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流量工程和路徑規(guī)劃
通過(guò)流量工程和路徑規(guī)劃，確定性網(wǎng)絡(luò)能夠避免網(wǎng)絡(luò)擁塞，確保數(shù)據(jù)在網(wǎng)絡(luò)中的傳輸路徑是優(yōu)的。流量工程技術(shù)通過(guò)智能的流量控制和路由選擇，確保網(wǎng)絡(luò)資源的優(yōu)分配，從而提高網(wǎng)絡(luò)性能。路徑規(guī)劃則負(fù)責(zé)尋找短、可靠的數(shù)據(jù)傳輸路徑。
短路徑依然會(huì)引起擁塞
如上圖，起初基于短路徑優(yōu)先（Shortest Path First, SPF）協(xié)議，流量選擇短的路徑（A-C-E）進(jìn)行數(shù)據(jù)傳輸。然而，當(dāng)多個(gè)流量流都選擇相同的路徑時(shí)，可能會(huì)出現(xiàn)擁塞，當(dāng)這條短路徑擁塞時(shí)，較長(zhǎng)路徑 A-B-D-E 可能是更優(yōu)路線。這就是為什么我們有時(shí)需要偏離SPF原則，而采用更為復(fù)雜的流量工程策略。通過(guò)流量整形、流量監(jiān)管、路由控制等手段，我們可以優(yōu)化網(wǎng)絡(luò)流量的路徑選擇，避免或減少擁塞，提高網(wǎng)絡(luò)的可靠性和性能。簡(jiǎn)單來(lái)說(shuō)，流量工程的目標(biāo)是確保網(wǎng)絡(luò)流量能夠根據(jù)其特性（如優(yōu)先級(jí)、QoS需求等）被合理地分配到不同的路徑上，從而避免網(wǎng)絡(luò)擁塞、提高網(wǎng)絡(luò)資源利用率。
硬實(shí)時(shí)通信機(jī)制
硬實(shí)時(shí)通信機(jī)制是實(shí)現(xiàn)確定性網(wǎng)絡(luò)中關(guān)鍵數(shù)據(jù)傳輸?shù)闹匾夹g(shù)，對(duì)于一些需要控制時(shí)延的應(yīng)用，確保數(shù)據(jù)的傳輸在預(yù)定的時(shí)間內(nèi)完成。這需要在網(wǎng)絡(luò)中實(shí)施實(shí)時(shí)調(diào)度機(jī)制，以確保實(shí)時(shí)數(shù)據(jù)包的及時(shí)傳輸。
時(shí)間感知整形器（IEEE 802.1Qbv）是一種用于實(shí)現(xiàn)硬實(shí)時(shí)通信機(jī)制的技術(shù)，它的主要功能是在以太網(wǎng)幀上標(biāo)識(shí)優(yōu)先級(jí)，并將其指派給基于優(yōu)先級(jí)的VLAN Tag。它通過(guò)定義時(shí)間表來(lái)控制隊(duì)列流量，每個(gè)隊(duì)列在時(shí)間表中都有一個(gè)時(shí)間段，該時(shí)間段定義了隊(duì)列中數(shù)據(jù)幀的發(fā)送窗口。當(dāng)數(shù)據(jù)幀到達(dá)隊(duì)列時(shí)，時(shí)間感知整形器會(huì)根據(jù)其優(yōu)先級(jí)和時(shí)間表進(jìn)行調(diào)度，以確保關(guān)鍵數(shù)據(jù)幀在預(yù)定的時(shí)間內(nèi)發(fā)送。
Traffic engineering and path planning
Through traffic engineering and path planning, deterministic networks can avoid network congestion and ensure that the transmission path of data in the network is optimal. Traffic engineering technology ensures optimal allocation of network resources through intelligent traffic control and routing selection, thereby improving network performance. Path planning is responsible for finding the shortest and most reliable data transmission path.
The shortest path still causes congestion
As shown in the above figure, initially based on the Shortest Path First (SPF) protocol, the traffic selects the shortest path (A-C-E) for data transmission. However, when multiple traffic flows choose the same path, congestion may occur, and when the shortest path is congested, the longer path A-B-D-E may be the better route. That's why sometimes we need to deviate from the SPF principle and adopt more complex traffic engineering strategies. Through methods such as traffic shaping, traffic supervision, and routing control, we can optimize the path selection of network traffic, avoid or reduce congestion, and improve the reliability and performance of the network. Simply put, the goal of traffic engineering is to ensure that network traffic can be reasonably allocated to different paths based on its characteristics (such as priority, QoS requirements, etc.), thereby avoiding network congestion and improving network resource utilization.
Hard real-time communication mechanism
Hard real-time communication mechanism is an important technology for achieving key data transmission in deterministic networks. For some applications that require precise control of latency, it ensures that data transmission is completed within the predetermined time. This requires implementing real-time scheduling mechanisms in the network to ensure timely transmission of real-time data packets.
Time aware shaper (IEEE 802.1Qbv) is a technology used to implement hard real-time communication mechanisms. Its main function is to identify priorities on Ethernet frames and assign them to priority based VLAN Tags. It controls queue traffic by defining a schedule, where each queue has a time period that defines the sending window for data frames in the queue. When a data frame reaches the queue, the time aware shaper schedules it based on its priority and schedule to ensure that key data frames are sent within the predetermined time.
