| As the Internet continues to grow both in size and in terms of the volume of traffic it carries, more and more networks in the different parts of the world are relying on an increasing number of distinct ways to exchange traffic with one another. As a result, simple questions such as "What is the application mix in today's Internet?" may produce non-informative simple answers unless they are refined by specifying the vantage point where the traffic is observed, the networks that are involved, or even the type of interconnection used. In this paper, we revisit the question of the application mix in today's Internet and make two main contributions. First, we develop a methodology for classifying the application mix in packet-sampled traces collected at one of the largest IXPs in Europe and worldwide. We show that our method can classify close to 95% of the traffic by relying on a stateful classification approach that uses payload signatures, communication patterns, and port-based classification only as a fallback. Second, our results show that when viewed from this vantage point and aggregated over all the IXP's public peering links, the Internet's application mix is very similar to that reported in other recent studies that relied on different vantage points, peering links or classification methods. However, the observed aggregate application mix is by no means representative of the application mix seen on individual peering links. In fact, we show that the business type of the ASes that are responsible for much of the IXP's total traffic has a strong influence on the application mix of their overall traffic and of the traffic seen on their major peering links. |