一台 IP 机器 Q 有一条通过三个 IP 路由器 R1、R2 和 R3 到另一台 IP 机器 H 的路径。
Q—R1—R2—R3—H H 充当 HTTP 服务器，Q 通过 HTTP 连接到 H 并下载文件。使用会话层加密，DES 作为共享密钥加密协议。考虑以下四个信息：
[I1] The URL of the file downloaded by Q
[I2] The TCP port numbers at Q and H
[I3] The IP addresses of Q and H
[I4] The link layer addresses of Q and H 入侵者仅通过嗅探 R2 可以学习 I1、I2、I3 和 I4 中的哪一个?
(A)只有 I1 和 I2
(B)只有 I1
(C)只有 I2 和 I3
(D)只有 I3 和 I4答案： (C)
解释：
An Intruder can’t learn [I1] through sniffing at R2 because
URLs and Download are functioned at Application layer of OSI Model.
An Intruder can learn [I2] through sniffing at R2 because
Port Numbers are encapsulated in the payload field of IP Datagram.
An Intruder can learn [I3] through sniffing at R2 because IP
Addresses and Routers are functioned at network layer of OSI Model.
An Intruder can’t learn [I4] through sniffing at R2 because
it is related to Data Link Layer of OSI Model.
这个问题的测验