None, they communicate to the layer 7, however they do not operate at that layer(application)
email messages can be sent directly from user to user over the internet, whereas word processing software operates offline
The application layer (layer 7) is responsible for file transfer operations.
datalink layer
Network layer
TCP operates at transport layer
Layer 3-7
datalink layar
IGMP
generally layer 4, but SOCKS operates at layer 5, which allows it to work well with applications
TELNET
Layer 7, Aplication
FTP operates in application layer of ISO OSI layered model.