ZyXEL Communications P-334WT Support Notes page 36

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.
3. What are most common VPN protocols?
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).
4. What is PPTP?
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.
5. What is L2TP?
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.
6. What is IPSec?
IPSec is a set of IP extensions developed by IETF (Internet Engineering Task Force) to provide security services compatible with the
existing IP standard (IPv.4) and also the upcoming one (IPv.6). In addition, IPSec can protect any protocol that runs on top of IP, for
instance TCP, UDP, and ICMP. The IPSec provides cryptographic security services. These services allow for authentication, integrity,
access control, and confidentiality. IPSec allows for the information exchanged between remote sites to be encrypted and verified. You can
create encrypted tunnels (VPNs), or just do encryption between computers. Since you have so many options, IPSec is truly the most
extensible and complete network security solution.
7. What secure protocols does IPSec support?
There are two protocols provided by IPSec, they are AH (Authentication Header, protocol number 51) and ESP (Encapsulated Security
Payload, protocol number 50).
8. What are the differences between 'Transport mode' and 'Tunnel mode?
The IPSec protocols (AH and ESP) can be used to protect either an entire IP payload or only the upper-layer protocols of an IP payload.