Secure Network Protocols

SSH - Secure SHell
used to execute remote shell commands over a secure network
replacement for rsh (remote shell) protocol
http://en.wikipedia.org/wiki/Secure_Shell
SSH Communications Security (now Tectia) is a Finnish company that developed the Secure Shell protocol.

SCP - Secure CoPy
http://en.wikipedia.org/wiki/Secure_copy
uses SSH, used to securely transfer files between a local and a remote host
replacement for rcp, which stands for remote copy command in Unix
command-line arguments are based on the cp command to copy files locally

SFTP - Ssh File Transfer Protocol
http://en.wikipedia.org/wiki/SSH_file_transfer_protocol
extension of SSH2 to provide secure file transfers
not to be confused with FTPS which is FTP over SSL
http://en.wikipedia.org/wiki/FTPS

More to read
http://en.wikipedia.org/wiki/Portal:Cryptography

TLS/SSL
http://en.wikipedia.org/wiki/Transport_Layer_Security

TCP
http://en.wikipedia.org/wiki/Transmission_Control_Protocol

UDP
http://en.wikipedia.org/wiki/User_Datagram_Protocol

Packet analyzer
http://en.wikipedia.org/wiki/Packet_analyzer