一個同儕式現場媒體串流初始遲滯最小化的方法

Abstract

目前許多普及的網際網路服務使用傳統的用戶伺服器(client-server)模式，其中包含，電子郵件(E-mail)、檔案傳輸協定(File Transfer Protocol)、隨選視訊(Video on Demand)、網路電視(Internet Protocol Television)及全球資訊網(World Wild Web)。然而，當用戶量劇增時，用戶伺服器模式將面臨可容納度及高成本問題。在所有網際網路服務中，網路電視需要佔用最多的資源，例如，儲存空間、頻寬，而且可能容易遇到大量使用者同時使用的瓶頸。為了降低網路電視系統資源的需求，越來越多網路電視服務已利用同儕式(Peer-to-Peer)架構。不過同儕式網路電視系統在切換頻道或節目時不夠靈活，使用者必需花一段時間等待節目的出現，比起傳統電視，同儕式網路電視的人機介面相對地緩慢。而初始遲滯(Start-up delay)是影嚮使用者收看同儕式網路電視意願的關鍵因素。一般而言，除了免費節目，使用者會抱怨頻道切換時間或起始放映遲滯太長。事實也確是如此，目前同儕式網路電視系統的初始遲滯從數十秒到數分鐘不等，因此初始遲滯有很大的改善空間。 在這篇論文中，我們提出一個嶄新的方法用於降低同儕式網路電視初始遲滯。我們讓系統中每個同儕(peer)記錄伙伴(partner)的傳輸率，週期性地推荐傳輸率符合某些條件的伙伴給追縱者伺服器(tracker server)，並視這些被推荐的伙伴為超級同儕(super-peer)。追縱者伺服器將超級同儕及鄰居同儕(neighbor peer)分配給新進同儕。新進同儕能從超級或鄰居同儕快速地接收影像內容而降低初始遲滯。 我們發展一套模擬軟體並和網路模擬器相互合作用以評估我們所提出的方法。數值結果顯示我們所提出的方法能有效地降低初始遲滯。

Many popular services currently deployed on Internet are based on the traditional client-server model, these include E-mail, FTP, Video on Demand (VoD), Internet Protocol Television (IPTV) and World Wild Web (WWW). However, client-server model faces the scalability and high cost problems when the number of client grows up. Among these services IPTV needs the largest amount of resources such as storage and bandwidth, and it may easily encounter the bottleneck with only small number of users. To reduce IPTV system resource requirement, more and more IPTV services are deployed based on Peer-to-Peer (P2P) architecture. Unfortunately, P2P IPTV system always starts slowly whenever you switch to a new channel or program, and it seems awkward comparing with traditional TV if users have to spend quite a while waiting for the program to show up in P2P IPTV. Start-up delay is a key factor which affects user’s willing regarding whether to subscribe P2P IPTV. In general, unless the program is free, users may complain if the content switching time or the initial video playback delay is too long. Unfortunately, start-up delay in current P2P IPTV systems range from tens of seconds to few minutes, it still has a lot of room to improve. In this thesis, we propose a novel scheme to reduce P2P IPTV start-up delay. We make every peer in the system to record its partners’ sending rate and periodically recommend thosae partners whose sending rate satisfies some criteria to tracker server as “super-peers”. Tracker server dispatches both super and neighbor peers to the newly joined peer, which then can rapidly receive video content from either super or neighbor peers and reduce start-up delay. We develop a simulation program to cooperate with network simulator to evaluate our proposed scheme. The numerical result shows that our proposed scheme is able to reduce the start-up delay significantly.