Remote Access Protocols
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Serial Line Internet Protocol (SLIP)- A very simple protocol, which transmits signals over a serial line, which generally means a modem and a phone line. SLIP does not provide advanced control functions, like error detection, network layer identification, encryption or any sort of security. It is a very efficient and easy to implement protocol, but it has some limitations that make it almost useless in today’s networking world. As it is so simple, it cannot carry IP addresses of the systems it is in communication with, so they must be preconfigured with the IP addresses of each other computer that will be talking. It also cannot detect errors, nor can it correct them (there is no CRC, etc…), and it also cannot identify network layer protocols, making it impossible to multiplex different network layer protocols over the same connection.

Point to Point Protocol (PPP)- PPP adds only 8 bits to the network layer datagram, but it provides so much more functionality than SLIP that it has pretty much replaced it completely. It can carry/exchange IP addresses, multiplex network layer protocols, and perform authentication with authentication protocol support (using PAP, or Password Authentication Protocol, or CHAP, Challenge Handshake Protocol).

Point to Point Protocol over Ethernet (PPPoE)- This protocol is a manner by which computers on an Ethernet local area network, and remote devices which connect through other services (like DSL or Cable), communicate.

Virtual Private Network (VPN)- A VPN is basically a tunnel through the internet, connecting a computer and a sever remotely and securely.

Point to Point Tunneling Protocol (PPTP)- This is the primary protocol used with VPNs. It functions in conjunction with PPP to create an internet connection, and then establishes a TCP control connection to the server with which the host is connecting. This will be the tunnel that the information travels through. The connection is secured using an authentication protocol, and all of the information in actually included in the IP datagrams being transmitted- this included the PP frames, and whatever else is needed to be sent.