Chapter 2 Flashcards
What is a network application?
-The software packages that run in the applicationlayer.
What is an application architecture?
-The way in which the functions of the application layer software are spread among the clients and servers in the network.
What are the four general functions of the work done by an application program?
- Data storage
- data access logic
- application logic
- presentation logic
Describe data storage.
-programs require data to be stored and retrieved.
Describe data access logic.
-the processing required to access data such as database queries(SQL)
Describe application logic.
-business logic, simple or complex depending on the application
Presentation logic.
-the presentation of information to the user and the acceptance of the user’s commands.
What are the four fundamental application architectures?
- host-based architectures
- client-based architectures
- client-server architectures
- peer-to-peer architectures.
Describe host-based architecture.
-A server or large mainframe performs all four functions.
What are two problems with host based architectures?
- server must process all messages. Server can become overloaded.
- can’t prioritize, slow response time.
- lumpy upgrades
Describe client based architecture.
- client and server are both personal computers.
- client responsible for presentation, application, and data access logic.
- server responsible for data storage
What is a drawback to the client based architecture?
- all data on server must transfer to client for processing.
- can overload network circuits.
Describe client-server architectures.
- balance the processing between the client and the server by having both do some of the logic.
- client responsible for presentation logic
- server responsible for data access logic and data storage.
- application logic can reside on both or be split between both.
What is a strength and disadvantage of the client-server architecture?
-software and hardware from different vendors can be used but it’s hard to get them to work together and you need middleware.
What is middleware?
-software that sits between the application software on the client and the application software on the server.
What two things does middleware do?
- provides standard way of communicating that can translate between software from different vendors.
- manage message transfer from clients to servers
Describe a two-tier architecture?
-only uses one set of clients and one set of servers.
Describe a three-tier architecture
- uses three sets of computers.
- Client: presentation logic.
- server: application logic
- server: data access logic and data storage.
Describe a n-tier architecture
- client responsible for presentation logic.
- database server responsible for data access logic and data storage.
- application logic is spread across two or more different sets of servers.
What is an advantage of an n-tier architecture?
- separates processing that occurs to better balance the load on the different servers.
- is more scalable.
What are the disadvantages to an n-tier architecture?
- puts a greater load on the network.
- much more difficult to program and test software.
Describe a thin-client.
-little or no application on the client.
Describe a thick-client.
-places all or almost all of the application logic on the client.
Describe the distributed computing model.
-application systems use web browser as client software with java javascriptor AJAX downloaded as needed.
Describe a peer-to-peer architecture.
- all computers act as both a client and a server.
- all clients perform all four function
What is scalability?
-the ability to increase or decrease the capacity of the servers to meet changing needs.
Describe the benefits of the client-server architecture.
- more scalable
- more reliable
- the cheapest.
- enables cloud computing
What is server virtualization?
- the opposite of scaling.
- install many virtual or logical servers on the same physical computer.
What is green computing?
-environmentally sustainable computing.
What is HTTP?
-the standard protocol for communication between a web broser and a web server.
What is a HTTP request?
-special packet that contains URL and other information
What is an HTTP response?
-response or error message from server.
What are the three parts of an HTTP request?
- request line: starts with command “get”, provides web page, ends with HTTP version number.
- request header: variety of option info(browser used and date)
- request body(info user has typed)
What are the three parts of the HTTP response?
- response status: http version number and status code
- response header: web server, date, and exact URL
- response body: web page
Describe SMTP
- Simple Mail transfer protocol: most commonly used email standard
- implemented as a two-tier thick client-server application.
Describe a two-tier email architecture.
- each client computer runs an application layer software package called a mail user agent(email client)
- user agent sends SMTP packet to a mail server running a mail transfer agent software packet.
- covers transmission between mail servers.
What do POP and IMAP do?
-get mail between receiver’s email client and his or her mail server.
Describe POP.
-before email can be read, must be copied to clients hard disk and deleted from server.
Describe IMAP.
-email messages can remain stored on the mail server after they are read.
Describe a three-tier thin client-server email architecture.
- uses web server and web browser to provide access to your email.(web-based email).
- browser sends form information inside http request.
- server takes http request, builds SMTP packet, sends HTTP response back to client, sends SMTP packet to mail server
- mail server processes SMTP packet as though it came from a client computer.
Describe an SMTP packet.
-heasder: source and destination email address, date, subject
-body: word DATA followed by the message.
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What does MIME software do?
- Multipurpose Internet Mail Extension.
- takes nontext files and translates each byte into a special code that looks like regular text.
Describe telnet.
- enables users to log in to servers.
- uses account name and password of an authorized user to log in.
- keystrokes sent over in plain text.
What is videoconferencing?
-provides real-time transmission of video and audio signals to enable people in two or more locations to have a meeting.
What is webacsting
-one-directional videoconferencing.
