適用於第三代UMTS核心網路之全面應用多協定標籤交換的方法

Abstract

在本論文中，我們將提出第三代行動電話核心網路全面應用多協定標籤交換 (MPLS) 的可行方法。GTP-tunnel 是在第三代行動電話核心網路中的傳輸機制，且已經由第三代聯盟制定為標準規格。在每一個封包傳送過程中，需要額外的GTP，UDP及IP的標頭 (總計40 bytes)。針對短的封包，例如語音承載，其傳輸的負荷非常高。Enhanced-GTP被提出來，它去除了GTP標頭需求。但是它的工作模式受到侷限，僅適用於不透明的模式，即GGSN需要支援網路住址轉譯的功能。此外，它所能提供的效能改善仍然有限，因為它仍需要一個額外的IP標頭。為了克服這些缺點，我們提出整合多協定標籤交換的技術到第三代行動電話核心網路。我們使用兩階層的多協定標籤交換標籤(8 bytes)當作傳輸的機制以取代GTP-tunnel。就我們所知, 這是一個全新的方法，因為從來都沒有以多協定標籤交換為基礎的方法曾經被應用於第三代行動電話核心網路。我們的方法是可行的，因為有愈來愈多的路由器支援多協定標籤交換的協定。透過將標頭負擔由40位元組降至8位元組，我們所提出的方法，可以針對語音封包將傳輸效能由56.5% ~ 63%提高至86.6% ~ 89.5%。除此之外，我們的方法可提供較佳的封包傳送效率，較佳的負載平衡，較佳的服務彈性，以及較佳的服務品質支援。

In this thesis, we present an all-MPLS approach for UMTS 3G core networks. GTP-tunnel has been defined by 3GPP as the transport mechanism for UMTS. For each packet transmission, extra GTP, UDP, and IP headers (40-byte) are required. For short packets, such as VoIP payloads, transmission overhead is very high. Enhanced-GTP was proposed to eliminate the need for a GTP header. Since its operation mode is limited to non-transport mode only, NAT is required in GGSN. Furthermore, its performance improvement is limited, because an extra IP header (20-byte) is still needed. In response to these drawbacks, we propose to integrate MPLS technology to UMTS 3G core networks. We use MPLS-tunnel as the transport mechanism by using two-level MPLS labels (8-byte) to replace the GTP-tunnel. To the best of our knowledge, this is a novel approach, since no MPLS-based approach was ever proposed for UMTS 3G core networks. Our approach is feasible, since more and more routers are MPLS-capable. By reducing header overhead from 40-byte to 8-byte, our new approach improves transmission efficiency from 56.5% ~ 63% to 86.6% ~ 89.5% for VoIP payloads and also enhance packet forwarding efficiency. In addition, our all-MPLS approach offers better load balancing, better service resilience, and better QoS support, compared to existing approaches.