Programmable device deployment for efficient network function offloading

Network functions (NFs) play an important role in ensuring network security and performance. To improve the NF throughput performance, an emerging method is to offload NFs on programmable devices, bringing orders-of-magnitude improvements. A primary task for efficient NF offloading is how to deploy programmable devices (e.g., programmable switches) for network upgrades. Although programmable switches have powerful computing resources, their memory resources are usually limited, which poses a challenge of offloading stateful NFs (e.g., load balancer, NAT) with a large-size memory requirement. A promising solution to break the memory limitation is using external memory (e.g., on commodity servers) with the help of remote direct memory access (RDMA) supported by SmartNIC. Therefore, this paper studies the problem of upgrading networks by replacing legacy switches with programmable switches and equipping commodity servers with SmartNICs so that NFs can be offloaded on programmable switches with external memory expansion. We prove that this problem is NP-Hard, and there is no polynomial-time algorithm with an approximation ratio of (1−ϵ)⋅lnh, where ϵ is an arbitrarily small value, and h is the total number of requests in the network. Then we design an efficient algorithm with an approximation ratio of 2.5⋅H(m⋅n), where m is the number of NF types, n is the maximum number of requests through a switch, and H(m⋅n) is the (m⋅n)th harmonic number. The simulation results show that our solution can reduce the upgrade cost by about 70% compared with the state-of-the-art approaches while preserving the same system throughput.