COP 4600 Operating Systems Fall 2010

Dan C. Marinescu

Office: HEC 439 B

Office hours: Tu-Th 3:30-4:30 PM

Last time: Soft modularity

Procedure call conventions and the memory map; the stack; Errors Strongly-typed languages help enforce modularity.

Today: Problem solving – problem 2.2 Enforced modularity; message passing and the client-server model.

Example of a client –server system: WWW Client-server organization

Next time: Heterogeneity; little-endian and big-endian representation Timing, response time. Trusted intermediaries Case study the X11 system.

Peer-to-peer systems Remote Procedure Calls Domain Name Service (DNS)

Lecture 11 – Tuesday September 29, 2010

Lecture 11 2

3

D ata

S erver residence tim e.W eb page is created onthe fly

U ser's H TTP request S YN

S YN

A C K

A C K + H TTP request

TC P connectionestab lishm ent

R TT

U ser's H TTP requestfor an im age

S erver residence tim e.Im age is re trived fromdisk

D ata

H TTP request

A C K

A C K

Browser W eb Server

Lecture 11

Lecture 11 4

Threadhandlingan HTTPrequest

W eb Server

H T T P request

R esourceR eposito ry

Loca l cache

Threadhandlingan HTTPrequest

H T T Presponse

W ebBrowser

C lient

P ersisten t/N onP ersistent

H TTPconnection

C lien t

TC Pport

H T T P request

H T T P response

A n H TTP requst con ta ins one o f the fo llow ing m ethods:G E T - ge t a resourceH E A D - verify the link and cond itions o f a resourceP O S T - input to a resource , usua lly a C G I scrip tP U T - s to re a resource a t the serverD E LE TE - de le te a resourceTR AC E - inc lude a ll headers in a response

W eb Cache

S am ple H TTP sta tus code in a response100 - C ontinue200 - O K205 - R eset C onnection301 - M oved P erm anently402 - Paym ent R equried404 - N ot Found405 - M ethod N ot A llowed407 - P roxy A uthentica tion R equ ired415 - U nsupported M ed ia Type500 - In terna l S erver E rro r504 - G ateway T im eout505 - H TTP version N ot S upported