Dial-on-demand routing
(also DDR)
Dial-on-demand routing definition
Dial-on-demand routing (DDR) is a networking technique that allows a router to establish a connection only when it is required. The sending router only connects to the receiving router for the transmission, terminating the connection immediately once the data transfer has been completed.
While inherently flexible, DDR connections are also slow. Furthermore, the act of establishing a DDR connection itself can take anywhere from 3 to 20 seconds, which quickly adds up over multiple transfers. On the other hand, DDR connections are also generally cheaper than leasing dedicated lines.
See also: diverse routing, internet routing, metered connection
Dial-on-demand routing uses
Today, dial-on-demand routing setups are typically only used in two situations: To connect to a remote location that is only accessed rarely, and as a backup connection that supplements a dedicated line. In both cases, the DDR sits in the background until there is a need to transfer data.
Dial-on-demand routing is particularly useful when the entity wishing to transfer data must pay for the duration of a connection — for example, if it is using a pay-per-minute plan for its WAN setup. By only establishing connections when strictly necessary, the entity doesn’t have to pay for idle time when no data is being transmitted.