1. Virtual private networks
Virtual private networks are used by many organizations and individuals for different purposes.
1.1. Site-to-site v*n
Each site is connected to the Internet via a v*n router.
1.2. Point-to-point v*n
Run a v*n server where this server is not blocked from accessing the associated servers.
1.3. Better security
1.4. v*n protocols
PPTP, L2TP/IPSec, Openv*n, SSL, SSH
2. Questions
Q1: State the possible functions of v*ns.
internal meetings/remote desktop connection
Q2: Consider the following two cases:
− Case 1: Peter uses his smart phone to directly access a
website.
− Case 2: Peter uses his smart phone to access the same
website via v*n.
Give three reasons to explain why Case 2 is slower.
reason1: Data encryption is time-consuming
reason2: Not direct access, but indirect access
reason3: The v*n server may be in a far-away place
Q3: In the following site-to-site v*n, a source computer sends an IP datagram to a destination computer.
Source IP: IPx
Destination IP: IPy
Q4: In the following point-to-point v*n, a user’s computer sends an IP datagram to a remote server computer through a v*n server.
When the v*n server sends this IP datagram to the remote server,
what are the following quantities in this datagram:
Source IP: IP2
Destination IP: IP3
3. 总结
重点1：v*n分类上站对站，点对点的类型讨论。
重点2：v*n数据包数据加密，源IP和目标IP不加密等特点以及应用。