Understanding Network Performance - A Simple Guide
When you click a link or make an API call, various factors affect how quickly you get a response. Let’s break down the key terms with real-world examples.
| Term | Meaning | Example |
|---|---|---|
| Latency | Time it takes for round trip (request + response ) | When you click a link, it takes 100ms to get a response |
| Bandwidth | Maximum possible speed | Your ISP provides 100 Mbps internet connection |
| Throughput | Actual speed achieved | You download a file at 80 Mbps |
| Jitter | If latency varies across calls, that’s jitter | Lag in your video calls. |
| Cache | Temporarily stored data for faster access | Browser remembering your login details. |
| Proxy | Network middleman | A company’s firewall. |
Note - API technologies like RESTful, GraphQL at most basic level use socket interface for process identification, connection establishment and inter-process communication.
Latency Breakdown
Latency = Transmission + Propagation + Queuing + Processing
- Transmission delay - Time to push bits onto the wire.
- Propagation delay - Travel time across the network.
- Queuing delay - Waiting at routers or switches.
- Processing delay - Time for servers to compute results.
Bandwidth-Delay Product (BDP)
Latency × Bandwidth = how many bits the “pipe” can hold.
In simple terms it is maximum amount of data that can be “in flight”. Useful when optimizing for data transfers, we can keep buffer !
Simple Example
Let’s see what happens when you visit csprimer.in with a 40 Mbps connection:
-
Bandwidth = 40Mbps (your connection speed)
-
Actual Throughput ≈ 32 Mbps (due to network conditions)
-
Latency = 110 ms (includes the 4 kind of delays discussed below)
Breakdown of latency →
- DNS lookup (Processing + Propagation ~10ms ) - DNS server looks up the address.
- TCP handshake (Transmission + Propagation ~25ms) - Packets travel from client to server.
- Server processing (Processing + Queuing ~50ms) - Server prepares the response.
- Response travel (Propagation+ Queuing ~25ms) - Packets travels from server to client.
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BDP = 40 Mbps × 0.11s = 4.4 Mb → Network path can hold 4.4Mb data in flight.
So a website like csprimer.in which is fairly small ~ 200 KB, at 32 Mbps throughput, transfer time will be 200 KB * 8 / 32 Mbps ⇒ 0.05 seconds, but may increase upto 0.2 seconds on delays.