Technique for performing a context transfer
A technique for performing a context transfer from a first session management entity to a second session management entity in a mobile communication system is provided, wherein the context transfer concerns a data session associated with a User Equipment, UE, wherein the data session is handled by the first session management entity via a first gateway entity and wherein, after the context transfer, the data session is to be handled by the second session management entity via a second gateway entity. A method implementation of the technique is performed by the second session management entity and comprises, while the UE is in an inactive state, triggering (S 302 ) sending, to the second gateway entity, a session establishment request to establish a new session handling the data session via the second gateway entity, and triggering (S 304 ) providing, to the second gateway entity, an old Internet Protocol, IP, address assigned to the UE as part of an old session handling the data session via the first gateway entity, requesting the second gateway entity to assign the old IP address to the UE as part of the new session, besides a new IP address assigned to the UE as part of the new session, and, when the UE enters an active state from the inactive state, triggering (S 306 ) providing the new IP address to the UE.
1 . A method for performing a context transfer from a first session management entity to a second session management entity in a mobile communication system, the context transfer concerning a data session associated with a User Equipment (UE), the data session handled by the first session management entity via a first gateway entity and, after the context transfer, the data session handled by the second session management entity via a second gateway entity, the method being performed by the second session management entity and comprising:
while the UE is in an inactive state:
triggering sending, to the second gateway entity, a session establishment request to establish a new session handling the data session via the second gateway entity;
triggering providing, to the second gateway entity, an old Internet Protocol (IP) address assigned to the UE as part of an old session handling the data session via the first gateway entity, and requesting the second gateway entity to assign the old IP address to the UE as part of the new session, besides a new IP address assigned to the UE as part of the new session;
receiving, from the second gateway entity, tunnel endpoint information regarding the second gateway entity, the tunnel endpoint information comprising a tunnel endpoint identifier of a radio access node and the second gateway entity that is to be used by the first gateway entity; and
triggering providing the tunnel endpoint information to the first gateway entity and requesting the first gateway entity to forward DL packets directed to the old IP address to the second gateway entity for further delivery to the UE; and
when the UE enters an active state from the inactive state, triggering providing the new IP address to the UE.
2 . The method of claim 1 , wherein, in the inactive state, the UE is in at least one of an unconnected Non-Access Stratum (NAS) state and an inactive Radio Resource Control (RRC) state and wherein, in the active state, the UE is in a connected NAS state and in an active RRC state.
3 . The method of claim 1 , wherein triggering providing the new IP address to the UE is performed after the UE has stopped exchanging traffic.
4 . The method of claim 1 , wherein the first gateway entity maintains forwarding downlink (DL) packets directed to the old IP address according to a forwarding rule by which DL packets directed to the old IP address have been forwarded prior to providing the old IP address to the second gateway entity.
5 . The method of claim 1 , wherein the tunnel endpoint information is provided to the first gateway entity via the first session management entity, and wherein the tunnel endpoint information is included in a context request for the data session sent from the second session management entity to the first session management entity.
6 . The method of claim 5 , wherein the context request for the data session includes a gateway change indication indicating to the first session management entity to request the first gateway entity to forward DL packets directed to the old IP address to the second gateway entity for further delivery to the UE.
7 . The method of claim 1 , further comprising, while the UE is in the inactive state, triggering providing the tunnel endpoint information to a mobility management entity requesting the mobility management entity to configure, using the tunnel endpoint information, an Access Network (AN) node to forward uplink (UL) packets arriving from the UE to the second gateway entity.
8 . The method of claim 1 , further comprising, while the UE is in the inactive state, triggering providing a time indication to the first gateway entity, optionally via the first session management entity, indicating a maintenance time until which a packet forwarding state associated with the old session is at least to be maintained by the first gateway entity.
9 . The method of claim 1 , wherein the old IP address is provided to the second gateway entity in a session modification request sent to the second gateway entity to modify the new session.
