第一章
R1. What is the difference between a host and an end system? List several different types of end
systems. Is a Web server an end system?
没有什么不同。PC、服务器、手机等。Web 服务器是端系统。
R2. The word protocol is often used to describe diplomatic relations. How does Wikipedia
describe diplomatic protocol?
Protocol is commonly described as a set of international courtesy rules. These well-established and
time-honored rules have made it easier for nations and people to live and work together. Part of
protocol has always been the acknowledgment of the hierarchical standing of all present. Protocol rules
are based on the principles of civility. — Dr. P.M. Forni on behalf of the International Association of
Protocol Consultants and Officers.
R3. Why are standards important for protocols?
协议如果没有标准就无法创建一个可以互动的网络系统
R4. List six access technologies. Classify each one as home access, enterprise access, or wide
area wireless access.
住宅接入：DSL、电缆、FTTH、卫星、拨号接入、以太网、WiFi 等
公司接入：以太网、WiFi 等
广域无线接入：3G、4G、LTE 等
R5. Is HFC transmission rate dedicated or shared among users? Are collisions possible in a
downstream HFC channel? Why or why not?
HFC 是用户间共享的。在下行 HFC 信道中，所有的数据包都是从一个来源发出的，即头端，因此
没有碰撞
R6. List the available residential access technologies in your city. For each type of access,
provide the advertised downstream rate, upstream rate, and monthly price.
DSL、电缆、FTTH、拨号接入、以太网、WiFi 等
电信的光纤到户：
R7. What is the transmission rate of Ethernet LANs?
从 10Mbps，100Mbps，1Gbps 到 10Gbps
R8. What are some of the physical media that Ethernet can run over?
双绞铜线，光纤
R9. Dial-up modems, HFC, DSL and FTTH are all used for residential access. For each of these
access technologies, provide a range of transmission rates and comment on whether the
transmission rate is shared or dedicated.
拨号调制解调器：最高速度为 56 Kbps，专用的
HFC：高达 42.8 Mbps 下行速率和高达 30.7 Mbps 的上行速率，共享的
DSL：最高 24 Mbps 下行速率和最高 2.5 Mbps 上行速率，专用的
FTTH: 最高 4Mbps 上行，100Mbps 下行速率，专用的
R10. Describe the most popular wireless Internet access technologies today. Compare and
contrast them
WiFi 和 4G。
WIFI 是短距离的高速无线网络传输，可不用手机卡。它的使用有一定的距离范围，比如距离发射
地点不能超过几十米等，距离过远信号就会不稳，甚至连接不上。
4G 可以认为是远距离的高速网络，它是 2G、3G 后的新一代产物，但手机必须插上手机卡(此卡
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