UPF(User Plane Function,用户面功能): ts 29.244 23.501[5.8]
SMF 执行选择 UPF,选择的具体细节在 TS 23.501 的 6.3.3 章节
UPF 流量检测能力可以被 SMF 用来控制,如下功能列表:
核心网隧道信息是 PDU session 忠的 N3 / N9 隧道,包括 TEID 和 IP 地址
SMF 负责指示 UPF 怎么检测用户数据流量,这个定义 PDR(Packet Detection Rule),SMF 控制 UPF 的流量检测,其提供每个 PDR 的检测信息。
IPv4 IPv6 IPv4v6 类型的 PDU Session,检测信息包括:
- CN tunnel info.
- Network instance.
- QFI.
- IP Packet Filter Set as defined in clause 5.7.6.2.
- Application Identifier: The Application ID is an index to a set of application detection rules configured in UPF.
以太网类型的 PDU Session,检测信息包括:
- CN tunnel info.
- Network instance.
- QFI.
- Ethernet Packet Filter Set as defined in clause 5.7.6.3.
- Apply N3 /N9 tunnel related handling, i.e. encapsulation.
- Forward the traffic to/from the SMF, e.g. as described in Table 5.8.2.5.2-1.
- Forward the SM PDU DN Request Container from SMF to DN-AAA server
- Forward the traffic according to locally configured policy for traffic steering.
- Forward the traffic according to N4 rules of a 5G VN group for 5G VN group communication.
|
Scenario description |
Data forwarding direction |
1 |
Forwarding of user-plane packets between the UE and the SMF e.g. DHCP signalling. |
UPF to SMF SMF to UPF |
2 |
Forwarding of packets between the SMF and the external DN e.g. with DN-AAA server |
UPF to SMF SMF to UPF |
3 |
Forwarding of packets subject to buffering in the SMF. |
UPF to SMF SMF to UPF |
4 |
Forwarding of End Marker Packets constructed by the SMF to a downstream node. |
SMF to UPF |
5 |
Forwarding of user data using Control Plane CIoT 5GS Optimisation |
UPF to SMF SMF to UPF |
Table 5.8.2.5.1-1: Scenarios for data forwarding between the SMF and UPF
S-NSSAI Single Network Slice Selection Assistance Information 的简称,标识了一个网络切片,其组成包括:
Slice/Service type |
SST value |
Characteristics |
eMBB
|
1 |
Slice suitable for the handling of 5G enhanced Mobile Broadband. |
URLLC |
2 |
Slice suitable for the handling of ultra- reliable low latency communications. |
MIoT |
3 |
Slice suitable for the handling of massive IoT. |
V2X |
4 |
Slice suitable for the handling of V2X services. |
Table 5.15.2.2-1 - Standardised SST values
S-NSSAI可以是标准值(SST取值为标准值,SD不存在),也可以是非标准值(也就是SST和SD同时存在、或者仅有SST但其取值为非标准值)。
Anchor point for Intra-/Inter-RAT Mobility
External PDU Session point of interconnect to Data Network.
Packet routing & forwarding (e.g. support of Uplink classifier to route traffic flows to an instance of a data network, support of Branching point to support multi-homed PDU Session).
Packet inspection (e.g. Application detection based on service data flow template and the optional PFDs received from the SMF in addition).
User Plane part of policy rule enforcement, e.g. Gating, Redirection, Traffic steering).
Lawful intercept
Traffic usage reporting.
QoS handling for user plane, UL/DL rate enforcement, Reflective QoS marking in DL.
Uplink Traffic verification
Transport level packet marking in the uplink and downlink.
Downlink packet buffering and downlink data notification triggering.
Sending and forwarding of one or more "end marker" to the source NG-RAN node.
ARP proxying and / or IPv6 Neighbour Solicitation Proxying functionality for the Ethernet PDUs. The UPF responds to the ARP and / or the IPv6 Neighbour Solicitation Request by providing the MAC address corresponding to the IP address sent in the request.
