Bài giảng môn Mạng máy tính - Chapter 2: Communicating over the Network

Chapter 2- Communicating over the Network CCNA Exploration 4.0 Học viện mạng Bach Khoa - Website: www.bkacad.com 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. Học viện mạng Bach Khoa - Website: www.bkacad.com The Platform for Communication Học viện mạng Bach Khoa - Website: www.bkacad.com The Elements of Communication 1. Message source (sender) 2. The channel 3. Message destination (receiver) 2.1.1 Học viện mạng Bach Khoa - Website: www.bkacad.com Communicating the Messages • A better approach is to divide the data into smaller, more manageable pieces to send over the network. This division of the data stream into smaller pieces is called segmentation. • Segmenting messages has 2 primary benefits: – First, by sending smaller individual pieces from source to destination, many different conversations can be interleaved on the network. (multiplexing) – Second, segmentation can increase the reliability of network communications. Học viện mạng Bach Khoa - Website: www.bkacad.com Communicating the Messages 2.1.2 Học viện mạng Bach Khoa - Website: www.bkacad.com Communicating the Messages Học viện mạng Bach Khoa - Website: www.bkacad.com Components of the Network – Hardware: Devices and media – Software: Services and processes Học viện mạng Bach Khoa - Website: www.bkacad.com Components of the Network • Media: Physical elements, often visible but occasionally not be visible. Học viện mạng Bach Khoa - Website: www.bkacad.com Components of the Network • Services and processes: are the communication programs, called software, that run on the networked devices. Học viện mạng Bach Khoa - Website: www.bkacad.com Components of the Network • A network service provides information in response to a request. – Services include many of the common network applications people use every day, like e-mail hosting services and web hosting services. • Processes provide the functionality that directs and moves the messages through the network. – Processes are less obvious to us but are critical to the operation of networks. Học viện mạng Bach Khoa - Website: www.bkacad.com Extra: Windows service • A Windows service is an application that starts when the Microsoft Windows operating system is booted and runs in the background as long as Windows is running. • Typically, it does not have a user interface and is a long-running executable application that can run in its own session. It is very similar in concept to a Unix daemon. Học viện mạng Bach Khoa - Website: www.bkacad.com Extra: Windows service Học viện mạng Bach Khoa - Website: www.bkacad.com Extra: ProcessExplorer tool Học viện mạng Bach Khoa - Website: www.bkacad.com End Devices and their Role on the Network • The network devices that people are most familiar with are called end devices. These devices form the interface between the human network and the underlying communication network. • Some examples of end devices are: – Computers (work stations, laptops, file servers, web servers) – Network printers – VoIP phones – Security cameras – Mobile handheld devices (such as wireless barcode scanners, PDAs) 2.1.4 Học viện mạng Bach Khoa - Website: www.bkacad.com End Devices and their Role on the Network • Host: In the context of a network, end devices are referred to as hosts. A host device is either the source or destination of a message transmitted over the network. • Servers are hosts that have software installed that enables them to provide information and services, like e-mail or web pages, to other hosts on the network. • Clients are hosts that have software installed that enables them to request and display the information obtained from the server. Học viện mạng Bach Khoa - Website: www.bkacad.com Intermediary Devices and their Role on the Network • Intermediary devices to provide connectivity and to work behind the scenes to ensure that data flows across the network. • These devices connect the individual hosts to the network and can connect multiple individual networks to form an internetwork. • Examples of intermediary network devices are: – Network Access Devices (Hubs, switches, and wireless access points) – Internetworking Devices (routers) – Communication Servers and Modems – Security Devices (firewalls) 2.1.5 Học viện mạng Bach Khoa - Website: www.bkacad.com Intermediary Devices and their Role on the Network • Processes running on the intermediary network devices perform these functions: 1. Regenerate, retime and retransmit data signals 2. Maintain information about what pathways exist through the network and internetwork 3. Notify other devices of errors and communication failures 4. Direct data along alternate pathways when there is a link failure 5. Classify and direct messages according to QoS priorities 6. Permit or deny the flow of data, based on security settings Học viện mạng Bach Khoa - Website: www.bkacad.com Networking Media Học viện mạng Bach Khoa - Website: www.bkacad.com Networking Media • Criteria for choosing a network media are: 1. The distance the media can successfully carry a signal. 