networked applications
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Networked Applications. Chapter 11 Updated January 2009 Raymond Panko’s Business Data Networks and Telecommunications, 7th edition May only be used by adopters of the book . Client Program. Server Program. Client/Server Computing. The client does at least some of the work. Client PC. - PowerPoint PPT PresentationTRANSCRIPT
© 2009 Pearson Education, Inc. Publishing as Prentice Hall
Networked Applications
Chapter 11Updated January 2009
Raymond Panko’sBusiness Data Networks and Telecommunications, 7th edition
May only be used by adopters of the book
© 2009 Pearson Education, Inc. Publishing as Prentice Hall11-2
Client/Server Computing
• The client does at least some of the work
ServerClient PC
Client ProgramServer Program
© 2009 Pearson Education, Inc. Publishing as Prentice Hall11-3
11-2: Client/Server Computing
File Server
Client PC
Use larger server as number of clients increases
Client/Server Processing with Request-Response Cycle
Client Program Server Program
Request Message
Response Message
Does Light I/O andPost-DownloadProcessing
Does HeavyDatabase
and Other HeavyProcessing
3
© 2009 Pearson Education, Inc. Publishing as Prentice Hall11-4
11-3: Web-Enabled Application
E-Mail Server
Client PC
Client is Browser Server Program
HTTP Request Message
HTTP Response Message
Web-enabled applications:Form of client server processing
that uses browsers as clients.Almost all client PCsnow have browsers.
No need to install new software.
© 2009 Pearson Education, Inc. Publishing as Prentice Hall
© 2009 Pearson Education, Inc. Publishing as Prentice Hall11-6
Each e-mail user has a mail server.The sender transmits a message to its mail server.
The sender’s mail server delivers the messageto the receiver’s mail server.
The receiver’s mail server delivers the messageto the receiver.
The E-Mail Delivery Process
SendingE-MailClient
ReceivingE-MailClient
Sender’s MailServer
Receiver’s MailServer
© 2009 Pearson Education, Inc. Publishing as Prentice Hall11-7
11-5: E-Mail Standards: Sending
2.SMTP
To Send1.SMTP
To Send
SendingE-Mail Client
(Outlook, etc.)
ReceivingE-Mail Client
(Outlook, etc.)
Sender’s MailServer
Receiver’s MailServer
Simple Mail Transfer Protocol (SMTP) is used to transmit mail
in real time to a user’s mail server or between mail servers
Sender-initiated
Note that SMTP provides immediate delivery—usually in a few seconds.
© 2009 Pearson Education, Inc. Publishing as Prentice Hall11-8
11-5: E-Mail Standards: Receiving
Sender’s MailServer
Receiver’s MailServer
3.POP orIMAP
to Receive
POP or IMAP to download mail to receiver when the receiver next
downloads mail
Receiver-initiated
SendingE-Mail Client
(Outlook, etc.)
ReceivingE-Mail Client
(Outlook, etc.)
© 2009 Pearson Education, Inc. Publishing as Prentice Hall11-9
On the left, we have just seen thattraditional e-mail clients send with
SMTP and receive with POP or IMAP.On the right, Web-based e-mail clientsonly need a browser and use HTTP
both to send and to receive.Server-server communication always
uses SMTP.
11-5: E-Mail Standards: Web-Based E-Mail
TraditionalE-Mail Client
(Outlook, etc.)
Web-BasedE-MailClient
Browser
SMTP
POP orIMAP
HTTP
SMTP
© 2009 Pearson Education, Inc. Publishing as Prentice Hall
HTML and HTTP
© 2009 Pearson Education, Inc. Publishing as Prentice Hall11-11
11-7: HTML and HTTP
The Hypertext Transfer Protocol (HTTP)is the standard for transferring messages between
the client (browser) and the server (webserver).
The Hypertext Markup Language (HTML)is a standard for text documents that have tags to indicate
formatting and other files to be downloaded
© 2009 Pearson Education, Inc. Publishing as Prentice Hall
Peer-to-Peer Computing
© 2009 Pearson Education, Inc. Publishing as Prentice Hall11-13
11-15: Traditional Client/Server Application
Client PC Client PC Client PC Client PCClient PC
Server Does Heavy Processing Work
Disadvantages:Network Overload at Server
Underused Client PowerCentral Control
Advantage:Central Control
© 2009 Pearson Education, Inc. Publishing as Prentice Hall11-14
P2P Applications
• Direct service, although most P2P systems use facilitating servers for some of the work
Peer Peer
Peer
PeerPeer
Peer
© 2009 Pearson Education, Inc. Publishing as Prentice Hall11-15
Figure 11-16: Simple Peer-to-Peer (P2P) Application
Client PC Client PC
Request
Response
Benefits:End User Freedom
No Network Bottleneck at ServerUses Client Capacity Better
Problems:Transient Presence of ClientsTransient Client IP AddressesSecurity (No Central Control)