Patent ID: 12261915

DETAILED DESCRIPTION

A. Enhanced DNS Solution

Since the PGW/SMF pertaining to the same PGW/SMF set will have the same functionalities, the PDN connection created by any of these PGWs can be handover or served by any other PGW in the same PGW/SMF set. That means that, when the MME performs the DNS procedure to select a PGW, all PGWs in the same set will appear in the response message. In one embodiment, information is added in the PGW Name Authority Pointer (NAPTR) records in the DNS to enable the MME to know that these PGWs pertain to the same PGW set.

Hence, in one embodiment of the present disclosure, the PGW NAPTR record is enhanced, considering support of the NF set concept as a new network capability. In one example embodiment, “+nc-set<setId>” is appended to the “app-protocol” name as specified in 3 GPP TS 23.003 (see, e.g., V16.3.0), clause 19.4.3, where the set<setId> is set to the first label of NF Set Id of a SMF set, as specified in clause 28.12 of 3 GPP TS 23.003. In one embodiment, a completely new character string e.g. “+set-<setId>” is appended to the “app-protocol” name as specified in TS 23.003, clause 19.4.3.

For example, in one embodiment, the follow string is added into a PGW NAPTR record:x-3gpp-pgw: x-s5-gtp+nc-set<setId>”, “x-3gpp-pgw: x-s8-gtp+nc-set<setId>” orx-3gpp-pgw: x-s5-gtp+set-<setId>”, “x-3gpp-pgw: x-s8-gtp+set-<setId>”

In this example, the MME is trying to select a PGW for the Access Point Name (APN) “imsTV1”. Therefore, the MME uses the APN's Fully Qualified Domain Name (FQDN) to perform a DNS query for the NAPTR record of the PGW. Then, in the DNS server, it may configure as below for PGW/SMFs pertaining to a PGW/SMF set.

imsTV1.apn          (; IN NAPTR order pref. flag service       regexp replacementIN NAPTR 100 999 “a” “x-3gpp-pgw:x-s5-gtp+nc-set100:x-s8-gtp+nc-set100”   “”topoff.vip1.gw01.nodes )IN NAPTR 200 999 “a” “x-3gpp-pgw:x-s5-gtp+nc-set100:x-s8-gtp+nc-set100”   “”topoff.vip1.gw21.nodes;;

In above example, both gw01 and gw21 are pertaining to (e.g., belong to) a set with setId=100.

In this example, the PGW/SMF SET FQDN will be“set100.smfset.5gc.mnc012.mcc345”

The bolded+nc-set100, may use a new character string, e.g. set-100, instead.

Note that, with Solution A, there will be even less SGW impact. The only impact is that the new PGW (taking over the old PGW) may still use Update Bearer Request message to inform the MME. See Enhancement 4 in Solution B below. While not essential for understanding the solutions described herein, the interested reader can also refer to 3 GPP TS 29.303, clause 5.8.2 SGW, PGW and GGSN Selection Procedure.

B. Enhancements to the Proposed Solution of CR C4-204184

In some embodiments, systems and methods are disclosed herein that use one or more of the following enhancements to the solution described in CR C4-204184.

Enhancement 1: In the Create Session Response message sent from the PGW, in addition to the PGW SET FQDN, the PGW may include a list of alternative PGW IP Addresses to be used by the MME in case the serving PGW has failed;

Enhancement 2: In addition to using PGW Restart Indication message to notify the MME that PGW has restarted or has failed, the MME can derive the PGW failure and re-select another alternative PGW if it receives a GTPv2 cause #100 (See clause 8.4 of TS 29.274) “Remote peer not responding” from the SGW. This is to solve the PGW partial failure.

Enhancement 3: When the MME has decided to reselect an alternative PGW, the MME uses (e.g., always) a Create Session Request message as in an SGW relocation procedure (as specified in 5.10.4 in TS 23.401) instead of using a Modify Bearer Request message. The MME sends the Create Session Request message with new PGW F-TEID of the alternative PGW to a (new) SGW. If the Create Session Request message was sent to the existing SGW, the existing SGW should consider this as a colliding case, as specified in 7.2.1 of TS 29.274 as below, but the SGW should keep the same SGW-U tunnel over S1 (towards eNB) and over S5/S8 (towards PGW-U) to avoid the signaling towards the SGW-U considering the remote S1 eNB GTP-U tunnel endpoint if available and remote S5/S8 PGW-U GTP-U tunnel endpoint provided by the MME in the Create Session Request message is the same as the existing ones (since user plane path is not impacted).If the new Create Session Request received by the SGW collides with an existing active PDN connection context (the existing PDN connection context is identified with the tuple [IMSI, EPS Bearer ID], where IMSI shall be replaced by TAC and SNR part of ME Identity for emergency or RLOS attached UE without UICC or authenticated IMSI), this Create Session Request shall be treated as a request for a new session. Before creating the new session, the SGW should delete:the existing PDN connection context locally, if the Create Session Request is received with the TEID set to zero in the header, or if it is received with a TEID not set to zero in the header and it collides with the default bearer of an existing PDN connection context;the existing dedicated bearer context locally, if the Create Session Request collides with an existing dedicated bearer context and the message is received with a TEID not set to zero in the header.In the former case, if the PGW S5/S8 IP address for control plane received in the new Create Session Request is different from the PGW S5/S8 IP address for control plane of the existing PDN connection, the SGW should also delete the existing PDN connection in the corresponding PGW by sending a Delete Session Request message.
NOTE that, the MME need not immediately to send Create Session Request message, e.g. for those UEs in idle mode.

Enhancement 4: When the failed PGW or a new PGW (taking over the PDN connection) wants to update the PGW F-TEID for a given PDN connection, it can send a Create/Update/Delete Bearer Request message, but it does not require SGW to store the new PGW F-TEID. Instead, the MME performs an SGW relocation procedure as described in the Enhancement 3 using the new PGW F-TEID as received in the Create/Update/Delete Bearer Request message.

There are, proposed herein, various embodiments which address one or more of the issues disclosed herein.

Certain embodiments may provide one or more of the following technical advantage(s). Embodiments of the solutions described herein enable the restoration of PDN connection(s) at the failure of the serving PGW (of the said PDN connection(s)), where the embodiments of the solutions described herein have very few impact on the legacy system, e.g. in the MME and SGW.

