NAT Implementation for the NetFPGA Platform Omar Choudary and David Miller University of Cambridge...

NAT Implementation for the NetFPGA Platform

Omar Choudary and David MillerUniversity of Cambridge

Computer Laboratory

Outline• Hardware

o Designo TCAM memory: LPM and NATo Performance

• Softwareo Functionality

• Advanced Feature: NATo Hardwareo Software

• NAT Demoo Case 1: client-server transfer crossing two nf-test machineso Case 2: ttcp performance test

NAT implementation for the NetFPGA (Omar Choudary; David Miller) Slide 2

Advanced Feature.NAT

NAT implementation for the netFPGA (Omar Choudary; David Miller) Slide 8

Hardware.Design


NAT.Hardware• Tables to store NAT translations• 2 CAMs + 2 RAMs• 1 RAM for update counter (to solve TCP State issue)• Registers for software communication• Synchronisation with LPM and Routing functionality


Hardware.Performance

• TTCP (Test TCP, sourcing data from Linux OS)o 976Mbps = 122 MB/s o Limited by the OS and NF2 framework

• Router_perf (sourcing data directly from the FPGA): o 2909 Mbps = 363MB/s for 64-byte packet sizeo 3751 Mbps = 469MB/s for 1500-byte packet size o Limited by the NF2 framework


Software.Functionality• Process packets sent by the Hardware to the CPU

o Send and receive ICMP and ARP packets• Implement and run the OSPF protocol• Insert and update entries into the hardware tables: IP filter,

ARP, ROUTE, NAT|• Implement the CLI


NAT.Software• Create entries in the NAT table when TCP/UDP packet

arrives on INBOUND interfaces• Checks the hardware counter on each entry to delete

unused entries• Handles incorrect UDP/TCP packets (possibly due to

incorrect header checksum)• Implements DHCP server to automatically provide hosts

connected to INBOUND interfaces with IP addresses


NAT.DEMO


CASE 1: HTTP Transfer


CASE 2: TTCP Test


Questions


Problems Encountered


• NF2 framework limitations -> issues with out_rdy signal• Bad hardware design• Hidden hardware bugs; hard to debug using chipscope• NetFPGA ports are only Gigabit-capable; not possible to

plug in a laptop Fast-Ethernet-only capable• Problems when dealing with slow devices; either web

server or our software making problems

CASE 3: Open Internet


CASE 4: Speed Test


Hardware.TCAM• Fastest LPM hardware solution• Based on a Ternary CAM => Each bit in the CAM memory

contains 3 states: 0, 1 and X (don't care)• My implementation uses 2 CAMs for each bit of the 32

composing an IP address => 64 Block RAMs


NAT Implementation for the NetFPGA Platform Omar Choudary and David Miller University of Cambridge...

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