ETSI TS 129 388 V14.2.0 (2019-10)

TECHNICAL SPECIFICATION
LTE;
V2X Control Function to Home Subscriber Server (HSS)
aspects (V4);
Stage 3
(3GPP TS 29.388 version 14.2.0 Release 14)

3GPP TS 29.388 version 14.2.0 Release 14 1 ETSI TS 129 388 V14.2.0 (2019-10)

Reference
RTS/TSGC-0429388ve20
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3GPP TS 29.388 version 14.2.0 Release 14 2 ETSI TS 129 388 V14.2.0 (2019-10)
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Contents
Intellectual Property Rights . 2
Legal Notice . 2
Modal verbs terminology . 2
Foreword . 5
1 Scope . 6
2 References . 6
3 Definitions and abbreviations . 7
3.1 Definitions . 7
3.2 Abbreviations . 7
4 General Description . 7
4.1 Introduction . 7
5 Procedure Description . 7
5.1 Introduction . 7
5.2 V2X Subscriber Information Retrieval . 7
5.2.1 General . 7
5.2.2 Detailed Behaviour of the V2X Control Function . 8
5.2.3 Detailed Behaviour of the HSS . 8
5.3 Update V2X Subscriber Data . 9
5.3.1 General . 9
5.3.2 Detailed behaviour of the V2X Control Function . 10
5.3.3 Detailed behaviour of the HSS . 11
5.4 Notification Procedure . 11
5.4.1 General . 11
5.4.2 Detailed Behaviour of the V2X Control Function . 12
5.4.3 Detailed Behaviour of the HSS . 12
5.5 Reset . 13
5.5.1 General . 13
5.5.2 Detailed behaviour of the V2X Control Function . 13
5.5.3 Detailed behaviour of the HSS . 14
6 Protocol Specification and Implementations . 14
6.1 Introduction . 14
6.1.1 Use of Diameter base protocol . 14
6.1.2 Securing Diameter Messages . 14
6.1.3 Accounting Functionality . 14
6.1.4 Use of Sessions . 14
6.1.5 Transport Protocol . 14
6.1.6 Routing Considerations . 15
6.1.7 Advertising Application Support . 15
6.1.8 Diameter Application Identifier . 15
6.1.9 Use of the Supported-Features AVP . 15
6.2 Commands . 16
6.2.1 Introduction. 16
6.2.2 Command-Code Values . 16
6.2.3 ProSe-Subscriber-Information-Request (PIR) Command . 16
6.2.4 ProSe-Subscriber-Information-Answer (PIA) Command . 17
6.2.5 Update-ProSe-Subscriber-Data-Request (UPR) Command . 17
6.2.6 Update-ProSe-Subscriber-Data-Answer (UPA) Command . 18
6.2.7 ProSe-Notify-Request (PNR) Command . 18
6.2.8 ProSe-Notify-Answer (PNA) Command . 18
6.2.9 Reset-Request (RSR) Command . 19
6.2.10 Reset-Answer (RSA) Command . 19
6.3 AVPs . 20
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6.3.1 General . 20
6.3.2 V2X-Subscription-Data . 21
6.3.3 V2X-PC5-Allowed-PLMN . 21
6.3.4 V2X-Update-Flags . 21
6.3.5 V2X-Notify-Flags . 21
6.3.6 OC-Supported-Features . 22
6.3.7 OC-OLR . 22
6.3.8 DRMP . 22
6.3.9 Load . 22
6.4 Result-Code AVP and Experimental-Result AVP Values . 22
6.4.1 General . 22
6.4.2 Success . 22
6.4.3 Permanent Failures . 22
6.4.3.1 General . 22
6.4.3.2 DIAMETER_ERROR_USER_UNKNOWN (5001) . 23
6.4.3.3 DIAMETER_ERROR_UNKNOWN_V2X_SUBSCRIPTION (5690) . 23
6.4.3.4 DIAMETER_ERROR_V2X_NOT_ALLOWED (5691) . 23
Annex A (normative): Diameter overload control mechanism . 24
A.1 General . 24
A.2 HSS behaviour . 24
A.3 V2X Control Function behaviour . 24
Annex B (Informative): Diameter overload node behaviour . 25
B.1 Message prioritization . 25
Annex C (normative): Diameter message priority mechanism . 26
C.1 General . 26
C.2 V4 interface . 26
C.2.1 General . 26
C.2.2 HSS and V2X Control Function behaviour . 26
D.1 General . 26
D.2 HSS behaviour . 26
D.3 V2X Control Function behaviour . 27
Annex E (informative): Change history . 28
History . 29

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Foreword
rd
This Technical Specification has been produced by the 3 Generation Partnership Project (3GPP).
