Bài giảng Network - Chapter 01

Chapter Overview Network CommunicationsThe OSI Reference Model 1Signals and Protocols A data network is a group of computers connected by a network medium. The network medium carries signals between computers.Signals reduce complex information to the simplest possible form.Computers communicate by using a language called a protocol. 2Protocol Services Packet acknowledgmentSegmentationFlow controlError detectionError correctionData compressionData encryption 3A Protocol Stack4Protocol Interaction 5Local Area Networks A local area network (LAN) is a collection of computers located in a relatively small area and connected by a common medium.The pattern in which computers in a LAN are connected is called the topology.LAN topologies include bus, star, and ring.The defining protocols for a LAN are the data-link layer protocols. 6Wide Area Networks 7Packet Switching 8Half-Duplex and Full-Duplex Communications 9Backbone Network 10Client/Server and Peer-to-Peer Networking On a client/server network, computers function as either clients or servers.On a peer-to-peer network, computers can function as both clients and servers.Microsoft Windows, UNIX, and Linux are peer-to-peer operating systems.Novell NetWare is a client/server operating system. 11The OSI Reference Model 12Data Encapsulation 13PDU Names at Different OSI Layers OSI LayerProtocol Data Unit (PDU) Name Application Message Transport Segment or datagram Network Datagram Data-link Frame (Any layer) Packet 14The Physical Layer Defines the hardware elements of the network, includingThe network mediumHow the network is installedThe type of signaling Includes the following elements:CablesNetwork interface adapters (also called network interface cards, or NICs)Hubs 15The Data-Link Layer Includes the following protocols:EthernetToken RingFiber Distributed Data Interface (FDDI)Serial Line Internet Protocol (SLIP)Point-to-Point Protocol (PPP) 16The Data-Link Layer (Cont.) Includes the following protocol components:Frame formatMedia Access Control (MAC) mechanismPhysical layer specifications Performs the following functions:Hardware addressingError detection and correctionProtocol identification 17The Network Layer Includes the following protocols: Internet Protocol (IP)Internetwork Packet Exchange (IPX)NetBIOS Extended User Interface (NetBEUI)AppleTalkPerforms the following functions:AddressingFragmentingRoutingProtocol identification 18The Transport Layer Includes the following protocols:Transmission Control Protocol (TCP)User Datagram Protocol (UDP)IPXNetWare Core Protocol (NCP)Sequenced Packet Exchange (SPX) Performs the following functions:Packet acknowledgmentData segmentationFlow controlError detection 19Connection-Oriented and Connectionless Protocols Connection-Oriented (CO) Protocols Connectionless (CL) Protocols Require a handshake Do not require a handshake Have larger headers and more overhead Have smaller headers and less overhead Provide packet acknowledgments, data segmentation, flow control, and error detection and correction Do not provide additional services Acknowledge transmitted packets, so they are considered reliable Do not acknowledge transmitted packets, so they are considered unreliable 20The Session Layer The two most important functions at this layer areDialog controlDialog separation 21The Presentation Layer The presentation layer uses the following translation process: 1. The sender translates its abstract syntax to transfer syntax. 2. The sender transmits data to the receiver. 3. The receiver translates transfer syntax to it in abstract syntax.22The Application Layer Includes the following protocols:File Transfer Protocol (FTP)Hypertext Transfer Protocol (HTTP)Simple Mail Transfer Protocol (SMTP)Post Office Protocol, Version 3 (POP3)Internet Mail Access Protocol (IMAP)Simple Network Management Protocol (SNMP)Domain Name System (DNS)Dynamic Host Configuration Protocol (DHCP) 23Lesson 1 Summary: Network Communications Computers communicate by using languages called protocols.Protocols provide services to other protocols operating above and below them.A LAN uses a common network medium to connect computers in a relatively small area.A WAN uses an external network provider to connect LANs.Broadband networks carry multiple signals at once, while baseband networks carry only one signal.A backbone network connects segments together, forming an internetwork.Most operating systems today use the peer-to-peer model, which allows computers to function as both clients and servers. 24Lesson 2 Summary: The OSI Reference Model OSI Model LayerFunctionPhysicalDefines the hardware elements and structure of the network installationData-linkProvides addressing, data encapsulation, and media access control NetworkProvides end-to-end routing and addressing TransportProvides packet acknowledgment, flow control, and error detectionSessionProvides dialog control and dialog separationPresentationTranslates syntaxes between different systemsApplicationProvides an interface to applications running on the computer25