TCP switching: exposing circuits to IP

Abstract

Circuit switches have simpler data paths and are potentially much faster than packet switches. Taking advantage of this difference makes very high capacity all-optical circuit switches feasible, whereas all-optical packet switches are a long way from commercial practicality. Peak-allocation, that is eliminating the benefits of statistical multiplexing, is circuit switches' main disadvantage, and what prevents their widespread adoption. However, the rising amount of already abundant link capacity will eliminate this drawback. Our research focuses on how the existing IP infrastructure can incorporate fast, simple (and perhaps optical) circuit switches. Several approaches to this already exist, 1-5 but we propose a technique called transmissioncontrol protocol (TCP) switching in which each application flow (usually an individual TCP connection) triggers its own end-to-end circuit creation across a circuit switched core. Based on IP switching, 6 TCP switching incorporates modified circuit switches that use existing IP routing protocols to establish circuits. Routing occurs hop by hop, and circuit maintenance uses soft state, that is, it is removed through an inactivity timeout.Many believe that only routers, links, and end hosts, all using packet switching, comprise the Internet. In reality, the Internet uses circuit switching, both at its core (Sonet, SDH, dense wave digital multiplexing or DWDM), and in its last mile (modems, DSL). Internet Protocol treats these circuits as static, point-to-point links connecting adjacent nodes; the physical circuits and IP belong to different layers, and they are completely decoupled since they operate autonomously and without cooperation. Decoupling of layers has many advantages. It lets the circuit switched physical layer evolve independently of IP-to both Sonet/SDH, and DWDM. IP runs over a huge variety of physical layers regardless of the underlying technology. However, a lot of repetition exists between the packet-switched IP layer and the circuitswitched physical layer. For example, a network must route both IP datagrams and circuit paths, yet, they use different routing protocols, and their implementations are incompatible. This makes simple and obvious operations infeasible. For example, if traffic increases between two neighboring routers, no simple or standard way exists to automatically increase the capacity between them. The problem is with how circuit switches interact with IP routers. TCP switching presents a method of interaction, promising automatic and dynamic circuit allocation.