【5G核心网】 NGAP 消息

Love The Way You Lie 2023-03-02 04:56 67阅读 0赞

![20200728171912306.png][]

# 0. NGAP 服务概述 #

NGAP 提供了在 NG-RAN 和 AMF 之间的信令服务，NGAP 服务分为两类：

*     Non UE-associated services: 非 UE 相关服务，在 NG-RAN 和 AMF 间 NG 接口实例

接口管理流程

配置传递流程

警报消息传送流程

*     UE-associated services: UE 相关服务，为 UE 提供信令和连接

PDU 会话管理流程，PDU 会话相关资源管理

UE 上下文管理流程，包括 UE 上下文建立，修改，释放

UE 移动性管理流程，切换，路径变更请求

寻呼流程，寻呼 UE

NAS 消息传送流程，传递上下行 5G-NAS 消息

NGAP Elementary Procedures 分为类型：

*     Class1：需要响应，有 request 和r esponse，response 响应 success / failure

-  Successful，信令消息明确表明EP成功完成，  
         - Unsuccessful，信令消息表明EP失败，  
         - Successful & Unsuccessful，信令消息中同时带有成功和失败结果。

*     Class2：通知类消息，发送 notify，不用等 response

###    0.1 NG Control Plane ###

![20200727181504467.png][]

**Figure** **7****.1****-1****:** **NG Interface Control Plane**** **

###    0.2 NG User Plane ###

NG-U 定义在 NG-RAN 和 UPF 之间

![20200727190051133.png][] Figure 7.2-1: NG-U protocol structure

![20200728172254542.png][]

N2 接口在 5G-AN 和 AMF，协议 NGAP，传输层为 SCTP，上层用户可以是 NAS，包括 MM 和 SM

NGAP 按流程功能分类，可以分为以下：

<table style="width:664px;"> 
 <thead> 
 <tr> 
 <th style="text-align:left;width:268px;">功能</th> 
 <th style="text-align:left;width:393px;">过程</th> 
 </tr> 
 </thead> 
 <tbody> 
 <tr> 
 <td style="border-color:#dddddd;width:268px;">接口管理过程</td> 
 <td style="border-color:#dddddd;width:393px;">NG Setup RAN Configuration Update AMF Configuration Update NG Reset Error Indication Overload Start Overload Stop AMF Status Indication</td> 
 </tr> 
 <tr> 
 <td style="border-color:#dddddd;width:268px;">寻呼过程</td> 
 <td style="border-color:#dddddd;width:393px;">Paging</td> 
 </tr> 
 <tr> 
 <td style="border-color:#dddddd;width:268px;">UE上下文管理过程</td> 
 <td style="border-color:#dddddd;width:393px;">Initial Context Setup UE Context Release Request (NG-RAN initiated) UE Context Release Request (AMF initiated) UE Context Modification RRC Inactive Transition Report</td> 
 </tr> 
 <tr> 
 <td style="border-color:#dddddd;width:268px;">UE移动性管理过程</td> 
 <td style="border-color:#dddddd;width:393px;">Handover Preparation Handover Resource Allocation Handover Notification Path Switch Request Handover Cancellation Uplink RAN Status Transfer Downlink RAN Status Transfer</td> 
 </tr> 
 <tr> 
 <td style="border-color:#dddddd;width:268px;">UE无线能力管理过程</td> 
 <td style="border-color:#dddddd;width:393px;">UE Radio Capability Info Indication UE Radio Capability Check</td> 
 </tr> 
 <tr> 
 <td style="border-color:#dddddd;width:268px;">PDU会话管理过程</td> 
 <td style="border-color:#dddddd;width:393px;">PDU Session Resource Setup PDU Session Resource Release PDU Session Resource Modify PDU Session Resource Notify PDU Session Resource Modify Indication</td> 
 </tr> 
 <tr> 
 <td style="border-color:#dddddd;width:268px;">NAS消息传输过程</td> 
 <td style="border-color:#dddddd;width:393px;">Initial UE Message Downlink NAS Transport Uplink NAS Transport NAS Non Delivery Indication Reroute NAS Request</td> 
 </tr> 
 <tr> 
 <td style="border-color:#dddddd;width:268px;">位置报告过程</td> 
 <td style="border-color:#dddddd;width:393px;">Location Reporting Control Location Reporting Failure Indication Location Report</td> 
 </tr> 
 </tbody> 
</table>

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3pob25nbGluemhhbmc_size_16_color_FFFFFF_t_70][]

