The Sx Service provides an interface mentioned as the following reference points:

• Sxa: Reference point between SGW-C and SGW-U.

• Sxb: Reference point between PGW-C and PGW-U.

• Sxc: Reference point between Traffic Detection Function-C (TDF-C) and TDF-U.

The Sx service is agnostic of the interface it supports. A single Sx service instance is capable of running on Sxa, Sxb, and Sxb interfaces. The Sx service runs in two different modes:

• Sx-Control instance

• Sx-Data instance

The Sx service is associated with the SAEGW service at the Control-Plane and User-Plane service at the User-Plane. There is one-to-one mapping of the Sx service with the Control-Plane and Data Plane.

The association of the SAEGW service occurs as follows:

saegw-service saegw-service
      associate sgw-service sgw-service
      associate pgw-service pgw-service
      associate gtpu-service control_gtpu up-tunnel
      associate sx-service sxc

The association of the User-Plane service occurs as follows:

user-plane-service user-plane-service
      associate gtpu-service sx-gtpu-service pgw-ingress
      associate gtpu-service sx-sgw_ingress_gtpu sgw-ingress
      associate gtpu-service sx-sgw_egress_gtpu sgw-egress
      associate gtpu-service control_gtpu cp-tunnel
      associate sx-service sxu

At the Control-Plane for SAEGW service (legacy SAEGW Service), CUPS-enabled flag in EGTPC service determines whether SAEGW is CUPS enabled or not. If SAEGW service is CUPS enabled, then Sx service is a mandatory parameter for SAEGW service to start. Only having association at the SAEGW service does not make Sx a mandatory parameter for SAEGW service.

If Sx service is a mandatory parameter (because of CUPS-enabled flag), then Sx service stop and Sx IP address brings down the SAEGW service.

For information about configuring the Sx Service, see the “Configuring Sx Service” section.

This section explains the interaction between the Sx-u Interface, User-Plane-service, and SAEGW-service.

Sx-u is the User-Plane interface over the Sxa and Sxb reference points. The protocol used on the Sx-u Interface is GTP-U. Both IPv4 and IPv6 transport is supported.

At the User-Plane, Sx-u service is a mandatory parameter for User-Plane service to start. Being a mandatory parameter, Sx-u Interface stops and Sx-u IP address brings down the User-Plane service.

The Control-Plane establishes one Sx-u tunnel per function or session as described in the section below.

Sx-u Tunnel per PDN session

Control-Plane establishes one Sx-u tunnel per PDN session for router advertisement and router solicitation messages.

In this scenario, Control-Plane uses the existing Sx tunnel per PDN (created during GTP-C initial attach procedure) for installing Packet Detection Rule (PDR) or Forwarding Action Rule (FAR) related to data forwarding between the Control-Plane and User-Plane functions on the User-Plane.

For information about configuring the Sx-u Interface, see the Configuring Sx-u Interface section.

The Sx Demux provides session de-multiplexing functionality on the Data plane. One instance of Sx Demux is started per context. When implemented, the Sx Demux supports the following behavior:

1. Works as Sx Control-Plane Demux when implemented on the Control-Plane and supports handling of Node level messages such as Prime PDF Management Messages.

2. Works as Sx Data Plane Demux when implemented on the Data Plane and supports:

   • Handling of Session level messages such as Session Establish Request.

   • Handling of Session level messages such as Session Establish Request.

3. Works as Sx Data Pane Demux performing load balancing of Session Establish Request between all Session Managers.

4. Supports default PFCP packet receiver port 8805.

The Sx service is associated with SAEGW service at Control-Plane and is associated with User-Plane Service at User-Plane. Sx Demux is initiated when the first Sx service is created with the minimum mandatory parameter in the context.

The Sx Demux functions as follows:

• When working as Sx Data Demux

  The Session Manager (Data Plane) sends the add session response indicating addition of new session and delete session request on deletion of session on Session Manager. Sx Data Demux maintains session count per session manager.

• When working as Sx Control Demux

  The Sx Control Demux uses Prime PDF Management Messages (proprietary messages) to communicate static and dynamic rule configuration from Control-Plane to associated Data plane.

