On the impact of TCP segmentation: Experience in VoIP monitoring

Quality of Service (QoS) and Experience (QoE) monitoring is a must during the management of services deployed over the Internet. This is particularly critical for Voice over IP (VoIP), as its degradation is immediately perceived by end users. From our experience, we highlight the impact that TCP segmentation exerts on online VoIP monitoring systems. On the one hand, it makes difficult to interpret the segmented signaling messages for application monitoring. On the other hand, complete messages do not provide information about packet level behavior, which is necessary for internetworking layer monitoring. Paradoxically, the Network Management community has not paid much attention to this fact, although it compromises several VoIP management tasks. To fill in this gap, we provide an empirical evaluation of its impact for the most popular VoIP signaling protocols using traces from enterprise networks, and present the architecture and heuristic that we are currently developing to partially solve the effect of the segmentation. Our proposal avoids the overhead of reconstructing the entire data stream and, at the same time, it enables the analysis of the packets that are actually sent. To do so, it maps TCP flags with segmented application messages, and exploits data structures that reduce latency. In this way, our solution paves the way for online monitoring tools that take into account both internetworking and application layers performance.