| 摘要: | 進入2020 年，多媒體服務尤其是video streaming 已經成為了互聯網流量重要的組成部
分，以及不斷增長的視頻服務提供者，如Netflix、Amazon、YouTube 等等，隨著多媒體內
容和使用者爆發式增長，網路資源比如頻寬會越發緊張。用戶的使用習慣中，會出現大量
用戶在某一時間中觀看同一個視頻的情況，如體育賽事直播。在傳統的單播（unicast）網路
視頻分發服務中，就會出現鏈路上有過多的重複的內容，令原本緊張的頻寬資源雪上加霜。
群播（multicast）是一種一個發送者和多個接收者之間進行通訊的方法，能夠很好地解決這
種情況，但傳統IP multicast 由於其分散式的設計，很難全盤考慮網路頻寬資源來建造群播
分發樹。另外面對網路頻寬瓶頸，VSP 還通過HTTP Adaptive Streaming，根據伺服器端到
用戶端的鏈路頻寬狀況，動態調整使用者接收的video 的碼率（bit rate），來避免暫停事件
（stalling event），但這是基於單播傳輸下使用的，其配合使用的H.264 AVC 視頻編碼格式
直接在群播使用的話，也同樣會造成頻寬資源浪費。
面對現有的IP multicast 很難根據網路拓撲全域頻寬狀況來建造群播分發樹和在群播中
怎樣使用adaptive streaming 的問題。可以利用SDN 網路的集中式控制和對網路有全域視野
（global view）以及H.264 SVC 視頻編碼格式來進行基於SDN 的群播視頻內容分發。本論
文提出一種新的entry 配置方法叫VLAN based multicast，首先使用基於Prim 演算法建造群
播分發樹，提高總體鏈路頻寬使用率來提高使用者接收視頻的bit rate，其次為每段（發送
者節點到分支點，分支點到下一級分支點，分支點到各接收者節點的路徑稱為段）配置不
同VLAN， 能夠以較低成本調整使用者接收的video 的碼率（bit rate）， 實現adaptive
streaming，同時能節省中間節點的TCAM 空間。;In 2020,multimedia services,especially video streaming,have become an important part of
Internet traffic, as well as increasing video service providers, such as Netflix, Amazon, YouTube,
etc, with the explosive growth of multimedia content and users, network resources such as
bandwidth will become increasingly scarce. In users′ usage habits, there will be a large number of
users watching the same video at a certain time, such as sports live events. In the traditional
unicast network video distribution service, there will be too many duplicate content on the link,
which makes the originally strained bandwidth resources worse. Multicast is a method of
communication between one sender and multiple receivers, which can solve this problem well.
However, due to the decentralized design of traditional IP multicast, it is difficult to construct a
multicast distribution tree with full consideration of network bandwidth resources. In addition, in
the face of network bandwidth bottleneck, VSP also uses HTTP adaptive streaming to
dynamically adjust the bit rate of video received by users according to the link bandwidth
condition from server to client, so as to avoid stalling events. However, this is based on the use of
unicast transmission, which is used in combination with H.264 AVC. If H.264 AVC video coding
format is directly used in multicast, it will also cause waste of bandwidth resources.
In the face of the existing IP multicast difficult to construct the multicast distribution tree
according to the whole domain bandwidth of the network topology and how to use adaptive
streaming in the multicast. SDN based multicast video content distribution can be achieved by
using the centralized control of SDN network, global view of network and H.264 SVC video
coding format. In this paper, a new entry configuration method called VLAN based multicast is
proposed. Firstly, a multicast distribution tree is constructed based on prim algorithm to improve
the overall link bandwidth utilization rate to improve the bit rate of video received by users,
Secondly, configure different VLANs for each segment (the path from sender Node to Branch
Node, Branch Node to next level Branch Node, Branch Node to each receiver Node is called
segment), the bit rate of the video received by the user can be adjusted at a lower cost, realize
adaptive streaming, and save TCAM space of intermediate nodes. |