Some of the embodiments contemplated herein will now be described more fully with reference to the accompanying drawings. Other embodiments, however, are contained within the scope of the subject matter disclosed herein, the disclosed subject matter should not be construed as limited to only the embodiments set forth herein; rather, these embodiments are provided by way of example to convey the scope of the subject matter to those skilled in the art.

Radio Node: As used herein, a “radio node” is either a radio access node or a wireless communication device.

Radio Access Node: As used herein, a “radio access node” or “radio network node” or “radio access network node” is any node in a Radio Access Network (RAN) of a cellular communications network that operates to wirelessly transmit and/or receive signals. Some examples of a radio access node include, but are not limited to, a base station (e.g., a New Radio (NR) base station (gNB) in a Third Generation Partnership Project (3 GPP) Fifth Generation (5 G) NR network or an enhanced or evolved Node B (eNB) in a 3 GPP Long Term Evolution (LTE) network), a high-power or macro base station, a low-power base station (e.g., a micro base station, a pico base station, a home eNB, or the like), a relay node, a network node that implements part of the functionality of a base station (e.g., a network node that implements a gNB Central Unit (gNB-CU) or a network node that implements a gNB Distributed Unit (gNB-DU)) or a network node that implements part of the functionality of some other type of radio access node.

Core Network Node: As used herein, a “core network node” is any type of node in a core network or any node that implements a core network function. Some examples of a core network node include, e.g., a Mobility Management Entity (MME), a Packet Data Network Gateway (P-GW), a Service Capability Exposure Function (SCEF), a Home Subscriber Server (HSS), or the like. Some other examples of a core network node include a node implementing a Access and Mobility Management Function (AMF), a User Plane Function (UPF), a Session Management Function (SMF), an Authentication Server Function (AUSF), a Network Slice Selection Function (NSSF), a Network Exposure Function (NEF), a Network Function (NF) Repository Function (NRF), a Policy Control Function (PCF), a Unified Data Management (UDM), or the like.

Communication Device: As used herein, a “communication device” is any type of device that has access to an access network. Some examples of a communication device include, but are not limited to: mobile phone, smart phone, sensor device, meter, vehicle, household appliance, medical appliance, media player, camera, or any type of consumer electronic, for instance, but not limited to, a television, radio, lighting arrangement, tablet computer, laptop, or Personal Computer (PC). The communication device may be a portable, hand-held, computer-comprised, or vehicle-mounted mobile device, enabled to communicate voice and/or data via a wireless or wireline connection.

Wireless Communication Device: One type of communication device is a wireless communication device, which may be any type of wireless device that has access to (i.e., is served by) a wireless network (e.g., a cellular network). Some examples of a wireless communication device include, but are not limited to: a User Equipment device (UE) in a 3 GPP network, a Machine Type Communication (MTC) device, and an Internet of Things (IoT) device. Such wireless communication devices may be, or may be integrated into, a mobile phone, smart phone, sensor device, meter, vehicle, household appliance, medical appliance, media player, camera, or any type of consumer electronic, for instance, but not limited to, a television, radio, lighting arrangement, tablet computer, laptop, or PC. The wireless communication device may be a portable, hand-held, computer-comprised, or vehicle-mounted mobile device, enabled to communicate voice and/or data via a wireless connection.

Network Node: As used herein, a “network node” is any node that is either part of the RAN or the core network of a cellular communications network/system.

Note that the description given herein focuses on a 3 GPP cellular communications system and, as such, 3 GPP terminology or terminology similar to 3 GPP terminology is oftentimes used. However, the concepts disclosed herein are not limited to a 3 GPP system.

Note that, in the description herein, reference may be made to the term “cell”; however, particularly with respect to 5 G NR concepts, beams may be used instead of cells and, as such, it is important to note that the concepts described herein are equally applicable to both cells and beams.

FIG.5

FIG.5illustrates one example of a cellular communications system500in which embodiments of the present disclosure may be implemented. In the embodiments described herein, the cellular communications system500is a system that enables interworking between a 5 G system (5 GS) including a Next Generation RAN (NG-RAN) and a 5 G Core (5 GC) and an Evolved Packet System (EPS) including an Evolved Universal Terrestrial RAN (E-UTRAN) and a Evolved Packet Core (EPC). In this example, the RAN includes base stations502-1and502-2, which in the NG-RAN include NR base stations (gNBs) and optionally next generation eNBs (ng-eNBs) (e.g., LTE RAN nodes connected to the 5 GC) and in the E-UTRAN include eNBs, controlling corresponding (macro) cells504-1and504-2. The base stations502-1and502-2are generally referred to herein collectively as base stations502and individually as base station502. Likewise, the (macro) cells504-1and504-2are generally referred to herein collectively as (macro) cells504and individually as (macro) cell504. The RAN may also include a number of low power nodes506-1through506-4controlling corresponding small cells508-1through508-4. The low power nodes506-1through506-4can be small base stations (such as pico or femto base stations) or Remote Radio Heads (RRHs), or the like. Notably, while not illustrated, one or more of the small cells508-1through508-4may alternatively be provided by the base stations502. The low power nodes506-1through506-4are generally referred to herein collectively as low power nodes506and individually as low power node506. Likewise, the small cells508-1through508-4are generally referred to herein collectively as small cells508and individually as small cell508. The cellular communications system500also includes a core network(s)510, which in the 5 G System (5 GS) is referred to as the 5 GC and in the EPS is referred to as the EPC. The base stations502(and optionally the low power nodes506) are connected to the core network510.

The base stations502and the low power nodes506provide service to wireless communication devices512-1through512-5in the corresponding cells504and508. The wireless communication devices512-1through512-5are generally referred to herein collectively as wireless communication devices512and individually as wireless communication device512. In the following description, the wireless communication devices512are oftentimes UEs, but the present disclosure is not limited thereto.

