Content for  TS 23.304  Word version:  19.1.0

ProSe Application ID is defined in TS 23.303.

Destination Layer-2 ID is defined in clause 5.6.1 of TS 23.287. The Destination Layer-2 ID for 5G ProSe Direct Discovery with Model A is selected based on the configuration as described in clause 5.1.2.1. The Destination Layer-2 ID for a Solicitation message for Model B is selected based on the configuration as described in clause 5.1.2.1. The Destination Layer-2 ID for 5G ProSe UE-to-UE Relay Discovery is selected as described in clause 5.8.4.2. For Group member discovery:

• If an Application Layer Group ID has a configured Layer-2 Group ID, which is provisioned as specified in clause 5.1.2.1, the UE uses this Layer-2 Group ID as the Destination Layer-2 ID,
• otherwise, the UE converts the Application Layer Group ID into a Destination Layer-2 ID.

Source Layer-2 ID is defined in clause 5.6.1 of TS 23.287. The UE self-selects a Source Layer-2 ID for 5G ProSe Direct Discovery and Group member discovery. The Source Layer-2 ID for 5G ProSe UE-to-UE Relay Discovery is selected as described in clause 5.8.4.2.

ProSe Application Code is defined in TS 23.303.

ProSe Restricted Code is defined in TS 23.303.

ProSe Query Code is defined in TS 23.303.

ProSe Response Code is defined in TS 23.303.

User Info ID (including Announcer Info, Discoverer Info, Discoveree Info) is defined in clause 3.1.

ProSe Discovery UE ID is defined in TS 23.303.

Restricted ProSe Application User ID is defined in TS 23.303.

Announcing PLMN ID is defined in TS 32.277.

Announcer Info is one of the uses of User Info ID as described in clause 5.8.1.8.

Discoverer Info is one of the uses of User Info ID as described in clause 5.8.1.8.

Target Info provides information about the targeted discoveree in the Group Member Discovery Solicitation message specified in clause 6.3.2.2.3 and in the 5G ProSe UE-to-Network Relay Discovery Solicitation message specified in clause 6.3.2.3.3. The Target Info is the User Info ID of the discoveree.

Discoveree Info is one of the uses of User Info ID as described in clause 5.8.1.8.

Application Layer Group ID is defined in TS 23.303.

Monitored PLMN ID is defined in TS 32.277.

Each UE has one or more Layer-2 IDs for 5G ProSe direct communication over PC5 reference point, consisting of:

• Source Layer-2 ID(s); and
• Destination Layer-2 ID(s).

Source and Destination Layer-2 IDs are included in layer-2 frames sent on the layer-2 link of the PC5 reference point identifying the layer-2 source and destination of these frames. Source Layer-2 IDs are always self-assigned by the UE originating the corresponding layer-2 frames. The selection of the Source and Destination Layer-2 ID(s) by a UE depends on the communication mode of 5G ProSe direct communication over PC5 reference point for this layer-2 link, as described in clauses 5.8.2.2, 5.8.2.3 and 5.8.2.4. The Source Layer-2 IDs may differ between different communication modes.

For broadcast mode of 5G ProSe direct communication over PC5 reference point, the UE is configured with the Destination Layer-2 ID(s) to be used for ProSe applications. The Destination Layer-2 ID for a 5G ProSe direct communication is selected based on the configuration as described in clause 5.1.3.1. The UE self-selects a Source Layer-2 ID.

For groupcast mode of 5G ProSe direct communication over PC5 reference point, the application layer may provide Application Layer Group ID. The UE determines a Destination Layer-2 ID as below:

• When the Application Layer Group ID is provided by the application layer,
  • and when ProSe Layer-2 Group ID is configured for the Application Layer Group ID provided by the application layer as specified in clause 5.1.3.1, the UE uses the ProSe Layer-2 Group ID as the Destination Layer-2 ID; or
  • and when ProSe Layer-2 Group ID is not configured for the Application Layer Group ID provided by the application layer, the UE converts the Application Layer Group ID into a Destination Layer-2 ID.
• When the Application Layer Group ID is not provided by the application layer, the UE determines the Destination Layer-2 ID based on configuration of the mapping between ProSe Identifier and Layer-2 ID, as specified in clause 5.1.3.1.

The UE self-selects a Source Layer-2 ID.