Proprietary Prime PFD message format

Cisco PFD Management Request

Cisco PFD Management Response

Header information

Proprietary Sx Stats Query Req/Rsp/Ack

PFCP Header format for Subscriber/Session level Query Message

IEs and Message Formats

Stats reporting framework shall use the messages and IE types as outlined below.

IE Type: 201

IE Name: PFCP_IE_UPDATE_ADDNL_FORW_PARAMS

IE Format and Encoding Information

Sx Message(s) Using the IE: Update FAR IE within Sx Session Modification Request.

IE Type: 202

IE Name: PFCP_IE_CONFIG_ACTION

IE Format and Encoding Information

IE Type: 203

IE Name: PFCP_IE_CORRELATION_ID

IE Format and Encoding Information

Sx Message(s) Using the IE: Sx Prime PFD MGMT Request for configuring the UP with various configurations.

Sx Prime PFD MGMT Response

IE Type: 204

IE Name: PFCP_IE_SUB_PART_NUMBER

IE Format and Encoding Information

Sx Message(s) Using the IE: Sx Prime PFD MGMT Request for configuring the UP with various configurations.

IE Type: 205

IE Name: PFCP_IE_SUB_PART_INDEX

IE Format and Encoding Information

Sx Message(s) Using the IE: Sx Prime PFD MGMT Request for configuring the UP with various configurations.

Sx Prime PFD MGMT Response.

IE Type: 206

IE Name: PFCP_IE_CONTENT_TLV

IE Format and Encoding Information

Sx Message(s) Using the IE: Sx Prime PFD MGMT Request for configuring the UP with various configurations.

IE Type: 207

IE Name: PFCP_IE_RBASE_NAME

IE Format and Encoding Information

Note	Octets 1-2—Indicates Rulebase IE. Type 202 Reserved Octets 3-4—Indicates the length of rulebase name Octets 5-n—Rulebase name This IE contains the active Rulebase Name for a subscriber to be communicated to User Plane.

IE Type: 208

IE Name: NSH-INFO

IE Format and Encoding Information

IE Type: 209

IE Name: Stats request IE

IE Format and Encoding Information

This IE are be of grouped type and consist of two IEs: Query Params IE and the Classifier Params IE. Multiple instances of Classifier Params IE can be present.

IE Type: 210

IE Name: Query Params IE

IE Format and Encoding Information

Query Params is encoded as follows:

Octet 7: ENTITY TYPE – Numeric Identifier. Indicates the type of entity being queried:

1: Network Instance (APN name) – [PFCP IE ID: 22] 2: Rulebase etc. (Future use) – [PFCP IE ID: 207]

Octet 8 encodes following flags:

• QUERY ALL—Indicates whether we are querying one instance of the specified entity or all of them.

• QUERY TYPE—Indicates whether we are querying individual ENTITY of the given type or we are expecting aggregated node level statistics. It takes values as follows:

  • 0: Bit when unset, indicates individual statistics.

  • 1: Bit when set indicates aggregated statistics.

Valid combinations of above flags are used to realize the use cases.

IE Type: 211

IE Name: Classifier Params IE

IE Format and Encoding Information

Classifier Params IE is encoded as follows:

Octet 5: Encodes the type of the classifier. It is defined by the context set by entity type.

So, same numeric identifiers may mean different for two different entity types.

Octet 6 encodes the length of classifier. The maximum of 256 byte long classifier is accommodated.

Octet 7 onwards is used to encode the classifier content. This content is encoded as an octet string. In case of numeric classifiers, the numbers are appropriately converted into string format and are delivered as is to the application. This process removes the length limitation on type of encoded numeric identifiers.

IE Type: 212

IE Name: Stats response IE

IE Format and Encoding Information

ENTITY TYPE is same as the one that is received in request. Else, Control Plane rejects the response from the User Plane.

The response from User plane can span across multiple messages depending upon the amount of data that needs to be sent to Control Plane.

• Message ID identifies one subpart of the response.

• Total number of messages this response consists of.

Blob of data consists of compressed context specific data. Contents of the same are uncompressed at Control Plane and interpreted as per the identifiers received (ENTITY TYPE).

IE Type: 213

IE Name: Stats response ACK/NACK

IE Format and Encoding Information

RESPONSE TYPE is: 0: ACK (success) if all parts of the response are correctly received at CP 1: NACK (failure) - CP responds with the message parts that were not received within the specified time.

