Virtual Private Networks (VPNs) are specifically designed to provide a secure communication channel over an insecure public network like the Internet. VPNs use cryptographic tunneling protocols, such as IPsec or TLS/SSL, to encapsulate and encrypt data packets. This process ensures the confidentiality, integrity, and authenticity of the data in transit, effectively creating a private, secure "tunnel" through the public infrastructure. This directly addresses the requirement of sending data in a secure format.

A. Serial Line Interface Protocol: This is an obsolete data link layer protocol for point-to-point serial connections that provides no security features like encryption or authentication.

B. Point-to-Point Protocol: While it replaced SLIP and includes authentication mechanisms (PAP, CHAP), PPP does not inherently encrypt the data payload, failing to secure the data's content.

C. Browsing: This is a user activity performed with a web browser. While browsing can be secured using protocols like HTTPS, "browsing" itself is not the method that provides security.

1. Kurose

J. F.

& Ross

K. W. (2021). Computer Networking: A Top-Down Approach (8th ed.). Pearson. In Chapter 8

Section 8.6

"Network Layer Security: IPsec and Virtual Private Networks

" the text explains

"A VPN is created by using IPsec to create an encrypted tunnel between two hosts

between two routers

or between a host and a router." (p. 757).

2. Kent

S.

& Seo

K. (2005). Security Architecture for the Internet Protocol. IETF. RFC 4301. Section 1.1

"Introduction

" states that IPsec is designed to provide security services for IP packets

including access control

connectionless integrity

data origin authentication

protection against replays

and confidentiality (encryption). This RFC forms the basis for most modern VPNs. (https://doi.org/10.17487/RFC4301)

3. Simpson

W. (Ed.). (1994). The Point-to-Point Protocol (PPP). IETF. RFC 1661. This document defines the PPP standard. The abstract and subsequent sections detail its function for encapsulating datagrams over serial links and establishing link control

but its security scope is limited to authentication (e.g.

LCP Authentication-Protocol)

not payload encryption. (https://doi.org/10.17487/RFC1661)