For unicast mode of 5G ProSe direct communication over PC5 reference point, the Destination Layer-2 ID used depends on the communication peer. The Layer-2 ID of the communication peer, identified by the peer's Application Layer ID, may be discovered during the establishment of the PC5 unicast link, or known to the UE via prior ProSe direct communications, e.g. existing or prior unicast link to the same Application Layer ID, or obtained from 5G ProSe direct discovery process. The initial signalling for the establishment of the PC5 unicast link may use the known Layer-2 ID of the communication peer, or a default destination Layer-2 ID associated with the ProSe service (i.e. ProSe identifier) configured for PC5 unicast link establishment, as specified in clause 5.1.3.1. During the PC5 unicast link establishment procedure, Layer-2 IDs are exchanged and should be used for future communication between the two UEs, as specified in clause 6.4.3. The UE maintains a mapping between the Application Layer IDs and the source Layer-2 IDs used for the PC5 unicast links, as the ProSe application layer does not use the Layer-2 IDs. This allows the change of source Layer-2 ID without interrupting the ProSe applications. When Application Layer IDs change, the source Layer-2 ID(s) of the PC5 unicast link(s) shall be changed if the link(s) was used for 5G ProSe communication with the changed Application Layer IDs. Based on privacy configuration as specified in clause 5.1.3.1, the update of the new identifiers of a source UE to the peer UE for the established unicast link may cause the peer UE to change its Layer-2 ID and optionally IP address/prefix if IP communication is used as defined in clause 6.4.3.2.

The following parameters are used for the 5G ProSe UE-to-Network Relay Discovery Announcement message (Model A), where Source Layer-2 ID and Destination Layer-2 ID are used for sending and receiving the message and Announcer Info and Relay Service Code are contained in the message:

• Source Layer-2 ID: the 5G ProSe UE-to-Network Relay self-selects a Source Layer-2 ID for 5G ProSe UE-to-Network Relay Discovery.
• Destination Layer-2 ID: the Destination Layer-2 ID for 5G ProSe UE-to-Network Relay Discovery is selected based on the configuration as described in clause 5.1.4.1.
• Announcer Info: provides information (i.e. User Info ID) about the announcing user.
• Relay Service Code: parameter identifying a connectivity service the 5G ProSe UE-to-Network Relay provides to a 5G ProSe Remote UE. The Relay Service Codes are configured in a 5G ProSe UE-to-Network Relay for advertisement. Additionally, the Relay Service Code may also identifies authorized users the 5G ProSe UE-to-Network Relay would offer service to and may be used to select the related security policies or information e.g. necessary for authentication and authorization between the 5G ProSe Remote UE and the 5G ProSe UE-to-Network Relay (e.g. a Relay Service Code for relays for police members only would be different than a Relay Service Code for relays for Fire Fighters only, even though potentially they provided connectivity to same DN e.g. to support Internet Access).

The 5G ProSe UE-to-Network Relay Discovery Announcement message (Model A) is extended and modified as follows when used for 5G ProSe multi-hop UE-to-Network Relay discovery:

• Hop-Count: This value reflects the number of PC5 hops for the 5G ProSe Remote UE to reach the network. It is set to 1 by the 5G ProSe UE-to-Network Relay and shall be incremented by 1 every time the 5G ProSe UE-to-Network Relay Discovery Announcement message is forwarded by a 5G ProSe Intermediate UE-to-Network Relay.
  A 5G ProSe Intermediate UE-to-Network Relay shall only process the 5G ProSe UE-to-Network Relay Discovery Announcement if the Hop-Count is present and the value is less than the (pre-)configured maximum number of hops for the associated RSC and the optional Hop-Limit in the message.
• Source Layer-2 ID: the 5G ProSe UE-to-Network Relay or the 5G ProSe Intermediate UE-to-Network Relay self-selects a Source Layer-2 ID when sending the discovery message.
• Destination Layer-2 ID: the 5G ProSe Intermediate UE-to-Network Relay sets the Desination Layer-2 ID of the 5G ProSe UE-to-Network Relay Discovery Announcement message based on configuration described in clause 5.1.4.1.
• Announcer Info: identify information (i.e. User Info ID) of the announcing 5G ProSe UE-to-Network Relay or the 5G ProSe Intermediate UE-to-Network Relay.
• (optional) Root Relay Info: this is the User Info ID of the 5G ProSe UE-to-Network Relay. A 5G ProSe Intermediate UE-to-Network Relay may stored it in the discovery entry and included it in the 5G ProSe UE-to-Network Relay Discovery Announcement message. This information can be used in the relay selection at the 5G ProSe Remote UE or other 5G ProSe Intermediate UE-to-Network Relays.
• (optional) Accumulated QoS for PC5 link: this reflects the QoS supported over all the PC5 links to the Root Relay, i.e. the 5G ProSe UE-to-Network Relay, for this RSC.
• (optional) Hop-Limit: this is the hop limit set by the announcing 5G ProSe UE-to-Network Relay to a value smaller than the configured maximum number of hops.

