近年來，隨著網路直播與視訊串流需求的增加，群播 (IP multicast) 技術變得越來越熱門。群播可以實現發送端傳送一個群播訊息；訊息可以在路徑分岔處的交換機或路由器被複製；最後所有的接收端都收到訊息。然而，在傳統網絡中，群播需要特殊的高性能硬件來支持 IGMP、PIM、MBGP 和 MSDP ... 等協議。由於群播協議會產生大量開銷並且有時會降低網絡效能，因此即使支持群播，傳統網絡中也經常會關閉它。然而，這些群播的缺點可以在軟件定義網絡（software defined networking, SDN）中克服。在 SDN 中，OpenFlow group 實現了群播和多路徑路由。有了多路徑路由，每個目標的吞吐量可以大於單個路徑的帶寬。
在本篇論文中，我們提出了一種基於單播的多路徑群播路由演算法，我們稱之為Maximum Concurrent Multicast Flow algorithm (MCMF)，以確保可以達到接收端的最小速率要求。 MCMF 的主要概念是藉由遞迴地將圖劃分為子圖，從而將多播多路徑路由問題簡化為多商品流問題，使得子圖可以本質上由多商品流問題解決。我們的實驗結果顯示我們的方法在吞吐量和延遲方面都比 SDN 中的傳統群播路由演算法具有更好的性能。

In recent years, with the increase in demand for live streaming and video streaming, IP multicasting becomes a popular issue. IP multicasting allows a source to send only one copy of a multicast message; copies of the message is made only at the switches/routers where paths diverge; and eventually all destinations receive the message. However, in traditional networking, IP multicasting requires specific high performance hardware that supports IP multicast protocols such as IGMP, PIM, BGMP, and MSDP. Since the IP multicast protocols incur large overhead and sometimes degrade network performance, IP multicasting is often turned off in traditional networking even when it is supported. However, these disadvantages of IP multicasting can be overcome in software defined networks (SDNs). In SDNs, OpenFlow groups facilitate both IP multicasting and multipath routing. With multipath routing, the per-destination throughput can be greater than the bandwidth of a the single path.
In this thesis, we proposed a multicast multipath routing algorithm based on unicast called Maximum Concurrent Multicast Flow algorithm (MCMF), which guarantees to achieve the minimum rate requirements of the destinations. The main idea of MCMF is to reduce the multicast multipath routing problem into the multi-commodity flow problem by recursively partitioning the graph into sub-graphs such that the sub-graphs can be essentially solved by the multi-commodity flow problem. Our experiment results show that our method has better performance than traditional multicast routing algorithms in SDN in terms of both throughput and latency.

Abstract-----------------------------------------------i
中文摘要------------------------------------------------iii
Contents-----------------------------------------------iv
List of Figures----------------------------------------vi
1 Introduction-----------------------------------------1
1.1 Software Defined Networking------------------------1
1.2 OpenFlow-------------------------------------------2
2 Related Work-----------------------------------------5
2.1 Software Defined Networking------------------------5
2.2 Multicast Routing in Traditional Networks----------6
2.3 Multicast and Multipath Routing in SDN-------------7
3 System Model-----------------------------------------8
3.1 System Model---------------------------------------8
4 Proposed Algorithm-----------------------------------11
4.1 Maximum Concurrent Flow Problem (MCFP)-------------11
4.2 Bounded Maximum Concurrent Flow Problem (bMCFP)----12
4.3 Maximum Concurrent Multicast Flow algorithm (MCMF)-13
4.4 Time Complexity------------------------------------27
5 Implementation---------------------------------------29
5.1 Modify Open vSwitch (OVS)--------------------------29
5.1.1 Introduce to Open vSwitch------------------------30
5.1.2 Modified Open vSwitch----------------------------33
5.2 Flow installation----------------------------------34
5.2.1 Flow Installation Data Structure-----------------35
5.2.2 Flow Installation Module-------------------------36
6 Experiment Evaluation--------------------------------37
6.1 Environment----------------------------------------37
6.1.1 Hardware-----------------------------------------38
6.1.2 Docker Information-------------------------------39
6.1.3 Topology-----------------------------------------39
6.2 Compared Algorithm---------------------------------40
6.3 Performance Evaluation-----------------------------41
7 Conclusion-------------------------------------------44
Reference----------------------------------------------45

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