# 1. Interface Management Procedures 接口管理 #

###    1.1 NG Setup ###

NG Setup 流程用来交换 NG-RAN 节点和 AMF 在 NG-C 接口上正确互操作所需的应用程序数据，该程序应是 TNL 关联开始运行后触发的第一个 NGAP 程序。该过程使用 非UE 相关的信令。

此过程将擦除两个节点中的现有应用程序级别配置数据，将其替换为接收到的数据，并清除 NG-RAN 节点上的 AMF 超载状态信息。

如果 NG-RAN 和 AMF 不同意保留 UE 上下文，这个过程也会重发起 NGAP UE 相关上下文，以及擦除相关信令连接

![2020072719244750.png][]   **Figure 8.7.1.2-1: NG setup: successful operation**

NG-RAN 节点发起这个过程，发送 NG SETUP REQUEST message 包括一些合适的数据到 AMF。

![20200727192949736.png][]**Figure 8.7.1.3-1: NG setup: unsuccessful operation**

如果 AMF 不接受 setup，将以 NG SETUP FAILURE message 响应

**1.1.1 NG SETUP REQUEST**

**         **从 NG-RAN 到 AMF 的请求

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3pob25nbGluemhhbmc_size_16_color_FFFFFF_t_70 1][] NG SETUP REQUEST

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3pob25nbGluemhhbmc_size_16_color_FFFFFF_t_70 2][] NGSetupRequest

**1.1.2 NG SETUP RESPONSE**

**          **从 AMF -> NG-RAN 的 response

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3pob25nbGluemhhbmc_size_16_color_FFFFFF_t_70 3][] NG SETUP RESPONSE

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3pob25nbGluemhhbmc_size_16_color_FFFFFF_t_70 4][] NGSetupResponse

# 2. Transport of NAS Messages Procedures #

###    2.1 Initial UE Message ###

由 NG-RAN -> AMF 的 INITIAL UE MESSAGE

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3pob25nbGluemhhbmc_size_16_color_FFFFFF_t_70 5][] 9.2.5.1 INITIAL UE MESSAGE

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3pob25nbGluemhhbmc_size_16_color_FFFFFF_t_70 6][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3pob25nbGluemhhbmc_size_16_color_FFFFFF_t_70 7][]

# 3. UE Context Management Procedures(UE 上下文管理流程) #

###    3.1 Initial Context Setup ###

Initial Context Setup procedure 的目的是在需要时在 NG-RAN 节点上建立必要的整体初始 UE 上下文，包括 PDU 会话上下文，安全密钥，移动性限制列表，UE 无线电能力和 UE 安全能力等。 如果存在与 UE 相关的 UE 逻辑 NG 连接，或者 AMF 已在 ***INITIAL UE MESSAGE*** 消息中接收到 ***RAN UE NGAP ID IE***，或者 NG-RAN 节点已经发起与 UE 相关的逻辑 NG 连接，其经由另一个 NG 接口实例发送 ***INITIAL UE MESSAGE*** 消息，。 ，则 AMF 可以发起 Initial Context Setup procedure。 该过程使用与 UE 相关的信令。

**3.1.1 INITIAL CONTEXT SETUP REQUEST**

AMF --> NG-RAN

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3pob25nbGluemhhbmc_size_16_color_FFFFFF_t_70 8][] INITIAL CONTEXT SETUP REQUEST

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3pob25nbGluemhhbmc_size_16_color_FFFFFF_t_70 9][] InitialContextSetupRequest, Registration accept

###     **3.1.1 INITIAL CONTEXT SETUP RESPONSE** ###

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3pob25nbGluemhhbmc_size_16_color_FFFFFF_t_70 10][] 9.2.2.2 INITIAL CONTEXT SETUP RESPONSE

###    3.2 UE Context Release Request (NG-RAN node initiated) ###

![20200824134517506.png][] Figure 8.3.2.2-1: UE context release request

控制与 UE 相关的逻辑 NG 连接的 NG-RAN 节点，通过向受影响的 AMF 发送 UE CONTEXT RELEASE REQUEST 消息来启动该过程。

UE CONTEXT RELEASE REQUEST 消息应指示适当的原因值，例如，用于请求的与 UE 相关联的逻辑 NG 连接释放的“ TXnRELOCOverall Expiry”，“ Redirection”。

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3pob25nbGluemhhbmc_size_16_color_FFFFFF_t_70 11][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3pob25nbGluemhhbmc_size_16_color_FFFFFF_t_70 12][]