The following parameters are used for the 5G ProSe UE-to-Network Relay Discovery Solicitation message (Model B), where Source Layer-2 ID and Destination Layer-2 ID are used for sending and receiving the message and Discoverer Info and Relay Service Code are contained in the message:

• Source Layer-2 ID: the 5G ProSe Remote-UE self-selects a Source Layer-2 ID for 5G ProSe UE-to-Network Relay Discovery.
• Destination Layer-2 ID: the Destination Layer-2 ID for 5G ProSe UE-to-Network Relay Discovery is selected based on the configuration as described in clause 5.1.4.1.
• Discoverer Info: provides information (i.e. User Info ID) about the discoverer user.
• Target Info: provides information (i.e. User Info ID) about the targeted discoveree user.
• Relay Service Code: information about connectivity that the discoverer UE is interested in. The Relay Service Codes are configured in the 5G ProSe Remote UEs interested in related connectivity services.

To support Multi-hop 5G ProSe UE-to-Network Relay discovery the following parameters are added:

• (Optional) Hop count: indicates the number of hops that the message is already relayed. It is increased by 1 per hop.
• (Optional) Hop-Limit: a unmodified value that indicates the hop limit of the message. It is set, by the 5G ProSe Remote UE, to a value smaller than the (pre)configured maximum number of hops.
• Path information: an (ordered) list of User Info ID(s) of Intermediate UE-to-Network Relay(s) that indicates the transmitted path of the message.

The following parameters are used in the 5G ProSe UE-to-Network Relay Discovery Response message (Model B), where Source Layer-2 ID and Destination Layer-2 ID are used for sending and receiving the message and Discoveree Info and Relay Service Code are contained in the message:

• Source Layer-2 ID: the 5G ProSe UE-to-Network Relay self-selects a Source Layer-2 ID for 5G ProSe UE-to-Network Relay Discovery.
• Destination Layer-2 ID: set to the Source Layer-2 ID of the received 5G ProSe UE-to-Network Relay Discovery Solicitation message.
• Relay Service Code: identifies the connectivity service the 5G ProSe UE-to-Network Relay provides to 5G ProSe Remote UEs that matches the Relay Service Code from the corresponding Discovery Solicitation message.
• Discoveree Info: provides information (i.e. User Info ID) about the discoveree.

To support Multi-hop 5G ProSe UE-to-Network Relay discovery the following parameters are added:

• (Optional) Hop count: indicates the number of hops between the 5G ProSe Remote UE and the 5G ProSe UE-to-Network Relay on the path selected by the 5G ProSe UE-to-Network Relay.
• (Optional) Path information: an (ordered) list of User Info ID(s) of Intermediate UE-to-Network Relay(s) on the path selected by the 5G ProSe UE-to-Network Relay.

The following parameters may be used in the Relay Discovery Additional Information message (using Model A) based on the procedure defined in clause 6.5.1.3 for 5G ProSe UE-to-Network Relay and clause 6.3.2.5.4 for 5G ProSe multi-hop UE-to-Network Relay where Source Layer-2 ID and Destination Layer-2 ID are used for sending and receiving the message and the other parameters are contained in the message:

• Source Layer-2 ID: the 5G ProSe UE-to-Network Relay or the 5G ProSe Intermediate UE-to-Network Relay self-selects a Source Layer-2 ID to send the Relay Discovery Additional Information message.
• Destination Layer-2 ID: the Destination Layer-2 ID to send the Relay Discovery Additional Information message is selected based on the configuration as described in clause 5.1.4.1.
• Relay Service Code: the Relay Service Code associated with the message. The Relay Service Code is used to identify the security parameters needed by the receiving UE to process the discovery message.
• Announcer Info: provides information about the announcing user (i.e. User Info ID of the 5G ProSe UE-to-Network Relay).
• Hop-Count: This value reflects the number of PC5 hops for the 5G ProSe Remote UE to reach the network. It is set to 1 by the 5G ProSe UE-to-Network Relay and shall be incremented by 1 every time the Relay Discovery Additional Information message is forwarded by a 5G ProSe Intermediate UE-to-Network Relay.
  A 5G ProSe Intermediate UE-to-Network Relay shall only process the Relay Discovery Additional Information message if the Hop-Count is present and the value is less than the (pre-)configured maximum number of hops for the associated RSC and the optional Hop-Limit in the message.
• Announcer Info of 5G ProSe Intermediate UE-to-Network Relay: identify information (i.e. User Info ID) of the 5G ProSe Intermediate UE-to-Network Relay connected to 5G ProSe UE-to-Network Relay. This parameter is only applicable to the additional parameter announcement procedure over 5G ProSe multi-hop UE-to-Network Relay specified in clause 6.3.2.5.4.
• (optional) Hop-Limit: this is the hop limit set by the announcing 5G ProSe UE-to-Network Relay to a value smaller than the configured maximum number of hops.
• Additional parameters: the additional parameters for 5G ProSe Layer-3 UE-to-Network Relay (when applicable) are defined in clause 5.8.3.2.

For 5G ProSe Layer-3 UE-to-Network relay, a Relay Service Code in the Announcement Message is associated with a set of PDU session parameters (e.g. PDU Session type, DNN, SSC Mode, S-NSSAI, Access Type Preference). The Relay Service Code may also represent if the relay UE can provide secure N3IWF connection. For 5G ProSe Layer-3 Remote UE discovering 5G ProSe Layer-3 UE-to-Network relay, the Relay Service Code in the Solicitation Message represents the PDU session parameters that a PDU session of the relay should be able to support. The Relay Service Code may also represent if the remote UE requires secure N3IWF connection. The following additional parameters may be used in the Relay Discovery Additional Information message (using Model A) for 5G ProSe Layer-3 UE-to-Network Relay:

• NCGI: indicates the NCGI of the serving cell of the 5G ProSe Layer-3 UE-to-Network Relay. This parameter may be requested by application running on 5G ProSe Layer-3 Remote UE.
• TAI: indicates the Tracking Area Identity of the serving cell of the 5G ProSe Layer-3 UE-to-Network Relay. This parameter may be used by 5G ProSe Layer-3 Remote UE to select a N3IWF.
• NCGI of 5G ProSe Intermediate UE-to-Network Relay: indicates the NCGI of the serving cell of the 5G ProSe Intermediate UE-to-Network Relay connected to the 5G ProSe UE-to-Network Relay. This parameter may be requested by application running on 5G ProSe Layer-3 Remote UE and is only applicable to the additional parameter announcement procedure over 5G ProSe multi-hop UE-to-Network Relay specified in clause 6.3.2.5.4.

The following parameters may be used in Announcement message (Model A) or Response message (Model B) in addition to the parameters as specified in clause 5.8.3.1:

• NCGI: indicates the NCGI of the serving cell of the 5G ProSe Layer-2 UE-to-Network Relay for 5G ProSe Layer-2 UE-to-Network Relay (re)selection.
• RRC Container: An RRC container, as defined in TS 38.331, which includes the cell access related information for the serving cell of the 5G ProSe Layer-2 UE-to-Network Relay.

The 5G ProSe UE-to-UE Relay Discovery message contains two sets of identifiers, a Direct Discovery set and a UE-to-UE Relay Discovery set.

• The Direct Discovery set of identifiers are part of the contents of the 5G ProSe Direct Discovery message as defined in clause 5.8.1. This set of identifiers provides information about the 5G ProSe End UE(s) (e.g. user info (i.e. Application Layer ID)) to be discovered via 5G ProSe UE-to-UE Relay.
• The UE-to-UE Relay Discovery set of identifiers as defined in clause 5.8.4.2 contain information to support the discovery of the 5G ProSe UE-to-UE Relay and extensions of the Direct Discovery.

5G ProSe UE-to-UE Relay shall modify the UE-to-UE Relay Discovery set of identifiers and forward the Direct Discovery set and the UE-to-UE Relay Discovery set of identifiers during the discovery procedures. The Direct Discovery set can be protected using different keys as used to protect the UE-to-UE Relay Discover set according to TS 33.503.

