Show Lecture.Definitions as a slide show.
CT320 Definitions
Definition: definition
- I’m going to present definitions of several terms.
- Other sources (e.g., the Chicago Manual of Style,
the Associated Press Stylebook, the MLA Handbook, etc.)
will disagree.
- I’m right, they’re wrong.
- More precisely, I’m defining terms as part of technical jargon,
which often disagrees with common usage.
- For example, my wife once informed me that there is
“no such thing as a vegetable”. From her point of view as
a horticulturist, she is correct. However, common usage
disagrees with her.
Definition: host
A host is a thing on a network; anything with an IP address.
My house contains these hosts:
- my library Linux laptop
- my CSU Linux/Windows laptop
- my Android phone
- desktop Linux/Windows system
- NAS
|
- wife’s Windows laptop
- wife’s Android tablet
- wife’s Android phone
- Wi-Fi DD-WRT router
- Wi-Fi DD-WRT repeater
|
- cable modem
- TV
- DVR
- Blu-ray player
- Wi-Fi thermostat
|
Definition: medium
- A medium is a single means of transmitting information, including:
- Cat-5 cable
- cable-tv cable
- fiber-optics
- phone lines
- power lines
- lasers
- short-wave radio
- Wi-Fi
- infrared light (same medium as previous three?)
- sub-space pulses
Singular: “medium”
Plural: “media”
Definition: network
A network is hosts connected by a single medium.
Your laptop and eBay are not on the same network.
┌────────┐ ┌────────┐ ┌─────────┐
│ │ │ │ │ │
│ laptop │···········│ router │··········│ Blu-Ray │
│ │ Wi-Fi │ │ Wi-Fi │ │
└────────┘ └────────┘ └─────────┘
Definition: LAN
- A LAN is a Local Area Network; a small-scale network.
- I have three LANs in my house: wired Ethernet, powerline, and Wi-Fi.
- Ethernet ≠ LAN
- Ethernet ⊂ LAN
Variations on a theme
Definition: internet
What is a (lower-case “i”) internet(work)?
It’s a collection of connected networks.
┌────────┐ ┌────────┐ ┌─────────┐
│ │ │ │ │ │
│ laptop │···········│ router │··············│ printer │
│ │ Wi-Fi │ │ ethernet │ │
└────────┘ └────────┘ └─────────┘
- I have an internet at home:
- Wi-Fi (wireless)
- Ethernet (wired over Cat-5 cable)
- Ethernet over 120VAC powerlines
Definition: Internet
- What is the (upper-case “I”) Internet?
- It’s all the connected networks in the world.
- There are many internets, but only one Internet.
It’s a proper noun, like “The Moon”.
┌────────┐ ┌────────┐ ┌──────┐
│ │ │ │ │ │
│ laptop │···········│ router │··············│ eBay │
│ │ Wi-Fi │ │ Internet │ │
└────────┘ └────────┘ └──────┘
or, more simply:
┌────────┐ ┌──────┐
│ │ │ │
│ laptop │··············│ eBay │
│ │ Internet │ │
└────────┘ └──────┘
Definition: World-Wide-Web
What is the (World-Wide-)Web?
It’s a use of the Internet.
- The Web is built on top of the Internet.
- My personality is built on top of my brain.
Definition: End system
┌────────┐ ┌──────┐
│ laptop │··············│ eBay │
└────────┘ Internet └──────┘
- Consider a web browser, on your laptop, connected to ebay.com.
- The laptop and the web server are both end systems, or hosts.
- End systems can also include printers, surveillance cameras,
cell phones, and generally any device using the network to communicate.
- End systems are located at the network edge and connected to the
network using communication links.
- Routers are not usually considered end systems.
Definition: Client/Server
┌────────┐ ┌──────┐
│ laptop │··············│ eBay │
└────────┘ Internet └──────┘
End systems may be clients, servers, both, or neither.
- Client: a program that requests services:
- web browser requests a page
- email reader requests messages
- scp program requests files
- Dropbox client stores and fetches files
- Server: a program that listens for requests and provides services
- web server, email server, ssh server, printer, etc.
Client vs. server depends on what programs the end system is running.
A given host may be both. Most hosts are DNS clients.