The contents of the present document are subject to continuing work within the TSG and may change following formal
TSG approval. Should the TSG modify the contents of the present document, it will be re-released by the TSG with an
identifying change of release date and an increase in version number as follows:
Version x.y.z
where:
x the first digit:
1 presented to TSG for information;
2 presented to TSG for approval;
3 or greater indicates TSG approved document under change control.
y the second digit is incremented for all changes of substance, i.e. technical enhancements, corrections,
updates, etc.
z the third digit is incremented when editorial only changes have been incorporated in the document.
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1 Scope
The present document describes the Diameter-based V4 interface between the V2X Control Function and the Home
Subscriber Server (HSS) defined for V2X services.
This specification defines the Diameter application for V4 reference point between the V2X Control Function and the
HSS. The interactions between the V2X Control Function and the HSS are specified.
The stage 2 description for V2X service features in EPS is specified in 3GPP TS 23.285 [2].
2 References
The following documents contain provisions which, through reference in this text, constitute provisions of the present
document.
- References are either specific (identified by date of publication, edition number, version number, etc.) or
non-specific.
- For a specific reference, subsequent revisions do not apply.
- For a non-specific reference, the latest version applies. In the case of a reference to a 3GPP document (including
a GSM document), a non-specific reference implicitly refers to the latest version of that document in the same
Release as the present document.
[1] 3GPP TR 21.905: "Vocabulary for 3GPP Specifications".
[2] 3GPP TS 23.285: "Architecture enhancements for V2X services; Stage 2".
[3] IETF RFC 6733: "Diameter Base Protocol".
[4] 3GPP TS 33.210: "3G Security; Network Domain Security; IP Network Layer Security".
[5] IETF RFC 4960: "Stream Control Transmission Protocol".
[6] 3GPP TS 29.229: "Cx and Dx interfaces based on the Diameter protocol".
[7] IETF RFC 5234: "Augmented BNF for Syntax Specifications: ABNF".
[8] 3GPP TS 23.003: "Numbering, addressing and identification".
[9] 3GPP TS 29.228: "IP multimedia (IM) Subsystem Cx and Dx Interfaces; Signalling flows and
Message Elements".
[10] 3GPP TS 29.272: "Evolved Packet System; MME and SGSN Related Interfaces Based on
Diameter Protocol".
[11] 3GPP TS 29.329: "Sh Interface based on the Diameter protocol".
[12] IETF RFC 7683: "Diameter Overload Indication Conveyance".
[13] IETF RFC 7944: "Diameter Routing Message Priority".
[14] 3GPP TS 23.007: "Restoration procedures".
[15] 3GPP TS 29.344: "Proximity-services (ProSe) Function to Home Subscriber Server (HSS)
aspects".
[16] IETF RFC 8583: "Diameter Load Information Conveyance".
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3 Definitions and abbreviations
3.1 Definitions
For the purposes of the present document, the terms and definitions given in 3GPP TR 21.905 [1] and the following
apply. A term defined in the present document takes precedence over the definition of the same term, if any, in
3GPP TR 21.905 [1].
example: text used to clarify abstract rules by applying them literally.

3.2 Abbreviations
For the purposes of the present document, the abbreviations given in 3GPP TR 21.905 [1] and the following apply. An
abbreviation defined in the present document takes precedence over the definition of the same abbreviation, if any, in
3GPP TR 21.905 [1].