FIG.6

FIG.6illustrates one example of the cellular communications system500in which embodiments of the present disclosure may be implemented. In this example, the cellular communications system500includes both a 5 GS and an EPS with interworking between the 5 GS and EPS. As illustrated, in regard to the EPS, the cellular communications system500includes an E-UTRAN600, which includes one or more base stations502that are, in this case, eNBs and a number of core network nodes of the EPC. As illustrated, the network nodes of the EPC include, in this example, an MME602and a SGW604. In regard to the 5 GS, the cellular communications system500includes a NG-RAN606, which includes one or more base stations that are, in this case, gNBs or ng-eNBs and a number of NFs of the 5 GC. As illustrated, the NFs include an AMF608and a PCF610. In addition, to enable interworking between the 5 GS and the EPS, the cellular communications system500includes a number of combined, or joint, NFs. The combined NFs include, in this example, a combined HSS and UDM612(also referred to herein as HSS+UDM612or HSS/UDM612), a combined SMF and PGW-C614(also referred to herein as a SMF+PGW-C614or SMF/PGW-C614), and a combined UPF and PGW-U616(also referred to herein as a UPF+PGW-U616or UPF/PGW-U616). The cellular communications system500, and in particular the MME602, is able to communicate with a DNS618as described herein.

Embodiments of the present disclosure provide a new DNS solution and some enhancements to the solution proposed in C4-204184 to enable restoration of the PDN connections when the serving SMF/PGW-C has failed while the failed SMF/PGW-C belongs to a PGW/SMF-C set. The embodiments of the present disclosure described herein include either or both of the following two aspects:A. new DNS solution, andB. enhancements to the proposed solution (C4-204-184), each of which is described below.
A. Enhanced DNS Solution

Since the SMF/PGW-C's (e.g., two or more instances of the SMF/PGW-C614, which are denoted herein as SMF/PGW-C614-1,614-2, etc.) belonging to the same SMF/PGW-C set will have the same functionalities, the PDN connection created by any SMF/PGW-C614-xin the same SMF/PGW-C set (which are sometimes referred to simply as “PGW-Cs” or “PGWs” when referring to EPS functionality) can be handed over or served by any other SMF/PGW-C614-yin the same SMF/PGW-C set. That means that, when the MME602performs a DNS procedure to select a PGW (i.e., to select a SMF/PGW-C614), all PGWs (i.e., all SMF/PGW-C's) in the same SMF/PGW-C set will appear in the DNS response message. In one embodiment, information is added in the PGW Name Authority Pointer (NAPTR) records in the DNS618to enable the MME602to know that these PGWs (i.e., SMF/PGW-C's) pertain to the same PGW set (i.e., the same SMF/PGW-C set).

Hence, in one embodiment of the present disclosure, the PGW NAPTR record for the SMF/PGW-C614is enhanced, considering support of the NF set concept as a new network capability. In one example embodiment, a string (e.g., “+nc-set<setid>”) is appended to the “app-protocol” name as specified in 3 GPP TS 23.003 (see, e.g., V16.3.0), clause 19.4.3, where string indicates the NF Set ID. In one particular example described herein, the string appended to the “app-protocol” name is “+nc-set<setId>”, where the set<setId> is set to the first label of NF Set Id of a SMF set (i.e., a SMF/PGW-C set), as specified in clause 28.12 of 3 GPP TS 23.003. Thus, in one embodiment, a completely new character string e.g. “+set-<setId>” is appended to the “app-protocol” name as specified in TS 23.003, clause 19.4.3.

For example, in one embodiment, the follow string is added into a PGW NAPTR record:x-3gpp-pgw: x-s5-gtp+nc-set<setId>”, “x-3gpp-pgw: x-s8-gtp+nc-set<setId>” orx-3gpp-pgw: x-s5-gtp+set-<setId>”, “x-3gpp-pgw: x-s8-gtp+set-<setId>”

As one example, consider a scenario in which the MME602is trying to select a PGW for the Access Point Name (APN) “imsTV1”. Therefore, the MME602uses the APN's Fully Qualified Domain Name (FQDN) to perform a DNS query for the NAPTR record of the PGW. Then, in the DNS618, the PGW NAPTR record may be configured as shown below for SMF/PGW-Cs614pertaining to a PGW/SMF set that satisfies the DNS query.

imsTV1.apn          (; IN NAPTR order pref. flag service       regexp replacementIN NAPTR 100 999 “a” “x-3gpp-pgw:x-s5-gtp+nc-set100:x-s8-gtp+nc-set100”   “”topoff.vip1.gw01.nodes )IN NAPTR 200 999 “a” “x-3gpp-pgw:x-s5-gtp+nc-set100:x-s8-gtp+nc-set100”   “”topoff.vip1.gw21.nodes;;
In above example, both gw01 and gw21 are pertaining to (e.g., belong to) a set with setId=100. In this example, the PGW/SMF SET FQDN will be“set100.smfset.5gc.mnc012.mcc345”
The bolded+nc-set100, may use a new character string, e.g. set-100, instead.

Note that, with Solution A, there will be even less SGW impact. The only impact is that the new PGW (taking over the old PGW) may still use Update Bearer Request message to inform the MME. See Enhancement 4 in Solution B below. While not essential for understanding the solutions described herein, the interested reader can also refer to 3 GPP TS 29.303, clause 5.8.2 SGW, PGW and GGSN Selection Procedure.

B. Enhancements to the Proposed Solution of CR C4-204184

In some embodiments, systems and methods are disclosed herein that use one or more of the following enhancements to the solution described in CR C4-204184.

Enhancement 1: In the Create Session Response message sent from the PGW, in addition to the PGW SET FQDN, the PGW may include a list of alternative PGW IP Addresses to be used by the MME in case the serving PGW has failed;

Enhancement 2: In addition to using PGW Restart Indication message to notify the MME that PGW has restarted or has failed, the MME can derive the PGW failure and re-select another alternative PGW if it receives a GTPv2 cause #100 (See clause 8.4 of TS 29.274) “Remote peer not responding” from the SGW. This is to solve the PGW partial failure.

