What Causes Slow Internet?

Proper Understanding (the Truth About) INTERNET BANDWIDTH
Nowadays, many people frequently complain about Internet Bandwidth issues. Some say downloading data or movies is slow, while others complain that simply loading a web page takes an unusually long time — even with bandwidth as high as 200 Mbps download and 100 Mbps upload. Furthermore, some even mention that despite using a dedicated leased line, it is still very slow just to stream or download a movie.
The key point is not necessarily the speed package of the internet service you subscribe to; rather, the issue depends on several critical factors:

1. The speed of your service: Is your internet service plan shared? For packages costing around 700 to over 1,000 THB per month, they are all shared connections. You then need to look at what sharing ratio is used — such as 1:10, 1:20, 1:30, or higher. The more people sharing the same bandwidth pipe, the longer delays you will experience due to bandwidth contention. You may notice that speeds fluctuate between fast and very slow depending on the time of day. When you complain to your Internet Service Provider (ISP), they simply move you to another shared pipe that is less congested at that moment, making you feel an immediate improvement.

2. MTU (Maximum Transmission Unit) packet size: What size packets are you using? The smaller the packet size, the more time and overhead required to transmit data. From testing different ISPs, packet sizes vary. The smaller the packet size, the more users an ISP can pack into a shared pipe (comparable to a road with limited surface area: large vehicles occupy a lot of lane space, reducing the number of vehicles the road can accommodate and complicating traffic flow). You can test this using the command: ping -l 1472 -f followed by a destination. If it fails, you will see a message indicating that the packet is too large and needs fragmentation. Gradually decrease the packet size until you find the maximum value that successfully pings without fragmentation. That is the maximum packet size permitted by your ISP. Based on past tests, each ISP allows different sizes.

3. If you lease a dedicated leased line, you do not share bandwidth with external users; however, performance still depends on the bandwidth allocated and how many concurrent users are on the internet. More importantly, if you connect via Wi-Fi, the Wi-Fi system itself is the ultimate shared bandwidth medium. If you wonder who is sharing your Wi-Fi, try using tools like CommView for WiFi. You might find that while sitting next to the Access Point, multiple other users are connected and sharing bandwidth on your Access Point. Once Wi-Fi bandwidth is heavily congested, a high-speed leased line barely helps. (According to Cisco recommendations, a single Access Point should generally not exceed 25 concurrent users.)

4. Number of hops between your connection, the ISP, and international destinations: You can test this using the command tracert followed by the destination IP. A higher number of hops generally results in slower speeds and higher latency. Observe the latency (delay) at each hop, especially at the final destination; if it exceeds 250-300 ms, performance will feel sluggish.

5. Issues at the destination server: The destination server may suffer from insufficient processing capacity (CPU/RAM), or its network may lack adequate bandwidth or be fully saturated.

6. User expectations and impatience (haha): Having been accustomed to high speeds previously, encountering anything slower feels frustrating.

7. Video file size, video compression encoding, and the streaming platform being used also play a significant role.

8. Internal local network bottlenecks: The local network routing your traffic out to the internet may experience bottlenecks or congestion, including improperly configured firewall rules and policies.
These are merely the primary causes. Therefore, getting an upgraded promotional package for faster internet may only bring a brief smile to the corner of your mouth, before reality sets in and things feel as slow as before.