物聯網中邊緣輔助的流量工程和應用

本文為SIGCOMM 2018 Workshop (Mobile Edge Communications, MECOMM)論文。

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本文作者包含3位，Nikos Fotiou, Dimitrios Mendrinos, George C. Polyzos@Mobile Multimedia Laboratory, Athens University of Economics and Business

ABSTRACT (摘要）

Software-Defned Networking (SDN) promises novel traffic engineering capabilities transforming every network from a mere packet forwarding fabric into an intelligent distribution medium. We extend the functionality of the core SDN component, the SDN controller, to perform path computations over “annotated” topologies. Specifcally, we exploit the use of tags, which describe network node properties and capabilities, enabling a new type of network control applications and thus connecting user applications and traffic ?ows with network decisions and management. Tags can be set and modifed in a number of di?erent ways, supporting context awareness and cognition in the network in a lightweight and loosely integrated way. Intelligent applications running at edge nodes may request unicast, anycast, or multicast paths among nodes with specifc tags or tag properties, realizing efficiently traffic engineering goals and supporting network slicing, virtualization, finer resource control, and easier management. We illustrate this new capability in the IoT domain by demonstrating how CoAP group communication can be implemented in a seamless, lightweight, and effucient way, releasing the constrained endpoints from the requirement to support IP multicast.

軟件定義網絡（SDN）給新型流量工程功能（將每個網絡從單純的數據包轉發結構轉變為智能分發介質）帶來希望。我們擴展了核心SDN組件（SDN控制器）的功能，以通過“帶註釋的”拓撲執行路徑計算。具體而言，我們利用標簽來描述網絡節點的屬性和功能，實現新型網絡控制應用，從而將用戶應用和流量與網絡決策和管理相連接。標簽可以通過多種不同的方式進行設置和修改，以輕量級和松散集成的方式支持網絡中的上下文感知和認知。在邊緣節點上運行的智能應用程序可以在具有特定標簽或標簽屬性的節點之間請求單播，任播或多播路徑，實現有效的流量工程目標並支持網絡切片、虛擬化、更精細的資源控制和更容易的管理。我們通過演示如何以無縫、輕量和高效的方式實現CoAP組通信來說明IoT領域內的這種新功能，從支持IP多播的需求中釋放受限端點。

1 INTRODUCTION （引言）

Nowadays, it is evident that the Internet has evolved from a facility that interconnects static end-hosts, into a dynamic ecosystem which extends to our physical world. Smartphones, Things and home appliance with interconnection capabilities, portable computing devices, powerful personal workstations, all compose a powerful toolset that o?ers to end-users endless possibilities. Application providers create novel services that can be accessed through multiple devices, expand to multiple network locations, and generate vast amounts of traffic. Struggling to cope with this vivid environment, network operators seek to transform the traditionally static networks into an elastic, intelligent platform, that will not merely transfer packets from the “dump” edge to the “smart” core, but it will also provide in-network functions and services, making end-user experience even richer. A critical technology allowing the realization of this goal is SoftwareDefned Networking (SDN) [11].

如今，互聯網顯然已從一個互連靜態終端主機的設施發展成一個延伸到我們物理世界的動態生態系統。 具有互連功能的事物和家用電器，便攜式計算設備，功能強大的個人工作站，都構成了一個功能強大的工具集，可為最終用戶提供無限可能。 應用程序提供商創建可以通過多個設備訪問，擴展到多個網絡位置並生成大量流量的新穎服務。 為了應對這種生動的環境，網絡運營商試圖將傳統的靜態網絡轉變為一個彈性的智能平臺，不僅可以將數據包從“轉儲”邊緣轉移到“智能”核心，而且還可以提供 網內功能和服務，使最終用戶體驗更加豐富。 軟件定義網絡（SDN）[11]是實現這一目標的關鍵技術。

SDN allows the use of centrally managed switches, enabling network operators to leverage the full capabilities of their network. These switches are programmable in the sense that using a specialized protocol (such as OpenFlow), they can be confgured with rules to forward data “?ows” towards their destinations through specifc node and link paths, facilitating in this way load-balancing, service di?erentiation, in-network functions, and providing novel network services [5]. At the heart of an SDN-based network is an SDN controller, which is responsible for dynamically setting up switch ?ow tables based on confgurations–usually expressed using a scripting or programming language–that capture the requirements and the business processes of the network operator.

