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access the correctly configured access server.　　1.3 Key technologies involved in VPNVPN is a virtual network. Its important significance lies in "virtual" and "dedicated ". In order to transmit private data over the public network, the security of private data must be met. VPN technology is mainly reflected in two technical points: Tunnel, related tunnel protocols (including PPTP, l2f, L2TP), and data security protocol (IPSec ). The following describ

IETF by member companies of the PPTP forum, including Microsoft, Ascend,3com, and ECI, in June 1996. You can see the online copy of the draft at the following site http://www.ietf.org http://www.ietf.org. PPTP maintains a tunnel using a TCP connection and uses Universal Routing Encapsulation (GRE) technology to encapsulate data into a PPP data frame for transmission through the tunnel. Load data in the encapsulated PPP frame can be encrypted or compressed. Figure 7 shows how to assemble a PPTP

1 IntroductionFeatures: Developed by the vendor alliance, mainly composed of Microsoft Term: PAC------PPTP Access Concentrator, location and functionality similar to NAs in l2fPNS------PPTP network server, location and functionality similar to the end gateway in l2fPurpose: Forward PPP data to PNS through the Internet. In the tunneling mode, the PAC accepts the customer's call, LCP negotiation, and some necessary verification, then, the PAC and PNS establish a tunnel. PNS performs ppp chap or PA

companies of the PPTP forum, including Microsoft, Ascend,3com, and ECI, in June 1996. You can see the online copy of the draft at the following site http://www.ietf.org http://www.ietf.org. PPTP maintains a tunnel using a TCP connection and uses Universal Routing Encapsulation (GRE) technology to encapsulate data into a PPP data frame for transmission through the tunnel. Load data in the encapsulated PPP frame can be encrypted or compressed. Figure 7 shows how to assemble a PPTP packet before t

protocol of Layer 3 or layer 2nd respectively. The above layers are divided by reference models of Open Systems Interconnection (OSI. The layer-3 tunnel protocol corresponds to the data link layer in the OSI model and uses the token as the data exchange unit. Both PPTP, L2TP, and l2f (layer-3 forwarding) are layer-3 tunnel protocols that encapsulate data in Point-to-Point Protocol (PPP) routers and send data over the interconnected network. The layer

gives the customer the initiative to establish a tunnel, but the customer needs to configure PPTP on its PC. This will increase the user's workload and cause network security risks. In addition, PPTP only works on IP addresses and does not have the function of verifying the tunnel endpoint. It depends on user verification. L2F/L2TP protocol: The L2F (Layer 2 Forwarding) protocol is proposed by Cisco to est

, minimize packet loss and resend. PPTP gives the customer the initiative to establish a tunnel, but the customer needs to configure PPTP on its PC. This will increase the user's workload and cause network security risks. In addition, PPTP only works on IP addresses and does not have the function of verifying the tunnel endpoint. It depends on user verification. L2F/L2TP protocol: The L2F (Layer 2 Forwardin

As we all know, because VPN (Virtual Private Network) transmits private information, VPN users are concerned about data security. Currently, VPN uses four technologies to ensure security. These four technologies are Tunneling, Encryption and Decryption, and Key Management) user and device Authentication technology (Authentication ). 1. Tunneling Technology: The tunneling technology is a basic VPN technology similar to the point-to-point connection technology. It establishes a data channel (Tunne

First, the planSecond, the program interface designIii. Results of operationIv. part of the codepublic class Match{public int id;public int h1f;public int h2f;public int h3f;public int l1f;public int l2f;public int l3f;}public class Dal{Public Match Select (int id){String Strcon = "server=.; Database=pqmatch;integrated Security=true ";SqlConnection con = new SqlConnection (Strcon);String sql = "SELECT * from Match where id=" +ID;SqlCommand comm = new

protocol for transmission of a third-tier network protocol. The third Layer Tunneling protocol mainly includes the GRE (Gre,generic Routing encapsulation,rfc1701) protocol [2] and the IETF IPSec protocol. 3.1.1 Second-tier tunneling protocol The second Layer Tunneling Protocol encapsulates various network protocols into PPP, and then wraps the whole data into the tunneling protocol, and the data packets formed by the Double-layer encapsulation method are transmitted by the second Layer protoc

