How to measure Network Stability? The Shannon-Hartley Theorem

Before we can analyze the flow of data, we must understand the container. Bandwidth is fundamentally a measurement of the range of frequencies (spectrum) available for transmission. This relationship is defined by the Shannon-Hartley Theorem:

Where:

• $C$ is the Channel Capacity (theoretical bandwidth).
• $B$ is the bandwidth (in Hertz).
• $S/N$ is the Signal-to-Noise ratio.

What defines Effective Throughput? The Impact of Protocol Overhead

Throughput is the rate of *successful* message delivery over a communication channel. It is always less than the bandwidth due to several factors:

• L2/L3 Overhead: Ethernet frames and IP headers occupy space that isn't raw user data.
• TCP Handshakes: Connection-oriented protocols require back-and-forth signaling that consumes time without moving data.
• Retransmissions: If a packet is dropped due to structural interference (common in wireless infrastructure), it must be sent again, effectively halving the throughput for that segment.

How does Congestion affect Network Stability?

When demand (load) exceeds capacity (bandwidth), packets must wait in queues. As we explored in our guide to Jitter, these queues introduce delay variation. If the buffers overflow, we experience Bufferbloat, leading to a catastrophic drop in throughput known as "Congestion Collapse."