Scalable control plane architecture for optical flow switched networks

In OFS, users employ an off-band signaling protocol to request lightpaths for their large unscheduled bursty transactions, and the network dynamically schedules a dedicated, end-to-end lightpath for the duration (≥100mS transaction times) of the transfer avoiding collisions due to contention, Fig.1. For OFS the scheduling and network control is dynamic and when a transaction finishes, the network resources are immediately relinquished to other users. The key to high utilization of backbone wavelength channels - a precious network resource owing to the necessary use of optical amplifiers and dispersion management - is statistical multiplexing of large flows from many users in a scheduled fashion. Efficient, dynamically assigned multi-access broadcast groups can be arranged for multiple transaction durations using the node architecture. We have shown, [1,2,3,4,6], that our approach provides significant cost savings over other transport mechanism for large transactions. OFS is technically a circuit switched service. The major difference between OFS and traditional circuit switching is the fast dynamic session setup (&#60;100mS). This presents tremendous stresses on the network control plane. Many detractors of this technology (who mostly favors IP packet switching) question the scalability of this technology. The purpose of this paper is to address all the critical problems that prevent affordable scalability and fast dynamic setup for OFS. Major attributes in our architecture that simplify network control and potentially can realize significant simplicity and cost saving are: 1. Use of broadcast/narrowcast all-optical access network with a MAC protocol for efficient statistical multiplexing of bursty large transactions bypassing routers. This avoids fast (per session switching in the LAN and MAN) eliminating stringent hardware requirements on fast optical switching and control network signaling and decision making. In this scheme the only fast per flow hardware tuning is the transmitter/receiver wavelength of operation. 2. Use of efficient optically switched MAN mesh network topologies that minimize switching and amplifier resources to organize access to the precious WAN transport. The MAN architecture supports efficient aggregation of flow traffic without fine grain switching and only reconfigures the hardware in response to medium time scale average load changes (>100S). We use a MAN network architecture that exhibits a decreasing cost/user/data-rate as the number of users and user data-rates increase. The following are key design features for the MAN architecture: a. Minimize average lightpath lengths, in terms of the number of OXCs traversed. b. Use of quasi-static MAN/LAN broadcast groups to eliminate fast per session, &#60;100mS, network reconfigurations and only use MAC for efficient statistical multiplexing. c. The MAN/WAN interface is quasi-static and the WAN wavelength highways are dedicated exclusively to MAN source/destination pairs essentially decoupling the numerous MAN source/destination pairs' MAC protocol and control. 3. Use of efficient scheduling algorithms for the contention of WAN resources. Quasi-static WAN “highway” wavelength provisioning is used to slow down control plane traffic and computation loads for reconfigurations. This slowing down of the WAN control plane is important to perform near optimum global coordination of the WAN without having to perform per flow signaling and control and making the architecture unattainable. 4. Scalable ultra-fast setup using entropy function as state information reducing the complexity of network sensing, management and control.