用於對等式通訊及IPv4網際網路之具延展性網路名稱轉換器

Abstract

近年來網路閘道器如網路名稱轉換器需處理越來越多來自對等式應用軟體的流量。在以往主從架構下，這些設備總能正常運作因為伺服器是公開可路由的，然而這些設備在遇到對等式通訊時，卻會遇到問題，因為雙方可能都是使用私有位址而沒有任何一方可被路由。本文透過三種方向來檢視這樣的問題，其一利用使用者端軟體的複雜度，其二採用新的中介者及協定，其三改良網路名稱轉換器本身。使用者端的解決方案如UDP/TCP打洞機制仍會受到時間敏感度的問題，而閘道器端的解決方案都有互通問題及建置的負荷。與其期待IPv6的來臨及忽略任何改進NAT本身的可能性，本文提出一個具延展性網路名稱轉換器，此方法有很小或可忽略的時間及空間複雜度，並可大幅改進傳統網路名稱轉換器的連線能力及延展性：其一，降低對等式通訊的打洞機制會遇到的時間敏感性問題，其二，讓可使用的阜號超過65535，其三允許多台伺服器在同一個阜提供服務。

It is becoming increasingly common for network gateways, especially the network address translation (NAT), to handle traffic introduced by emerging peer-to-peer (P2P) applications. These NATs could work fine with client-server applications since servers are by default public addressable, but they could encounter problems with P2P communications in opposing NATs because both peers are using private addresses and neither side has global visibility. This article therefore examines such issue from three approaches, 1) leveraging the complexity of client application, 2) introducing additional intermediate gateways and protocols and 3) enhancing the NAT itself. Client-based solutions like UDP/TCP hole punching still suffers from timing sensitivity while gateway-based solutions tend to encounter overhead for interoperability and deployment. Instead of anticipating the wide deployment of IPv6 and passing over any possibility that improves the troublemaker NAT, this paper proposes a scalable NAT (SNAT), which introduces little or neglectable time and space complexity, that would significantly improves the connectivity and scalability of a conventional NAT by 1) lessening the timing sensitivity problem of P2P traversals in opposing NATs, 2) making the numbers of available ports to exceed 65535 and 3) allowing more servers to bind to a specific port.