Figure 4.2 CRAFT network topology in Oklahoma
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There are 3 major aspects in the analysis for the CRAFT network: bandwidth, local buffer (queue), and latency. Bandwidth examines whether the link usage is close to optimal, which then results in being queued in the local buffer. Local buffer examines whether the buffer size is adequate for storing several days’ worth of data before data loss happens. Latency examines the delay in the packet transfer, which is an important key to deciding the usability of data in a time-critical event.
When the radar generates data in a rate of which it exceeds the link capacity, the data are stored temporary in a queue in LDM. The data generation rate is based heavily on the weather condition. On average, the compressed data rate is approximately 40 kbps. In a heavy weather condition, the rate might exceed 56 kbps.
The following figure shows the capacity of each link in the CRAFT network in Oklahoma:
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Figure 4.2 CRAFT network topology in Oklahoma |
OneNet is connected to Abilene using a T3 line (45 Mbps). The Abilene backbone is connected with a speed of 2.4 gigabit/seconds. Therefore, bandwidth is not an issue when considering the aggregated data transfer of 6 radars producing only several hundreds of kilobits per second from Norman to NCDC (through OneNet and Abilene).
On the other hand, some radars are connected to the Internet using 56 kbps phone lines. This causes problem when the data are generated at a rate higher than 56 kbps. Therefore, for this particular situation, the local buffer is needed to store the data (either in memory or on disk) in order to prevent data loss.