Special Report: Network Provisioning

Optical networking technologies have seen significant advances recently both in terms of routers, switches and provisioning platforms as well as high bandwidth long-haul links. Because of the Internet demands, a good number of these components are targeted towards supporting the IP networks, in particular by providing high capacity backbones and faster connectivity to the end users. Several of these technologies can also facilitate the provisioning of dedicated channels at various levels. A number of flexible, agile and configurable routers, switches, and provisioning platforms are also becoming available both commercially as well as for conducting research and development activities. Figure 6. Lower level provisioning modes for dedicated channels. Most current production networks, if not all, that support DOE large-science applications are based on IP. Since IP networks utilize packet switching over shared links wherein the packets are "queued" at the routers, there are certain inherent end-to-end characteristics of such connections. The queue occupancy levels depend on the competing traffic streams, and hence the "available" bandwidth levels and the packet delays. As a result, source nodes have very limited control either on throughput or packet delay, particularly under high traffic conditions. The implications are two-fold: (a) transport methods must account for the congestion levels and resultant losses to ensure reliable delivery, and (b) there are fundamental limitations on the packet delays and hence the end-to-end stability of the control channels implemented on such networks. In particular, large jitter levels can introduce high frequency components into control loops, which can seriously damage instruments at user facilities. Note that a number of DOE user facilities such as SNS are extremely expensive and should be safeguarded against such problems.

The dedicated channels provisioned between the hosts provide capabilities that are not normally possible in IP networks, such as the absence of competing traffic which altogether avoids the difficult congestion control problems. But to share the underlying network between the nodes, it is essential to circuit-switch the paths, preferably dynamically at various bandwidth resolutions and on-demand. Such channels can potentially simplify several design aspects of transport protocols since congestion control is no longer needed and the channel bandwidths are known. But channel utilization is a primary goal and must be explicitly incorporated into the protocols. Furthermore, they can also provide low jitter control channels since variations due to competing traffic streams are no longer present. Note however, that the delay measurements between the application modules that utilize such paths may still experience certain levels (albeit lower than Internet levels) of jitter due to the dynamics of other components such as NICs, provisioning platforms, SONET multiplexing and application modules. Furthermore, the provisioning of dedicated channels necessitates scheduling mechanisms to allocate the paths, and signaling mechanisms to setup and teardown the paths. While such circuit-switched networks may not necessarily be suitable for deployment of the scale of the Internet, they are still viable candidates for specialized deployments for connecting a small number of DOE largescale science nodes.

4.1 Recommendations in Provisioning To support DOE large-science applications, there is a need for next generation provisioning methods with the following capabilities: Recommendation 1: Agile Optical Network infrastructure: A scalable architecture is needed that enables fast provisioning of circuit switched dedicated channels specified on-demand by the applications. This system accepts application requests and optimally allocates the bandwidths on various links. It then prepares and maintains a schedule of allocations. Then it utilizes a signaling mechanism to setup and teardown the paths as per the schedule.

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