This Recommendation specifies the operation between two IP network gateways to facilitate the end-to-end connection of V-series DCEs over an IP network. The gateways are specified herein in terms of their functionality, signals and messages and operating procedures. The principal characteristics of these gateways are as follows: a) Support of a mechanism to allow the transparent transport of modem signals end-to-end. B) Support of mechanisms to allow the termination of modem signals at the gateways and the transport of the data between gateways. C) The definition of a transport protocol, which can be used to relay the data between gateways. D) The definition of procedures to allow gateways to transition between Voice-over-Internet Protocol and Modem-over-Internet Protocol operation. This Recommendation includes mandatory requirements, recommendations and options; these are designated by the words "shall," "should," and "may" respectively.