Octets 6 and onwards specifies missing part numbers at CP in case CP sends out a NAck.

Use of NAck mechanism is not envisaged as of now. These will be incorporated in call flows, if required in future.

IE Type: 214

IE Name: PFCP_IE_PACKET_MEASUREMENT

IE Format and Encoding Information

The Packet Measurement IE contains the measured traffic volume in packets. This IE is encoded as shown below:

The following flags are coded within Octet 5:

• Bit 1 – TOVOL— If this bit is set to "1", then the Total Packets field appears. Else, the Total Packets field is does not appear.

• Bit 2 – ULVOL—If this bit is set to "1", then the Uplink Packets field appears. Else, the Uplink Packets field does not appear.

• Bit 3 – DLVOL—If this bit is set to "1", then the Downlink Packets field appears. Else, the Downlink Packets field does not appear.

• Bit 4 to bit 8—These are spare bits for future use, and are set to 0.

At least one bit is set to 1. However, you can set many bits to 1.

The Total Packets, Uplink Packets, and Downlink Packets fields are encoded as an Unsigned64 binary integer value. They contain the total, uplink, or downlink number of packets respectively.

This is not a mandatory IE for any Message.

This IE is available in the following Messages between Control Plane and User Plane.

• Sx Session Modification over SxA, SxB, SxC, SxAB

• Sx Usage Report Session Deletion Response over SxA, SxB, SxC, SxAB

• Sx Usage Report Session Report Request over SxA, SxB, SxC, SxAB

IE Type: 215

IE Name: PFCP_IE_EXTENDED_MEASUREMENT_METHOD

IE Format and Encoding Information

A new IE (215 - Extended Measurement Method) is encoded as shown below. This IE indicates the method for measuring the usage of network resources.

Figure Extended Measurement Method

Octet 5 is encoded as follows:

• Bit 1 – Pkt (Packet)—When set to 1, this bit indicates a request for measuring the usage of the traffic in packets.

• Bit 2 to 8—These are spare bits for future use, and are set to 0.

Note	Only one bit is set to 1.

This is not a mandatory IE for any Message.

This IE can be available in the following message between Control Plane and User Plane.

• Sx Session Establishment over SxA, SxB, SxC, SxAB

Similarly, Usage Report from User Plane is enhanced to support the packet information.

IE Type: 216

IE Name: PFCP_IE_RECALCULATE_MEASUREMENT

IE Format and Encoding Information

This private IE has been added to support "Max number of change conditions" trigger for offline charging records, such as Gz and Rf.

The following flags are coded within Octet 5:

• Bit 1 – RCDUR (Re-calculate Duration Measurement)—When set to 1, this flag indicates a request for resetting the Duration Measurement to ‘0’ by the UP function.

• Bit 2 – RCVOL (Re-calculate Volume Measurement)—When set to 1, this flag indicates a request for resetting the Volume Measurement to ‘0’ by the UP function. Then, the UP function proceeds to repopulate the Volume Measurement. The repopulation is done by aggregating the Volume Measurement of all the URRs that contain Linked URR ID as the URR ID sent in Update URR IE.

• Bit 3 to 8—Spare bits for future use, and are set to 0.

1. PFCP Session Modification Request

2. PFCP Session Report Response

IE Type: 217

IE Name: PFCP_IE_SUB_INFO

IE Format and Encoding Information

Octets 5-5: BitOctet. Indicates the available fields.

• Bit 1—IMSI

• Bit 2—MSISDN

• Bit 3—IMEI

• Bit 4—Call ID

IE Type: 218

IE Name: PFCP_IE_INTR_INFO

IE Format and Encoding Information

The IE is part of Create Dupl Params and Update Duplicate Params IE.

Create Duplicate Params IE can be part of SX Establishment Req and SX Session Modify Request.

Update Duplicate Params IE can be part of SX Session Modify Request.

Octets 5-5: BitOctet. Indicates the available fields.

• Bit 1—Intercept ID

• Bit 2—Charging ID

• Bit 3—Bearer ID

• Bit 4—Context name

IE Type: 219

IE Name: PFCP_IE_NODE_CAPABILITY

IE Format and Encoding Information

The Max Sessions Supported value are encoded as an Unsigned32 binary integer value.

