T90NL

The ITU-T recommendation T.90NL, NL stands for Network Layer, specifies the protocols within the link layer and the network layer, for the Group 4 fax service and the Teletex service in ISDN. The recommendation T.90NL represents a transport protocol, which, however, is located in the network layer. The T.90NL corresponds exactly to the transport protocol of the fourth layer according to ISO 8208.