Telnet does not encrypt anything; that is why it is too insecure to use as a network protocol.
SFTP stand for "Secure File Transfer Protocol" or Secure FTP. It is a program that uses SSH to transfer files. Unlike standard FTP, it encrypts both commands and data, preventing passwords and sensitive information from being transmitted in the clear over the network.
L2TP is a tunneling protocol for an IP network. L2 data is transmitted over the network but has no encryption or authentication abilities. This type of protocol is usually paired with IPSec to provide encryption and authentication.
Network Control Protocol is uses to identify the Network layer protocol used in the packet
TCP is the protocol of network layer, It is connection oriented protocol. UDP is the protocol of network layer, It is connection less protocol.
NTP(Network Time Protocol)
mlma protocol in network
SNMP is the most widely used protocol for network monitoring
Ping uses ICMP, and therefore resides at layer 3 (Network layer)
NTP (Network Time Protocol)
Simple Network Management Protocol (SNMP)
A protocol is a set of rules that are standard for a telecommunications network. These rules will outline procedures and controls that are in place for the network.
Virtual Private Network (VPN)