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

1. Overall Description:
3GPP working group SA2 (System Architecture) would like to inform the IETF that
SA2 has defined three SSC (Session and Service Continuity) modes in 3GPP TS
23.501 ("Architecture for the 5G System") clause 5.6.9 as follows: -       With
SSC mode 1, the network preserves the connectivity service provided to the UE.
For the case of PDU Session of IPv4 or IPv6 type, the IP address is preserved.
-       With SSC mode 2, the network may release the connectivity service
delivered to the UE and release the corresponding PDU Session. For the case of
IPv4 or IPv6 type, the network may release IP address(es) that had been
allocated to the UE. -       With SSC mode 3, changes to the user plane can be
visible to the UE, while the network ensures that the UE suffers no loss of
connectivity. A connection through new PDU Session Anchor point is established
before the previous connection is terminated in order to allow for better
service continuity. For the case of IPv4 or IPv6 type, the IP address is not
preserved in this mode when the PDU Session Anchor changes. SA2 has also
adopted the use of IPv6 multi-homing in a PDU Session (referred to as
"multi-homed IPv6 PDU Session") as described in 3GPP TS 23.501 clause 5.6.4.3,
a PDU Session being an association between the UE and a Data Network that
provides a data connectivity service, which is also defined in 3GPP TS 23.501.
When a new IPv6 Prefix is assigned to the UE for a multi-homed IPv6 PDU
Session, SA2 has decided to use the Router Advertisement message according to
IETF RFC 4191 to deliver the new IPv6 prefix to the UE and configure the
Routing Rules in the UE by using the Route Information Option. SA2 is looking
for a mechanism to deliver information regarding the service continuity usage
(e.g. whether the prefix can be replaced with or without grace period)
associated with the new IPv6 prefix to the UE via the 5G System user plane.

SA2 understands that the IETF draft "draft-ietf-dmm-ondemand-mobility-12"
defines four IP address types that can be mapped to the three SSC modes as
follows:

-       SSC mode 1 corresponds to either FIXED or SESSION_LASTING;
-       SSC mode 2 corresponds to NON_PERSISTENT;
-       SSC mode 3 corresponds to GRACEFUL_REPLACEMENT.

SA2 would like to understand if there is any IETF work related to delivery of
the IP address type (according to IETF draft
"draft-ietf-dmm-ondemand-mobility-12") in the Router Advertisement message,
which could be used for delivery of the service continuity usage associated
with a new IPv6 prefix in a multi-homed IPv6 PDU Session.

2. Actions:
To IETF Internet Area, DMM, 6MAN:
ACTION:         SA2 respectfully asks IETF Internet Area, DMM and 6MAN to
provide feedback on any IETF work related to delivery of IP address type
(according to IETF draft "draft-ietf-dmm-ondemand-mobility-12") in the Router
Advertisement message.

3. Date of Next SA2 Meetings:
 3GPPSA2#125  OR 22 - 26 Jan 2018    Gothenburg         SE
 3GPPSA2#126  OR 26 Feb - 2 Mar 2018    US              US