In-Network Applications: Beyond Single Switch Pipelines
Xin Zhe Khooi, Levente Csikor, Jialin Li, Dinil Mon Divakaran · 2021
The emergence of commodity programmable switches have spawned a series of innovations in the network data plane. By making the traditionally stateless network architectures to be stateful, we can realize a diverse set of applications, e.g., networking monitoring, load-balancing, firewalls, entirely in the data plane. On the other hand, many existing in-network applications assume that the underlying switch is single-pipelined, however, in reality, commodity programmable switches are designed with multiple pipelines in mind. While this approach enables high scalability, it has introduced a serious disadvantage: maintaining states across the pipelines is non-trivial. For instance, without involving the control plane it is infeasible to keep track of a request and its response in different pipelines, thereby rendering many in-network proposals impractical.In this paper, we highlight this fundamental limitation that holds back the practical widespread adoption of stateful applications in today’s multi-pipeline switches. By scrutinizing recent in-network approaches, we identify that majority of them cannot operate as they are proposed on multi-pipeline switches. After raising awareness of this inevitable consequence, we discuss a set of possible workarounds for in-network applications to overcome this issue on multi-pipeline switches.