ProSe Proximity-based Services
V2X Vehicle-to-Everything
4 General Description
4.1 Introduction
The V4 reference point between the V2X Control Function and the HSS is defined in the 3GPP TS 23.285 [2].
This document describes the V4 interface related procedures, message parameters and protocol specifications.
The V4 interface allows the V2X Control Function to retrieve V2X related subscription data in order to authorise access
from the UE for V2X services.
5 Procedure Description
5.1 Introduction
This clause describes the Diameter-based V4 interface related procedures and information elements exchanged between
the V2X Control Function and the HSS.
In the tables that describe the Information Elements transported by each Diameter command, each Information Element
is marked as (M) Mandatory, (C) Conditional or (O) Optional in the "Cat." column. For the correct handling of the
Information Element according to the category type, see the description detailed in clause 6 of the 3GPP TS 29.228 [9].
5.2 V2X Subscriber Information Retrieval
5.2.1 General
This procedure shall be used between the V2X Control Function and the HSS for authorization of the UE for V2X
services. The procedure shall be invoked by the V2X Control Function and is used:
- to request V2X related subscription data.
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This procedure is mapped to the commands ProSe-Subscriber-Information-Request/Answer (PIR/PIA) in the Diameter
application specified in clause 6. Table 5.2.1-1 and table 5.2.1-2 detail the involved information elements.
Table 5.2.1-1: V2X Subscriber Information Retrieval Request
Information Element Mapping to Diameter Cat. Description
Name AVP
IMSI User-Name (See M This information element shall contain the user IMSI,
IETF RFC 6733 [3]) formatted according to 3GPP TS 23.003 [8],
clause 2.2.
Supported Features Supported-Features O If present, this information element shall contain the
(See list of features supported by the origin host.
3GPP TS 29.229 [6])
Table 5.2.1-2: V2X Subscriber Information Retrieval Answer
Information Element Mapping to Cat. Description
Name Diameter AVP
Result Result-Code / M This IE shall contain the result of the operation.
(See 6) Experimental- The Result-Code AVP shall be used to indicate success / errors as
Result defined in the Diameter base protocol.
The Experimental-Result AVP shall be used for V4 errors. This is
a grouped AVP which shall contain the 3GPP Vendor ID in the
Vendor-Id AVP, and the error code in the Experimental-Result-
Code AVP.
The following errors are applicable:
- User Unknown
- Unknown V2X Subscription
- V2X Not Allowed
V2X Subscription Data V2X-Subscription- C This information element shall contain the V2X Subscription Data
(See 6.3.2) Data that gives the user permission to use V2X.
MSISDN MSISDN C This information element shall contain the user MSISDN,
(See 3GPP TS 29.329 formatted according to 3GPP TS 29.329 [11]. It shall be present if
[11]) available.
Visited PLMN Id Visited-PLMN-Id C This IE shall contain the MCC and the MNC of the PLMN where
(See the UE is registered, see 3GPP TS 23.003 [8].
3GPP TS 29.272 [10]) It shall be present if the UE is roaming in a PLMN different from
the Home PLMN.
Supported Features Supported- O If present, this information element shall contain the list of features
(See Features supported by the origin host.
3GPP TS 29.229 [6])
Reset-IDs Reset-ID O The Reset-ID uniquely identifies a fallible resource in the HSS's
(See realm on which the user (IMSI) depends. In the event of a restart
3GPP TS 29.272 [10]) of the fallible resource a Reset message containing the Reset-ID
will exactly identify the impacted subscribers.

5.2.2 Detailed Behaviour of the V2X Control Function
The V2X Control Function shall make use of this procedure to request V2X related subscription data.
If the V2X Control Function retrieved the V2X related subscription data, the V2X Control Function shall perform the
authorisation for V2X as described in the 3GPP TS 23.285 [2].
