Dial-up networking technology allows PCs and other network devices to connect to remote networks over standard telephone lines. When the World Wide Web exploded in popularity during the 1990s, dial-up was the most common form of internet service available, but much faster broadband internet services have almost completely replaced it today.
Using a Dial-Up Network
Getting online via dial-up works the same today as it did during those early days of the web. A household subscribes to a service plan with a dial-up internet provider, connects a dial-up modem to their home telephone line, and calls a public access number to make an online connection. The home modem calls another modem belonging to the provider (making a distinctive range of sounds in the process). After the two modems have negotiated mutually compatible settings, the connection is made, and the two modems continue exchanging network traffic until one or the other disconnects.
Sharing dial-up internet service among multiple devices inside the home network can be achieved via several methods. Note that modern broadband routers do not support dial-up connection sharing, however.
Unlike fixed broadband internet services, a dial-up subscription can be used from any location where public access phones are available. EarthLink dial-up onternet, for example, provides several thousand access numbers covering the United States and North America.
Speed of Dial-Up Networks
Dial-up networking performs extremely poorly by modern standards due to the limitations of traditional modem technology. The very first modems (created in the 1950s and 1960s) operated at speeds measured as 110 and 300 baud (a unit of analog signal measurement named after Emile Baudot), equivalent to 110-300 bits per second (bps). Modern dial-up modems can only reach a maximum of 56 Kbps (0.056 Mbps) due to technical limitations.
Providers like Earthlink advertise network acceleration technology that claims to significantly improve the performance of dial-up connections using compression and caching techniques. While dial-up accelerators do not increase the maximum limits of the phone line, they can help utilize it more efficiently in some situations. The overall performance of dial-up is barely adequate for reading emails and browsing simple web sites.
Dial-Up vs. DSL
Dial-up and Digital Subscriber Line (DSL) technologies both enable internet access over telephone lines. DSL achieves speeds more than 100 times that of dial-up through its advanced digital signaling technology. DSL also functions at very high signal frequencies that allows a household to use the same phone line for both voice calls and internet service. In contrast, dial-up requires exclusive access to the phone line; when connected to dial-up internet, the household cannot use it to make voice calls.
Dial-up systems utilize special-purpose network protocols like Point-to-Point Protocol (PPP), that later became the basis for the PPP over Ethernet (PPPoE) technology used with DSL.