Enhancement 3: When the MME has decided to reselect an alternative PGW, the MME uses (e.g., always) a Create Session Request message as in an SGW relocation procedure (as specified in 5.10.4 in TS 23.401) instead of using a Modify Bearer Request message. The MME sends the Create Session Request message with new PGW F-TEID of the alternative PGW to a (new) SGW. If the Create Session Request message was sent to the existing SGW, the existing SGW should consider this as a colliding case, as specified in 7.2.1 of TS 29.274 as below, but the SGW should keep the same SGW-U tunnel over S1 (towards eNB) and over S5/S8 (towards PGW-U) to avoid the signaling towards the SGW-U considering the remote S1 eNB GTP-U tunnel endpoint if available and remote S5/S8 PGW-U GTP-U tunnel endpoint provided by the MME in the Create Session Request message is the same as the existing ones (since user plane path is not impacted).If the new Create Session Request received by the SGW collides with an existing active PDN connection context (the existing PDN connection context is identified with the tuple [IMSI, EPS Bearer ID], where IMSI shall be replaced by TAC and SNR part of ME Identity for emergency or RLOS attached UE without UICC or authenticated IMSI), this Create Session Request shall be treated as a request for a new session. Before creating the new session, the SGW should delete:the existing PDN connection context locally, if the Create Session Request is received with the TEID set to zero in the header, or if it is received with a TEID not set to zero in the header and it collides with the default bearer of an existing PDN connection context;the existing dedicated bearer context locally, if the Create Session Request collides with an existing dedicated bearer context and the message is received with a TEID not set to zero in the header.In the former case, if the PGW S5/S8 IP address for control plane received in the new Create Session Request is different from the PGW S5/S8 IP address for control plane of the existing PDN connection, the SGW should also delete the existing PDN connection in the corresponding PGW by sending a Delete Session Request message.
NOTE that, the MME need not immediately to send Create Session Request message, e.g. for those UEs in idle mode.

Enhancement 4: When the failed PGW or a new PGW (taking over the PDN connection) wants to update the PGW F-TEID for a given PDN connection, it can send a Create/Update/Delete Bearer Request message, but it does not require SGW to store the new PGW F-TEID. Instead, the MME performs an SGW relocation procedure as described in the Enhancement 3 using the new PGW F-TEID as received in the Create/Update/Delete Bearer Request message.

There are, proposed herein, various embodiments which address one or more of the issues disclosed herein.

Certain embodiments may provide one or more of the following technical advantage(s). Embodiments of the solutions described herein enable the restoration of PDN connection(s) at the failure of the serving PGW (of the said PDN connection(s)), where the embodiments of the solutions described herein have very few impact on the legacy system, e.g. in the MME and SGW.

FIGS.7A-7C

FIGS.7A-7Cillustrate the operation of the cellular communications system500ofFIGS.5and6in accordance with at least some aspects of Solutions A and B described above. Note that, in this example, there is a SMF/PGW-C set (also referred to herein as a PGW set) that includes two (or more) SMF/PGW-C instances, which are denoted here as SMF/PGW-C614-1and SMF/PGW-C614-2. Further note that the SMF/PGW-C614-1and the SMF/PGW-C614-2are sometimes referred to as PGW-C's or PGWs when referring to the PGW-C/PGW functionality of the SMF/PGW-C's614-1and614-2.FIGS.7A-7Cillustrate a first alternative that uses an enhanced NAPTR DNS record in accordance with an embodiment of the present disclosure. The steps of the process ofFIGS.7A-7Care as follows:Step700: The UE512sends an attach request to the MME602via the E-UTRAN600.Step702: The MME602sends an Update Location Request to the HSS/UDM612.Step704: The HSS/UDM612returns an Update Location Acknowledgement to the MME602.Step706: The MME612sends, to the DNS618, a DNS Query Request containing, in this example, an application string “APN FQDN” (i.e., a DNS Query Request for the desired APN FQDN). The DNS Query Request is for a NAPTR in this embodiment.Step708: The DNS server618sends, in response to the MME602, a DNS Query Response that includes information that identifies a number of candidate PGWs (i.e., a number of candidate SMF/PGW-C's614) that satisfies the DNS Query Request of step706. Th DNS Query Response also includes information that identifies two or more PGWs that belong to the same PGW set (i.e., two or more SMF/PGW-C's that belong to the same SMF/PGW-C set). In this example, the SMF/PGW-C614-1and the SMF/PGW-C614-2belong to the same set and are indicated as such. In this particular example, the DNS Query Response includes NAPTR information for the candidate PGWs. This NAPTR information includes a string (e.g., “+nc-set<setId>”) is appended to the “app-protocol” name as specified in 3 GPP TS 23.003 (see, e.g., V16.3.0), clause 19.4.3, where string indicates the NF Set ID, as described above. In one particular example described herein, the string appended to the “app-protocol” name is “+nc-set<setId>”, where the set<setId> is set to the first label of NF Set Id of a SMF set (i.e., a SMF/PGW-C set), as specified in clause 28.12 of 3 GPP TS 23.003.Step710: The MME612selects, in this example, SMF/PGW-C614-1(also referred to as SMF/PGW-C 1 or PGW 1) from the candidates identified in the DNS Query Response.Step712: The MME612sends a create session request to the SGW604.Step714: The SGW604forwards the create session request to SMF/PGW-C614-1.Step716: The SMF/PGW-C614-1sends a create session response to the SGW604.Step718: The SGW604forwards the create session response to the MME602.Step720: The MME602sends an attach accept message to the UE512.Step722: At some point, the SMF/PGW-C614-1fails.Step724: The SGW604detects the failure of the SMF/PGW-C614-1.Step726: The SGW604sends a PGW restart notification to the MME602in response to detecting the failure. In addition or alternatively, the MME602can derive the PGW failure and re-select another alternative PGW if it receives a GTPv2 cause #100 (See clause 8.4 of TS 29.274) “Remote peer not responding” from the SGW.Step728: The MME602sends, to the SGW604or a new SGW, a create session request that contains the F-TEID of another SMF/PGW-C in the same SMF/PGW-C set as the failed SMF/PGW-C614-1, which in this example is the SMF/PGW-C614-2, based on the information contained in the DNS query response of step708.In one embodiment, when determining to reselect an alternative SMF/PGW-C, the MME602uses Create Session Request message as in an SGW relocation procedure (as specified in5.10.4in TS 23.401) instead of using Modify Bearer Request message. The MME602sends Create Session Request message with new PGW F-TEID (of alternative PGW) to a (new) SGW. In one embodiment, if the Create Session Request message is sent to the existing SGW, the existing SGW considers this as colliding case, as specified in7.2.1of TS 29.274 as below, but the SGW keeps the same SGW-U tunnel over S1 (towards eNB) and over S5/S8 (towards PGW-U) to avoid the signaling towards the SGW-U considering the remote S1 eNB GTP-U tunnel endpoint if available and remote S5/S8 PGW-U GTP-U tunnel endpoint provided by the MME602in the Create Session Request message is the same as the existing ones (since user plane path is not impacted.“If the new Create Session Request received by the SGW collides with an existing active PDN connection context (the existing PDN connection context is identified with the tuple [IMSI, EPS Bearer ID], where IMSI shall be replaced by TAC and SNR part of ME Identity for emergency or RLOS attached UE without UICC or authenticated IMSI), this Create Session Request shall be treated as a request for a new session. Before creating the new session, the SGW should delete:the existing PDN connection context locally, if the Create Session Request is received with the TEID set to zero in the header, or if it is received with a TEID not set to zero in the header and it collides with the default bearer of an existing PDN connection context;the existing dedicated bearer context locally, if the Create Session Request collides with an existing dedicated bearer context and the message is received with a TEID not set to zero in the header.In the former case, if the PGW S5/S8 IP address for control plane received in the new Create Session Request is different from the PGW S5/S8 IP address for control plane of the existing PDN connection, the SGW should also delete the existing PDN connection in the corresponding PGW by sending a Delete Session Request message.”NOTE that, the MME need not immediately to send Create Session Request message, e.g. for those UEs in idle mode.Step730: The SGW604(or new SGW) sends a modify bearer request to the SMF/PGW-C614-2. This is done since the MME602triggers SGW relocation procedure (see clause 5.10.4 of TS 23.401).Step730: The SMF/PGW-C614-2sends a modify bearer response to the SGW604(or new SGW).Step732: The SGW604(or new SGW) sends a create session response to the MME602.Step734(Optional): At some point, the SMF/PGW-C614-1is back online (i.e., the failure is over) and wants to take over the PDN connection. As such, the SMF/PGW-C614-1sends an update (or create or delete) bearer request to the SGW604(or new SGW) that contains the F-TEID of the SMF/PGW-C614-1and an indication that it wants to take over the PDN connection.Step736(Optional): The SGW604(or new SGW) forwards the update (or create or delete) bearer request to the MME602.Step738(Optional): The MME602understands that the SMF/PGW-C614-1wants to take over the PDN connection. So, the MME602sends a create session request with the F-TEID of the SMF/PGW-C614-1(received in the update (or create or delete) bearer request) and steps728through734are repeated.
FIGS.8A-8C

