This proposal suggests the development of innovative methods and tools to address the scale and heterogeneity of the Internet protocols. We will focus on what we consider to be the key challenges: scaling and protocol interaction issues in integrated services internets. While the long-term objective of a scalable, multiprotocol, composable virtual internet testbed is very ambitious, we propose the following areas for the focus of our work: detailed simulator, session-level simulator, visualization front-end, and libraries.
Our composable component framework will allow component modules from multiple contributors. This mirrors network development and is feasible because of the modularity inherent in the network protocols themselves. For example, we wish to enable the designers of a reliable multicast transport protocol to evaluate their design in the presence of simulation modules that represent dynamic multicast routing and packet scheduling algorithms. Or similarly, we want to allow the designers of packet scheduling and reservation protocols to evaluate their design in the presence of simulation modules that represent various subnet technologies (e.g., wireless, ATM).
In addition to creating the composable framework, as part of the VINT project we will implement key protocol modules, including unicast routing, multicast routing, reservation, transport and session protocols. This will allow us to evaluate and improve the simulator framework, and more importantly, will give other researchers a relatively complete ``internet context'' in which to plug their components for evaluation.
One of the most significant impediments to more extensive simulation use is the amount of effort typically involved in setting up and interpreting simulations. Graphical manipulation of inputs and animation of simulation processes and outputs should provide the same benefits to network simulation as they have to so many other areas of computer aided design and visualization.
In summary, our goal for the detailed simulator component of VINT is to enable extensive simulations by innovating in the area of simulator composability and visualization. However, such a system alone is not adequate because the detail necessarily limits the tractability of studying very large networks. Therefore, we include the second component of our system described in the next section.
One of the greatest challenges, with respect to this component of VINT, is to develop methods for moving between detailed and high level abstraction: for example, creation of static scenarios at one level based on results at the other, and dynamic interfacing of detailed and abstract modules. In addition, we will investigate tools for creation of session level protocol modules based on detailed simulation or implementation modules.
Special visualization techniques will be needed for the session level simulator to allow graphical definition and manipulation of the very large networks, and visualization of their processes (intermediate states) and results.
In summary, session level simulations will emphasize scaling issues in addition to multiprotocol composability. We will develop and apply validation techniques by correlating session-level simulation results with both detailed simulations, smaller scale testbed experiments, and operational network measurement.
To achieve this last goal, we will use early prototypes of VINT in an active research effort. This will provide initial experience with VINT and provide feedback to its design. These research efforts will explore interactions between component protocols that constitute any integrated services internet. In particular we will study: the interaction of routing and reservation setup protocols and mobility; IP integrated services support over diverse subnet technologies such as ATM and wireless; security (e.g., access control and authentication) mechanisms in IP, routing, and RSVP; reliable multicast transport and underlying multicast routing; Web caching mechanisms and multicast routing; switch packet scheduling algorithms and end node application performance.
Some of these issues require a detailed study of protocol interaction to evaluate their functional correctness; others require coarser grained evaluation to characterize performance issues. For example, we require a detailed protocol simulator and associated visualization tools to evaluate the functional interactions between the stack of protocols needed to support integrated services. Reservation setup protocol messages travel along the multicast distribution trees established by the multicast routing protocols, which in turn depend on the unicast routing protocol; moreover, the protocols' behavior is affected by the presence of multiaccess subnets and must be studied in topologies with both these and point-to-point links.
A second set of examples involves the performance of web protocols. For instance, it has been proposed that the web-cache placement could make use of either network topology information provided by monitoring of network paths, by the routing protocol, or by a network management function such as the Internet Routing Registry. We could use a session level simulator to evaluate the tradeoffs associated with the granularity at which such topology information is provided. On the other hand, a detailed simulator would be needed to study another frequently discussed performance issue associated with the World Wide Web, namely, the interaction between HTTP and the congestion control mechanisms being used by other types of traffic.
We will promote the use of VINT through the following activities: Research community: demonstrate VINT to Sigcomm and Infocom communities through publications, advertisement of tool availability, and conducting of network-based teleconferences to demonstrate capabilities and obtain early feedback from users and potential users. Investigate initiation of VINT related IRTF research group. Promote VINT simulations as community standard for comparisons in published work.To view the quad chart for VINT click here
Vendors and large users (e.g. private networks and service providers): illustrate utility of techniques through application of VINT to problem areas in the community. Build modules corresponding to active design and standardization discussions. (IETF, ATM forum, Nanog).