Communication Manager 6.2 and earlier used pass-through and relay modes for modem transport. Only the following Avaya gateways support the protocols used for the earlier modem transport modes: G430, G450. These methods did not work well with all modem terminals. V.150.1 Modem-over-IP feature implements modem features according to the V-series industry standard to interoperate with non-Avaya modem equipment, trunk-side and line-side, for end-to-end secure connections over IP. V.150.1 specifies a protocol for transport of end-to-end modem signals, for devices designed to transport V-series modem signals across an IP network. This feature provides a connection path between two modems such that the modem signals are fully terminated in the gateway.