FIGS.8A-8Cillustrate the operation of the cellular communications system500ofFIGS.5and6in accordance with at least some aspects of Solutions A and B described above. Note that, in this example, there is a SMF/PGW-C set (also referred to herein as a PGW set) that includes two (or more) SMF/PGW-C instances, which are denoted here as SMF/PGW-C614-1and SMF/PGW-C614-2. Further note that the SMF/PGW-C614-1and the SMF/PGW-C614-2are sometimes referred to as PGW-C's or PGWs when referring to the PGW-C/PGW functionality of the SMF/PGW-C's614-1and614-2.FIGS.8A-8Cillustrate a second alternative that uses existing NAPTR DNS record in accordance with an embodiment of the present disclosure. The steps of the process ofFIGS.8A-8Care as follows:Step800: The UE512sends an attach request to the MME602via the E-UTRAN600.Step802: The MME602sends an Update Location Request to the HSS/UDM612.Step804: The HSS/UDM612returns an Update Location Acknowledgement to the MME602.Step806: The MME602sends, to the DNS618, a DNS Query Request containing, in this example, an application string “APN FQDN” (i.e., a DNS Query Request for the desired APN FQDN). The DNS Query Request is for a NAPTR in this embodiment.Step808: The DNS server618sends, in response to the MME602, a DNS Query Response that includes information that identifies a number of candidate PGWs (i.e., a number of candidate SMF/PGW-C's614) that satisfies the DNS Query Request of step806. In this embodiment, the DNS Query Response does not include information about the NF set. In this particular example, the DNS Query Response includes NAPTR information for the candidate PGWs.Step810: The MME602selects, in this example, SMF/PGW-C614-1(also referred to as SMF/PGW-C1or PGW1) from the candidates identified in the DNS Query Response. However, unlike in the embodiment ofFIGS.7A-7C, the MME602does not know that the SMF/PGW-C614-1and the SMG/PGW-C614-2belong to the same SMF/PGW-C set.Step812: The MME602sends a create session request to the SGW604.Step814: The SGW604forwards the create session request to SMF/PGW-C614-1.Step816: The SMF/PGW-C614-1sends a create session response to the SGW604. In this embodiment, the create session response includes 6a FQDN of the SMF/PGW-C set and a list of alternative IP addresses of other SMF/PGW-C's in the same SMF/PGW-C set. In this example, the list includes the IP address of the SMF/PGW-C614-2.Step818: The SGW604forwards the create session response to the MME602.Step820: The MME602sends an attach accept message to the UE512.Step822: At some point, the SMF/PGW-C614-1fails.Step824: The SGW604detects the failure of the SMF/PGW-C614-1.Step826: The SGW604sends a PGW restart notification to the MME602in response to detecting the failure. In addition or alternatively, the MME602can derive the PGW failure and re-select another alternative PGW if it receives a GTPv2 cause #100 (See clause 8.4 of TS 29.274) “Remote peer not responding” from the SGW.Step828: The MME602sends, to the SGW604or a new SGW, a create session request that contains the F-TEID of another SMF/PGW-C in the same SMF/PGW-C set as the failed SMF/PGW-C614-1, which in this example is the SMF/PGW-C614-2, based on the list of alternative IP addresses received in step818.8In one embodiment, when determining to reselect an alternative SMF/PGW-C, the MME602uses Create Session Request message as in an SGW relocation procedure (as specified in 5.10.4 in TS 23.401) instead of using Modify Bearer Request message. The MME602sends Create Session Request message with new PGW F-TEID (of alternative PGW) to a (new) SGW. In one embodiment, if the Create Session Request message is sent to the existing SGW, the existing SGW considers this as colliding case, as specified in 7.2.1 of TS 29.274 as below, but the SGW keeps the same SGW-U tunnel over S1 (towards eNB) and over S5/S8 (towards PGW-U) to avoid the signaling towards the SGW-U considering the remote S1 eNB GTP-U tunnel endpoint if available and remote S5/S8 PGW-U GTP-U tunnel endpoint provided by the MME602in the Create Session Request message is the same as the existing ones (since user plane path is not impacted.“If the new Create Session Request received by the SGW collides with an existing active PDN connection context (the existing PDN connection context is identified with the tuple [IMSI, EPS Bearer ID], where IMSI shall be replaced by TAC and SNR part of ME Identity for emergency or RLOS attached UE without UICC or authenticated IMSI), this Create Session Request shall be treated as a request for a new session. Before creating the new session, the SGW should delete:the existing PDN connection context locally, if the Create Session Request is received with the TEID set to zero in the header, or if it is received with a TEID not set to zero in the header and it collides with the default bearer of an existing PDN connection context;the existing dedicated bearer context locally, if the Create Session Request collides with an existing dedicated bearer context and the message is received with a TEID not set to zero in the header.In the former case, if the PGW S5/S8 IP address for control plane received in the new Create Session Request is different from the PGW S5/S8 IP address for control plane of the existing PDN connection, the SGW should also delete the existing PDN connection in the corresponding PGW by sending a Delete Session Request message.”NOTE that, the MME need not immediately to send Create Session Request message, e.g. for those UEs in idle mode.Step830: The SGW604(or new SGW) sends a modify bearer request to the SMF/PGW-C614-2. This is done since the MME602triggers SGW relocation procedure (see clause 5.10.4 of TS 23.401).Step832: The SMF/PGW-C614-2sends a modify bearer response to the SGW604(or new SGW).Step834: The SGW604(or new SGW) sends a create session response to the MME602.Step836(Optional): At some point, the SMF/PGW-C614-1is back online (i.e., the failure is over) and wants to take over the PDN connection. As such, the SMF/PGW-C614-1sends an update bearer request to the SGW604(or new SGW) that contains the F-TEID of the SMF/PGW-C614-1and an indication that it wants to take over the PDN connection.Step838(Optional): The SGW604(or new SGW) forwards the update bearer request to the MME602.Step840(Optional): The MME602understands that the SMF/PGW-C614-1wants to take over the PDN connection. So, the MME602sends a create session request with the F-TEID of the SMF/PGW-C614-1and steps7828through7834are repeated.
FIG.9

