The team at YouTube channel The Serial Port have successfully streamed a video of 12 phone lines being combined to demonstrate the hidden potential of legacy technology. They claim this may be the first documented use of more than 4 modems being combined in practice.
The team at YouTube channel The Serial Port have successfully streamed a video of 12 phone lines being combined to demonstrate the hidden potential of legacy technology. They claim this may be the first documented use of more than 4 modems being combined in practice.
YouTube channel The Serial Port has done what seemed impossible in the era of broadband Internet: stream over a dial-up connection. In their new experiment, the team combined 12 modems using Multilink PPP technology, achieving a total download speed of 668 kbps on a Windows XP desktop. This turned out to be enough to stream video without buffering, writes TechSpot.
At the peak of dial-up usage in the late 1990s, the fastest publicly available connections maxed out at 56 kbps. By 2000, the U.S. Federal Communications Commission defined broadband as a connection with speeds of 200 kbps or higher, which already pushed dial-up beyond its capabilities.
Websites of that era were mostly text and compressed images, but downloading music, videos, or other large files could overload a phone line for hours. The growing demand for speed eventually pushed DSL and cable internet into the mainstream.
A temporary solution was the Multilink PPP protocol, standardized in 1994. It allowed combining several telephone lines into a single high-speed channel. Among the commercial projects was the "Shotgun" PCI card from Diamond Multimedia, which connected two 56K modems. However, its use required multiple telephone lines and support from an Internet service provider, which significantly hindered its spread.
Thirty years later, the YouTube channel The Serial Port returned to this idea, using VoIP line simulators and legacy corporate networking equipment to test how scalable MPPP can be.
The experiment required both contemporary client hardware and a reliable backend. The first test machine was a 2001 IBM NetVista computer running Windows ME. Although it successfully combined two modems, further scaling quickly ran into limitations, including a lack of serial ports and driver support.
The project then moved to a 2004 IBM ThinkCentre running Windows XP, which provided wider compatibility. Equipped with an Equinox expansion card and a four-port Digi card, the system had 13 available COM ports. With XP's built-in support for simultaneous dialing, several external US Robotics Courier modems were connected, powered on, and configured with synchronized DIP switches to avoid conflicts.
On the ISP side, the team used Cisco VoIP infrastructure to create multiple phone lines, which were connected to modems. The connections were terminated on a Total Control dial-up access hub, a piece of equipment that was once common among small ISPs in the 1990s. Unlike client setup, which required a lot of trial and error, the ISP's equipment could easily handle multiple sessions.
Gradually scaling from two to four and then to twelve combined modems, the experiment achieved a combined connection speed of 668.8 kbps. This bandwidth exceeded the FCC's original broadband definition from 2000 and, more importantly, allowed smooth YouTube playback at 144p and 240p.
The Serial Port team noted that they could not find any evidence that more than four modems had ever been connected using MPPP—neither in practice nor in reference books like the Guinness Book of World Records.
