HA/TCP

Layer 7 network functions (NFs) are a critical piece of modern network infrastructure. As a result, the scalability and reliability of these NFs are important but challenging because of the complexity of layer 7 NFs. This paper presents HA/TCP, a framework that enables migration and failover of layer 7 NFs. HA/TCP uses a novel replication mechanism to synchronize the state between replicas with low overhead, enabling seamless migration and failover of TCP connections. HA/TCP encapsulates the implementation details into our replicated socket interface to allow developers to easily add high availability to their layer 7 NFs such as WAN accelerators, load balancers, and proxies. Our benchmarks show that HA/TCP provides reliability for a 100 Gbps NF with as little as 0.2% decrease in client throughput. HA/TCP transparently migrates a connection between replicas in 38 µs, including the network latency. We provide reliability to a SOCKS proxy and a WAN accelerator with less than 2% decrease in throughput and a modest increase in CPU usage.