ZyXEL 35 Guia Do Utilizador

 

 

All contents copyright (c) 2006 ZyXEL Communications Corporation.   

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There are some reasons to use a VPN. The most common reasons are because of security and cost. 

 

Security 

1). Authentication 

With authentication, VPN receiver can verify the source of packets and guarantee the data integrity. 

2). Encryption   

With encryption, VPN guarantees the confidentiality of the original user data. 

 

Cost 

1). Cut long distance phone charges 

Because users typically dial the their local ISP for VPN, thus, long distance phone charge is reduced than 

making a long direct connection to the remote office.   

2).Reducing number of access lines   

Many companies pay monthly charges for two types access lines: (1) high-speed links for their Internet 

access and (2) frame relay, ISDN Primary Rate Interface or T1 lines to carry data. A VPN may allow a 

company to carry the data traffic over its Internet access lines, thus reducing the need for some installed 

lines. 

 

 

There are currently three major tunneling protocols for VPNs. They are Point-to-Point Tunneling Protocol 

(PPTP), Layer 2 Tunneling Protocol (L2TP) and Internet Protocol Security (IPSec). 

 

 

PPTP is a tunneling protocol defined by the PPTP forum that allows PPP packets to be encapsulated 

within Internet Protocol (IP) packets and forwarded over any IP network, including the Internet itself. The 

PPTP is supported in Windows NT and Windows 98 already. For Windows 95, it needs to be upgraded by 

the Dial-Up Networking 1.2 upgrade. 

 

Layer Two Tunneling Protocol (L2TP) is an extension of the Point-to-Point Tunneling Protocol (PPTP) 

used by an Internet service provider (ISP) to enable the operation of a virtual private network (VPN) over 

the Internet.