DSSR: Balancing semantics and speed requirements in packet trace replay

As new network services and middleboxes proliferate, it is important to have reliable means to test these services and devices, and a common practice to generate realistic testing traffic is through replaying previously recorded packet traces. However, existing trace replay tools are highly specialized for particular protocols and scenarios. In this paper, we present a general trace replay tool called DSSR. We show that in a directional trace replay, where outbound and inbound packets are simulated by two (logically) distinct sets of hosts, the timestamps of packets handled by the host(s) simulating external destinations must be adjusted to accurately re-create the effect of network latency. Interestingly, the timestamp adjustment can boost the replay speed. Moreover, we identify the range of timestamp adjustment that will guarantee to preserve the semantic orderings of packets pertaining to client-server protocol interactions. Therefore, our solution provides an effective tuning knob for a user to balance the speed and semantics requirements in a trace replay. Equally important, it requires no clock synchronization between the replaying hosts, as the hosts leverage the arrivals of incoming packets as a clocking mechanism for generating outgoing packets.