2. The environment in which the media is to be installed. 3. The amount of data and the speed at which it must be transmitted. 4. The cost of the media and installation. Học viện mạng Bach Khoa - Website: www.bkacad.com Networking Media • The signal encoding that must occur for the message to be transmitted is different for each media type. 2.1.6 Học viện mạng Bach Khoa - Website: www.bkacad.com LAN, WAN and Internetworks Học viện mạng Bach Khoa - Website: www.bkacad.com Networks infrastructures • Networks infrastructures can vary greatly in terms of: 1. The size of the area covered 2. The number of users connected 3. The number and types of services available Học viện mạng Bach Khoa - Website: www.bkacad.com Local Area Networks • Local Area Network (LAN): An individual network usually spans a single geographical area, providing services and applications to people within a common organizational structure, such as a single business, campus or region LAN • A LAN is usually in a single geographical area. • The network is administered by a single organization. • A LAN provides network services and access to applications for users within a common organization. Học viện mạng Bach Khoa - Website: www.bkacad.com Học viện mạng Bach Khoa - Website: www.bkacad.com Wide Area Networks • LANs separated by geographic distance are connected by a network known as a Wide Area Network (WAN). • WANs use specifically designed network devices to make the interconnections between LANs. – Telecommunications Service Provider (TSP) Q/A • TSP • ISP (Internet Service Provider) • OSP (Online Service Provider) • IXP (Internet Exchange Provider) Học viện mạng Bach Khoa - Website: www.bkacad.com Học viện mạng Bach Khoa - Website: www.bkacad.com The Internet – A Network of Networks • Although there are benefits to using a LAN or WAN, most of us need to communicate with a resource on another network, outside of our local organization. • Examples of this type of communication include: – Sending an e-mail to a friend in another country – Accessing news or products on a website – Getting a file from a neighbor's computer – Instant messaging with a relative in another city – Following a favorite sporting team's performance on a cell phone Học viện mạng Bach Khoa - Website: www.bkacad.com The Internet – A Network of Networks • A global mesh of interconnected networks (internetworks) meets these human communication needs. • The Internet is created by the interconnection of networks belonging to Internet Service Providers (ISPs). • Intranet is often used to refer to a private connection of LANs and WANs that belongs to an organization, and is designed to be accessible only by the organization's members, employees, or others with authorization. Học viện mạng Bach Khoa - Website: www.bkacad.com Network Representations Học viện mạng Bach Khoa - Website: www.bkacad.com Lab 2.2.4.2 • In this activity, you will gain experience with data network symbols by creating a simple logical topology. Học viện mạng Bach Khoa - Website: www.bkacad.com Extra: ping • Verifies IP-level connectivity to another TCP/IP computer by sending Internet Control Message Protocol (ICMP) Echo Request messages. The receipt of corresponding Echo Reply messages are displayed, along with round-trip times. • ping 127.0.0.1 – This ping is unique and is called an internal loopback test. It verifies the operation of the TCP/IP stack and NIC transmit/receive function. • ping IP-address-of-host-computer • A ping to a host PC verifies the TCP/IP address configuration for the local host and connectivity to the host. • ping default-gateway-IP-address • A ping to the default gateway verifies whether the router that connects the local network to other networks can be reached. • ping remote-destination-IP-address • A ping to a remote destination verifies connectivity to a remote host. Học viện mạng Bach Khoa - Website: www.bkacad.com Lab 2.2.5: tracert • Determines the path taken to a destination by sending Internet Control Message Protocol (ICMP) Echo Request messages to the destination with incrementally increasing Time to Live (TTL) field values. Học viện mạng Bach Khoa - Website: www.bkacad.com Lab 2.2.5 • This lab also assumes the installation of NeoTrace. Học viện mạng Bach Khoa - Website: www.bkacad.com Học viện mạng Bach Khoa - Website: www.bkacad.com Extra: nslookup • Displays information that you can use to diagnose Domain Name System (DNS) infrastructure. Before using this tool, you should be familiar with how DNS works. The Nslookup command-line tool is available only if you have installed the TCP/IP protocol. Học viện mạng Bach Khoa - Website: www.bkacad.com Extra: ARP • Displays and modifies entries in the Address Resolution Protocol (ARP) cache, which contains one or more tables that are used to store IP addresses and their resolved Ethernet or Token Ring physical addresses. There is a separate table for each Ethernet or Token