Network Performance Diagnostics: Packet Loss, Latency, and Buffer Sizing
Packet loss percentage, round-trip latency, bandwidth-delay product, and packet transmission time — four calculations for diagnosing network performance.
Diagnosing a "slow" or "unreliable" connection usually comes down to a handful of specific numbers rather than a vague feeling.
Packet loss: how much data isn't arriving at all
Packet loss is lost packets divided by packets sent. Losing 15 out of 1,000 sent packets is 1.5% loss — under 1% is generally considered good for most applications, while above 2-3% noticeably degrades video calls and online gaming.
Round-trip time: the "ping" that gamers care about
RTT is typically twice the one-way latency. A 25ms one-way latency implies roughly a 50ms round-trip time — the number that directly determines how quickly your actions register on a game server or how responsive a video call feels.
Bandwidth-delay product: sizing buffers correctly
BDP estimates how much data can be "in flight" on a link at once: bandwidth × RTT / 8 (to convert bits to bytes). A 100 Mbps link with 50ms RTT has a BDP of 625,000 bytes — informing how large a TCP buffer needs to be to fully utilize that link's capacity without stalling.
Packet transmission time: how long it takes to push data onto the wire
Transmission time is packet size in bits divided by bandwidth in bits per second. A 1,500-byte (12,000-bit) packet over a 1 Mbps link takes 12 milliseconds to transmit — distinct from propagation delay, which depends on physical distance, not packet size.
Reading network performance holistically
Packet loss tells you how much data is missing, RTT and transmission time tell you how long everything takes, and BDP tells you how to size buffers for the link you actually have. Try the packet loss calculator, round-trip latency calculator, bandwidth-delay product calculator, and packet transmission time calculator.