第九章 快速、穩(wěn)定、安全和共享上網(wǎng)——業(yè)務通道
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第九章 快速、穩(wěn)定、安全和共享上網(wǎng)——業(yè)務通道
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正文——
第九章 快速、穩(wěn)定、安全和共享上網(wǎng)——業(yè)務通道
接上一章節(jié)的話題，第八章 5G上網(wǎng)的先決條件——信令通道
當某個終端用戶的第一個PDU Session已經(jīng)建立完成之后，就意味著該用戶就具有了上傳或下載網(wǎng)絡數(shù)據(jù)的資格和機會。下面的事情就自然而然地時去發(fā)起數(shù)據(jù)的傳送了。
但是，必須明確一點的是，PDU Session建立完成，手機獲得了一個IP地址，但并不表示從UE到UPF的所有接口或信道都是已經(jīng)開通，而事實上應該是通過PDU session的建立，AMF/SMF已經(jīng)為這個用戶設置好了數(shù)據(jù)傳輸?shù)南嚓P(guān)接口以及每一個相關(guān)協(xié)議棧的屬性參數(shù)。而具體的這些屬性參數(shù)的真正實施，要在該用戶有了數(shù)據(jù)要發(fā)送或接收時候進行。
這就相當于作為一個經(jīng)常收寄快件的老客戶，比如在淘寶上長期賣充電寶的商家，于某快遞公司簽定好了一個長期寄送快件的協(xié)議，對于自己發(fā)送充電寶的通用的要求做好了協(xié)商，比如包裝大小、保價額度、每天及時取貨、包裝上寫的內(nèi)容的固定格式等等。
等這些全部準備好之后，真正這個商家有客人買了充電寶之后，就按照與快遞公司的約定在某個時間、某個地點去取件并辦理自動登記手續(xù)。
9.1 快遞公司收到了一個包裹，先做優(yōu)先級評估 - QoS Flow
歡迎Mr. ChatGPT發(fā)言：
Quality of Service (QoS) flow attributes are conveyed in packets forwarded to the gNB (5G base station). In 5G networks, packets are typically carried over an IP-based transport, and QoS information is usually conveyed using the Differentiated Services Code Point (DSCP) field in the IP header. Here's a breakdown of the relevant packet structure and attributes:
1. Ethernet Frame Header:
? Destination MAC Address: Specifies the MAC address of the destination device (e.g., gNB).
? Source MAC Address: Specifies the MAC address of the sender.
? EtherType: Identifies the type of payload. In IP networks, it typically indicates the presence of an IP packet.
2. IP Header:
? Version: Indicates the IP version being used (IPv4 or IPv6).
? DSCP (Differentiated Services Code Point): This is a 6-bit field in the IP header that is used to mark packets with QoS information. It is sometimes referred to as the Differentiated Services (DS) field. The DSCP value is set to indicate the desired QoS treatment for the packet.
? Total Length: Specifies the total length of the IP packet, including the header and payload.
? Identification, Flags, Fragment Offset: Used for fragmentation and reassembly of IP packets (not directly related to QoS).
? Time To Live (TTL): Indicates how many hops the packet can traverse before being discarded.
? Protocol: Specifies the transport layer protocol (e.g., TCP, UDP) used in the packet.
? Source IP Address: The IP address of the sender.
? Destination IP Address: The IP address of the destination (gNB).
3. Transport Layer Header (e.g., TCP/UDP):
? Source Port: Specifies the source port number.
? Destination Port: Specifies the destination port number.
? Sequence Number, Acknowledgment Number, Flags, Window Size: These fields are specific to the transport layer protocol (TCP, UDP) and are used for flow control and error detection but do not directly carry QoS information.
4. Payload:
? The payload contains the actual data being transmitted, which could be application data, voice packets, video packets, etc. QoS-related information is typically not found in the payload itself but rather in the IP header's DSCP field.
5. DSCP Field:
? The DSCP field in the IP header is crucial for conveying QoS information. It consists of 6 bits that are used to mark packets with a specific QoS value. These markings are used by network devices (routers, switches) to determine how to prioritize and treat the packets.
?
參考網(wǎng)絡用戶數(shù)據(jù)的轉(zhuǎn)發(fā)過程（4G網(wǎng)絡）：
https://www.bilibili.com/video/BV1fZ4y1M7jR/?vd_source=2b72fcc3835291472da2743d71001857
9.1.1 評估本次包裹內(nèi)容是在快件協(xié)議定義的范圍內(nèi) - PDU Session約定
9.1.2 快件寄送約定范圍中可以有多種寄送模板 - TFT
TFT、QFI、SDF的關(guān)系
? TFT to QFI: TFT is responsible for packet classification and filtering based on various attributes. When a packet matches the criteria defined in a TFT, it is associated with a specific QFI. TFT acts as a bridge between the characteristics of incoming traffic and the identification of the corresponding QoS flow (QFI).
? QFI to SDF: QFIs are components used within SDFs to define and enforce QoS at a granular level. An SDF may include multiple QFIs, each with its own unique QoS rules, as part of the end-to-end QoS management for a specific service or application.
TFT and QFI for SDF: When defining an SDF for a particular service, the operator specifies the QFIs associated with that service and the TFTs that will be used to classify incoming traffic into those QFIs. The combination of TFTs and QFIs within an SDF allows for comprehensive QoS management for that service, ensuring that the right packets are mapped to the appropriate QoS flows.
9.1.3 快件的寄送模板僅僅適用于物流總站向分站傳遞包裹
9.2 本地遞送需要把通用的快件優(yōu)先級轉(zhuǎn)化成具體的運送方式 - QFI和DRB的轉(zhuǎn)換
9.2.1 本地第一道工序就是根據(jù)協(xié)議在包裹上打遞送優(yōu)先級的標簽 - SDAP
? 在SDAP包頭
? 根據(jù)PDU Session定義好的規(guī)則
9.2.2 具體實現(xiàn)由底層來完成
9.3 統(tǒng)一化的包裹（層三IP包）交給了5G的層二
9.4 安全性和完整性保護 - PDCP
9.5 選擇不同級別的傳遞方式 - RLC
根據(jù)MAC層的AMC的結(jié)果確定分段和級聯(lián).
9.6 現(xiàn)場分派快件和調(diào)度 - MAC
9.7 萬事俱備具體的快遞遞送 - 物理層和物理信道
9.8 整體來說京東快遞要比其他快遞相對快捷和可靠 - VoNR(VoLTE) vs 微信通話
