On Using Virtual-Circuit Networks for File Transfers

It has become clear that widespread collaboration in the scientific community, which can increasingly be characterized by geographically distributed and large-scale projects, requires predictable network service [1]. Predictable network service needed by applications such as large file transfers, remote visualization, and remote instrumentation can only be offered on connection-oriented networks. Circuit-switched and virtual-circuit networks offer connection-oriented services1. Significant work in the CHEETAH project [2] focused on various problems related to using circuit-switched networks for file transfers. (e.g., [3]–[7]). In this work, the focus is on using virtual-circuit networks for file transfers. There are four compelling reasons to study the use of virtual circuits for file transfers. 1) By using a single substrate of packet switches, a network could offer both connection-oriented (with virtual circuits) and connectionless services. The availability of both connection-oriented and connectionless services allows a file transfer to use the service appropriate to its size. Small file transfers use connectionless service to avoid the setup-delay overhead cost associated with connection-oriented service, while large file transfers use connection-oriented service if rate guarantees are desired. 2) The pervasive technology of end hosts’ network interface cards is packet based, i.e. Ethernet, which is a compelling reason to address problems in the packet-switched network context. 3) There is a flexibility advantage with virtual circuits when compared to circuits. Circuit switches necessarily have a base crossconnect rate, which is the unit rate of the demultiplexed streams. While there may be technological limits on how many virtual circuits can be supported with guaranteed bandwidth on a virtual-circuit switch, theoretically there is more flexibility with respect to adjusting the number of admitted calls and the corresponding bandwidth allocations. 4) Internet2 [8] and the Department of Energy’s Energy Sciences Network (ESnet) [9] have responded to a need for dedicated high-bandwidth circuits/VCs by deploying the Dynamic Circuit (DC) Network [10] and the Science Data Network (SDN) [11], respectively. Virtual circuits are used in both networks. This work addresses three problems related to supporting file transfers on virtual-circuit networks. First, this work answers the question of what transport protocol is appropriate for use in virtual circuits. Data-plane functions such as policing and scheduling are used to ensure rate guarantees on virtual circuits. As the data-plane characteristics of virtual circuits with rate guarantees are different from the data-plane characteristics of connectionless networks for which today’s transport protocols have been designed, a new transport protocol is required for rate-guaranteed virtual circuits. Section II describes the design, implementation, and experimentation work planned to develop a novel transport protocol for use in virtual-circuit networks.