Building a Programmable Multiplexing Service Using Concast

Concast is a scalable “inverse-multicast” network service: messages sent from multiple sources toward the same destination are merged into a single message that is delivered to the destination. The mapping from sent messages to received messages is programmable, so the service can be tailored to the needs of specific applications. However, the service can also be used as a building block for other generic network services, such as a packet multiplexing service that encapsulates multiple small packets into a single larger packet and then unencapsulates the small packets at their (common) destination. Such a service offers several potential benefits, including reduced packet processing overhead and increased fate-sharing, but must also be carefully designed to avoid problems caused by added packet delays. In this paper we show how concast can serve as the basis for a multiplexing service that can be tailored to the needs of the application. We present simulation results showing that the benefits of our multiplexing service vary with delay. We also show that given certain queuemanipulation capabilities, benefits can be achieved with zero added delay.