单项选择题
A. application
B. presentation
C. session
D. transport
E. network
F. data link
G. physical
单项选择题 You have set up an Internet based FTP server, where people can upload and download files. In terms of the OSI model, what is the highest layer used during the FTP sessions.（）
单项选择题 Which of the following layers of the TCP/IP model most closely corresponds to the network layer of the OSI model?（）
多项选择题 Which three of the protocols below belong to the application layer?（）