###    3.3 UE Context Release (AMF initiated) ###

# 4. PDU Session Management Procedures （PDU 会话管理流程） #

###    4.1 PDU Session Resource Setup ###

PDU 会话资源设置过程的目的是为一个或多个 PDU 会话和相应的 QoS 流分配 Uu 和 NG-U 上的资源，并为给定的 UE 设置相应的 DRB。，这个流程使用 UE 相关的信令，由 AMF 发起 *PDU SESSION RESOURCE SETUP REQUEST* 消息到 NG-RAN 节点

PDU SESSION RESOURCE SETUP REQUEST 消息应包含 NG-RAN 节点设置与 PDU 会话相关的 NG-RAN 配置所需的信息，该配置由至少一个 PDU会 话资源组成，并包括要在 PDU 会话资源设置的每个 PDU会话资源。

对于每个请求的 PDU 会话，如果资源可用于请求的配置，则 NG-RAN 节点应建立至少一个 DRB，并将 PDU 会话的每个接受的 QoS 流与建立的 DRB 相关联。

对于每个 PDU 会话，NG-RAN 节点应存储包含在 PDU SESSION RESOURCE SETUP REQUEST Transer 消息中包含的 PDU 会话资源建立请求 IE 中的 UL NG-U UP TNL 信息 IE，并将其用作用户面数据的上行链路终止点

对于每个PDU会话，如果 PDU SESSION RESOURCE SETUP REQUEST 消息中包含的 *PDU Session Resource Setup Request Transfer* IE 中包含其他 UL NG-U UP TNL 信息 IE，

![20200728153409127.png][]

Figure 8.2.1.2-1: PDU session resource setup: successful operation

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3pob25nbGluemhhbmc_size_16_color_FFFFFF_t_70 13][]

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3pob25nbGluemhhbmc_size_16_color_FFFFFF_t_70 14][]

# 5. UE Mobility Management Messages （UE 移动管理消息） #

##   Handover Preparation ##

切换准备过程的目的是通过 5GC 请求在目标端准备资源。 对于某个 UE，仅同时进行一个切换准备过程。

![20200730163607433.png][]  Figure 8.4.1.2-1: Handover preparation: successful operation

源 NG-RAN 节点通过将 ***HANDOVER REQUIRED*** 消息发送到服务 AMF 来启动切换准备。 当源 NG-RAN 节点发送 ***HANDOVER REQUIRED*** 消息时，它将启动定时器 TNGRELOCprep。 源 NG-RAN 节点应在原因 IE 中指示用于切换的适当原因值。

在接收到 ***HANDOVER REQUIRED*** 的消息后，对于在 PDU 会话 ID IE 中指示的每个 PDU 会话，AMF 将透明地 *Handover Required Transfer* IE 传递给与有关 PDU 会话相关的 SMF。

当已经准备，包括目标侧保留资源也准备就绪，AMF 回复 HANDOVER COMMAND 消息给 S-NG-RAN，

S-NG\_RAN 收到 HNADOVER COMMAND 消息后停止计时器 。

如果目标侧不能接受任何 PDU 会话资源，将指示在 PDU 会话释放列表。或在切换准备过程中发生错误，AMF 发送 HANDOVER PREPARATION FAILURE 消息。如果在计时器超时前 AMF 没有回复消息，S-NG-RAN 通过发起切换取消进程取消切换准备进程，忽略之后收到的 HANDOVER COMMAND 消息或 HANDOVER FAILURE 消息

###    5.1 HANDOVER REQUIREDR （NG-RAN -> AMF） ###

源 NG-RAN 节点发送该消息到 AMF 来请求资源的准备在目标 NG-RAN

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3pob25nbGluemhhbmc_size_16_color_FFFFFF_t_70 15][] NGAP S-NG-RAN- -> AMF 9.2.3.1 HANDOVER REQUIREDR

###    5.2 HANDOVER COMMAND ###

AMF -> S-NG-RAN，在目标侧准备切换的资源

![watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L3pob25nbGluemhhbmc_size_16_color_FFFFFF_t_70 16][] AMF-->S-NG-RAN 9.2.3.2 HANDOVER COMMAND

## ##

###    5.2 Handover Resource Allocation ###

Handover Resource Allocation 目的是在目标 NG-RAN 为切换的 UE 保留资源。

![20200730172135456.png][]**Figure 8.4.2.2-1: Handover resource allocation: successful operation**

T-NG-RAN 收到 HANDOVER REQUEST 消息将执行：

>      -  尝试执行请求的 PDU 会话配置以及相关安全，
> 
>     -  存储 UE 上下文的 AMBR（Aggregate Maximum Bit Rate）
> 
>     -  存储 UE 上下文的 Mobility Restriction
> 
>     -  存储 UE 上下文的 Secuity Capabilities  / Context