The following parameters are used as UE-to-UE Relay Discovery set of identifiers for the 5G ProSe UE-to-UE Relay Discovery Announcement message (Model A), where Source Layer-2 ID and Destination Layer-2 ID are used for sending and receiving the message and User Info ID and Relay Service Code are contained in the message:

• Source Layer-2 ID: the 5G ProSe UE-to-UE Relay self-selects a Source Layer-2 ID for 5G ProSe UE-to-UE Relay Discovery Announcement message.
• Destination Layer-2 ID: the Destination Layer-2 ID for 5G ProSe UE-to-UE Relay Discovery Announcement message is selected based on the configuration as described in clause 5.1.5.1.
• User Info ID of 5G ProSe UE-to-UE Relay: provides information about the 5G ProSe UE-to-UE Relay.
• Relay Service Code: information to indicate the connectivity service the 5G ProSe UE-to-UE Relay provides to 5G ProSe End UEs.

The following parameters are used as UE-to-UE Relay Discovery set of identifiers for the 5G ProSe UE-to-UE Relay Discovery Solicitation message (Model B) between discoverer 5G ProSe End UE and 5G ProSe UE-to-UE Relay, where Source Layer-2 ID and Destination Layer-2 ID are used for sending and receiving the message and User Info ID and Relay Service Code are contained in the message:

• Source Layer-2 ID: the discoverer 5G ProSe End UE self-selects a Source Layer-2 ID for 5G ProSe UE-to-UE Relay Discovery Solicitation message.
• Destination Layer-2 ID: the Destination Layer-2 ID for 5G ProSe UE-to-UE Relay Discovery Solicitation message is selected based on the configuration as described in clause 5.1.5.1.
• Relay Service Code: information about connectivity service that the discoverer 5G ProSe End UE is interested in.

The following parameters are used as UE-to-UE Relay Discovery set of identifiers in the 5G ProSe UE-to-UE Relay Discovery Response message (Model B) between discoverer 5G ProSe End UE and 5G ProSe UE-to-UE Relay, where Source Layer-2 ID and Destination Layer-2 ID are used for sending and receiving the message and User Info ID and Relay Service Code are contained in the message:

• Source Layer-2 ID: the 5G ProSe UE-to-UE Relay self-selects a Source Layer-2 ID for 5G ProSe UE-to-UE Relay Discovery Response message.
• Destination Layer-2 ID: set to the Source Layer-2 ID of the received 5G ProSe UE-to-UE Relay Discovery Solicitation message.
• User Info ID of 5G ProSe UE-to-UE Relay: provides information about the 5G ProSe UE-to-UE Relay.
• Relay Service Code: identifies the connectivity service the 5G ProSe UE-to-UE Relay provides to 5G ProSe End UEs that matches the Relay Service Code from the corresponding Discovery Solicitation message.

The following parameters are used as UE-to-UE Relay Discovery set of identifiers for the 5G ProSe UE-to-UE Relay Discovery Solicitation message (Model B) between 5G ProSe UE-to-UE Relay and discoveree 5G ProSe End UE, where Source Layer-2 ID and Destination Layer-2 ID are used for sending and receiving the message and User Info ID and Relay Service Code are contained in the message:

• Source Layer-2 ID: the 5G ProSe UE-to-UE Relay self-selects a Source Layer-2 ID for 5G ProSe UE-to-UE Relay Discovery Solicitation message.
  When a 5G ProSe UE-to-UE Relay self-selects a Source Layer-2 ID for a received 5G ProSe UE-to-UE Relay Discovery Solicitation message, it selects a different Source Layer-2 ID values for each 5G ProSe UE-to-UE Relay Discovery Solicitation message, so that the 5G ProSe UE-to-UE Relay can correlate the 5G ProSe UE-to-UE Relay Discovery Response message with the 5G ProSe UE-to-UE Relay Discovery Solicitation message. The 5G ProSe UE-to-UE Relay can determine the discoverer 5G ProSe End UE that triggered the 5G ProSe UE-to-UE Relay Discovery Solicitation based on the destination Layer-2 ID of the received 5G ProSe UE-to-UE Relay Discovery Response message.
• Destination Layer-2 ID: the Destination Layer-2 ID for 5G ProSe UE-to-UE Relay Discovery Solicitation message is selected based on the configuration as described in clause 5.1.5.1.
• User Info ID of 5G ProSe UE-to-UE Relay: provides information about the 5G ProSe UE-to-UE Relay.
• Relay Service Code: identifies the connectivity service the 5G ProSe UE-to-UE Relay provides to 5G ProSe End UEs.

