X.25

X.25
is a reliable layer 2 and layer 3 protocol that can scale up to 2 megabits per second (Mbps),
although most installations stop at 56Kbps. The X.25 protocol was intended to provide reliable
data transfer over unreliable circuits. Currently, X.25 is typically used for terminal emulation
and small file transfers. Due to its low bandwidth and high overhead, X.25 is losing favor as a
remote access technology. Originally, it was designed to address the higher error rates that were
experienced on analog circuits. This high degree of overhead makes the protocol very inefficient
but well suited to less-advanced telecommunications infrastructure such as old carrier management
systems.
Designers typically find that X.25 is one of the most widely available technologies on an
international basis. This availability greatly adds to the desirability of the protocol. However,
it is likely that demands for greater bandwidth and the proliferation of fiber-based networks
will continue to erode X.25’s market share. Although a migration to Ethernet has already
begun, it is important to note that many telecommunications carriers continue to use X.25 for
management of their switches and other systems.