Decoding Internet Speeds: Bit Rate, Bandwidth, and Latency Explained

All computing devices on the Internet communicate using binary. Whether connected via wired or wireless methods, they send electromagnetic signals representing streams of 1s and 0s. Let's explore how those bits are sent and how quickly they can be transmitted.

Sending Streams of 1s and 0s

When computers internally represent the number 5 (101 in binary), they can use three wires to represent the three bits: one wire on, one wire off, and one wire on.

Imagine this: if a computer wants to send the number 5 to another computer, it might have only a single wire to send information over. Instead of multiple wires, it sends the number over three time periods: first sending an on pulse (and waiting), then sending nothing (and waiting), and finally sending an on pulse again.

As long as the two computers agree on the time period, they can transfer information, converting binary data into signals and back to binary data.

In an electrical connection (like Ethernet), the signal would be a voltage or current. In an optical connection (like fiber-optic cable), the signal would be the intensity of light. The process of turning binary data into a time-based signal is known as line coding, with various schemes available based on connection needs.

Bit Rate

Network connections can send bits very quickly. The speed is measured using the bit rate, the number of bits of data sent each second. The earliest Internet connections were just 75 bps (bits per second). These days, connections are often measured in Mbps (megabits per second).

A megabit is huge: 1 million bits! A 10 Mbps connection transfers data at 10 million bits per second, or one bit every 100 nanoseconds (0.0000001 seconds).

We also measure bit rate in smaller units like kilobits (1 thousand bits) or much bigger units like gigabits (1 billion bits) and even petabits (1 quadrillion bits).

Bandwidth

Bandwidth describes the maximum bit rate of a system. If a network connection has a bandwidth of 100 Mbps, it can't transfer more than 100 megabits per second. Fortunately, that's still a lot!

"Broadband Internet" refers to a connection with a minimum bandwidth of 256 Kbps, enough for basic Internet use like checking emails and reading websites but not quite enough for watching online videos. As of 2016, only 40% of people in developing nations have access to broadband Internet.

For instance, an older Internet connection with a bandwidth of 51 Kbps could transfer 51,000 bits per second.

Latency

Another way to measure network speed is latency, which measures how late the bits arrive. Formally, latency is the time between the sending and receiving of a data message, measured in milliseconds.

We typically measure the "round-trip" latency of a request. For example, if my computer sends a message to a Google server, 30 milliseconds later, Google receives the message. Another 40 milliseconds later, my computer gets an acknowledgment from Google, totaling 70 ms round-trip latency. Latency depends on various factors like the type of connection, the distance to the servers, and network congestion.

A major limiting factor to latency is the speed of light, which is 1 foot per nanosecond, implying a minimum trip length of at least 30 ms from Los Angeles to Tokyo. While we can't change the speed of light, we can decrease latency by reducing congestion and improving physical connections.

Internet Speed

Speed is a combination of bandwidth and latency. Computers split messages into packets and can't send another message until the first packet is received. Even with high bandwidth, the speed of sending and receiving messages is limited by the connection's latency.

You can measure network speed using an Internet speed test, which downloads and uploads data while tracking transfer speed. For example, my home laptop's speed test showed:

• Ping: 18 ms
• Download: 39.09 Mbps
• Upload: 5.85 Mbps

The low latency is fast enough for most multi-player online games. The download bit rate is higher than the upload bit rate, which is common since users typically download more data than they upload.

Understanding these concepts helps demystify how our devices communicate over the Internet, shedding light on the speed and efficiency of our digital connections.