Flexible Notification Forwarding for Content-Based Publish/Subscribe Using P4

Publish/subscribe is a versatile communication pattern for realizing loosely coupled distributed applications. In its content-based variant, the content of each published notification is matched against the active subscriptions to determine the set of subscribers that shall receive the notification. The fact that this set may be completely different compared to that of a preceding or a succeeding notification makes it difficult to find and install beneficial forwarding rules on the network switches. In this paper, we present novel forwarding schemes based on the P4 language that (i) use dynamic forwarding information placed in the notification's header, (ii) use static forwarding rules installed on the network switches, and (iii) combine dynamic forwarding information with static forwarding rules to precisely set the respective trade-off. We evaluate our forwarding strategies, show their applicability as well as their benefits for content-based publish/subscribe, and discuss future research directions.