The PackMime Internet traffic model was developed by researchers in the Internet Traffic Research group at Bell Labs, based on recent Internet traffic traces. PackMime includes a model of HTTP traffic, called PackMime-HTTP. The traffic intensity generated by PackMime-HTTP is controlled by the rate parameter, which is the average number of new HTTP connections started each second. The PackMime-HTTP implementation in ns-2, developed at UNC-Chapel Hill, is capable of generating HTTP/1.0 and HTTP/1.1 (persistent, non-pipelined) connections.
The goal of PackMime-HTTP is not to simulate the interaction between a single web client and web server, but to simulate the TCP-level traffic generated on a link shared by many web clients and servers.
A typical PackMime-HTTP instance consists of two ns nodes: a server node and a client node. It is important to note that these nodes do not correspond to a single web server or web client. A single PackMime-HTTP client node generates HTTP connections coming from a ``cloud'' of web clients. Likewise, a single PackMime-HTTP server node accepts and serves HTTP connections destined for a ``cloud'' of web servers. A single web client is represented by a single PackMime-HTTP client application, and a single web server is represented by a single PackMime-HTTP server application. There are many client applications assigned to a single client ns node, and many server applications assigned to a single server ns node.
In order to simulate different RTTs, bottleneck links, and/or loss rates for each connection, PackMime-HTTP is often used in conjunction with DelayBox (see Chapter 22). DelayBox is a module developed at UNC-Chapel Hill for delaying and/or dropping packets in a flow according to a given distribution. See Section 43.3 for more information on using PackMime-HTTP and DelayBox together.
The PackMime HTTP traffic model is described in detail in the following paper: J. Cao, W.S. Cleveland, Y. Gao, K. Jeffay, F.D. Smith, and M.C. Weigle , ``Stochastic Models for Generating Synthetic HTTP Source Traffic'', Proceedings of IEEE INFOCOM, Hong Kong, March 2004.