FIG.9is a schematic block diagram of a network node900according to some embodiments of the present disclosure. Optional features are represented by dashed boxes. The network node900may be, for example, a core network node (e.g., SMF/PGW-C614,614-1, or614-2, MME602, SGW604, DNS618, HSS/UDM606, PCF612, or a network node that performs all or at least some of the functionality of any such core network node as described herein). As illustrated, the network node900includes one or more processors904(e.g., Central Processing Units (CPUs), Application Specific Integrated Circuits (ASICs), Field Programmable Gate Arrays (FPGAs), and/or the like), memory906, and a network interface908. The one or more processors904are also referred to herein as processing circuitry. The one or more processors904operate to provide one or more functions of the network node900as described herein (e.g., one or more functions of SMF/PGW-C614,614-1, or614-2, MME602, SGW604, DNS618, HSS/UDM606, or PCF612, as described herein). In some embodiments, the function(s) are implemented in software that is stored, e.g., in the memory906and executed by the one or more processors904.

FIG.10

FIG.10is a schematic block diagram that illustrates a virtualized embodiment of the network node900according to some embodiments of the present disclosure. Again, optional features are represented by dashed boxes. As used herein, a “virtualized” network node is an implementation of the network node900in which at least a portion of the functionality of the network node900is implemented as a virtual component(s) (e.g., via a virtual machine(s) executing on a physical processing node(s) in a network(s)). As illustrated, in this example, the network node900includes one or more processing nodes1000coupled to or included as part of a network(s)1002. Each processing node1000includes one or more processors1004(e.g., CPUs, ASICs, FPGAs, and/or the like), memory1006, and a network interface1008.

In this example, functions1010of the network node900described herein (e.g., one or more functions of SMF/PGW-C614,614-1, or614-2, MME602, SGW604, DNS618, HSS/UDM606, or PCF612, as described herein) are implemented at the one or more processing nodes1000or distributed across the two or more of the processing nodes1000in any desired manner. In some particular embodiments, some or all of the functions1010of the network node900described herein are implemented as virtual components executed by one or more virtual machines implemented in a virtual environment(s) hosted by the processing node(s)1000.

In some embodiments, a computer program including instructions which, when executed by at least one processor, causes the at least one processor to carry out the functionality of the network node900or a node (e.g., a processing node1000) implementing one or more of the functions1010of the network node900in a virtual environment according to any of the embodiments described herein is provided. In some embodiments, a carrier comprising the aforementioned computer program product is provided. The carrier is one of an electronic signal, an optical signal, a radio signal, or a computer readable storage medium (e.g., a non-transitory computer readable medium such as memory).

FIG.11

FIG.11is a schematic block diagram of the network node900according to some other embodiments of the present disclosure. The network node900includes one or more modules1100, each of which is implemented in software. The module(s)1100provide the functionality of the network node900described herein (e.g., one or more functions of SMF/PGW-C614,614-1, or614-2, MME602, SGW604, DNS618, HSS/UDM606, or PCF612, as described herein). This discussion is equally applicable to the processing node1000ofFIG.10where the modules1100may be implemented at one of the processing nodes1000or distributed across multiple processing nodes1000.

Some Embodiments

Some embodiments described above may be summarized in the following manner:

1. A method of operation of a cellular communications system (500), the method comprising one or more of the following:at a Mobility and Management Entity, MME, (602):receiving (700) an attach request from a User Equipment, UE, (512);sending (702) a location update request to a Home Subscriber Station, HSS, (606);receiving (704) a location update acknowledgement from the HSS (606);sending (706) a Domain Name Server, DNS, query request to a DNS (618), the DNS query comprising an Access Point Name, APN, Fully Qualified Domain Name, FQDN;receiving (708) a DNS query response from the DNS (618), the DNS query response comprising information that:indicates a plurality of candidate Packet Gateways, PGWs, (614) that satisfy the DNS query request; andindicates at least two PGWs (614-1and614-2) belong to a same PGW set, the at least PGWs comprising a first PGW (614-1) and a second PGW (614-2);selecting (710) the first PGW (614-1);sending (712), to a Serving Gateway, SGW, (604), a first create session request that comprises information that indicates the first PGW (614-1);receiving (718) a first create session response from the SGW (604);sending (720) an attach accept to the UE (512); andat the SGW (604):receiving (712) the first create session request from the MME (602);forwarding (714) the first create session request to the first PGW (614);receiving (716) the first create session response from the first PGW (614); andforwarding (718) the first create session response to the MME (602).