10 . A method for performing a context transfer from a first session management entity to a second session management entity in a mobile communication system, the context transfer concerning a data session associated with a User Equipment (UE) the data session handled by the first session management entity via a first gateway entity and, after the context transfer, the data session handled by the second session management entity via a second gateway entity, the method being performed by the second gateway entity and comprising:
while the UE is in an inactive state:
receiving, from the second session management entity, a session establishment request to establish a new session handling the data session via the second gateway entity;
triggering establishing the new session;
receiving, from the second session management entity, an old Internet Protocol (IP) address assigned to the UE as part of an old session handling the data session via the first gateway entity;
receiving, from the second gateway entity, tunnel endpoint information regarding the second gateway entity, the tunnel endpoint information comprising a tunnel endpoint identifier of a radio access node and the second gateway entity that is to be used by the first gateway entity; and
triggering providing the tunnel endpoint information to the first gateway entity and requesting the first gateway entity to forward DL packets directed to the old IP address to the second gateway entity for further delivery to the UE; and
triggering assigning the old IP address to the UE as part of the new session, besides a new IP address assigned to the UE as part of the new session, the new IP address provided to the UE when the UE enters an active state from the inactive state.
11 . The method of claim 10 , wherein, in the inactive state, the UE is in at least one of an unconnected Non-Access Stratum (NAS) state and an inactive Radio Resource Control (RRC) state and wherein, in the active state, the UE is in a connected NAS state and in an active RRC state.
12 . The method of claim 10 , wherein the new IP address is to be provided to the UE after the UE has stopped exchanging traffic.
13 . The method of claim 10 , wherein the first gateway entity maintains forwarding downlink (DL) packets directed to the old IP address according to a forwarding rule by which DL packets directed to the old IP address have been forwarded prior to receiving the old IP address from the second session management entity.
14 . The method of claim 10 , further comprising:
receiving, from the first gateway entity, DL packets directed to the old IP address; and
triggering delivering the DL packets to the UE.
15 . The method of claim 10 , wherein the old IP address is received from the second session management entity in a session modification request to modify the new session.
16 . A method for performing a context transfer from a first session management entity to a second session management entity in a mobile communication system, the context transfer concerning a data session associated with a User Equipment (UE), the data session handled by the first session management entity via a first gateway entity and, after the context transfer, the data session handled by the second session management entity via a second gateway entity, the method being performed by the first session management entity and comprising:
while the UE is in an inactive state:
triggering providing, to the second session management entity, an old Internet Protocol (IP) address assigned to the UE as part of an old session handling the data session via the first gateway entity, the old IP address is to be provided to the second gateway entity requesting the second gateway entity to assign the old IP address to the UE as part of a new session established by the second gateway entity for handling the data session via the second gateway entity, besides a new IP address assigned to the UE as part of the new session, the new IP address provided to the UE when the UE enters an active state from the inactive state;
receiving, from the second gateway entity, tunnel endpoint information regarding the second gateway entity, the tunnel endpoint information comprising a tunnel endpoint identifier of a radio access node and the second gateway entity that is to be used by the first gateway entity; and
triggering providing the tunnel endpoint information to the first gateway entity and requesting the first gateway entity to forward DL packets directed to the old IP address to the second gateway entity for further delivery to the UE.
17 . The method of claim 16 , wherein, in the inactive state, the UE is in at least one of an unconnected Non-Access Stratum (NAS) state and an inactive Radio Resource Control (RRC) state and wherein, in the active state, the UE is in a connected NAS state and in an active RRC state.
18 . A method for performing a context transfer from a first session management entity to a second session management entity in a mobile communication system, the context transfer concerning a data session associated with a User Equipment (UE) the data session handled by the first session management entity via a first gateway entity and, after the context transfer, the data session handled by the second session management entity via a second gateway entity, the method being performed by the first gateway entity and comprising:
while the UE is in an inactive state:
receiving, from the first session management entity, a session release request to release an old session handling the data session via the first gateway entity, an old Internet Protocol (IP) address assigned to the UE as part of the old session, the old IP address being provided to the second gateway entity requesting the second gateway entity to assign the old IP address to the UE as part of a new session being established by the second gateway entity for handling the data session via the second gateway entity, besides a new IP address assigned to the UE as part of the new session, the new IP address provided to the UE when the UE enters the active state from the inactive state;
receiving, from the second gateway entity, tunnel endpoint information regarding the second gateway entity, the tunnel endpoint information comprising a tunnel endpoint identifier of a radio access node and the second gateway entity that is to be used by the first gateway entity; and
triggering providing the tunnel endpoint information to the first gateway entity and requesting the first gateway entity to forward DL packets directed to the old IP address to the second gateway entity for further delivery to the UE; and
maintaining a packet forwarding state associated with the old session at least until an expected time at which the UE enters an active state from the inactive state.