Liaison statement
LS on indicating service continuity usage of the additional IPv6 prefix in Router Advertisement

1       Overall description

SA2 would like to thank the IETF DMM working group chairs for their LS reply on
indicating the mobility property of the additional IPv6 prefix in Router
Advertisement in S2-181481.

Regarding the following components in the IETF’s reply LS:
     1.) The approach of coloring IPv4 and IPv6 addresses/prefixes with
     mobility properties. 3.) The approach of indicating the coloring meta-data
     to the applications on the mobile node (UE in 3GPP terminology).

SA2 has noted that both aspects are covered in the IETF DMM draft
draft-ietf-dmm-ondemand-mobility-13 and has also noted that it will be released
soon as informational standard.

Regarding the following component in the IETF’s reply LS:
    2.) The approach of network including property meta-data in address
    assignment procedures

SA2 would like to point out that among the four mechanisms for address
configuration delivery mentioned in your LS reply (i.e. DHCPv4, DHCPv6, IPv6 ND
and IKEv2) only the IPv6 ND mechanisms, and in particular the Router
Advertisement message, seem to be applicable in the 5G System architecture in
the specific context of Multi-homed IPv6 PDU Sessions.

With respect to the following question in the IETF’s reply LS:
                We also like to point out that, all though the LS statement
                explicitly refers to both IPv4 and IPv6 address types, however
                it only mentions about (RA) (IPv6 ND implied) as the mechanism
                for address property delivery. It is to be noted that the
                approach of delivering coloring meta-data in RA messages will
                most likely be to limited to IPv6 address/prefix types and will
                not be extended to IPv4 addresses. If this capability is
                required for IPv4, we may have to possibly extend DHCP
                protocol(s).

                We request 3GPP to clarify if the Ask is explicitly for IPv6,
                or if its for both IPv4 and IPv6 address/prefix types.

SA2 would like to clarify that the request is explicitly for IPv6. SA2
discussed the example documents that were referenced in your LS reply and
concluded that the following draft seems to be the most promising candidate for
the problem under discussion in this correspondence:
https://www.ietf.org/id/draft-feng-dmm-ra-prefixtype-01.txt. SA2 would like to
kindly ask IETF DMM working group to keep SA2 updated of the work on the
subject of including property meta-data in IPv6 ND address assignment
procedures for potential use in the 5G System to indicate the mobility property
of additional IPv6 prefixes assigned as part of the Multi-homed IPv6 PDU
Session functionality.

2       Actions
To IETF DMM working group:
    ACTION: SA2 would like to kindly ask IETF DMM working group to keep SA2
    updated of the work on the subject of including property meta-data in IPv6
    ND address assignment procedures for potential use in the 5G System to
    indicate the mobility property of additional IPv6 prefixes assigned as part
    of the Multi-homed IPv6 PDU Session functionality.

3       Dates of next TSG SA WG2 meetings
TSG SA WG2 Meeting 127  16 - 20 Apr 2018        Sanya, CN
TSG SA WG2 Meeting 127-Bis      28 May – 1 Jun 2018     Newport Beach, US