目录
Protocol Configuration Option
PCO（Protocol Configuration Option，协议配置选项）用于为 UE 提供一些其连接到的网络相关的附加信息。这是一个可选的协议字段，只有当 UE 请求 PCO 选项时，PCO 才会出现在 Attach Accept 信令消息中。
PCO 包含两个子字段：
- Configuration Protocol options list（配置协议选项列表），是协议的标识符，与特定的配置协议（PPP）有关。
- Additional Parameter list（附加参数列表），包含了需要发送到 EPC 或 NGC 的特殊参数或请求，与特定的配置协议（PPP）无关。
Which message UE will put this filed:
- UE can put PCO optional IE’s in RRC Connection Setup Complete.
- It contains DedicatedInfoNAS fields which carries NAS Attach Request
- Under this ESM message Container filed and which carries PDP Connectivity Request
- Under this Protocol Configuration Options field present.
RRC Connection Setup Complete -> DeidicatedNASInfo -> ESM Message Container -> Protocol Configuration Options
Which message EPC will put this filed:
- EPC includes PCO fields in S1AP Initial Context Setup message
- It contains DedicatedInfoNAS fields carries Attach Accept message and information present for Activate Default Bearer Context request.
- Which carries ESM Message Container field.
- Inside this Protocol Configuration Options field present.
SIAP Initial Context Setup -> DedicatedInfoNAS -> ESM Message Container -> Protocol Configuration Options
Condition: EPC will includes only those filed in Attach Accept message that UE requested in Attach Request -> PCO fields. Refer Specification TS 24.008 V8.0 and clause 10.5.6.3 for more details.
UE to Network: Following fields UE may include in PCO fields:
- 0001H (P-CSCF Address Request);
- 0002H (IM CN Subsystem Signaling Flag);
- 0003H (DNS Server Address Request);
- 0004H (Not Supported);
- 0005H (UE Support of Network Requested Bearer Control indicator); and
- 0006H (Preferred Bearer Control Mode).
Network to UE direction: Following fields UE may include in PCO fields
- 0001H (P-CSCF Address);
- 0002H (IM CN Subsystem Signaling Flag);
- 0003H (DNS Server Address);
- 0004H (Policy Control rejection code) ; and
- 0005H (Selected Bearer Control Mode).
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