第三層交換器路由表之硬體設計與實現

Abstract

由於網際網路的快速成長，使得網路節點對路由器處理速度 的要求日益提高；例如，為了要傳送十億位元乙太網路的封包， 路由器在每個輸入埠必須每秒可以處理大約 1.5 百萬筆封包才 行，這個要求比現行路由器的負荷要高出許多。路由器性能無法 提升的一項重要因素便是路由表的查表速度，網際網路通訊協定 要求路由器對每一個引入封包要進行最長字首相匹配的位址查表 以決定封包的下一個目的地。 為了解決這個問題，在我們的第三層交換器中，我們設計了 一個以硬體為基礎的路由表控制晶片。這個路由表控制晶片不僅 有查路由表的能力，而且負責維護這個路由表。我們的目標是要 設計一個完全以硬體實現的路由表，它每秒能夠完成多於10百萬 筆封包的查表工作，這比目前的路由表快得多而且更適用於十億 位元乙太網路。

Growth of the Internet puts great demands on network routers; for instance, to route minimum sized Gigabit Ethernet packets, an IP router must process about 1.5 million packets per second per port. It is well above current router capabilities. One constraint on router performance is the routing lookup process. IP routing requires that a router perform longest-prefix-matching address lookup for each incoming packet in order to determine the packet's next hop. In order to solve this problem, we design a hardware based routing table controller in our layer 3 switch. The routing table controller not only has the ability to look up IP addresses but also takes charge of maintaining the routing table. Our objective is to design a hardware-based routing table, which can achieve more 10 million lookups per second. It is much faster than the current routing table and is suitable for the Gigabit Ethernet.