Service Based Interface

Service Based Interface

5G SBI Protocols

• HTTP/2 adopted as the application layer protocol for the service based interfaces
• TCP adopted as the transport layer protocol
• Use of QUIC, binary encoding (e.g. CBOR) and other aspects are left FFS for possible support in future releases
• JSON adopted as the serialization protocol
• REST-style service design whenever possible and custom (RPCbased) methods otherwise

Example 1

根據 3GPP 的定義，NF 之間的溝通都會依據 SBI (Service Based Interface) 進行實作，以 Nudm_UECM (UECM) service 為例，其他使用該服務的 NF 為 Consumer，提供服務的 UDM 在這裡則扮演 Producer。 如果其他 NF 想要註冊該服務，只需要調用 Nudm_UECM_Registration 即可。

Description: Register UE’s serving NF (if NF Type is AMF, SMSF, or NWDAF) or Session’s serving NF (if NF Type is SMF) on the UDM.

Example 2

SBI 讓網元之間可以使用一般的 http 請求溝通，並且 NF 在實作 Producer 的邏輯時，也可以採用 RestFul API 的設計。

Service Based Architecture

SBA Service Framework

SBA Example NF Services

• AMF (Access Management Function)
  • Communication – enables other NFs to communication with the UE / the access network
  • Mobility Event Exposure – other NFs can subscribe to notifications about the UE’s mobility events
• SMF (Session Management Function)
  • PDUSessions – Protocol Data Units exchange with the UE, including policy and charging.
• UDM (Unified Data Management)
  • Context – provides information about UEs serving NF & status (讓其他 NF 不需要存放 Context，實現無狀態的目的)
  • UEAuthentciation – provides authentication data & info

Reference

• 3gpp.org - webinar-ct-status-11-2017