tailieunhanh - Building Secure Wireless Networks with 802.11 phần 8

hình điểm truy cập mạng LAN không dây (AP) là thiết bị mạng LAN không dây mà làm cho phần trung tâm của một mạng LAN không dây hoạt động ở chế độ cơ sở hạ tầng. Tất cả các lưu lượng truy cập LAN trong một mạng LAN không dây hoạt động ở chế độ cơ sở hạ tầng phải đi qua một điểm truy cập | http . Data Privacy through Encryption VPN gateways use cryptographic encryption algorithms and protocols to provide data security. The most commonly used protocol is known as Internet Protocol Security IPSec and the most commonly used encryption algorithm is known as Triple-Digital Encryption Standard Triple-DES or 3-DES . Dynamic Host Configuration Protocol DHCP and Network Address Translation NAT Services VPN gateways act as a Dynamic Host Configuration Protocol DHCP server and assign each VPN peer a client or another gateway a unique IP address that does not belong to the protected LAN. When data is received from the VPN peer for the protected LAN or from the protected LAN for the VPN peer VPN gateway performs the translation of the addresses and transmits the data to the intended party. For example let s assume that upon successful authentication a VPN gateway assigns an IP address to a VPN peer and the LAN that the VPN gateway was protecting uses 100 IP addresses from to . In this case the VPN gateway may create an entry in a table called a network address table that consists of two IP addresses one that was assigned to the VPN peer and the other an unused IP address from the protected LAN. This entry could look like the one shown in Table . Table A Sample Network Address Table with One Entry PEER IP ADDRESS LAN IP ADDRESS When the VPN gateway receives data from the VPN peer it performs a network address table lookup and an address translation substitutes the address in the data packet from to so that the data packet can be recognized and properly delivered in the protected LAN. The VPN gateway performs a reverse translation when data originate from a protected LAN intended for the VPN peer. This translation of the IP address is known as Network Address Translation NAT . VPN gateways authenticate users provide data privacy and act as .