2. The method of embodiment 1 further comprising:at the MME (602):determining (726) that the first PGW (614-1) has failed;responsive to determining (726) that the first PGW (614-1) has failed:sending (728) a second create session request to the SGW (604) or a new SGW, the second create session request comprising information that indicates the second PGW (614-2); andreceiving (734) a second create session response from the SGW (604) or the new SGW;at the SGW (604) or the new SGW:receiving (728) the second create session request from the MME (602);sending (730) a modify bearer request to the second PGW (614-2);receiving (732) a modify fearer response from the second PGW (614-2); andsending (734) the second create session response to the MME (602).

3. The method of embodiment 2 further comprising, at the SGW (604):detecting (724) that the first PGW (614-1) has failed; andsending (726) a notification that the first PGW (614-1) has failed to the MME (602).

4. The method of embodiment 2 or 3 wherein the SGW (602) to which the second create session request is sent from the MME (602) is the SGW (602) that received the first create session request, and the SGW (602) keeps a same SGW-U tunnel over S1 and over S5/S8.

5. The method of any of embodiments 2 to 4 wherein determining (726) that the first PGW (614-1) has failed comprises either or both of:receiving (726) a restart notification from the SGW (602);determining that the failure has occurred based on reception of a GTPv2 cause #100 “Remote peer not responding” from the SGW (602).

6. The method of any of embodiments 2 to 5 further comprising:at the SGW (604) or the new SGW:receiving (736) an create/update/delete bearer request from the first PGW (614-1), the create/update/delete bearer request comprising information that indicates that the first PGW (614-1) desires to take over the session for the wireless communication device (512); andforwarding (738) the create/update/delete bearer request to the MME (602); andat the MME (602):receiving (738) the create/update/delete bearer request from the SGW (604) or the new SGW; andsending (740) a third create session request to the SGW (604), the new SGW, or a further new SGW, the third create session request comprising information that indicates the first PGW (614-1).

7. The method of any of embodiments 1 to 6 wherein the DNS query request is of a type NAPTR, and the information comprised in DNS query response comprises NAPTR information that indicates the plurality of candidate PGWs and the at least two candidate PGWs that are in the same PGW set.

8. The method of embodiment 7 wherein the NAPTR information comprises, for each of the at least two candidate PGWs that are in the same PGW set, a string appended to the “app-protocol” name, where the string indicates that the at least two candidate PGWs are in the same PGW set.

9 The method of claim8wherein:the at least two candidate PGWs (614-1,614-2) that are in the same PGW set are at least two candidate combined Session Management Function, SMF, and Packet Gateway Control Plane, PGW-C, instances;the PGW set is a SMF/PGW-C set; andthe string comprises set<setId>, where the set<setId> is set to a first label of a NF set ID of the SMF/PGW-C set.

10. A method of operation of a Mobility and Management Entity, MME, (602) for a cellular communications system (500), the method comprising one or more of the following:receiving (700) an attach request from a User Equipment, UE, (512);sending (702) a location update request to a Home Subscriber Station, HSS, (606);receiving (704) a location update acknowledgement from the HSS (606);sending (706) a Domain Name Server, DNS, query request to a DNS (618), the DNS query comprising an Access Point Name, APN, Fully Qualified Domain Name, FQDN;receiving (708) a DNS query response from the DNS (618), the DNS query response comprising information that:indicates a plurality of candidate Packet Gateways, PGWs, (614) that satisfy the DNS query request; andindicates at least two PGWs (614-1and614-2) belong to a same PGW set, the at least PGWs comprising a first PGW (614-1) and a second PGW (614-2);selecting (710) the first PGW (614-1);sending (712), to a Serving Gateway, SGW, (604), a first create session request that comprises information that indicates the first PGW (614-1);receiving (718) a first create session response from the SGW (604);sending (720) an attach accept to the UE (512).

11. The method of embodiment 10 further comprising:determining (726) that the first PGW (614-1) has failed;responsive to determining (726) that the first PGW (614-1) has failed:sending (728) a second create session request to the SGW (604) or a new SGW, the second create session request comprising information that indicates the second PGW (614-2); andreceiving (734) a second create session response from the SGW (604) or the new SGW.

12. The method of embodiment 11 wherein the SGW (602) to which the second create session request is sent from the MME (602) is the SGW (602) to which the first create session request is sent, and the SGW (602) keeps a same SGW-U tunnel over S1 and over S5/S8.

13. The method of embodiments 11 or 12 wherein determining (726) that the first PGW (614-1) has failed comprises either or both of:receiving (726) a restart notification from the SGW (602);determining that the failure has occurred based on reception of a GTPv2 cause #100 “Remote peer not responding” from the SGW (602).

14. The method of any of embodiments 11 to 13 further comprising:receiving (738) a create/update/delete bearer request from the SGW (604) or the new SGW, the create/update/delete bearer request comprising information that indicates that the first PGW (614-1) desires to take over the session for the wireless communication device (512); andsending (740) a third create session request to the SGW (604), the new SGW, or a further new SGW, the third create session request comprising information that indicates the first PGW (614-1).

15. The method of any of embodiments 10 to 14 wherein the DNS query request is of a type NAPTR, and the information comprised in DNS query response comprises NAPTR information that indicates the plurality of candidate PGWs and the at least two candidate PGWs that are in the same PGW set.

16. The method of embodiment 15 wherein the NAPTR information comprises, for each of the at least two candidate PGWs that are in the same PGW set, a string appended to the “app-protocol” name, where the string indicates that the at least two candidate PGWs are in the same PGW set.

17. The method of claim 16 wherein:the at least two candidate PGWs (614-1,614-2) that are in the same PGW set are at least two candidate combined Session Management Function, SMF, and Packet Gateway Control Plane, PGW-C, instances;the PGW set is a SMF/PGW-C set; andthe string comprises set<setId>, where the set<setId> is set to a first label of a NF set ID of the SMF/PGW-C set.

