建構高效率軟體定義網路環境之框架

Abstract

軟體定義網路 (SDN) 是一種集中式的網路,跟傳統的離散式網路不 同。它的特色是容易改變網路行為,具有高度的可塑性,也因此被許 多大型企業所採用作為工業用途。然而,雖謂為集中式的軟體定義網 路,它仍作用在為傳統離散式網路架構所設計的各種離散式網路協定 上,也因此我們發現有許多待改進的空間。 這篇論文提出了一個改進軟體定義網路效能的框架,包括在區域網 路 (LAN) 及廣域網路 (WAN) 的改善。在此框架下,藉由各種代理模組 來處理不同的廣播協定,區域網路中不再需要、也不再存有廣播封包。 此一改變能節省網路流量並增進網路協定的效能、縮短回應時間。同 時也排除了過去因為廣播封包造成的廣播風暴等問題。在廣域網路中, 此框架可容納多個網路匣道器 (gateway) 並充分使用它們,藉由將多個 匣道器在邏輯上抽象化成一個虛擬匣道器,可提升對廣域網路的頻寬, 並提供負載平衡及匣道備源等功能。此虛擬匣道器不限制連接匣道器 的數目,不像目前市售的匣道負載平衡器只支援 2-4 個匣道器。 我們在一個有 49 台電腦連線的真實辦公室裡用區域網路來做實驗, 證明此框架的有效性,並在 Mininet 上用實驗證明此框架在廣域網路上 確實可利用連接多個匣道器來達到 (可調整權重的) 匣道負載平衡、頻 寬提升及匣道備源等功能。

SDN (Software-Defined Network), unlike the distributed traditional net- work, is a centralized network. It features its highly configurable characteris- tic, and has been adopted by large corporations for industrial purposes. How- ever, since SDN operates on existing network protocols, which are designed for distributed networking systems, there is room for improvement to better adapt the SDN to existing network protocols. This thesis proposes a framework to improve the efficiency of SDN, both in LAN and WAN. In this framework, by handling broadcast packets in dif- ferent proxies, broadcast packets in LAN are no longer necessary and are thus eliminated. This saves the bandwidth wasted by broadcast packets and shortens the response time. This also solves the problem caused by broadcast packets, such as the broadcast storm. In WAN, the framework allows multiple gateways to be connected, and it aggregates them into a logically centralized virtual gateway. This virtual gateway is then able to provide bandwidth en- hancement, load balance and redundancy. The virtual gateway has no limit on the number of connected gateways (WAN ports), while existing commercial WAN load balancers are limited to only 2-4 WAN ports. Experiments conducted in a regular office with 49 hosts proved the effec- tiveness of our framework in LAN, and experiments on Mininet showed that our implementation of the virtual gateway provides (weighted) WAN load bal- ance, bandwidth enhancement and redundancy using multiple physical gate- ways.