- 學位論文
設計與實作即時通訊服務之標頭壓縮與封包串接機制
Design and Implementation of Header Compression and Packet Concatenation for Real-Time Communication Service
摘要
針對即時通訊服務，本論文提出了一個全新的標頭壓縮與封包串接機制(IP-Based Header Compression with Packet Concatenation, IHCPC)。IHCPC標頭壓縮與封包串接技巧提出之主要目的在於提升即時通訊服務在企業網路中的頻寬使用效率，特別是網路電話服務。本機制具有以下的特色：(1)以IP協定為基礎，經標頭壓縮與封包串接後仍是IP封包，可以使用在任何以IP為基礎的網路環境，(2)同時整合標頭壓縮與封包串接機制，而且封包串接的標的是標頭壓縮過後的IP封包，(3)不像傳統標頭壓縮技巧使用差值編碼，因此當封包遺失或封包延遲發生時，不必擔心RTP封包會被錯誤還原。 當IHCPC技巧應用在IPsec VPN時，除了可以提升頻寬使用效率，還可以降低IPsec VPN路由器的CPU負載，因為封包串接會使封包數量大幅減少，IPsec VPN路由器只需處理較少的封包，可以節省寶貴的CPU處理能力。 本論文另外提出推導效能公式，預測IHCPC機制的效能，由理論分析結果可知IHCPC機制會大幅提升即時通訊服務的頻寬使用效率。最後，IHCPC機制經實作為Linux模組，透過實驗來檢驗IHCPC機制是否正確運作，實驗結果也證明IPsec VPN路由器的負載真的可以大幅降低，而讓網路電話服務仍然可以維持不錯的通話品質。
並列摘要
For real-time communication service, we propose a novel mechanism of header compression and packet concatenation called IHCPC (IP-Based Header Compression with Packet Concatenation). The goal of the proposed mechanism is to provide better bandwidth utilization for real-time service, especially for Voice over IP. The proposed mechanism has the following three main features: (1) the mechanism is based on IP protocol, and it can be applied to any network environments using IP protocol, (2) it integrates packet concatenation with header compression, (3) for header compression, IHCPC doesn’t use delta coding, so that the header recovery isn’t influenced by packet loss or delay constraint violation. Besides, when IHCPC mechanism is applied to IPsec VPN, this mechanism also can reduce CPU load of IPsec VPN router. After such packet concatenation, the number of packets is reduced significantly, and the IPsec VPN router processes much less packets. Therefore processing CPU power can be saved for other purposes. We also derive performance formulas to predict the performance of IHCPC mechanism, and the derived results show that the bandwidth utilization is improved significantly. At the final stage, we already implement IHCPC mechanism on Linux platform, and setup an experimental environment to verify the proposed design. The experiment results show that the CPU load of IPsec VPN router is indeed reduced, and the QoS for Voice over IP can be better maintained.