Beyond folklore: observations on fragmented traffic

Fragmented IP traffic is a poorly understood component of the overall mix of traffic on the Internet. Many assertions about the nature and extent of fragmented traffic are anecdotal rather than empirical. In this paper we examine the causes and attributes of measured fragment traffic, in particular, the effects of NFS, streaming media, networked video games, tunneled traffic, and the prevalence of packet fragmentation due to improperly configured machines. To understand the prevalence, causes, and effects of fragmented IP traffic, we have collected and analyzed seven multiday traces from four sources. These sources include a university commodity access link, two highly aggregated commercial exchange points, and a local NAP. Although there is no practical method of ascertaining whether any data provide a representative sample of all Internet traffic, we include data sources that cover several different types of WAN with traffic from commercial entities, educational and research institutions, and large government facilities. The dominant causes of fragmentation are streaming media and tunneled traffic. Although rumored to be the main impetus for IP packet fragmentation, NFS is not among the top ten causes.