5.2.3 Detailed Behaviour of the HSS
When receiving a V2X Subscriber Information Retrieval Request the HSS shall check if the IMSI for whom data is
requested exists in the HSS. If not, an Experimental-Result of DIAMETER_ERROR_USER_UNKNOWN shall be
returned.
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If the IMSI exists but there is not any V2X subscription data for the IMSI, the HSS shall return an Experimental-Result
of DIAMETER_ERROR_UNKNOWN_V2X_SUBSCRIPTION.
If the UE is not allowed to use V2X in the visited PLMN, the HSS shall return an Experimental-Result of
DIAMETER_ERROR_V2X_NOT_ALLOWED. Otherwise, the HSS shall return a Result-Code of
DIAMETER_SUCCESS and shall store V2X Control Function identity (the V2X Control Function identity is received
within the Origin-Host AVP) and download the V2X subscription data to the V2X Control Function. The HSS shall
provide the Visited PLMN ID of where the UE is registered if the UE is roaming in a PLMN different from the Home
PLMN.
5.3 Update V2X Subscriber Data
5.3.1 General
The Update V2X Subscriber Data procedure shall be used between the V2X Control Function and the HSS to update
the subscriber related data downloaded by means of the V2X Subscriber Information Retrieval operation (see
clause 5.2) and stored in the V2X Control Function.
It shall be used to update subscriber related data in the V2X Control Function due to administrative changes of the user
data in the HSS, i.e. if the user was given a subscription and the subscription has changed. It shall be used at least to
perform the following:
- update of all of V2X subscription data of the subscriber,
- update of a subset of the V2X subscription data of the subscriber,
- deletion of the V2X subscription data of the subscriber.
The procedure will also be triggered when the VPLMN has changed.
This procedure is mapped to the commands Update-ProSe-Subscriber-Data-Request/Answer (UPR/UPA) in the
Diameter application specified in clause 6.
Table 5.3.1-1 specifies the involved information elements for the request.
Table 5.3.1-2 specifies the involved information elements for the answer.
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Table 5.3.1-1: Update V2X Subscriber Data Request
Information Mapping to Cat. Description
element name Diameter AVP
IMSI User-Name M This information element shall contain the user IMSI, formatted according
(See to 3GPP TS 23.003 [8], clause 2.2.
IETF RFC 673
3 [3])
Supported Supported- O If present, this information element shall contain the list of features
Features Features supported by the origin host.
(See
3GPP TS 29.2
29 [6])
V2X V2X- C This information element shall contain the V2X Subscription Data that gives
Subscription Subscription- the user permission to use V2X service.
Data (See Data
6.3.2)
Visited PLMN Visited-PLMN- C This IE shall contain the MCC and the MNC of the PLMN where the UE is
Id Id registered, see 3GPP TS 23.003 [8].
(See It shall be present if the UE is roaming in a PLMN different from the Home
3GPP TS 29.2 PLMN.
72 [10])
V2X Update V2X-Update- M This Information Element shall contain a bit mask. See clause 6.3.6 for the
Flags Flags meaning of the bits.
(See 6.3.4)
Reset-IDs Reset-ID O The Reset-ID uniquely identifies a fallible resource in the HSS's realm on
(See which the user (IMSI) depends. In the event of a restart of the fallible
3GPP TS 29.2 resource a Reset message containing the Reset-ID will exactly identify the
72 [10]) impacted subscribers.

Table 5.3.1-2: Update V2X Subscriber Data Answer
Information Mapping to Cat. Description
element name Diameter AVP
Supported Supported- O If present, this information element shall contain the list of features
Features Features supported by the origin host.
(See
3GPP TS 29.2
29 [6])
Result Result-Code / M This IE shall contain the result of the operation.
(See 6.4) Experimental- The Result-Code AVP shall be used to indicate success / errors as defined
Result in the Diameter base protocol.
The Experimental-Result AVP shall be used for V4 errors. This is a
grouped AVP which shall contain the 3GPP Vendor ID in the Vendor-Id
AVP, and the error code in the Experimental-Result-Code AVP.
