1. What Is Vpnt 3d38i

1. What is VPN? A VPN gives s a secure link to access corporate network over the Internet or other public or private networks without the expense of lease lines. A secure VPN is a combination of tunneling, encryption, authentication, access control and auditing technologies/services used to transport traffic over the Internet or any insecure network that uses the T/IP protocol suite for communication. 2. Why do I need VPN? 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 the source of packets and guarantee the data integrity. 2). Encryption With encryption, VPN guarantees the confidentiality of the original data. Cost 1). Cut long distance phone charges Because s 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 ed 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 one (IPv.6). In addition, IPSec can protect any protocol that runs on top of IP, for instance T, 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 ? 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. Transport mode is mainly for an IP host to protect the data generated locally, while tunnel mode is for security gateway to provide IPSec service for other machines lacking of IPSec capability. In this case, Transport mode only protects the upper-layer protocols of IP payload ( data). Tunneling mode protects the entire IP payload including data. There is no restriction that the IPSec hosts and the security gateway must be separate machines. Both IPSec protocols, AH and ESP, can operate in either transport mode and tunnel mode. 9. What is SA? A Security Association (SA) is a contract between two parties indicating what security parameters, such as keys and algorithms they will use.

10. What is IKE? IKE is short for Internet Key Exchange. Key Management allows you to determine whether to use IKE (ISAKMP) or manual key configuration to set up a VPN. There are two phases in every IKE negotiation- phase 1 (Authentication) and phase 2 (Key Exchange). Phase 1 establishes an IKE SA and phase 2 uses that SA to negotiate SAs for IPSec. 11. What is Pre-Shared Key? A pre-shared key identifies a communicating party during a phase 1 IKE negotiation. It is called 'Pre-shared' because you have to share it with another party before you can communicate with them over a secure connection. 12. What are the differences between IKE and manual key VPN? The only difference between IKE and manual key is how the encryption keys and SPIs are determined. 

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For IKE VPN, the key and SPIs are negotiated from one VPN gateway to the other. Afterward, two VPN gateways use this negotiated keys and SPIs to send packets between two networks. For manual key VPN, the encryption key, authentication key (if needed), and SPIs are predetermined by the when configuring the security association.

IKE is more secure than manual key, because IKE negotiation can generate new keys and SPIs randomly for the VPN connection