© 2007 Cisco Systems, Inc. All rights reserved.Cisco Public 1 Version 4.0 Communicating over the Network Network Fundamentals – Chapter 2

2 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Objectives  Describe the structure of a network, including the devices and media that are necessary for successful communications.  Explain the function of protocols in network communications.  Explain the advantages of using a layered model to describe network functionality.  Describe the role of each layer in two recognized network models: The TCP/IP model and the OSI model.  Describe the importance of addressing and naming schemes in network communications.

3 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Network Structure  The elements of communication –3 common elements of communication Message source The channel Message destination  A network: the definition –Data or information networks capable of carrying many different types of communications

4 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Network Structure  How messages are communicated? –Data is sent across a network in small “chunks” called segments

5 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Network Structure  The components of a network –Network components Hardware Software

6 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Network Structure  End Devices and their Role in the Network –End devices form interface with human network & communications network –Role of end devices: Client Server Both client and server

7 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Network Structure –Role of an intermediary device Provides connectivity and ensures data flows across network

8 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Network Structure  Network media  Criteria for making a network media choice –Network media – this is the channel over which a message travels

9 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Network Types  Local Area Networks (LANs) –A network serving a home, building or campus is considered a Local Area Network (LAN)

10 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Network Types  Wide Area Networks (WANs) –LANs separated by geographic distance are connected by a network known as a Wide Area Network (WAN)

11 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Network Types  The Internet –The internet is defined as a global mesh of interconnected networks

12 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Network Topology  Star Topology  Ring Topology  Bus Topology  Tree Topology  Mesh Topology  Hybrid Topology 

13 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Network Types  Network representations

14 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Function of Protocol in Network Communication  Protocols –A protocol is a set of predetermined rules –used to facilitate communication over data networks

15 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Function of Protocol in Network Communication  Network protocols –Network protocols are used to allow devices to communicate successfully

16 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Function of Protocol in Network Communication  Protocol suites and industry standardsindustry standards –A standard is a process or protocol that has been endorsed by the networking industry and ratified by a standards organization

17 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Function of Protocol in Network Communication  Protocols and how they interact Protocols  Ethernet  Local Talk  Token Ring  FDDI  ATM 

18 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Function of Protocol in Network Communication  Technology independent Protocols –Many diverse types of devices can communicate using the same sets of protocols –This is because protocols specify network functionality, not the underlying technology to support this functionality

19 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Layers with TCP/IP and OSI Model  Benefits of using a layered model –Benefits include Assists in protocol design Fosters competition Changes in one layer do not affect other layers Provides a common language

20 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Layers with TCP/IP and OSI Model  TCP/IP Model

21 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Layers with TCP/IP and OSI Model  The Communication Process

22 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public LayerDescriptionProtocols Application Defines TCP/IP application protocols and how host programs interface with transport layer services to use the network. HTTP, Telnet, FTP, TFTP, SNMP, DNS, SMTP, X Windows, other application protocols Transport Provides communication session management between host computers. Defines the level of service and status of the connection used when transporting data. TCP, UDP, RTP Internet Packages data into IP datagrams, which contain source and destination address information that is used to forward the datagrams between hosts and across networks. Performs routing of IP datagrams. IP, ICMP, ARP, RARP Network interface Specifies details of how data is physically sent through the network, including how bits are electrically signaled by hardware devices that interface directly with a network medium, such as coaxial cable, optical fiber, or twisted-pair copper wire. Ethernet, Token Ring, FDDI, X.25, Frame Relay, RS-232, v.35

23 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Layers with TCP/IP and OSI Model  Protocol data units (PDU) and encapsulation PDU

24 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Layers with TCP/IP and OSI Model  The process of sending and receiving messages TCP is one of the main protocols in TCP/IP networks. Whereas the IP protocol deals only with packets, TCP enables two hosts to establish a connection and exchange streams of data. TCP guarantees delivery of data and also guarantees that packets will be delivered in the same order in which they were sent.

25 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Layers with TCP/IP and OSI Model  Protocol and reference models –A protocol model provides a model that closely matches the structure of a particular protocol suite –A reference model provides a common reference for maintaining consistency within all types of network protocols and services

26 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Layers with TCP/IP and OSI Model  OSI

27 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public

28 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public  The sending process passes data to the application layer. The application layer attaches an application header and then passes the frame to the presentation layer.  The presentation layer can transform data in various ways, if necessary, such as by translating it and adding a header. It gives the result to the session layer. The presentation layer is not aware of which portion (if any) of the data received from the application layer is the application header and which portion is actually user data, because that information is irrelevant to the presentation layer's role.  The process of adding headers is repeated from layer to layer until the frame reaches the data link layer. There, in addition to a data-link header, a data-link trailer is added. The data-link trailer contains a checksum and padding if needed. This aids in frame synchronization. The frame is passed down to the physical layer, where it is transmitted to the receiving computer.  On the receiving computer, the various headers and the data trailer are stripped off one by one as the frame ascends the layers and finally reaches the receiving process.

29 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Layers with TCP/IP and OSI Model  OSI and TCP/IP model

30 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Addressing and Naming Schemes  Labels in encapsulation headers are used to manage communication in data networks.

31 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Addressing and Naming Schemes  Ethernet MAC Addresses, IP Addresses, and TCP/UDP Port numbers Layer 2 addresses (e.g., Ethernet) are used to move messages to the correct end device. Layer 3 addresses (e.g., IP addresses) are used to move message between different parts of the network and to identify the correct end device. IP addresses have two parts: -the network (e.g., the IP number assigned to google.com) and -the specific computer within that part of the network (e.g., a specific web server or server within the Google network). Layer 4 addresses (e.g., TCP port numbers) are used to move the message to correct Application layer conversation at the end device (e.g., the Web browser or software on your computer). Layer 7 addresses (e.g., a Web URL: are used by the Application layer programs.

32 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Addressing and Naming Schemes  Labels in encapsulation headers are used to manage communication in data networks

33 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Addressing and Naming Schemes  Information in the encapsulation header is used to identify the source and destination processes for data communication

34 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public Summary

35 © 2007 Cisco Systems, Inc. All rights reserved.Cisco Public