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Control (LLC) layer and the Media Access Control layer. The MAC layer interfaces directly with the network medium.
Consequently, each different type of network medium requires a different MAC layer.
DMZ – Demilitarized Zone – a computer or small subnetwork that sits between a trusted internal network, such as
a corporate private LAN, and an untrusted external network, such as the public internet.
UDP – User Datagram Protocol – a connectionless protocol that, like TCP, runs on top of IP networks. Provides
very few error recovery services, offering instead a direct way to send and receive datagrams over IP network.
VPN – Virtual Private Network – a network that is constructed by using public wires — usually the Internet — to
connect to a private network, such as a company's internal network.
VRRP – Virtual Router Redundancy Protocol - an election protocol that dynamically assigns responsibility for one
or more virtual router(s) to the VRRP router(s) on a LAN, allowing several routers on a multiaccess link to utilize the
same virtual IP address.
GRE Tunnel – Generic Routing Encapsulation - a tunneling protocol developed by Cisco Systems that can
encapsulate a wide variety of network layerprotocols inside virtual point-to-point links over an Internet Protocol
internetwork.
PPPD – Point to Point Protocol Daemon – it is used to manage network connections between two nodes on Unix-
likeoperating systems. It is configured using command-line arguments and configuration files.
SSH – Secure SHell - a program to log into another computer over a network, to execute commands in a remote
machine, and to move files from one machine to another. It provides strong authentication and secure communications
over insecure channels.
VRRPD – Virtual Router Redundancy Protocol – it is designed to eliminate the single point of failure associated
with statically routed networks by automatically providing failover using multiple LAN paths through alternate routers.
SNMP – Simple Network Management Protocol - a set of protocols for managing complex networks. SNMP works
by sending messages, called protocol data units (PDUs), to different parts of a network.
