In the late 1970s and into the early 1990s, the WAN technology joining the end sites was typically using the X.25 protocol. Now considered a legacy protocol, X.25 was a very popular packet switching technology because it provided a very reliable connection over unreliable cabling infrastructures. It did so by including additional error control and flow control.
X.25 is a legacy Network layer protocol that provides subscribers with a network address. Virtual circuits can be established through the network with call request packets to the target address. The resulting SVC is identified by a channel number. Data packets labeled with the channel number are delivered to the corresponding address. Multiple channels can be active on a single connection.
Typical X.25 applications are point-of-sale card readers. These readers use X.25 in dialup mode to validate transactions on a central computer. For these applications, the low bandwidth and high latency are not a concern, and the low cost makes X.25 affordable.
X.25 link speeds vary from 2400 b/s up to 2 Mb/s. However, public networks are usually low capacity with speeds rarely exceeding above 64 kb/s.
X.25 networks are now in dramatic decline being replaced by newer Layer 2 technologies such as Frame Relay, ATM, and ADSL. However, they are still in use in many portions of the developing world, where there is limited access to newer technologies.
X.25 is a legacy Network layer protocol that provides subscribers with a network address. Virtual circuits can be established through the network with call request packets to the target address. The resulting SVC is identified by a channel number. Data packets labeled with the channel number are delivered to the corresponding address. Multiple channels can be active on a single connection.
Typical X.25 applications are point-of-sale card readers. These readers use X.25 in dialup mode to validate transactions on a central computer. For these applications, the low bandwidth and high latency are not a concern, and the low cost makes X.25 affordable.
X.25 link speeds vary from 2400 b/s up to 2 Mb/s. However, public networks are usually low capacity with speeds rarely exceeding above 64 kb/s.
X.25 networks are now in dramatic decline being replaced by newer Layer 2 technologies such as Frame Relay, ATM, and ADSL. However, they are still in use in many portions of the developing world, where there is limited access to newer technologies.
However, these additional features added overhead to the protocol. Its major application was for processing credit card authorization and for automatic teller machines.