SDN允許使用集中化管理的交換機，使網絡運營商能夠充分利用其網絡的全部功能。 這些交換機在使用專用協議（例如OpenFlow）的意義上是可編程的，它們可以通過規則配置，通過特定的節點和鏈路路徑將數據“流”轉發到它們的目的地，從而以這種方式促進負載平衡、服務差異化 、網絡內功能，並提供新穎的網絡服務[5]。 基於SDN的網絡的核心是SDN控制器，它負責根據配置動態設置交換機流表（通常使用腳本或編程語言表示 ）捕獲網絡運營商的要求和業務流程。

In this paper, we propose an enhanced SDN-based architecture that extends traditional approaches in the following way: (i) network nodes are annotated with “tags” describing their properties and capabilities, (ii) SDN controllers act as “path computation elements” and are capable of calculating on-demand paths among or composed of nodes with specifc tags or tag properties, (iii) intelligent applications, running on edge nodes, are able to request paths from the SDN controller, as well as to set/delete their own application-specifc tags. These enhancements are supported by a Bloom flterbased forwarding technique that achieves seamless multicast communication. This technique requires minimum and fxed state in the switches, which can be installed during the bootstrap. Despite that the path requesting applications and the path computation process can be application aware and act based on the requirements of a specifc application, or even based on the context of a specifc user, our approach does not require from the SDN components to perform deep packet inspection (as for example in [3]), neither requires modifcations to already established standards (as for example in [6]). As a matter of fact, our proof of concept implementation is based on readily available software switches and the OpenFlow 1.2 standard. We argue that the extensions proposed in this paper, combined with the Bloom flter-based forwarding, although simple, create many opportunities for novel services. In particular, our approach facilitates group/anycast communication paradigms, supports service chaining and composition, improves network management, and facilitates new services and applications. In order to demonstrate the efficiency of our approach, we present how a group communication protocol designed for the Internet of Things (IoT), i.e., the Constrained Application Protocol (CoAP) extension for group communication, can be efciently implemented over an SDN network that supports tag-based path computation. Traditional CoAP group communication requires from CoAP endpoints to support the IP multicast protocol. Moreover, CoAP group related information is maintained by the endpoints, hence, the number of groups increases and managing them becomes hard. With our implementation, constrained endpoints can beneft from group communication using vanilla CoAP without the extensions, without modifcations, and without the need to support IP multicast. Moreover, the creation of a new group becomes easier and the management of existing groups becomes more efcient. Finally, using our approach, service providers can easily leverage existing IoT deployments and o?er new, group communication-based services.

在本文中，我們提出了一種增強的基於SDN的體系結構，它以下列方式擴展了傳統方法：（i）網絡節點註釋了描述其屬性和功能的“標簽”，（ii）SDN控制器充當“路徑計算元素”並且能夠計算具有特定標簽或標簽屬性的節點之間或由其組成的按需路徑，（iii）在邊緣節點上運行的智能應用程序能夠從SDN控制器請求路徑，以及設置/刪除它們的應用程序特定標簽。 Bloom基於flom的轉發技術支持這些增強，實現無縫多播通信。此技術需要交換機中的最小和固定狀態，可以在引導期間安裝。盡管請求應用程序和路徑計算過程的路徑可以是應用程序感知的並且基於特定應用程序的要求或甚至基於特定用戶的上下文來行動，但是我們的方法不需要來自SDN組件來執行深度分組檢查（例如在[3]中），既不需要對已經建立的標準進行修改（例如在[6]中）。事實上，我們的概念驗證實施基於現成的軟件開關和OpenFlow 1.2標準。我們認為本文提出的擴展與基於Bloom flter的轉發相結合，雖然簡單，但卻為新穎的服務創造了許多機會。特別是，我們的方法促進了組/任播通信範例，支持服務鏈和組合，改進了網絡管理，並促進了新的服務和應用。為了證明我們的方法的效率，我們介紹了如何通過SDN網絡有效地實現為物聯網（IoT）設計的群組通信協議，即用於群組通信的約束應用協議（CoAP）擴展。支持基於標簽的路徑計算。傳統CoAP組通信需要CoAP端點支持IP多播協議。此外，CoAP組相關信息由端點維護，因此，組的數量增加並且管理它們變得困難。通過我們的實現，受約束的端點可以使用沒有擴展的vanilla CoAP進行組通信，無需修改，也無需支持IP多播。此外，新組的創建變得更加容易，現有組的管理變得更加有效。最後，使用我們的方法，服務提供商可以輕松利用現有的物聯網部署和新的基於群組通信的服務。

Edge-assisted Tra?ic Engineering and applications in the IoT