The following parameters are used as UE-to-UE Relay Discovery set of identifiers in the 5G ProSe UE-to-UE Relay Discovery Response message (Model B) between 5G ProSe UE-to-UE Relay and discoveree 5G ProSe End UE, where Source Layer-2 ID and Destination Layer-2 ID are used for sending and receiving the message and User Info ID and Relay Service Code are contained in the message:

• Source Layer-2 ID: the discoveree 5G ProSe End UE self-selects a Source Layer-2 ID for 5G ProSe UE-to-UE Relay Discovery Response message.
• Destination Layer-2 ID: set to the Source Layer-2 ID of the received 5G ProSe UE-to-UE Relay Discovery Solicitation message.
• Relay Service Code: identifies the connectivity service the 5G ProSe UE-to-UE Relay provides to 5G ProSe End UEs that matches the Relay Service Code from the corresponding Discovery Solicitation message.

There are two types of discovery mechanisms for the support of 5G ProSe Multi-hop UE-to-UE Relays, i.e. for IP PDU type, and for non-IP PDU type (Ethernet or Unstructured). The 5G ProSe End UE and 5G ProSe Multi-hop UE-to-UE Relay choose the discovery mechanism based on the associated indication of the RSC, as defined in clause 5.1.5.1. The identifiers used for the two types of discovery mechanisms are specified in clause 5.8.6.2 and clause 5.8.3 respectively.

The Multi-hop UE-to-UE Relay Discovery Announcement message (Model A) is sent by the relay and contains the following information:

• Source Layer-2 ID: the 5G ProSe Layer-3 Multi-hop UE-to-UE Relay self-selects a Source Layer-2 ID. It is used for the transmitting the message at AS layer, and included in the AS layer headers only.
• Destination Layer-2 ID: the Destination Layer-2 ID for Multi-hop UE-to-UE Relay Discovery Announcement message (Model A) is selected based on the configuration (associated with the RSC) as defined in clause 5.1.5.1.
• User Info ID of 5G ProSe Multi-hop UE-to-UE Relay: provides information about the 5G ProSe Layer-3 Multi-hop UE-to-UE Relay.
• Relay Service Code: information to indicate the connectivity service the 5G ProSe Layer-3 Multi-hop UE-to-UE Relay provides to the 5G ProSe End UEs.

The 5G ProSe Multi-hop UE-to-UE Relay Discovery Solicitation message (Model B) is sent by the source 5G ProSe End UE or a 5G ProSe Layer-3 Multi-hop UE-to-UE Relay, and includes the following information:

• Source Layer-2 ID: the discoverer 5G ProSe End UE or 5G ProSe Layer-3 Multi-hop UE-to-UE Relay self-selects a Source Layer-2 ID.
• Destination Layer-2 ID: the Destination Layer-2 ID for 5G ProSe Multi-hop UE-to-UE Relay Discovery Solicitation message is selected based on the configuration (associated with the RSC) as defined in clause 5.1.5.1.
• (optional) User Info ID of discoverer: this may be used by the receiver of the message to determine whether to respond to the solicitation.
• Relay Service Code: information about connectivity service offered by the 5G ProSe Layer-3 Multi-hop UE-to-UE Relay(s).

The 5G ProSe UE-to-UE Relay Discovery Response message (Model B) sent by the 5G ProSe Layer-3 Multi-hop UE-to-UE Relay(s) matching the RSC includes the following:

• Source Layer-2 ID: the 5G ProSe Layer-3 Multi-hop UE-to-UE Relay self-selects a Source Layer-2 ID.
• Destination Layer-2 ID: set to the Source Layer-2 ID of the received 5G ProSe Multi-hop UE-to-UE Relay Discovery Solicitation message.
• User Info ID of discoverer: the User Info ID from the received Solicitation message, to ensure the response can be matched at the receiver.
• User Info ID of 5G ProSe UE-to-UE Relay: provides information about the 5G ProSe Multi-hop UE-to-UE Relay.
• Relay Service Code: information about connectivity service offered by the 5G ProSe Layer-3 Multi-hop UE-to-UE Relay.