Research And Design Of The Embedded IPv6 Gateway Based On LwIP

With the rapid development of Internet of Things, more and more traditional industrial devices have has the demand of getting access to the internet. Most of the traditional industrial devices use serial port and don’t have the network interface, so they can’t communicate through the internet. While some of the industrial devices have the network interface, they mostly only get the IPv4 support. The exhausted IPv4 address pool makes it hardly in coping with the huge number of address demand which comes from industrial devices.To solve the problem above, this thesis describes the method of designing a light-weight embedded gateway which is based on the in-depth researching of LwIP’s IPv6 core part. The embedded gateway is a device which can swap packages between serial port device and TCP/IPv6 device. The main question the thesis focuses on is the realization of IPv6 relavant protocols and the application of them, including data structure, method, interface, etc. It’s not a thesis concerning the design of protocols.This thesis first describes the IPv6-relevant protocols which emphasizes the IPv6 addressing system, IPv6 packet format, ICMPv6 packet format and neighbor discovery protocol. Then LwIP, a protocol stack, which have got IPv6 support from Git is deeply analyzed through these aspects: framework, architecture, dynamic memory management, network interface management, IPv6 and ICMPv6 core component. A improved method is proposed to solve the problem that LwIP’s fragment function can not deal with the packet containing extension header.This thesis also gives the hardware design of the gateway system, and behind which the transplanting method of LwIP is described in detail. The gateway system uses STM32F103ZET6 as the main controller and ENC28J60 as the Ethernet PHY. Transplanting work is implemented with Keil integrated development environment. And the Ping test result shows that the transplantation of LwIP is successful. Instead of using operating system, the whole software task architecture of the gateway is designed as endless-loop combining with interrupt. This is mainly for real-time considerations in data forwarding. For the gateway application layer protocol, the design is carried on in three elements: syntax, semantics and timing. Specific message forwarding rules are designed based on these elements. The final test results show that the gateway’s basic data forwarding function can work well, and it can withstand the stress tests under the condition 200 bytes per packet, 10 packets per second.