Internet Apps
What are the six things that you can use HTML elements to specify in a web document?
1. denote the structural semantics for text, 2. emphasize text 3. describe the structure of a web page 4. specify that objects be embedded into a web page 5. write embedded programs in a scripting language, 6. specify that a program written in a language be executed and that its output be imbedded into the web page.
What is the structure of a web document?
<!DOCTYPE html> <html> <head> <title>This is a title</title> </head> <body> . . . </body> </html>
What is network application architecture?
A network application architecture is a design that dictates how an application is structured over the various hosts.
What is the difference between a server and a server-class computer?
A server is a computer program that waits passively for communication whereas a server-class computer is a computer with fast CPU, large memories and powerful operating system that is dedicated to running one or more server programs.
What are the characteristics of a server-class computer?
A server-class computer has a large memory, a fast CPU, and a powerful and special operating system.
What is a web browser?
A web browser (commonly referred to as a browser) is a software application that receives HTML documents from an HTTP server or from the local storage and displays the corresponding web pages.
What is a web page?
A web page is a multimedia content that uses a combination of different content forms such as: text, audio, images, animations, video, and interactive content.
What is a web site?
A website, or simply a site, is a collection of related web documents (also called HTML or XHTML documents) and other resources that are published (or held) on at least one computer called web server.
What is an HTML document?
An HTML document is a text file with filename extension .HTML.
What is an internet application?
An internet application consists of two or more programs that run on different hosts and communicate with one another over the network.
Where does a web browser obtain non-textual contents that are inserted into a web page?
Any non-textual content on a web page is retrieved from a file or a database on the web server or is created as the results of running a program.
What are the major challenges of the peer-to-peer network application architecture?
Be ISP friendly: most ISP have been dimensioned for much more downstream than upstream traffic; but most P2P applications shift upstream traffic from servers to residential ISPs, thereby putting significant stress on ISPs Security: P2P applications can be a challenge to secure because of their highly distributed and open nature. Incentives: Their success depends on convincing users to volunteer their resources
What are the two predominant network application architectures used on modern network?
Client-server architecture and peer-to-peer (P2P) architecture
What are the technologies suggested to deal with the server bottleneck problem?
Content caching (Akamai), load balancers, Server virtualization, and Distributed data centers and replication
What are the two key aspects of application protocols, and what does each include?
Data Representation Specifies the following: Syntax of data items that are exchanged Specific form used during transfer Translation of integers, characters, and files sent between computers. Data Transfer Specifies the following: How interactions between a client and the server should be done. The syntax and the semantics of the messages How errors in the transmission should be handled, and How an interaction should be terminated.
Give an example of a HTTP server.
Examples of HTTP servers are: the Apache Tomcat web server, the Sun's Java web server, IBM WebSphere, BEA WebLogic, Macromedia's JRun, Caucho Resin, and Jetty.
A multi-national company can choose to divide its domain name hierarchy in such a way that the company has a domain name server in Europe, one in Asia, and one in North America.
False. The higher-level segment of a domain name depends on the region
Give two examples of internet application with the peer-to-peer application architecture.
File distribution application, file sharing application, and internet telephony.
What is the purpose of each of the protocol standards
HyperText Markup Language (HTML) - A representation standard used to specify the contents and layout of a web page Uniform Resource Locator (URL) - A representation standard that specifies the format and meaning of a web page identifier. Hypertex Transfer Protocol (HTTP) - A transfer protocol that specifies how a browser interacts with a web server to transfer data.
What are the three key protocol standards that are used to specify the data representation and data transfer of the Web?
HyperText Markup Language (HTML,), Uniform Resource Locator (URL), and Hypertex Transfer Protocol (HTTP).
How do you know that a file is a web document?
If its filename extension is .HTML.
What is the difference between a UDP and a TCP communication protocols?
In a UDP communication, processes communicate by sending and/or receiving packets from each other whereas TCP client processes communicate with the server process by using input/output data streams. In a UDP communication, no connection is established between the source process and the destination process whereas a connection must be established between a client process and a server process in a TCP communication. A UDP communication is unreliable whereas a TCP communication is reliable
Give a description of the client-server network application architecture.
