|
Home
Reading assignments
Programming Assignments
Resources
Syllabus
Slide Sets
Final Project Ideas
Updates
 |
|
Layers
Physical
Intenet protocol
connection
application
physical/media
Ethernet, modem, isdn, typical
physical addressing
packet limits
throughput vs. latency
availability
What is the internet protocol
packet transmission
unreliable delivery
fragmentation
addressing for distributed routing
network of networks
UDP
TCP -- the connection layer
Built on UDP
Establish connections / close connections
control throughput and demand
recover from errors
guarantee sequence of delivery
port numbers and services
TCP connection lifetime
Establishment
data exchange
teardown
In-band and out of band data.
programmer view: looks like a file + a litte asynchrony
setup process
are you there and willing to connect?
Yes, I am...
OK, let's start talking...
teardown process
I want to stop, and won't send more data, are you ready to stop?
Yes, I'm ready to stop, let's do it.
OK, I'm hanging up now
This can't always work
The two armies
two small armies want to attack the valley
The valley army can only be beaten if they attack at the same time
messengers must go through the valley, and thus can't necessarily get through.
No matter how many you send, you can't be sure to win
Naming on the internet
DNS is a thing of beauty
Root servers keep track of who owns chunks of the namespace
They delegate requests to others
Each piece of information has a lifetime, so it can be cached
responsibility for resolution is very widely distributed
It's mostly quite fast
This decouples structure of names from routing structure of network, as IP addresses decouple from physical structure
HTTP as an application protocol
lightness and speed
For who?
for the programmer
open a socket, ask a question, get an answer, close the socket
How many packets?
How much latency?
Proxy servers retransmit requests and data, and process them
clients want to cache data
character sets need to be represented
This is how http 1.1 got to be so huge
|