The following errors are applicable in this case:
- User Unknown
- Unknown V2X Subscription
5.3.2 Detailed behaviour of the V2X Control Function
When receiving an Update V2X Subscriber Data request, the V2X Control Function shall check whether the IMSI is
known.
If it is not known, a result code of DIAMETER_ERROR_USER_UNKNOWN shall be returned.
If it is known, the V2X Control Function shall update the corresponding data according to the indication as sent in the
request, and acknowledge the Update V2X Subscriber Data message by returning an Update V2X Subscriber Data
Answer. If the V2X-Update-Flags indicates that the V2X subscription data is to be deleted, the V2X Control Function
shall delete the associated V2X UE context if it has been stored before.
If the update of the subscription data succeeds in the V2X Control Function, the Result-Code shall be set to
DIAMETER_SUCCESS.
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If the V2X Control Function cannot fulfil the received request for other reasons, e.g. due to a database error, it shall set
the Result-Code to DIAMETER_UNABLE_TO_COMPLY. In this case, the V2X Control Function shall mark the
subscription record "Subscriber data to be restored in the HSS".
5.3.3 Detailed behaviour of the HSS
The HSS shall make use of this procedure to update the relevant subscriber related data in the V2X Control Function to
replace a specific part of the user data stored in the V2X Control Function with the data sent.
If the V2X related subscription data is updated or revoked, the HSS sends the updated V2X subscription data to the
V2X Control Function. The HSS shall include the V2X-Update-Flags to indicate which part of the data is updated. If all
of the V2X subscription data is to be removed, the HSS shall set the "Removal of all V2X Subscription Data" bit of the
V2X-Update-Flags, and the HSS shall delete the V2X Control Function Identity if it is stored for this subscriber.
5.4 Notification Procedure
5.4.1 General
This procedure shall be used between the V2X Control Function and the HSS when the HSS needs to be notified about:
- revocation of authorization for V2X service on one PLMN.
- removal of the subscription data from the V2X Control Function either by an MMI interaction or automatically.
This procedure is mapped to the commands ProSe-Notify-Request/Answer (PNR/PNA) in the Diameter application
specified in clause 6. Table 5.4.1-1 and table 5.4.1-2 detail the involved information elements.
Table 5.4.1-1: V2X Notify Request
Information Element Mapping to Diameter Cat. Description
Name AVP
IMSI User-Name (See C This information element shall contain the user IMSI,
IETF RFC 6733 [3]) formatted according to 3GPP TS 23.003 [8],
clause 2.2.
It shall be present if the revocation is for a specific UE.
Supported Features Supported-Features O If present, this information element shall contain the list
(See of features supported by the origin host.
3GPP TS 29.229 [6])
PLMN ID (see Visited-PLMN-Id C This information element shall contain the MCC and
3GPP TS 29.272 [10]) the MNC of the PLMN where the UE's authorization for
V2X service is revoked, see 3GPP TS 23.285 [2].
It shall be present if the V2X Control Function revokes
the authorization for V2X service in a specific PLMN.
V2X Notify Flags V2X-Notify-Flags C This Information Element shall contain a bit mask. See
(see 6.3.5) 6.3.7 for the meaning of the bits.

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Table 5.4.1-2: V2X Notify Answer
Information Element Mapping to Cat. Description
Name Diameter AVP
Result Result-Code / M This IE shall contain the result of the operation.
(See 6) Experimental- The Result-Code AVP shall be used to indicate success /
Result errors as defined in the Diameter base protocol.
The Experimental-Result AVP shall be used for V4 errors. This
is a grouped AVP which shall contain the 3GPP Vendor ID in
the Vendor-Id AVP, and the error code in the Experimental-
Result-Code AVP.
The following errors are applicable:
- User Unknown
- Unknown V2X Subscription
Supported Features Supported- O If present, this information element shall contain the list of
(See Features features supported by the origin host.
3GPP TS 29.229 [6])
5.4.2 Detailed Behaviour of the V2X Control Function
The V2X Control Function shall make use of this procedure to revoke authorization for V2X service.