l1sis line 1 start,l1fis line 1 finish, the rest goes accordingly. bool vec2LinesIntersect ( Vector2 l1s, Vector2 l1f, Vector2 l2s, Vector2 l2f ){Vector2 v1 = l1f - l1s;Vector2 v2 = l2s - l1s;Vector2 v3 = l2f - l1s;Real crossProd1 = v1.crossProduct(v2);Real crossProd2 = v1.crossProduct(v3);if ((crossProd1 > 0 crossProd2 true; } } return false;}

to the remote access server or the local router, which then sends the hidden IPX packets to the network and eventually to the appropriate destination. Protocol method Currently, several VPN protocols have surfaced in the industry, namely L2TP, IPSec and socks 5. Because of the tunneling capabilities, these protocols are the basic modules that are used to establish a VPN link. Some protocol functions are duplicated, and some offer similar but complementary functions. You need to investigate ea

security protocols used to implement a VPN 1. Two-layer protocol {PPTP L2TP l2f} 2. Three layer protocol {GRE IPSec} Classification of VPN 1.VPDN dial-up VPN PPTP L2TP stand-alone---network (user VPN) 2. Private Line VPN Network---Network (Enterprise network VPN) In this blog to achieve a small part of the first to implement a three-layer protocol GRE VPN, in the future of the article will also implement IPSec VPN Configuration tasks: 1. Cre

through the L2TP tunnel. The L2TP protocol combines the advantages of the PPTP protocol and the L2F (Layer 2 Forwarding) protocol and supports multi-channel tunneling, which enables users to access both the Internet and the Enterprise network. Configure L2TP with NetScreen SSG5 Experiment Effect Chart: Experimental purposes: Through the L2TP way dial-up to IDC room SSG5, automatic access to 192.168.24.0/24 network segment IP address, so 192.168

has various advantages, it has not been widely used on the Internet. The reason is that the Protocol is not mature, there are problems with multi-vendor interoperability, MPLS cross-AS or even cross-Area problems, VC Merge (VC merger) needs to be studied. However, at present, MPLS is the best solution to achieve network-based VPN and can implement traffic engineering. In the future, the possibility of adopting MPLS must be explored in the study of IP networks. The router device must consider im

unified transmission of voice, data, and video. VPN Virtual Private Network (VPN) refers to the establishment of a secure Network connection on a non-secure Network. Generally, it provides the following services: verification, encryption, and data integrity. VPN can be divided into leased line VPN and dial-up VPN (also known as VPDN, Virtual Private Dialing Network) according to the access method. According to the protocol type, the second layer tunnel protocol includes the point-to-point tunne

of the stack as "bitwise XOR" and press the result to the top of the stack. 0x84 Iinc Adds a specified value to the specified int type variable. 0x85 I2l Forcibly convert the int value at the top of the stack to a long value and press the result to the top of the stack. 0x86 I2f Forcibly convert the int value of the stack to a float value and press the result to the top of the stack. 0x87 I2d Forcibly convert the int value at the top o

The Cisco IOS naming convention is composed of three parts: the Cisco IOS binary file name. PPPPP = platform FFFF = feature MM = runtime memory and compression format. The following figure shows the topic: PPPPP is the platform identifier, which indicates that the ffff of the Cisco7200 series router is a feature of IOS (see the feature set of Cisco IOS ), for example, a in the c7200-ajs56-mz represents the Advanced Peer-to-Peer Networking (APPN) feature, j Represents the enterprise feature, s re

new enhanced security protocol developed on the basis of PPP. It allows remote users to access the enterprise network through direct connection to the Internet or other networks through the ISP. Due to its low performance, the PPTP protocol has been basically eliminated and is no longer used in VPN products. 2. L2TP: Unlike PPTP, it only requires a dedicated L2TP tunnel for point-to-point connection. Combining the advantages of the PPTP protocol and the L2 forwarding

: Point-to-point Channel Protocol (PPTP), and second-tier channel protocol L2TPTo point-to-channel protocol PPTP, the English full name is Point–to–point tunneling Protocol. is a new technology to support multi-protocol virtual private network, which can enable remote users to access the enterprise network securely through the Internet. This is the VPN technology used in peacetime. With this protocol, remote users can connect to the Internet through any of the network operating systems, and then