| The flourish development of Internet on which data flow doubled per 12 months lead to the enthusiastic research on internet technology, especially the design of routing component. A solution of IXP2350 IPv4 routing system is designed on the basis of deeply researching in network processor's architecture and programming style of micro engine.The implement and optimization of routing lookup sub-system, which include the coding running on ME and that running on XScale core mainly discussed.The core component running on XScale core focuses on the handling of exception packets. It validates the head of packets complied to RFC1812 and RFC2644, the invalid head packets will be discarded and generate an ICMP packet It also reserved the interface to the option rules that the client may need to add. Additionally, the code supports fragment function when the IP packet size is greater than MTU. The module is also responsible for the loading, initialization and configuration of Micro code modules.The routing lookup module is responsible for the routing information searching. The very popular Longest Prefix Match algorithm is adopted here. If implemented this algorithm without any modification, some defect will appeared. First, using two hardware threads to complete ONLY one task is a great waste, as the micro engine hardware thread is a very limited resource. Second, some synchronous method is needed between the two hardware threads in order to get the final result. This also reduces the efficiency, which will be the bottleneck of the system.An improvement is done to the algorithm after an analysis of the asynchronous memory read/write style in the micro engine. In this condition, only one thread is used to complete the whole process of route information searching. Additionally, multi threads do the searching work in parallel in order to improve the efficiency.At last, A constract test result shows the improvement of the system's performance with the new longest prefix match algorithm. |
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