The V2X Control Function shall make use of this procedure to inform the HSS when the subscription data is deleted
from the V2X Function database due to MMI interaction or automatically.
The V2X Control Function shall send the updated V2X Permission and the PLMN ID for which the V2X Permission is
to be updated. If the revocation is for a single UE in the indicated PLMN, the V2X Function shall include IMSI in the
request.
5.4.3 Detailed Behaviour of the HSS
When receiving a V2X Notify Request the HSS shall check if the IMSI, if present in the message, exists in the HSS. If
not, an Experimental-Result of DIAMETER_ERROR_USER_UNKNOWN shall be returned.
If the IMSI exists but there is not any V2X subscription data for the IMSI and the PLMN ID as indicated by the Visited-
PLMN-Id AVP in the request, the HSS shall return an Experimental-Result of
DIAMETER_ERROR_UNKNOWN_V2X_SUBSCRIPTION.
If the V2X-Notify-Flags indicates revocation of authorization for V2X service, and
- if the IMSI exists and there is V2X subscription data for the IMSI and the PLMN ID as indicated by the Visited-
PLMN-Id AVP in the request, the HSS shall revoke V2X service as indicated by the VNR Flags received in the
request on that PLMN for the user and update the V2X Subscription data accordingly. The HSS shall set the
result code to DIAMETER_SUCCESS.
- if IMSI is not present in the message, the HSS shall check if there are any users subscribed to V2X subscription
for the PLMN as indicated by the Visited-PLMN-Id AVP in the request, and if yes, revoke V2X service as
indicated by the VNR Flags received in the request on that PLMN for all the impacted users and update their
V2X Subscription data accordingly. The HSS shall set the result code to DIAMETER_SUCCESS.
If the VNR Flags indicates the subscription data is deleted from the V2X Control Function, the HSS shall remove the
V2X Function Identity for the subscriber and set the result code to DIAMETER_SUCCESS.
For any other reasons if the HSS cannot fulfil the received request, e.g. due to a database error, it shall set the result
code to DIAMETER_UNABLE_TO_COMPLY.
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5.5 Reset
5.5.1 General
The Reset Procedure shall be used by the HSS, after a restart, to indicate to the V2X Control Function that a failure has
occurred.
The Reset Procedure may also be used by the HSS as part of operation and maintenance actions e.g. to allow planned
HSS outage without service interruption.
This procedure is mapped to the commands Reset-Request/Answer (RSR/RSA) in the Diameter application specified in
clause 6.
Table 5.5.1-1 specifies the involved information elements for the request.
Table 5.5.1-2 specifies the involved information elements for the answer.
Table 5.5.1-1: Reset Request
Information Mapping to Cat. Description
element name Diameter AVP
User Id List User-Id O This IE shall contain a list of V2X User-Ids where an V2X User-Id
(See comprises the leading digits of an IMSI (i.e. MCC, MNC, leading digits of
3GPP TS 29.2 MSIN) and it shall identify the set of subscribers whose IMSIs begin with
72 [10]) the User-Id. The HSS may include this information element if the occurred
failure is limited to subscribers identified by one or more User-Ids.
Supported Supported- O If present, this information element shall contain the list of features
Features Features supported by the origin host.
(See
3GPP TS 29.2
29 [6])
Reset-IDs Reset-ID O If present, this information element identifies together with the HSS's realm
(See the set of impacted subscribers.
3GPP TS 29.2
72 [10])
Table 5.5.1-2: Reset Answer
Information Mapping to Cat. Description
element name Diameter AVP
Supported Supported- O If present, this information element shall contain the list of features
Features Features supported by the origin host.
(See
3GPP TS 29.2
29 [6])
Result Result-Code / M This IE shall contain the result of the operation.
(See 6.4) Experimental- The Result-Code AVP shall be used to indicate success / errors as defined
Result in the Diameter Base Protocol.
The Experimental-Result AVP shall be used for V4 errors. This is a
grouped AVP which shall contain the 3GPP Vendor ID in the Vendor-Id
AVP, and the error code in the Experimental-Result-Code AVP.