In a client-server architecture, there is a server-class computer called server (or server host) that is always on, and one or more standard computers called clients (or client hosts). The server host services requests from client hosts.
Give a description of the peer-to-peer network application architecture
In a peer-to-peer architecture, an application is based on direct communication between pairs of interconnected hosts called peers. Peers are desktops and laptops controlled by users and they communicate without passing through a dedicated server. A peer also makes a portion of its resources, such as processing power, disk storage or network bandwidth, directly available to other network participants, without the need for central coordination by servers
Give an example of internet application that uses the hybrid architecture.
Instant messaging application.
What is a communication port?
It is a number in the range 1-65535 that is used to identify an internet process on the computer on which it is running.
How is an internet process identified on the computer where it is running?
It is identified by its communication port.
Name two programming languages that are used to write programs that will be executed and their output embedded into a web page.
Java, C#
Name two programming language that are used to write programs that are embedded in a web document?
JavaScript, PHP, Python, VB.net
Are HTML elements displayed on web pages?
No
What is the major advantage of the peer-to-peer network application architecture?
P2P architectures are also cost effective: they do not require significant server infrastructure and server bandwidth.
Give two examples of internet applications with the client-server application architecture
Search engines, Internet commerce, and Web-based email.
. What are the two basic communication paradigms used in the Internet?
Stream paradigm and message paradigm.
What two identifiers are used to specify a particular server?
The IP address of the computer on which it runs and its port number.
. What is the overall purpose of the Domain Name System?
The overall purpose of the Domain Name System (DNS) is to provide a service that maps human-readable symbolic names to computer addresses.
When two applications communicate over the Internet, which one is the server?
The server is the application that starts first and awaits contacts
What is the software interface used by internet processes to send and receive data?
The software interface is called socket
What is the server bottleneck problem?
There is a server bottleneck problem when a server host is incapable of keeping up with all the requests from its clients.
How are sockets used by internet processes to send and receive data?
When a process wants to send a message, it loads it on its socket; the protocol transportation software carries the message to the receiving host and once the message arrives at the destination host, it passes through the receiving process's socket which then acts on the message.
How does a browser know whether an HTTP request is syntactically incorrect or whether the referenced item does not exists?
When it receives the status code 400 or 404.
Names three server operating systems.
Windows Server 2016, UNIX Solaris, BSD (Berkeley Software Distribution) UNIX, Ubuntu, and Red Hat.
What is a distributed data center?
With a distributed data centers, multiple data centers are placed in various geographic locations, and when a user enters a request, it is directed to the closest data center
Can a browser use transfer protocols other than HTTP? Explain.
Yes. Because the general form of a URL starts with the name of the protocol used by the browser to access the document
. If a company moves its web server from computer x to computer y, the names of the two computers must change.
Yes. Otherwise, the URL of the server will have to be changed (with machine name y instead of x).
Give a description of each of the following technologies:
a. Content caching. ISPs often have a cache memory that keeps a copy of each static web page after it has been requested for the first time so that any subsequent request of that web page is delivered from the cache memory. b. Distributed caching. Some companies such as Akamai have a set of servers located throughout the Internet, and an organization can contract with one of those companies to preload its caches with content. Visitors to the organization's web site obtain much of the content from that company's nearby cache rather than from the organization's central server. c. Load balancing A load balancer is a device that allows a company to replace a single server with a data center that contains multiple computers, each running an identical copy of a web server. To ensure that all servers return the same answer to a request, the servers use a common, shared database system. The load balancer distributes incoming requests among the physical servers as follows: It examines each incoming HTTP request and sends the request to one of the servers. It remembers recent requests and directs all requests from a given source to the same physical server. d. Server virtualization. With server virtualization, two or more server are run on virtual machines on the same physical computer and if a given physical computer becomes overwhelmed a manager migrates one or more VMs to other physical computers
A web server must have a domain name that begins with www.
alse. www is the name of the server (and it is used by convention)
What types of documents and resources are included in a web site?
graphics files, images files, videos files, PDF documents, and objects that perform complex tasks such as database lookup and web searches
What are the two communication protocols used on the Internet?
the UDP transport protocol and the TCP transport protocol.
What is the name of the organization that maintains the HTML standard?
the World Wide Web Consortium (W3C).