© 2007 Cisco Systems, Inc. All rights reserved.Cisco Public 1 Version 4.0 Network Services Networking for Home and Small Businesses – Chapter 6

2 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Objectives  Compare and contrast clients and servers and their interaction over the network.  Describe the type of interactions of Internet applications.  Describe the purpose of a layered model  Illustrate the interaction of various protocols.

3 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Compare and Contrast Clients and Servers  Server - host running a software application that provides information or services to other hosts connected to the network (Example - web server)  Use agreed standards and protocols.  Web browser is a good example of a client.

4 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Compare and Contrast Clients and Servers

5 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Compare and Contrast Clients and Servers

6 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Compare and Contrast Clients and Servers

7 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Compare and Contrast Clients and Servers

8 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Compare and Contrast Clients and Servers

9 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Compare and Contrast Clients and Servers

10 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Compare and Contrast Clients and Servers Activity

11 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Client-Server Protocols  Application, Transport, Internetwork and Network access protocols.

12 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public TCP and UDP Transport Protocols Use TCP if application requires acknowledgment that a message is delivered Similar to sending a registered letter through the postal system Breaks up a message into small pieces known as segments (numbered in sequence and passed to IP process for assembly into packets) Keeps track of the number of segments If the sender does not receive an acknowledgement within a certain period of time, it assumes that the segments were lost and retransmits them. Only the portion of the message that is lost is resent, not the entire message. FTP and HTTP use TCP to ensure delivery of data.

13 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public TCP and UDP Transport Protocols TCP acknowledgment protocol slows down information transfer UDP is a 'best effort' delivery system that does not require acknowledgment of receipt - similar to sending a standard letter through the postal system UDP is preferable with applications such as streaming audio, video and voice over IP (VoIP) application - Internet radio

14 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public  Using TCP or UDP, the protocols and services requested are identified by a port number (a numeric identifier within each segment that is used to keep track of specific conversations and destination services)  The combination of the source and destination IP address and the source and destination port number is known as a socket (used to identify the server and service being requested by the client)

15 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Types of Interactions of Internet Applications  Describe DNS and its purpose.

16 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public WEB Services  Client browser uses IP address and port 80 to request web services - sent to the server using the Hypertext Transfer Protocol (HTTP).  Server receives a port 80 request and sends the web page to the client  HTTP protocol not secure protocol  HTTPS protocol is secure - port 443 –

17 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Types of Interactions of Internet Applications  Describe the interaction between an FTP client and an FTP server.  Requests to begin an FTP session are sent to the server using destination port 21. Once the session is opened, the server will change to port 20 to transfer the data files.

18 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Types of Interactions of Internet Applications  Describe the interaction between clients and e- mail servers.

19 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Types of Interactions of Internet Applications  Describe the interaction between IM / Peer-to-Peer clients and servers.

20 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Types of Interactions of Internet Applications  Describe the interaction between voice clients and servers.

21 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public  Well-known ports 1 to 1023  Registered ports 1024 through  Private ports through 65535, often used as source ports ACTIVITY

22 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Purpose of a Layered Model  Protocols operate as an interdependent stack  Each layer provides and receives services Lower layers concerned with moving data over the network and providing services to the upper layers

23 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Purpose of a Layered Model

24 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Purpose of a Layered Model  Describe protocol operation when sending and receiving a message. Activity

25 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Purpose of a Layered Model  Describe the Open Systems Interconnect Model

26 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public

27 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public The web address is handled by HTTP. HTTP is used by browser software to connect the client to the server that holds the requested website. TCP formats the messages into segments, and reassembles the data into the proper form when it reaches its destination. IP assigns the logical address and encapsulates the packets for routing. The network access protocol puts the packets into frames and physically transmitting the data.

28 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Summary  Clients and servers use protocols and standards for exchanging information.  Client-server services are identified through the use of port numbers.  A protocol stack organizes the protocols in layers, with each layer providing and receiving services from the layers below and above it.  When sending messages, protocols interact from the top layer to the bottom of the stack.  When receiving messages, protocols interact from the bottom layer to the top of the stack.

29 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public