all unicast addresses, except those that start with the binary value 000, Interface IDs are required to be 64 bits long. If derived from an IEEE MAC-layer address, they must be constructed in Modified EUI-64 format." "The use of the universal/local bit in the Modified EUI-64 format identifier is to allow development of future technology that can take advantage of interface identifiers with universal scope." IPv6 unicast addresses consist of a prefix followed by an Interface Identifier (IID). The IID is supposed to be unique on the links reached by routing to that prefix, giving an IPv6 address that is unique within the applicable scope (link local or global). According to the IPv6 addressing architecture [RFC4291], when a 64-bit IPv6 unicast IID is formed on the basis of an IEEE EUI-64 address, usually itself expanded from a 48-bit MAC address, a particular format must be used: IPv6 unicast addresses consist of a prefix followed by an Interface Identifier (IID). The IID is unique on the links reached by routing to that prefix, giving an IPv6 address that is unique within the applicable scope (link local or global). According to the IPv6 addressing architecture [RFC4291], when a 64-bit IPv6 unicast IID is formed on the basis of an IEEE EUI-64 address, usually itself expanded from a 48-bit MAC address, a particular format must be used: