Paper:
    Evaluating Network Processors in IP Forwarding
        Tammo Spalink, Scott Karlin, Larry Peterson
       
Department of Computer Science, Princeton University

Intel IXP1200 network processor document:
    Intel IXP1200 Network Processor Family - Hardware Reference Manual
    Intel IXP1200 Network Processor Family - Software Reference Manual
    Intel IXP1200 Network Processor Family - Microcode Programmer's Reference Manual
    Intel ® IXA SDK ACE Programming Framework IXA SDK 2.0 Developers Guide
    Intel ® IXA SDK ACE Programming Framework SDK 2.0 Reference