Ring network adapter installed on your computer. Học viện mạng Bach Khoa - Website: www.bkacad.com Extra: Netstat • Displays active TCP connections, ports on which the computer is listening, Ethernet statistics, the IP routing table, IPv4 statistics (for the IP, ICMP, TCP, and UDP protocols), and IPv6 statistics (for the IPv6, ICMPv6, TCP over IPv6, and UDP over IPv6 protocols). Học viện mạng Bach Khoa - Website: www.bkacad.com Extra: netsh • You can use commands in the Netsh Interface IP context to configure the TCP/IP protocol (including addresses, default gateways, DNS servers, and WINS servers) and to display configuration and statistical information. Học viện mạng Bach Khoa - Website: www.bkacad.com Protocols Học viện mạng Bach Khoa - Website: www.bkacad.com Rules that Govern Communications • Protocol suite: a group of inter-related protocols that are necessary to perform a communication function. • Protocols are implemented in software and hardware that is loaded on each host and network device. • The protocols are viewed as a layered hierarchy, with each higher level services depending on the functionality defined by the protocols shown in the lower levels. 2.3.1 Học viện mạng Bach Khoa - Website: www.bkacad.com Rules that Govern Communications Học viện mạng Bach Khoa - Website: www.bkacad.com Network Protocols 1. The format or structure of the message 2. The process by which networking devices share information about pathways with other networks 3. How and when error and system messages are passed between devices 4. The setup and termination of data transfer sessions Networking protocols suites describe processes such as: Học viện mạng Bach Khoa - Website: www.bkacad.com Network Protocols 2.3.2 Học viện mạng Bach Khoa - Website: www.bkacad.com Network Protocols Học viện mạng Bach Khoa - Website: www.bkacad.com Network Protocols Học viện mạng Bach Khoa - Website: www.bkacad.com Network Protocols Học viện mạng Bach Khoa - Website: www.bkacad.com Protocol Suites and Industry Standards • Many of the protocols that comprise a protocol suite reference other widely utilized protocols or industry standards. • A standard is a process or protocol that has been endorsed by the networking industry and ratified by a standards organization, such as IEEE or IETF. • The use of standards in developing and implementing protocols ensures that products from different manufacturers can work together for efficient communications. 2.3.3 Học viện mạng Bach Khoa - Website: www.bkacad.com The Interaction of Protocols 2.3.4 Học viện mạng Bach Khoa - Website: www.bkacad.com 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. 2.3.5 Học viện mạng Bach Khoa - Website: www.bkacad.com Using Layered Models Học viện mạng Bach Khoa - Website: www.bkacad.com The Benefits of Using a Layered Model 1. Assists in protocol design. 2. Fosters competition because products from different vendors can work together. 3. Prevents technology or capability changes in one layer from affecting other layers above and below. 4. Provides a common language to describe networking functions and capabilities. 2.4.1 Học viện mạng Bach Khoa - Website: www.bkacad.com Protocol 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 primary purpose of a reference model is to aid in clearer understanding of the functions and process involved. There are 2 basic types of networking models: Học viện mạng Bach Khoa - Website: www.bkacad.com Protocol and Reference Models • The Open Systems Interconnection (OSI) model is the most widely known internetwork reference model. It is used for • Data network design • Operation specifications • Troubleshooting. Học viện mạng Bach Khoa - Website: www.bkacad.com Protocol and Reference Models Học viện mạng Bach Khoa - Website: www.bkacad.com The TCP/IP Model Học viện mạng Bach Khoa - Website: www.bkacad.com The Communication Process 1.Creation of data 2.Segmentation and encapsulation 3.Generation of the data onto the media 4.Transportation 5.Reception of the data 6.Decapsulation and reassembe 7.Passing this data to the destination application 2.4.4 Học viện mạng Bach Khoa - Website: www.bkacad.com Protocol Data Units and Encapsulation • Encapsulation process: – application data is passed down the protocol stack on its way to be transmitted across the network media, various protocols add information to it at each level • The form that a piece of data takes at any layer is called a Protocol Data Unit (PDU). • The PDUs are named according to the protocols of the TCP/IP suite: Data, Segement, Packet, Frame, Bit Học viện mạng Bach Khoa - Website: www.bkacad.com Extra: Peer-to-peer communications Học viện mạng Bach Khoa - Website: www.bkacad.com Extra: Detailed encapsulation process Học viện mạng Bach Khoa - Website: www.bkacad.com Application Header + data Extra: Data Encapsulation Example 010010100100100100111010010001101000 Application Layer Layer 4: Transport Layer Layer 3: Network Layer Layer 2: Network Layer Layer 1: Physical Layer Học viện mạng Bach Khoa - Website: www.bkacad.com Extra: abount network protocols 1.Define the structure of layer specific PDU's 2.Outline the functions necessary for communications between layers 3.Require layer dependent encapsulations Extra: Two functions of encapsulation 1. Identifies pieces of data as part of the same communication 2.Ensures that data pieces can be directed to the correct receiving end device Học viện mạng Bach Khoa - Website: www.bkacad.com Học viện mạng Bach Khoa - Website: www.bkacad.com The Sending and Receiving Process • Step 1: 2.4.6 Học viện mạng Bach Khoa - Website: www.bkacad.com The Sending and Receiving Process • Step 2 Học viện mạng Bach Khoa - Website: www.bkacad.com The Sending and Receiving Process • Step 3 Học viện mạng Bach Khoa - Website: www.bkacad.com The Sending and Receiving Process • Step 4 Học viện mạng Bach Khoa - Website: www.bkacad.com The Sending and Receiving Process • Step 5: Học viện mạng Bach Khoa - Website: www.bkacad.com The Sending and Receiving Process • Step 6: Học viện mạng Bach Khoa - Website: www.bkacad.com The Sending and Receiving Process • Step 7: Học viện mạng Bach Khoa - Website: www.bkacad.com The Sending and Receiving Process • Step 8: Học viện mạng Bach Khoa - Website: www.bkacad.com The Sending and Receiving Process • Step 9: Học viện mạng Bach Khoa - Website: www.bkacad.com The Sending and Receiving Process • Step 10: Học viện mạng Bach Khoa - Website: www.bkacad.com The OSI Model 2.4.7 Học viện mạng Bach Khoa - Website: www.bkacad.com The OSI Model Học viện mạng Bach Khoa - Website: www.bkacad.com The OSI Model Học viện mạng Bach Khoa - Website: www.bkacad.com Học viện mạng Bach Khoa - Website: www.bkacad.com Học viện mạng Bach Khoa - Website: www.bkacad.com The OSI Model Học viện mạng Bach Khoa - Website: www.bkacad.com The OSI Model Học viện mạng Bach Khoa - Website: www.bkacad.com The OSI Model Học viện mạng Bach Khoa - Website: www.bkacad.com The OSI Model Học viện mạng Bach Khoa - Website: www.bkacad.com Comparing the OSI Model with TCP/IP Model 2.4.8 Học viện mạng Bach Khoa - Website: www.bkacad.com Comparing the OSI Model with TCP/IP Model Học viện mạng Bach Khoa - Website: www.bkacad.com Lab 2.4.8.2 • In this activity, you will see how Packet Tracer uses the OSI Model as a reference to display the encapsulation details of a variety of the TCP/IP protocols. Học viện mạng Bach Khoa - Website: www.bkacad.com Network Addressing Học viện mạng Bach Khoa - Website: www.bkacad.com Addressing in the Network • There are various types of addresses that must be included to successfully deliver the data from a source application running on one host to the correct destination application running on another. • Using the OSI model as a guide, we can see the different addresses and identifiers that are necessary at each layer. Học viện mạng Bach Khoa - Website: www.bkacad.com Getting the Data to the End Device • During the process of encapsulation, address identifiers are added to the data as it travels down the protocol stack on the source host. • Multiple layers of addressing to ensure its delivery: – Ethernet MAC Addresses, – IP Addresses – TCP/UDP Port numbers Học viện mạng Bach Khoa - Website: www.bkacad.com Getting the Data through the Internetwork • Encapsulation headers are used to manage communication in data networks 2.5.3 Học viện mạng Bach Khoa - Website: www.bkacad.com Getting the Data to the Right Application 2.5.4 Học viện mạng Bach Khoa - Website: www.bkacad.com Warriors of the Net • See also: – Proxy Server – URL warriors-700-VBR_1.mpg 2.5.5 Học viện mạng Bach Khoa - Website: www.bkacad.com Lab 2.6.1 Học viện mạng Bach Khoa - Website: www.bkacad.com Lab 2.6.2: Introduction to Wireshark tool Học viện mạng Bach Khoa - Website: www.bkacad.com Lab 2.7.1 Q&A • The statements that are correct concerning network protocols: 1. define the structure of layer specific PDU's 2. outline the functions necessary for communications between layers 3. require layer dependent encapsulations Học viện mạng Bach Khoa - Website: www.bkacad.com Q&A • Two functions of encapsulation 1. identifies pieces of data as part of the same communication 2. ensures that data pieces can be directed to the correct receiving end device Học viện mạng Bach Khoa - Website: www.bkacad.com Q&A •What is a primary function of the trailer information added by the data link layer encapsulation? –supports error detection Học viện mạng Bach Khoa - Website: www.bkacad.com Q&A •What is a PDU? –a layer specific encapsulation Học viện mạng Bach Khoa - Website: www.bkacad.com Q&A •What is the purpose of the TCP/IP Network Access layer? –network media control Học viện mạng Bach Khoa - Website: www.bkacad.com Q&A •What is the proper order of the layers of the OSI model from the highest layer to the lowest layer? –application, presentation, session, transport, network, data link, physical Học viện mạng Bach Khoa - Website: www.bkacad.com Học viện mạng Bach Khoa - Website: www.bkacad.com Summary Học viện mạng Bach Khoa - Website: www.bkacad.com