Some pictures for class 1
cs480 spring 2016, NYU CS, Michael Walfish
The Internet is host-oriented and layered
application
transport
application
home laptop
Web server
transport
network
network
link
link
physical
physical
Much of the “intelligence” is implemented on the end-points.
The middle of the network is “dumb” (in principle).
The architecture is layered; each layer plays a different role.
Case study: Web browsing
DNS
home laptop
http://www.twitter.com
<a href=
http://www.nytimes.com/
politics/article.html>
cool story </a>
app
transport
network
Web server
www.nytimes.com?
link
physical
128.34.56.17
128.34.56.17
dst: 128.34.56.17
“GET /politics/article.html”
The browser first turns www.nytimes.com into a network location
Next, the browser forms an HTTP request
Case study: Web browsing
DNS
home laptop
TCP (transmission
control protocol),
UDP, …
app
Web server
transport
network
link
physical
128.34.56.17
dst: 128.34.56.17
1
“GET /po…”
TCP is a transport protocol.
It sequences data, decides when to send, and retransmits lost data
Case study: Web browsing
DNS
home laptop
IP
(Internet Protocol)
app
Web server
transport
network
link
physical
128.34.56.17
src: 2.5.1.12 dst: 128.34.56.17
src, dst 1 “GET /po…”
IP is a network-layer protocol.
Its main job is to get packets delivered to their destinations
Case study: Web browsing
DNS
home laptop
Ethernet, 802.11,
Infiniband, …
app
Web server
transport
network
link
physical
src: 2.5.1.12 dst: 128.34.56.17
src, dst 1 “GET /po…”
Ethernet is a link-layer protocol.
Its main job is to move packets around local networks
128.34.56.17
Case study: Web browsing
DNS
home laptop
app
Web server
transport
network
link
physical
src, dst 1 “GET /po…”
128.34.56.17
Case study: Web browsing
Web server
128.34.56.17
home laptop
Web serving software
app
transport
network
link
physical
2.5.1.12
src, dst 1 “GET /po…”
“GET /politics/article.html”
Case study: Web browsing
Web server
128.34.56.17
home laptop
Web serving software
app
transport
network
link
physical
2.5.1.12
“OK 200 <article text>”
Case study: Web browsing
Web server
128.34.56.17
home laptop
app
transport
network
link
physical
2.5.1.12
“OK <article>”
Case study: Web browsing
Web server
128.34.56.17
home laptop
app
<article>
transport
network
link
physical
2.5.1.12