The Internet $\ne$$\ne$!=\neq The Web
互联网 $\ne$$\ne$!=\neq 万维网

What is not part of the World Wide Web?
什么不属于万维网？

• Any program or service that needs to be connected to the internet to run, but does not use http (80) or https (443), e.g. https://en.wikipedia.org/wiki/List of TCP and UDP_port numbers
  任何需要连接互联网才能运行但不使用 http（80）或 https（443）的程序或服务，例如 https://en.wikipedia.org/wiki/List of TCP and UDP_port numbers
• Distinguishing the two is becoming more difficult with the rise of XML and service-oriented architecture (SOA).
  随着 XML 和面向服务架构（SOA）的兴起，区分这两者变得越来越困难。
• Examples  示例
• Spotify
• some multiplayer online games, e.g. Doom, Halo
  一些多人在线游戏，例如《毁灭战士》，《光环》
• some utility programs, typically Unix/Linux based, e.g. secure shell, secure copy, network time protocol
  一些实用程序，通常基于 Unix/Linux，例如安全外壳、安全复制、网络时间协议
• some Apple and Microsoft utilities, e.g. Apple Remote Desktop, Microsoft Sharepoint.
  一些苹果和微软的工具，例如苹果远程桌面，微软 Sharepoint。

IP Addresses and the DNS
IP 地址和 DNS

IP Addresses  IP 地址

• Every device connected to the Internet has a unique identifier called its IP address,
  每个连接到互联网的设备都有一个唯一的标识符，称为 IP 地址。
• e.g. 129.97.208.24 (IPv4),
  例如 129.97.208.24 (IPv4)，
• e.g. fe29::1725:c216:85fc:100d (IPv6).
  例如 fe29::1725:c216:85fc:100d (IPv6)。
• The world is running out of IPv4 addresses.
  世界上 IPv4 地址正在减少。
• Problem: Numbers are difficult to remember.
  问题：数字难以记忆。
• The domain name is the English-like name (i.e. using the English alphabet) that corresponds to the IP address: e.g. uwaterloo.ca
  域名是与 IP 地址对应的类似英语的名称（即使用英文字母）：例如 uwaterloo.ca
• You need to register (and pay) to get a domain name (e.g. https://www.cira.ca/.
  您需要注册（并支付）才能获得域名（例如：https://www.cira.ca/）。
• The Domain Name System (DNS) translates domain names into IP addresses.
  域名系统（DNS）将域名转换为 IP 地址。

IP Addresses and the DNS
IP 地址和 DNS

1. Your computer sends the domain name to a DNS server.
   您的计算机将域名发送到 DNS 服务器。
2. The DNS server responds with the IP address.
   DNS 服务器返回 IP 地址。
3. The pair is stored in a DNS cache on your computer.
   该对被存储在您计算机上的 DNS 缓存中。
4. To see what is in your DNS cache type ipconfig /displaydns
   要查看您的 DNS 缓存中的内容，请输入 ipconfig /displaydns。

IP Addresses and the DNS
IP 地址和 DNS

Internet Services  互联网服务

Voice Over IP (VoIP)
网络电话（VoIP）

• Voice over IP is a way of making telephone calls using the internet, as opposed to using the telephone system.
  网络电话是一种通过互联网拨打电话的方式，而不是使用电话系统。
• e.g. Skype  例如 Skype
• Can use your computer (if it has speakers and a microphone) or buy a VoIP telephone.
  可以使用您的计算机（如果它有扬声器和麦克风）或购买一部 VoIP 电话。
• Used as a way of cutting down communication costs.
  用作降低通信成本的一种方式。

Internet Services  互联网服务

Voice Over IP (VoIP)
网络电话（VoIP）

• Sound is digitized (sampled 8,000 times per second), broken up into packets, transported through the internet via IP, then reassembled at the other end.
  声音被数字化（每秒采样 8,000 次），分成数据包，通过互联网以 IP 传输，然后在另一端重新组装。
  

  

Internet Services  互联网服务

VPN Motivation  VPN 动机

• Goal: provide the ability to work remotely and securely access files, e-mails and business data from your company’s internal network.
  目标：提供远程工作能力，并安全访问公司内部网络中的文件、电子邮件和业务数据。
• Challenge: the Internet is not safe!
  挑战：互联网并不安全！
• Malicious people can intercept IP traffic (called packet sniffing).
  恶意人士可以拦截 IP 流量（称为数据包嗅探）。
• We need a way of securing data when using a public network.
  我们需要一种在使用公共网络时保护数据的方法。
• Idea: create a virtual private network (VPN).
  想法：创建一个虚拟私人网络（VPN）。

Internet Services  互联网服务

VPN  虚拟私人网络 (VPN)

• A virtual private network (VPN) is a computer network that provides secure access using a public infrastructure such as the Internet.
  虚拟私人网络 (VPN) 是一种计算机网络，通过公共基础设施（如互联网）提供安全访问。
• Avoid the need for many leased lines that individually connect remote offices (or remote users) to a private intranet.
  避免需要多条租用线路单独连接远程办公室（或远程用户）到私有内联网。
• VPN creates a secure virtual tunnel to transport the data.
  VPN 创建一个安全的虚拟隧道来传输数据。
• The original packet is encrypted (transformed into something unreadable) before being transmitted through the public network and then decrypted (transformed back) after reaching its destination.
  原始数据包在通过公共网络传输之前被加密（转变为不可读的形式），到达目的地后再被解密（转变回原来的形式）。

Radio Frequency Identification (RFID)
无线射频识别（RFID）

What is it?  这是什么？

Radio waves  无线电波

• Similar to a bar code, i.e. the tag stores a unique number that identifies an item (or type of item).
  类似于条形码，即标签存储一个唯一的号码，用于识别一个物品（或物品类型）。
• When the tag is placed close to an RFID reader, the identifier is read off of the tag and sent to a computer.
  当标签靠近 RFID 读取器时，标识符会从标签中读取并发送到计算机。
• Do not need line-of-sight (like the grocery store check out), the reader just has to be close to the tag.
  不需要视线接触（像超市结账一样），读取器只需靠近标签即可。
• An RFID reader powers the tag just like a wireless phone charger does a phone.
  RFID 阅读器为标签供电，就像无线手机充电器为手机充电一样。

Radio Frequency Identification (RFID)
无线射频识别（RFID）

Types and Uses of RFIDs
RFID 的类型和用途

• RFID tags come in many sizes and shapes but are generally fairly small and flat.
  RFID 标签有多种大小和形状，但通常相对较小且扁平。
• There are two types
  有两种类型
• passive: cost a few pennies, don’t need a battery, can only be read from within a few feet,
  被动式：花费几分钱，不需要电池，只能在几英尺内读取，
• active: cost a few dollars, need a battery, can be read from over 30 metres / 100 feet away.
  主动式：花费几美元，需要电池，可以在超过 30 米/100 英尺的距离内读取。
• Great for inventory management: How many xyz’s do we have in inventory and where are they?
  非常适合库存管理：我们在库存中有多少个 xyz，在哪里？
• Similar to tracking a package with Canada Post/UPS/Fedex.
  类似于使用加拿大邮政/UPS/Fedex 跟踪包裹。