Introduction to Networks PDF

Introduction to Networks Chapter 3: Network Protocols & Communication Part 1 3.1. Rules of Communication 3.2. Network Protocols and Standards © 2008 Cisco Presentati...

Introduction to Networks Chapter 3: Network Protocols & Communication Part 1 3.1. Rules of Communication 3.2. Network Protocols and Standards © 2008 Cisco Presentation_I Cisco Confidential 1  Chapter 3: Objectives After completing this chapter, you will be able to:  Explain how rules are used to facilitate communication.  Explain the role of protocols and standards organizations in facilitating interoperability in network communications.  Explain how devices on a LAN access resources in a small to medium-sized business network. Presentation_I © 2008 Cisco Systems, Inc. All rights Cisco 2  3.1 Rules of Communicati on Presentation_I © 2008 Cisco Systems, Inc. All rights Cisco 3 The Rules What is Communication? RULES OF COMMUNICATION:  An identified sender and receiver  Agreed upon method of communicating (face-to-face, telephone, letter)  Common language and grammar  Speed and timing of delivery  Confirmation or acknowledgment requirements Presentation_I © 2008 Cisco Systems, Inc. All rights Cisco 4 The Rules Message Encoding and Decoding The decoder performs the reverse process to recover the original message. The encoder takes the original message (such as text, images, or audio) and converts it into a signal that can be transmitted over a communication medium. The message must be encoded and decoded to be transmittable in Presentation_I networks © 2008 Cisco Systems, Inc. All rights Cisco 5 The Rules Message Formatting and Encapsulation Example: Personal letter contains the following elements:  Identifier of the recipient’s location  Identifier of the sender’s location  Salutation or greeting  Recipient identifier  Source identifier  The message content  End of message indicator Where is the greeting, the message content, and the end of message indicator? ENCAPSULATED INSIDE THE ENVELOPE Presentation_I © 2008 Cisco Systems, Inc. All rights Cisco 6 Recap Packet switched networks Source Destination … Message … Packets We cannot send an arbitrarily large message over packet switched networks The Rules Message Size An overview of the segmenting process:  The size restrictions of frames require the source host to break a long message into individual pieces (or segments) that meet the minimum and maximum size requirements.  Each segment is encapsulated in a separate frame with the address information and is sent over the network.  At the receiving host, the messages are de- encapsulated and put back together to be processed and interpreted. Presentation_I © 2008 Cisco Systems, Inc. All rights Cisco 8 The Rules Message Timing Message Timing refers to the coordination and management of the timing of communication between devices in a network.  Access Method (Defines when a device can send messages—prevents collisions.)  Flow Control (Manages data transfer rate—avoids data overflow.)  Response Timeout (Limits waiting time for a reply—ensures timely communication.) Presentation_I © 2008 Cisco Systems, Inc. All rights Cisco 9 The Rules Message Delivery Options UNICAST MULTICAST BROADCAST Sends a message to a Sends a message to Sends a message to single specific a specific group— all devices in the recipient—one-to- one-to-many network— one communication communication one-to-all communication Presentation_I © 2008 Cisco Systems, Inc. All rights Cisco 10 3.2 Network Protocols and Standards Protocols Rules that Govern Communications Presentation_I © 2008 Cisco Systems, Inc. All rights Cisco 11 Protocols Network Protocols What kind of things network protocols handle?  How the message is formatted or structured  The process by which networking devices share information about pathways with other networks  How and when error and system messages are passed between devices  The setup and termination of data transfer sessions Presentation_I © 2008 Cisco Systems, Inc. All rights Cisco 12 Why Layering? Approach to design/discuss complex systems:  explicit structure allows identification, relationship of system’s pieces layered reference model for discussion  modularization eases maintenance, updating of system change in layer's service implementation: transparent to rest of system Introduction: 1-13 Example: organization of air travel end-to-end transfer of person plus baggage ticket (purchase) ticket (complain) baggage (check) baggage (claim) gates (load) gates (unload) runway takeoff runway landing airplane routing airplane routing airplane routing How would you define/discuss the system of airline travel?  a series of steps, involving many services Introduction: 1-14 Layered model of air travel service ticket (purchase) ticketing service ticket (complain) baggage (check) baggage service baggage (claim) gates (load) gate service gates (unload) runway takeoff runway service runway landing airplane routing routing service airplane routing airplane routing layers: each layer implements a service  via its own internal-layer actions  relying on services provided by layer below Introduction: 1-15 Layered Internet protocol stack TCP/IP Layered Internet protocol stack  Application: supporting network applications HTTP, IMAP, SMTP, DNS application application  Transport: process-process data transfer TCP, UDP transport transport  Network: routing of datagrams (or packets) from source to destination network IP, routing protocols  Link: data transfer between neighboring link network elements physical Ethernet, 802.11 (WiFi), PPP  Physical: bits “on the wire” Introduction: 1-16 Services, Layers, and Encapsulation M Application exchanges messages to implement some application application service using services of transport layer application Transport Header Ht M transport Transport-layer protocol transfers M (e.g., reliably) from transport one process to another, using services of network layer network  transport-layer protocol encapsulates network application-layer message, M, with link transport layer-layer header Ht to create a link transport-layer segment physical Ht used by transport layer protocol to physical implement its service source destination Introduction: 1-17 Services, Layers, and Encapsulation M application application Ht M transport Transport-layer protocol transfers M (e.g., reliably) from transport one process to another, using services of network layer Network HeaderH network n Ht M network Network-layer protocol transfers transport-layer segment [Ht | M] from one host to another, using link layer services link link  network-layer protocol encapsulates transport-layer segment [Ht | M] with physical physical network layer-layer header Hn to create a network-layer datagram source Hn used by network layer protocol to destination implement its service Introduction: 1-18 Services, Layers, and Encapsulation M application application Ht M transport transport Hn Ht M network Network-layer protocol transfers transport-layer segment network [Ht | M] from one host to another, using link layer services link Hl Hn Ht M link Link-layer protocol transfers datagram [Hn| [Ht |M] from host to neighboring host, using network-layer services physical  link-layer protocol encapsulates network physical datagram [Hn| [Ht |M], with link-layer source destination header Hl to create a link-layer frame Introduction: 1-19 Services, Layers, and Encapsulation M application M application message Ht M transport Ht M transport segment Hn Ht M Hn Ht M network network datagram Hl Hn Ht M Hl Hn Ht M link link frame physical physical source destination Introduction: 1-20 Reference Models The OSI Reference Model (another layering model other than TCP/IP model) International Organization for Standards (ISO) MNEMONIC for OSI Model? Abdullah Prepares Sweet Tea Near Doha Port. Presentation_I © 2008 Cisco Systems, Inc. All rights Cisco 21 Reference Models OSI Model compared to TCP/IP model MNEMONIC for TCP/IP Model? Astronauts Take Infinite Naps. Presentation_I © 2008 Cisco Systems, Inc. All rights Cisco 22  Credits Presentation_I © 2008 Cisco Systems, Inc. All rights Cisco 23