There are no Experimental-Result codes applicable for this command.

5.5.2 Detailed behaviour of the V2X Control Function
When receiving a Reset message the V2X Control Function shall mark all impacted subscriber records "Subscriber Data
Confirmed in HSS" as "Not Confirmed", as defined in 3GPP TS 23.007 [14]. If the Reset-IDs IE is supported and
received, the V2X Control Function shall make use of the Reset-IDs (together with the HSS's realm) in order to
determine which subscriber records are impacted (i.e. check whether at least one received Reset-ID is associated with
the subscriber, and the HSS's realm identity received in the Origin-Realm AVP matches the value stored after
successful V2X-Subscriber-Information retrieval); otherwise the V2X Control Function shall make use of the HSS
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Identity received in the Origin-Host AVP (by comparing it with the value stored after successful V2X-Subscriber-
Information retrieval) and may make use of the received User-Id-List (if any) in order to determine which subscriber
records are impacted.
5.5.3 Detailed behaviour of the HSS
The HSS shall make use of this procedure in order to indicate to all relevant V2X Control Functions that the HSS has
restarted and may have lost the current V2X Control Function Identity of some of its subscribers who may be currently
roaming in the V2X Control Function Area and that the HSS, therefore, cannot send an Update V2X Subscriber Data
messages when needed.
If the Reset-ID feature is not supported by the V2X Control Function and the HSS, the HSS may include a list of User
Ids identifying a subset of subscribers served by the HSS, if the occurred failure is limited to those subscribers.
If the Reset-ID feature is supported by the V2X Control Function, the HSS optionally may include one (or several)
Reset-ID AVPs identifying e.g. failed hardware components if the occured failure is limited to those subscribers
associated with e.g. the identified failed hardware components.
6 Protocol Specification and Implementations
6.1 Introduction
6.1.1 Use of Diameter base protocol
The Diameter Base Protocol as specified in IETF RFC 6733 [3] shall apply except as modified by the defined support
of the methods and the defined support of the commands and AVPs, result and error codes as specified in this
specification. Unless otherwise specified, the procedures (including error handling and unrecognised information
handling) shall be used unmodified as specified in IETF RFC 6733 [3].
6.1.2 Securing Diameter Messages
For secure transport of Diameter messages, see 3GPP TS 33.210 [4].
6.1.3 Accounting Functionality
Accounting functionality (Accounting Session State Machine, related command codes and AVPs) shall not be used on
the V4 interface.
6.1.4 Use of Sessions
Between the V2X Control Function and the HSS, Diameter sessions shall be implicitly terminated. An implicitly
terminated session is one for which the server does not maintain state information. The client shall not send any re-
authorization or session termination requests to the server.
The Diameter base protocol includes the Auth-Session-State AVP as the mechanism for the implementation of
implicitly terminated sessions.
The client (server) shall include in its requests (responses) the Auth-Session-State AVP set to the value
NO_STATE_MAINTAINED (1), as described in IETF RFC 6733 [3]. As a consequence, the server shall not maintain
any state information about this session and the client shall not send any session termination request. Neither the
Authorization-Lifetime AVP nor the Session-Timeout AVP shall be present in requests or responses.
6.1.5 Transport Protocol
Diameter messages over the V4 interface shall make use of SCTP, see IETF RFC 4960 [5].
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6.1.6 Routing Considerations
This clause specifies the use of the Diameter routing AVPs Destination-Realm and Destination-Host.
The V4 reference point is defined as an intra-operator interface, and both the V2X Control Function and the HSS are
located in the home PLMN of the UE that requests V2X. If the V2X Control Function knows the address/name of the
HSS for a certain user, both the Destination-Realm and Destination-Host AVPs shall be present in the request.
Otherwise, the Destination-Realm AVP shall be present and the command shall be routed to the next Diameter node.
Consequently, the Destination-Host AVP is declared as optional in the ABNF for all requests initiated by the V2X
Control Function.
The HSS obtains the Destination-Host AVP to use in r
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