Calculating RAM Allocation Footprints for Wireless Mesh Nodes
Wireless mesh node RAM calculations require summing static link map data with dynamic scaling allocations for neighbor tables, queues, and security states.
Frame Queue Depth
Meaning
Buffer capacity in a network transceiver is defined by the maximum number of media access control frames that can wait in line for transmission or processing. System engineers adjust the frame queue depth to optimize the memory reserved for transient network spikes. Setting this value appropriately ensures that the transceiver can absorb bursts of data without stalling the host processor.
Latency Impact
Packets that reside in a deep buffer experience increased transit delay while waiting for earlier transmissions to complete. When the frame queue depth is too large, it causes bufferbloat where real time packets arrive too late to be useful. This delay degrades the responsiveness of interactive network protocols.
Buffer Overflow
Small values for this parameter cause frequent packet losses when the transmission medium experiences temporary congestion. If the frame queue depth is insufficient to hold incoming data, the network interface drops newly arrived frames immediately. The host application must then spend processing cycles retransmitting the lost data, which lowers overall system efficiency and increases power consumption.
This retry mechanism introduces further delays that can compound the congestion on the shared communication bus, resulting in a severe drop in data rate.
Throughput Tradeoff
High speed connections require sufficient queue space to maintain a continuous flow of packets during propagation delays. When analyzing frame queue depth, the optimal setting is determined by the product of the network bandwidth and the round trip time. If the buffer is smaller than this product, the transmitter cannot keep the communication channel fully utilized.