Abstract: Aiming to address the drawbacks in SRv6 technology, such as low network carrying efficiency caused by long packet header and inability to deploy in IPv4 networks, a segment routing technology SRv4 for IPv4 networks is proposed. The format of packets header in SRv4, the format of packet encapsulation of SRv4 in IPv4, the processing instructions and the forwarding process of SRv4 packets are designed. SRv4 is compatible with the IPv4 protocol and existing IPv4 network devices, and can be incrementally deployed in IPv4 networks. Compared to SRv6, SRv4 reduces the SID length by 75%, resulting in higher network carrying efficiency. The SRv4 module is developed in the Linux kernel using XDP technology to verify the feasibility of the SRv4. The function, performance and stability of the SRv4 module were tested using a network environment built in a server computer. The results show that the SRv4 module has the correct segment routing function and can run stably. 

Key words: segment routing, SRv6, SRv4, XDP, IPv4