An Access Router Based On IXP425 Network Processor

Featuring great balance between performance and flexibility, network processors find their wide application in every facet of network. Intel IXP425, aiming at the applications of SME and SOHO, is especially suitable for the development of edge network equipment, i.e. gateway and access router.This paper focuses on the development of access router using IXP425 network processor, which has the following features:1. Support for ADSL/Ethernet WAN access;2. IEEE802.3/IEEE802.11 Wire/Wireless LAN access;3. Transparent 802.x bridge between wire and wireless LAN segments;4. Suppport for packet route between WAN and LAN;5. Single WAN IP sharing using NAPT scheme;6. Software based fast packet forwarding.Using IXP425 as the functional core, we employ "core board plus expansion board" strategy to facilitate the hardware development flow. The universal core board, which is comprised of IXP425, power supply, memory circuits and expansion interface to form a minimal system, could be applied to different applications together with corresponding functional expansion board. Upon the successful completion of hardware system, we customized board support package for the board, using U-Boot as bootloader, and Snapgear Linux as Operation System. To meet the application requirement of a practical access router, we developed several software modules to realize the network functions, which include wireless access point software, software based fast packet forwarding infrastructure, NPE based wire/wireless transparent bridging and source MAC firewall, and NAPT kernel module to tackle the single WAN IP sharing problem. Last but no least, we introduce the procedure of hardware/software co-debugging and function verification result of the system.