Computer Networks 1 (CSE 231)

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Questions and Answers

What is the purpose of the status code in an HTTP response message?

To indicate the success or failure of a request (correct)

To specify the client's IP address

To specify the HTTP version

To specify the type of request

What does the HTTP status code 404 indicate?

The HTTP version is not supported

The request was bad

The requested document was not found (correct)

The request was successful

What is the default port number used by HTTP servers?

443

8080

80 (correct)

What is the purpose of the 'Host:' header in an HTTP request?

To specify the hostname of the server Signup and view all the answers

What is the format of an HTTP request?

GET /path HTTP/1.1 Signup and view all the answers

What tool can be used to establish a TCP connection to an HTTP server?

ncat Signup and view all the answers

What is the purpose of the 'Location:' header in an HTTP response?

To specify the new location of the requested object Signup and view all the answers

What is the HTTP status code for a bad request?

400 Signup and view all the answers

What is necessary to maintain in HTTP communication between the browser and the web server?

The past history of the state Signup and view all the answers

What is the primary difference between Non-Persistent HTTP and Persistent HTTP connections?

The number of objects sent over a single TCP connection Signup and view all the answers

What happens when an HTTP client initiates a TCP connection to an HTTP server?

The HTTP server accepts the connection and notifies the client Signup and view all the answers

What is the purpose of the HTTP client sending an HTTP request message?

To retrieve an object from the HTTP server Signup and view all the answers

What is the consequence of a server or client crash in HTTP communication?

The views of the state may be inconsistent Signup and view all the answers

How many TCP connections are required to download multiple objects using Non-Persistent HTTP?

Multiple TCP connections Signup and view all the answers

What is the benefit of using Persistent HTTP connections?

Fewer TCP connections Signup and view all the answers

What is the role of the HTTP server in the HTTP communication process?

To receive HTTP request messages Signup and view all the answers

What is the primary role of a client in the HTTP client-server model?

To request, receive, and display Web objects Signup and view all the answers

What is the default port number used by HTTP?

80 Signup and view all the answers

What is the characteristic of HTTP that makes it 'stateless'?

It does not maintain information about past client requests Signup and view all the answers

What is the purpose of the TCP connection in HTTP?

To send HTTP requests to the server Signup and view all the answers

What is the component of a URL that specifies the protocol being used?

Scheme Signup and view all the answers

What is the primary advantage of using HTTP as a stateless protocol?

It reduces the complexity of the server Signup and view all the answers

What is the role of the server in the HTTP client-server model?

To send Web objects in response to client requests Signup and view all the answers

What is the transport protocol used by HTTP?

TCP Signup and view all the answers

Study Notes

HTTP Overview

HTTP is the application-layer protocol of the web
It uses a client-server model
Client: a browser that requests, receives, and displays web objects
Server: a web server that sends objects in response to requests
HTTP uses TCP, typically on port 80
HTTP is "stateless", meaning the server maintains no information about past client requests

Persistent vs Non-Persistent HTTP

Non-persistent HTTP:
- A new TCP connection is opened for each object sent
- At most one object is sent over a TCP connection
- TCP connection is closed after each object is sent
Persistent HTTP:
- A single TCP connection is opened to a server
- Multiple objects can be sent over a single TCP connection
- TCP connection is closed after all objects are sent

Non-Persistent HTTP Example

A user enters a URL: www.someSchool.edu/someDepartment/home.index
The URL contains text and references to 10 jpeg images
The HTTP client initiates a TCP connection to the HTTP server
The HTTP client sends an HTTP request message containing the URL
The HTTP server receives the request message and sends the HTML file

HTTP Response Status Codes

Status code appears in the first line of the server-to-client response message
Sample codes:
- 200 OK: request succeeded, requested object is later in the message
- 301 Moved Permanently: requested object moved, new location specified later in the message
- 400 Bad Request: request message not understood by server
- 404 Not Found: requested document not found on this server
- 505 HTTP Version Not Supported: server does not support the HTTP version used in the request

Trying out HTTP

Use ncat to connect to a web server and send an HTTP request
Example: ncat www.menofia.edu.eg 80
Type in a GET HTTP request, e.g., GET /fee/NewsDetails/142317/en HTTP/1.1
The HTTP server will respond with a response message

Web and HTTP

A web page consists of objects, each of which can be stored on different web servers
An object can be an HTML file, JPEG image, Java applet, audio file, etc.
A web page consists of a base HTML file which includes several referenced objects, each addressable by a URL

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Description

This quiz covers the basics of HTTP protocol, including messages exchanged between HTTP client and server, and the importance of maintaining state in the presence of crashes.

Computer Networks 1 (CSE 231) - HTTP Protocol