AMF 收到 HANDOVER REQUEST ACKNOWLEDGE 消息后，AMF透明传输给SMF。如果NG-RAN不承认PDU会话资源，或切换准备中发生了错误，则发送 HANDOVER FAILURE 消息。

###    5.3 HANDOVER NOTIFY ###

![20200730191355691.png][] Figure 8.4.3.2-1: Handover notification

由 T-NG-RAN 发送的消息来通知 AMF UE 已经在目标小区标识，切换已经完成

<table style="margin-left:5.4pt;width:486pt;"> 
 <tbody> 
 <tr> 
 <td style="vertical-align:top;width:108pt;"> IE/Group Name </td> 
 <td style="vertical-align:top;width:54pt;"> Presence </td> 
 <td style="vertical-align:top;width:54pt;"> Range </td> 
 <td style="vertical-align:top;width:75.6pt;"> IE type and reference </td> 
 <td style="vertical-align:top;width:86.4pt;"> Semantics description </td> 
 <td style="vertical-align:top;width:54pt;"> Criticality </td> 
 <td style="vertical-align:top;width:54pt;"> Assigned Criticality </td> 
 </tr> 
 <tr> 
 <td style="vertical-align:top;width:108pt;"> Message Type </td> 
 <td style="vertical-align:top;width:54pt;"> M </td> 
 <td style="vertical-align:top;width:54pt;"> &nbsp; </td> 
 <td style="vertical-align:top;width:75.6pt;"> 9.3.1.1 </td> 
 <td style="vertical-align:top;width:86.4pt;"> &nbsp; </td> 
 <td style="vertical-align:top;width:54pt;"> YES </td> 
 <td style="vertical-align:top;width:54pt;"> reject </td> 
 </tr> 
 <tr> 
 <td style="vertical-align:top;width:108pt;"> AMF&nbsp;UE NGAP ID </td> 
 <td style="vertical-align:top;width:54pt;"> M </td> 
 <td style="vertical-align:top;width:54pt;"> &nbsp; </td> 
 <td style="vertical-align:top;width:75.6pt;"> 9.3.3.1 </td> 
 <td style="vertical-align:top;width:86.4pt;"> &nbsp; </td> 
 <td style="vertical-align:top;width:54pt;"> YES </td> 
 <td style="vertical-align:top;width:54pt;"> ignore </td> 
 </tr> 
 <tr> 
 <td style="vertical-align:top;width:108pt;"> Cause </td> 
 <td style="vertical-align:top;width:54pt;"> M </td> 
 <td style="vertical-align:top;width:54pt;"> &nbsp; </td> 
 <td style="vertical-align:top;width:75.6pt;"> 9.3.1.2 </td> 
 <td style="vertical-align:top;width:86.4pt;"> &nbsp; </td> 
 <td style="vertical-align:top;width:54pt;"> YES </td> 
 <td style="vertical-align:top;width:54pt;"> ignore </td> 
 </tr> 
 <tr> 
 <td style="vertical-align:top;width:108pt;"> Criticality Diagnostics </td> 
 <td style="vertical-align:top;width:54pt;"> O </td> 
 <td style="vertical-align:top;width:54pt;"> &nbsp; </td> 
 <td style="vertical-align:top;width:75.6pt;"> 9.3.1.3 </td> 
 <td style="vertical-align:top;width:86.4pt;"> &nbsp; </td> 
 <td style="vertical-align:top;width:54pt;"> YES </td> 
 <td style="vertical-align:top;width:54pt;"> ignore </td> 
 </tr> 
 </tbody> 
</table>

**  Handover Type**

<table style="margin-left:5.4pt;"> 
 <tbody> 
 <tr> 
 <td style="vertical-align:top;width:122.4pt;"> IE/Group Name </td> 
 <td style="vertical-align:top;width:54pt;"> Presence </td> 
 <td style="vertical-align:top;width:54pt;"> Range </td> 
 <td style="vertical-align:top;width:111.6pt;"> IE type and reference </td> 
 <td style="vertical-align:top;width:144pt;"> Semantics description </td> 
 </tr> 
 <tr> 
 <td style="vertical-align:top;width:122.4pt;"> Handover Type </td> 
 <td style="vertical-align:top;width:54pt;"> M </td> 
 <td style="vertical-align:top;width:54pt;"> &nbsp; </td> 
 <td style="vertical-align:top;width:111.6pt;"> ENUMERATED (Intra5GS, 5GStoEPS, EPSto5GS, …) </td> 
 <td style="vertical-align:top;width:144pt;"> Intra5GS: NG-RAN node to NG-RAN node 5GStoEPS: NG-RAN node to eNB EPSto5GS: eNB to NG-RAN node </td> 
 </tr> 
 </tbody> 
</table>

