Glossary · Speed and HTTP
Latency is the delay for data to travel between two points on a network, usually measured as round-trip time (RTT) in milliseconds: the time for a packet to reach a server and for the reply to come back.
Distance sets a floor. Light in optical fibre travels at about 200,000 km per second, so a round trip between Stockholm and New York, about 6,300 km apart, can’t take less than about 63 ms, and real routes add more. Every network hop, congested link and queue adds to it.
Latency multiplies. Opening an HTTPS connection takes round trips for TCP and then TLS before the request is even sent, so a far-away server feels slow even when it answers at once. CDNs and edge caches cut this by answering from nearby.
Ping measures latency with ICMP echo requests; the connect time in an HTTP or port check measures it for TCP.
Minimum round-trip time ≈ 2 × distance ÷ 200,000 km/s
Example: Stockholm to New York: 2 × 6,300 km ÷ 200,000 km/s ≈ 63 ms.
Uptimecheck ping monitors report the median round trip of three echo requests, and HTTP checks show connect and TLS time apart from the server’s own wait, so you can tell network latency from a slow application. Checks run from Stockholm today, which sets the baseline: a server in the US adds the round trip across the Atlantic.
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Monitoring 7 min read
Response time is how long your server takes to answer a request, not how long the page takes to load. What counts as good, why monitors and browsers measure differently, and what slows sites down.
ReadLatency is delay; bandwidth is capacity. A connection can move a lot of data per second and still take 100 ms for each round trip.
Within a country, under 20 to 30 ms is typical; across an ocean, 80 to 150 ms. Stability matters as much: sudden jumps point at routing changes or congestion.
Serve from closer to them with a CDN or regional servers, reuse connections (HTTP/2 and HTTP/3), and cut the round trips a page needs, such as redirects and requests to extra domains.
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