Internet 101 #2

IP address

Every device connected to the Internet has at least one unique IP address. The IP address has two parts - the network address and the host address. (How you split the IP address into network and host is a bit tricky for humans to do...)

Q: What has more than one IP address?

Notes

Name resolution

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Domain Name Space (DNS)

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Name Lookup

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Root Server Addresses

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Top level domain Country Code

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Top level domain Country Code 2

la -- Laos Currently being marketed as the unofficial domain for Los Angeles[9]
li -- Also used by Long Island
to -- Tonga: Toronto, Tokyo
tv -- Tuvalu: television (the domain is currently operated by dotTV, a VeriSign company; the Tuvalu government owns twenty percent of the company.)

Notes

Protocol: Layering Model 1

Layering is another innovation that was driven by a philosophy of connection.

Without layering, you designed an integrated network from top down. For example, every component of the (original) telephone network was designed for telephony. Every component of a utility network (think electricity, gas...etc) was designed for a specific use in mind.

The internet protocol was designed with a different ideology.

Layering is another innovation that is unique. Before, if you wanted a network, you designed it integrated top down. (Telephone). But once you designed it, you can't use it to carry gas, or water
If something that has depth has a white cloth on it, it is a bed. That is the definition of a bed.
Application sees a bed. It doesn't care.
TCP (remember routers can drop packets. the job of TCP is to keep track)
The most important is the physical layer is separated.
There are many networking device right - ether net, wi-fi, cell phone. if you have anything that transmit data, all you have to do is right code for the physical layer.

Wok

Lets imaging that you snuck in a cell-phone or a sattelite-phone into a remote censured village. Now you connect a USB-wireless device to a Wok and you can send the Internet signal all the way across the village.
It's very easy to connect to the Internet (or very hard to censure) because it can connect to so many thing.

Protocol: Wok as a Physical Layer

Youtube video

Nobody above the physical layer need to know that it is running on a Wok

Notes

iPhone Hotspot

Two physical devices: Cellular & WiFI

Notes

Hyperconnectivity

Easy to connect different devices (again, very resilient).
Devices can be very poor to very high-end. Doesn't matter. (Compare this with the ideology of telephone networks)
No need to change/modify application.
Chrome will work regardless of whether it is on a wireless network or on a wired network.

Use the bed analogy again.
As far as the application is concerned, it sees a bed and sends requests only pertinent to the application. (It does not have to worry about anything about the network whether it is sending something it using WI-FI or ethernet).
And on the other side, it looks as though something meaningful is coming out of the bed.

Protocol

Layering allows for layer to layer communication. From the application's point of view, it only has to think about the application to application communication method.

Communication between web browser and web server:

Using file transfer protocol

Protocol mismatch:

Application does not have to worry about whether it is going through a Wireless network or a wired network
All an application has to do is to worry about how to communicate with other applications. And this is called a protocol
A protocol is a predefined rule on how to communicate with the other end.

ftp, sftp, ssh, http, shttp manually telnet into web server and show 1. how simple the http protocol is. 2. how it has no concern for lower layers (it doesn't care whether it is on the cell network or not)

Making manual HTTP request

telnet www.reed.edu 80
   Trying 134.10.2.252...
   Connected to www.reed.edu.
   Escape character is '^]'.
GET / HTTP/1.1 
HOST: www.reed.edu

try

GET /about_reed/history.html  HTTP/1.1 
HOST: www.reed.edu

type enter twice.
the HTTP protocol specification

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