Chapter Communicating Over the Network Quangkien@gmail.com Overview 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 The Platform for Communications Elements of Communication Communicating the Messages Continuous stream of bits 00101010100101010101010101010101010 I have to wait… Single communications (e.g video, e-mail message) could be: Continuous stream of bits Take over (hog) the network Significant delays Inefficient use Any loss - resend entire message Communicating the Messages Segmentation 001010 001010 001010 001010 001010 001010 Better approach – segmentation Multiplexing: Different conversations can be interleaved Communicating the Messages X Benefits Reliability (3) Different paths Alternate path Only the missing segments need to be retransmitted Disadvantage of Segmentation Disadvantage – added level of complexity Analogy: 100 page letter one page at a time Separate envelopes Sequencing Components of the Network Devices (hardware) End devices, switch, router, firewall, hub Media (wired, wireless) Cables, wireless mediums Services (software) Network applications, routing protocols, processes, algorithms End devices End devices or hosts: The source or destination of a message 10 Using Layered Protocols Layered Model 39 Benefits of a Layered Model Using a layered model: Fosters competition because products from different vendors can work together Prevents changes in one layer from affecting other layers above and below Provides a common language to describe networking functions and capabilities 40 Protocol and Reference Models There are two basic types of networking models: protocol models and reference models A protocol model provides a model that closely matches the structure of a particular protocol suite Example: TCP/IP A reference model provides a common reference for maintaining consistency within all types of network protocols and services The Open Systems Interconnection (OSI) model is the most widely known internetwork reference model It is used for data network design, operation specifications, and troubleshooting 41 Protocol and Reference Models The Open Systems Interconnection (OSI) model is the most widely known internetwork reference model The International Organization for Standardization (ISO) released the OSI reference model in 1984, was the descriptive scheme they created 42 TCP/IP Model The first layered protocol model for internetwork communications was created in the early 1970s and is referred to as the Internet model 43 The Communication Process - Encapsulation Data Link Header IP Header TCP Header HTTP Header Data Data Link Trailer Server HTTP Data Encapsulation – Process of adding control information as it passes down through the layered model 44 The Communication Process - Decapsulation Data Link Header IP Header TCP Header HTTP Header Data Data Link Trailer Client HTTP Data Decapsulation – Process of removing control information as it passes upwards through the layered model 45 Wireshark will let us examine protocols! 46 The Communication Process Protocol Data Unit (PDU) - The form that a piece of data takes at any layer PDUs are named according to the protocols of the TCP/IP suite Data - Application layer PDU Segment - Transport Layer PDU Packet - Internetwork Layer PDU Frame - Network Access Layer PDU Bits - A PDU used when physically transmitting data over the medium 47 Layer Data Link Frame Dest Add Dest MAC MAC 0B-20 FF-FF 0B-31 00-10 Source Add MAC 0C-22 00-20 0A-10 Layer IP Packet Type 800 Dest IP 192.168.4.10 Source IP 192.168.1.10 IP fields Data Trailer The sending host builds message with multiple encapsulations Data Link Header IP Header TCP Header HTTP Header Data Data Link Trailer The receiving host receives the message with multiple decapsulations Data Link Header IP Header TCP Header HTTP Header Data Data Link Trailer 48 Getting Data to the Right Application Layer (TCP/UDP) contains a port number which represents the application or service carried in the IP packet Destination port – destination application Source port – source application 49 Getting Data to the Right Application Destination port number tells the OS (TCP/IP) stack which application to hand the data to Examples: 80 = HTTP (www) 23 = Telnet 20, 21 = FTP 25 = SMTP 50 Summary 51 Chapter Communicating Over the Network ...Overview 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. .. be installed – The amount of data and the speed at which it must be transmitted – The cost of the media and installation 17 Local Area Network (LAN) Local Area Network (LAN) An individual network. .. running on the intermediary network devices perform these functions: – Regenerate and retransmit data signals – Maintain information about what pathways exist through the network and internetwork