18. A network node (900) adapted to perform the method of any of embodiments 10 to 17.

19. A method of operation of a cellular communications system (500), the method comprising one or more of the following:at a Mobility and Management Entity, MME, (602):receiving (800) an attach request from a User Equipment, UE, (512);sending (802) a location update request to a Home Subscriber Station, HSS, (606);receiving (804) a location update acknowledgement from the HSS (606);sending (806) a Domain Name Server, DNS, query request to a DNS (618), the DNS query comprising an Access Point Name, APN, Fully Qualified Domain Name, FQDN;receiving (808) a DNS query response from the DNS (618), the DNS query response comprising information that indicates a plurality of candidate Packet Gateways, PGWs, (614) that satisfy the DNS query request;selecting (810) the first PGW (614-1);sending (812), to a Serving Gateway, SGW, (604), a first create session request that comprises information that indicates the first PGW (614-1);receiving (818) a first create session response from the SGW (604), the first create session response comprising one or more alternate Internet Protocol, IP, addresses for one or more other PGWs (614-2) in a same PGW set;sending (820) an attach accept to the UE (512); andat the SGW (604):receiving (812) the first create session request from the MME (602);forwarding (814) the first create session request to the first PGW (614);receiving (816) the first create session response from the first PGW (614); andforwarding (818) the first create session response to the MME (602).

20. The method of embodiment 19 further comprising:at the MME (602):determining (826) that the first PGW (614-1) has failed;responsive to determining (826) that the first PGW (614-1) has failed:sending (8828) a second create session request to the SGW (604) or a new SGW, the second create session request comprising information that indicates the second PGW (614-2) (e.g., the IP address or F-TEID of the second PGW (614-2); andreceiving (8834) a second create session response from the SGW (604) or the new SGW;at the SGW (604) or the new SGW:receiving (8828) the second create session request from the MME (602);sending (8830) a modify bearer request to the second PGW (614-2);receiving (8832) a modify fearer response from the second PGW (614-2); andsending (8834) the second create session response to the MME (602).

21. The method of embodiment 20 further comprising, at the SGW (604):detecting (824) that the first PGW (614-1) has failed; andsending (826) a notification that the first PGW (614-1) has failed to the MME (602).

22. The method of embodiment 20 or 21 wherein the SGW (602) to which the second create session request is sent from the MME (602) is the SGW (602) that received the first create session request, and the SGW (602) keeps a same SGW-U tunnel over S1 and over S5/S8.

23. The method of any of embodiments 20 to 22 wherein determining (726) that the first PGW (614-1) has failed comprises either or both of:receiving (826) a restart notification from the SGW (602);determining that the failure has occurred based on reception of a GTPv2 cause #100 “Remote peer not responding” from the SGW (602).

24. The method of any of embodiments 20 to 23 further comprising:at the SGW (604) or the new SGW:receiving (8836) an create/update/delete bearer request from the first PGW (614-1), the create/update/delete bearer request comprising information that indicates that the first PGW (614-1) desires to take over the session for the wireless communication device (512); andforwarding (8838) the create/update/delete bearer request to the MME (602); andat the MME (602):receiving (8838) the create/update/delete bearer request from the SGW (604) or the new SGW; andsending (8840) a third create session request to the SGW (604), the new SGW, or a further new SGW, the third create session request comprising information that indicates the first PGW (614-1).

25. A method of operation of a Mobility and Management Entity, MME, (602) for a cellular communications system (500), the method comprising one or more of the following:receiving (800) an attach request from a User Equipment, UE, (512);sending (802) a location update request to a Home Subscriber Station, HSS, (606);receiving (804) a location update acknowledgement from the HSS (606);sending (806) a Domain Name Server, DNS, query request to a DNS (618), the DNS query comprising an Access Point Name, APN, Fully Qualified Domain Name, FQDN;receiving (808) a DNS query response from the DNS (618), the DNS query response comprising information that indicates a plurality of candidate Packet Gateways, PGWs, (614) that satisfy the DNS query request;selecting (810) the first PGW (614-1);sending (812), to a Serving Gateway, SGW, (604), a first create session request that comprises information that indicates the first PGW (614-1);receiving (818) a first create session response from the SGW (604), the first create session response comprising one or more alternate Internet Protocol, IP, addresses for one or more other PGWs (614-2) in a same PGW set; andsending (820) an attach accept to the UE (512).

26. The method of embodiment 25 further comprising:determining (826) that the first PGW (614-1) has failed;responsive to determining (826) that the first PGW (614-1) has failed:sending (8828) a second create session request to the SGW (604) or a new SGW, the second create session request comprising information that indicates the second PGW (614-2) (e.g., the IP address or F-TEID of the second PGW (614-2); andreceiving (8834) a second create session response from the SGW (604) or the new SGW.

27. The method of embodiment 26 wherein the SGW (602) to which the second create session request is sent from the MME (602) is the SGW (602) that received the first create session request, and the SGW (602) keeps a same SGW-U tunnel over S1 and over S5/S8.

28. The method of any of embodiments 26 to 28 wherein determining (726) that the first PGW (614-1) has failed comprises either or both of:receiving (826) a restart notification from the SGW (602);determining that the failure has occurred based on reception of a GTPv2 cause #100 “Remote peer not responding” from the SGW (602).

29. The method of any of embodiments 26 to 28 further comprising:receiving (8838) a create/update/delete bearer request from the SGW (604) or the new SGW, the create/update/delete bearer request comprising information that indicates that the first PGW (614-1) desires to take over the session for the wireless communication device (512); andsending (8840) a third create session request to the SGW (604), the new SGW, or a further new SGW, the third create session request comprising information that indicates the first PGW (614-1).

30. A network node (900) adapted to perform the method of any of embodiments 25 to 29.

Any appropriate steps, methods, features, functions, or benefits disclosed herein may be performed through one or more functional units or modules of one or more virtual apparatuses. Each virtual apparatus may comprise a number of these functional units. These functional units may be implemented via processing circuitry, which may include one or more microprocessor or microcontrollers, as well as other digital hardware, which may include Digital Signal Processor (DSPs), special-purpose digital logic, and the like. The processing circuitry may be configured to execute program code stored in memory, which may include one or several types of memory such as Read Only Memory (ROM), Random Access Memory (RAM), cache memory, flash memory devices, optical storage devices, etc. Program code stored in memory includes program instructions for executing one or more telecommunications and/or data communications protocols as well as instructions for carrying out one or more of the techniques described herein. In some implementations, the processing circuitry may be used to cause the respective functional unit to perform corresponding functions according one or more embodiments of the present disclosure.

While processes in the figures may show a particular order of operations performed by certain embodiments of the present disclosure, it should be understood that such order is exemplary (e.g., alternative embodiments may perform the operations in a different order, combine certain operations, overlap certain operations, etc.).