tailieunhanh - MISSION CRITICAL! INTERNET SECURITY phần 6

Layer 2 Tunneling Protocol (L2TP) cung cấp chức năng tương tự như PPTP, nhưng vượt qua một số những hạn chế của các điểm tới điểm Tunneling Protocol. Nó không yêu cầu kết nối IP giữa các máy trạm client và máy chủ như PPTP. | Microsoft RAS and VPN for Windows 2000 Chapter 6 241 Layer 2 Tunneling Protocol L2TP The Layer 2 Tunneling Protocol L2TP provides the same functionality as PPTP but overcomes some of the limitations of the Point to Point Tunneling Protocol. It does not require IP connectivity between the client workstation and the server as PPTP does. L2TP can be used as long as the tunnel medium provides packet-oriented point-to-point connectivity which means it works with such media as Asynchronous Transfer Mode ATM Frame Relay and . L2TP can authenticate the tunnel endpoints and can be used in conjunction with secure ID cards on the client side and with firewalls on the server side. L2TP is an Internet Engineering Task Force IETF standard which was developed in a cooperative effort by Microsoft Cisco Systems Ascend 3Com and other networking industry leaders. It combines features of Cisco s Layer 2 Forwarding L2F protocol with Microsoft s PPTP implementation. L2TP can utilize IPSec to provide end-to-end security see the section on IPSec for more information . Using PPTP with Windows 2000 PPTP is installed with the Routing and Remote Access Service RRAS . It is configured by default for five PPTP ports. You can enable PPTP ports with the Routing and Remote Access wizard. The PPTP ports will be displayed as WAN miniports in the RRAS console as shown in Figure . Figure PPTP ports in the Routing and Remote Access RRAS console. You can view the status of each VPN port and refresh or reset it by double-clicking on the port name to display the status sheet and clicking on the appropriate button. 242 Chapter 6 Microsoft RAS and VPN for Windows 2000 How to Configure a PPTP Device To configure a port device right-click on Ports in the left panel of the console and select Properties. A dialog box similar to Figure is displayed. Figure Configuring the properties of a PPTP port device. Highlight the RRAS device you wish to configure and then click the .