Networking 101

Jessica McKellar
jesstess@mit.edu
web.mit.edu/jesstess/
scrubbing-bubbles.mit.edu

MIT owns 1/256 of IP addresses
everything that starts with 18 is MIT address. - class A network

e.g. class B network AAA.BBB.***.***

DNS translates IP addresses to hostnames.


Protocols: 4 Layers

[top]

HTTP(Application Layer)

* use "telnet" command to test

TCP(Transport Layer) - reliably delivers data across the internet

* other transport layers: UDP (no retransmission, unreliable, e.g. streaming video)

IP(Internet Layer) - Internet Protocol. IP handles addressing and routing

* use "traceroute" command to trace the routes from client to host.
* the speed of light is the lower bound on getting information from a distant server

Ethernet(Link Layer) - physical medium

[bottom]


Q. You type google.com into your browser bar and hit enter. What happens?

1. DNS lookup (local DNS -> .com DNS -> google.com DNS -> get IP address)
2. send http request (e.g. GET /), HTTP wrapped by TCP wrapped by IP 
3. open a socket on port 80 and send & receive the wrapped message. (packaging & unpackaging happens many times)


wireshark Demo

wireshark can listen all the wireless waves for you in this room.
* weather game(?) forum.oldweather.org



Governance

Internet Service Providers(ISPs)
Autonomous System (AS), BGP

* lookup "peering agreements" on wikipedia
* Tier 1 AS (means they don't need to talk to anyone, has complete picture of the internet)



Current Events

1. IPv4 address exhaustion (only has 2^32)
IANA released its remaining blocks on 2/3/2011

=> IPv6 address (has 2^128 addresses)
* 4.8*1028 addresses for each of the seven billion people alive in 2011
* still in experimental phase

2. Privacy
coffee shop wireless
=> HTTPS



Net neutrality, Internet Censorship

Oppressive regimes
Great Firewall of China
Tor (lookup!)
SOPA and PIPA