看考: http://www.freedomtutorials.com/5GSystem/use_plane_function.php
Figure 4.1-1: Control Plane stack over Sxa, Sxb, Sxc and combined Sxa/Sxb and N4
Figure 4.1-2: User Plane stack over Sxa, Sxb, combined Sxa/Sxb and N4
Figure 5.2.1-1: Packet processing flow in the UP function
CP 应该在一个 PFCP 会话中规定每个 PDR 仅提供一个 FAR,FAR 为 UP 提供如何处理与 PDR 匹配的指令。
通过在FAR中的Apply Action IE 中设置相应的 flag,CP 可以控制 UP 的功能:
通过设置 DUPL flag,来提供有关如何转发重复数据包的说明,从而复制数据包
BAR 提供指令以控制 PFCP 会话集的所有 FAR 的 UP 功能的缓冲行为。CP 功能可以修改 BAR 中提供的以下缓冲指令
注意:目前版本的规范中,每个 PFCP 会话最多可以创建一个 BAR
CP功能可以在BAR中提供以下缓冲参数:
CP 应在 PFCP 会话建立请求或 PFCP 会话修改请求中为 PFCP 会话提供 QER,来请求 UP 应用用户平面业务的 QoS
表5.3.1-1:CP和UP功能之间的数据转发方案
|
Scenario description |
Data forwarding direction |
For EPC applicable to |
For 5GC applicable to |
1 |
Forwarding of user-plane packets between the UE and the CP function. |
UP to CP function |
PGW |
UPF to SMF |
2 |
Forwarding of packets between the CP function and the external PDN (over SGi) / DN (over N6). |
UP to CP function |
PGW |
UPF to SMF |
3 |
Forwarding of packets subject to buffering in the CP function. |
UP to CP function |
SGW |
UPF to SMF |
4 |
Forwarding of End Marker Packets constructed by the CP function to a downstream node. |
CP to UP function |
SGW, PGW |
SMF to UPF |
5 |
Forwarding of user data using Control Plane CIoT 5GS Optimisation |
UP to CP function |
- |
UPF to SMF |
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Bits |
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Octets |
8 |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
|
|
1 to m |
PFCP message header |
|
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|
m+1 to n |
Zero or more Information Element(s) |
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|
|
|
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Figure 7.2.1-1: PFCP Message Format
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Bits |
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|
Octets |
8 |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
|
|
1 to m |
PFCP message 1 header |
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|
m+1 to n |
Zero or more Information Element(s) |
|
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|
n+1 to p |
PFCP message 2 header |
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p+1 to q |
Zero or more Information Element(s) |
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… |
… |
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… |
… |
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r to s |
PFCP message N header |
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s+1 to u |
Zero or more Information Element(s) |
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Figure 7.2.1A-1: PFCP messages bundled in one UDP/IP packet
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Bits |
|||||||
Octets |
|
8 |
7 |
6 |
5 |
4 |
3 |
2 |
1 |
1 |
|
Version |
Spare |
Spare |
FO |
MP |
S |
||
2 |
|
Message Type |
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3 |
|
Message Length (1st Octet) |
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4 |
|
Message Length (2nd Octet) |
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m to k(m+7) |
|
If S flag is set to "1", then SEID shall be placed into octets 5-12. Otherwise, SEID field is not present at all. |
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n to (n+2) |
|
Sequence Number |
|||||||
(n+3) |
|
Spare |
Figure 7.2.2.1-1: General format of PFCP Header
UDBC: UL/DL Buffering Control UL / DL 缓冲控制
URSP: UE Route Selection Policy UE 路由选择策略 TS 23.503 [45] clause 6.6.2
OAM:
DNAI:
TEID:Tunnel endpoint ID,隧道端点标识符。
参考:
http://www.freedomtutorials.com/5GSystem/use_plane_function.php