Tomorrow morning will be my exam for Computer Networking(A Top-Down Approach).

I coded lots of applications related with netwroking, whatever for small embedded server or large-scale high concurrency server, whatever TCP based or UDP based, including but not limited to ICMP, HTTP, FTP, SMTP, RTSP, RTP, SIP protocols.

I was so sure about this course once, but after attended this course then I found out that this is really different than what I thought, especially when I got the exercise materials. Because what I did is only the TOP rather than TOP-DOWN, although I don’t think I gonna get into the DOWN level in the furture(This is at least I’m thinking now). And what I’m familiar with is network programming, theoretical stuffs? Oops, no!

So I have to do more for passing this course.

There will be 5 big problems I need to get deep into, and here are the list, just for memo:

1. 距离适量(DV)路由选择算法（P144）

网络拓扑与边的当前代价如下图所示，节点E与A、B、D相邻。经过实测节点E到A、B、D的代价分别为1、8、2，节点E从A、B、D分别接收到的距离矢量如右下图所示，使用距离矢量（DV）算法，计算出节点E更新之后的路由表（表的结构是： 目标节点、下一跳、代价估计），并给出计算过程。

	来自目标	A	B	D
	A	0	6	3
	B	6	0	3
	C	5	1	2
	D	3	3	0
	E	1	8	2

2. 信道利用率(channel utilization)计算（P242）

2个端系统A和B通过10Mb/s的信道连接到一起，在2个端系统之间的传播延迟是2ms，A和B之间传输的分组总长为8000Bits。

1．如果采用停止等待协议(stop and wait protocol)，信道的利用率是多少？

如果采用管道协议(pipeline protocol ),为了能够时信道的利用率达到100%，发送窗口的尺寸最少应该是多少？

3. CRC计算，包括源端编码和目标端解码

4. CDMA原理及其计算

5. 安全电子邮件的过程（报文摘要、源端、目标端过程）