Performance Measurements and Analysis of TCP Flows in a Differentiated Services WAN

This paper presents results from performance measurements carried out in a Differentiated Services WAN connecting three major cities in Southern Finland. The target of the measurements was to collect precise information about the level of service, experienced by a user transmitting files with FTP in a network that implements service differentiation by using drop precedence levels and separate classes for realtime and non-realtime traffic. Special attention was paid to the behaviour of competing TCP flows produced by users with different service level specifications. Background traffic from ISP’s network was injected into our test network in order to create traffic profiles which are typical in a core network. The results show clearly that the SIMA model used for the implementation of the DS mechanisms in the network nodes can provide service differentiation in a useful and fair manner in traffic conditions varying from light load to severe overload.