Max Sessions supported value is the maximum number of sessions that are supported by User Plane for this association with Control Plane.

IE Type: 220

IE Name: INNER PACKET MARKING

IE Format and Encoding Information

The Inner Packet Marking IE type shall be encoded as shown below. It indicates the DSCP to be used for UL/DL Inner packet marking.

The ToS/Traffic Class shall be encoded on two octets as an OctetString. The first octet shall contain the DSCP value in the IPv4 Type-of-Service or the IPv6 Traffic-Class field and the second octet shall contain the ToS/Traffic Class mask field, which shall be set to "0xFC".

IE Type: 221

IE Name: TRANSPORT LEVEL MARKING OPTIONS

IE Format and Encoding Information

TRANSPORT LEVEL MARKING OPTIONS shall be encoded as shown below. It indicates the copy-inner/outer flags for encaps-header marking.

Copy-Inner/Outer flags shall be encoded on 1 Octet.

IE Type: 223

PFCP_IE_CHARGING_PARAMS

IE Format and Encoding Information

IE Type: 224

IE Name: PFCP_IE_GY_OFFLINE_CHARGE

IE Format and Encoding Information

IE Type: 226

PFCP_IE_SUB_PARAMS

IE Format and Encoding Information

IE Type: 227

IE Name: PFCP_IE_RULE_NAME

IE Format and Encoding Information

IE Type: 228

IE Name: LAYER2 MARKING

IE Format and Encoding Information

To pass the L2 Marking information to the UP for the bearer, a new custom-IE is defined and the FAR is modified to include it as follows. It identifies the Layer 2 Marking to be applied for the packets matching this FAR.

The length of the IE could be either 0 or 1.

IE Type: 229

IE Name: PFCP_IE_MONITOR_SUBSCRIBER_INFO

IE Format and Encoding Information

Action: STOP / START monitor subscriber tracing. STOP =1, START =2.

D = DATA events tracing is ON if D=1. The 8 octets (d to d+7) contain data events tracing (fastpath) information should be present only when D=1.

C = CONTROL events tracing is ON if C=1.

Data Tracing (fastpath) Information (8 octets): It will contain the data filter parameters like Packet capture, Packet capture size, and MEH header.

Octet 1:

• Bit 1 – VPP enable/disable

• Bit 2 – FCAP - Packet capture

• Bit 3 – MEH present

• Bit 4 to 6 - Priority

Octet 2 to 3: Packet size

Octet 4 – 8: Reserved for future use. Currently, all set to 0.

Protocol Tracing Information (16 octets/128 bits): The 16 octets (p to p+15) contain protocol tracing information and should be present only when either control flag (C) or data flag (D) is enable. Each bit represents a unique protocol to monitor. E.g. If 49th bit is 1, PFCP events tracing is ON. Protocol Tracing ‘Rulematch Events (Option 34)’, ‘L3 Data (Option 19)’, ‘EDR (Option 77)’ and ‘Subscriber Summary After Call Disconnect’ are controlled by control event flag.

IE Type: 230

IE Name: PFCP_IE_MON_SUB_REPORT_SESS_REP_REQ

IE Format and Encoding Information

Status code: It indicates the acceptance or the rejection of the subscriber trace at UP. Status code = 0 will mean a success. Values 1-255 will uniquely specify the specific error code or notification.

IE Type: 237

IE Name: PFCP_IE_RATING_GRP

IE Format and Encoding Information

IE Type: 238

IE Name: PFCP_IE_NEXTHOP

IE Format and Encoding Information

IE Type: 239

IE Name: PFCP_IE_NEXTHOP_ID

IE Format and Encoding Information

IE Type: 240

IE Name: PFCP_IE_NEXTHOP_IP

IE Format and Encoding Information

IE Type: 241

PFCP_IE_QGR_INFO

IE Format and Encoding Information

IE Type: 242

IE Name: PFCP_IE_UE_IP_VRF

IE Format and Encoding Information

IE Type: 246

IE Name: PFCP_IE_GX_ALIAS

IE Format and Encoding Information

The IE to communicate a Gx-Alias GoR(Group-of-Ruledef) name, Start and End PDR IDs and also the operation to perform, from CP to UP during Sx Session Establishment/Modification Request message. There can be multiple instances of same IE in an Sx-message.