# 5. Elements for NGAP Communication  #

###    5.1 NAS Transport Messages （NAS 传输消息） ###

**    5.1.1 UPLINK NAS TRANSPORT**

<table style="margin-left:5.4pt;"> 
 <tbody> 
 <tr> 
 <td style="vertical-align:top;width:108pt;"> IE/Group Name </td> 
 <td style="vertical-align:top;width:54pt;"> Presence </td> 
 <td style="vertical-align:top;width:75.6pt;"> IE type and reference </td> 
 <td style="vertical-align:top;width:153px;"> Criticality </td> 
 <td style="vertical-align:top;width:155px;"> Assigned Criticality </td> 
 </tr> 
 <tr> 
 <td style="vertical-align:top;width:108pt;"> Message Type </td> 
 <td style="vertical-align:top;width:54pt;"> M </td> 
 <td style="vertical-align:top;width:75.6pt;"> 9.3.1.1 </td> 
 <td style="vertical-align:top;width:153px;"> YES </td> 
 <td style="vertical-align:top;width:155px;"> ignore </td> 
 </tr> 
 <tr> 
 <td style="vertical-align:top;width:108pt;"> AMF UE NGAP ID </td> 
 <td style="vertical-align:top;width:54pt;"> M </td> 
 <td style="vertical-align:top;width:75.6pt;"> 9.3.3.1 </td> 
 <td style="vertical-align:top;width:153px;"> YES </td> 
 <td style="vertical-align:top;width:155px;"> reject </td> 
 </tr> 
 <tr> 
 <td style="vertical-align:top;width:108pt;"> RAN&nbsp;UE NGAP ID </td> 
 <td style="vertical-align:top;width:54pt;"> M </td> 
 <td style="vertical-align:top;width:75.6pt;"> 9.3.3.2 </td> 
 <td style="vertical-align:top;width:153px;"> YES </td> 
 <td style="vertical-align:top;width:155px;"> reject </td> 
 </tr> 
 <tr> 
 <td style="vertical-align:top;width:108pt;"> NAS-PDU </td> 
 <td style="vertical-align:top;width:54pt;"> M </td> 
 <td style="vertical-align:top;width:75.6pt;"> 9.3.3.4 </td> 
 <td style="vertical-align:top;width:153px;"> YES </td> 
 <td style="vertical-align:top;width:155px;"> reject </td> 
 </tr> 
 <tr> 
 <td style="vertical-align:top;width:108pt;"> User Location Information </td> 
 <td style="vertical-align:top;width:54pt;"> M </td> 
 <td style="vertical-align:top;width:75.6pt;"> 9.3.1.16 </td> 
 <td style="vertical-align:top;width:153px;"> YES </td> 
 <td style="vertical-align:top;width:155px;"> ignore </td> 
 </tr> 
 </tbody> 
</table>

###    5.2 Information Element Definitions 信息元素定义 ###

5.2.1 MessageType

<table style="margin-left:5.4pt;width:486pt;"> 
 <tbody> 
 <tr> 
 <td style="vertical-align:top;width:122.4pt;"> IE/Group Name </td> 
 <td style="vertical-align:top;width:54pt;"> Presence </td> 
 <td style="vertical-align:top;width:111.6pt;"> IE type and reference </td> 
 </tr> 
 <tr> 
 <td style="vertical-align:top;width:122.4pt;"> Procedure Code </td> 
 <td style="vertical-align:top;width:54pt;"> M </td> 
 <td style="vertical-align:top;width:111.6pt;"> INTEGER (0..255) </td> 
 </tr> 
 <tr> 
 <td style="vertical-align:top;width:122.4pt;"> Type of Message </td> 
 <td style="vertical-align:top;width:54pt;"> M </td> 
 <td style="vertical-align:top;width:111.6pt;"> CHOICE&nbsp;(Initiating&nbsp;Message, Successful&nbsp;Outcome, Unsuccessful&nbsp;Outcome, …) </td> 
 </tr> 
 </tbody> 
</table>

# 信息元素的定义 #

##   SMF 相关的 IE（用来向 AMF 传输） ##

###    1.1 PDU Session Resource Setup Request Transfer ###

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名词缩写：

**RNL：** Radio Network Layer，无线电网络层

**TNL：** Transport Network Layer，传输网络层

参考：

TS 38.413

TS 38.410

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