2TCP/IP Structure and Addressing - OSI Model Review Primary Functions of the OSI Model LayersThe OSI Model Layers Table provides an overview of each OSI model layer’s primary functions.OSI Model LayerUnit of InformationLayer FunctionAddress typeApplicationUser FunctionalityProgramPresentationCharacter representation Compression SecurityCharacter and wordsSessionEstablishing, conducting, and ending sessionsTransmitting messages from sending computer process to receiving computer processMessageProcess to process between applicationsTransport
3Primary Functions of the OSI Model Layers TCP/IP Structure and Addressing - OSI Model ReviewPrimary Functions of the OSI Model LayersOSI Model LayerUnit of InformationLayer FunctionAddress typeNetworkTransmitting individual packets across a networkPacketPacket address identifying receiver’s network and host locationData LinkTransmitting frames containing a packet across a link en route to final destinationFrameNIC (next node in network)PhysicalTransmitting bits in the form of signals across physical mediaBit
4OSI Reference Model Review Allows users to transfer files, send mail, etc.Only layer that users can communicate with directlyKey features are ease of use and functionality7ApplicationProvidesServicesStandardized data encoding and decodingData compressionData encryption and decryption6PresentationManages user sessionsReports upper-layer errorsSupports Remote Procedure Call activities5SessionConnectsprocessesConnection management (e.g., TCP)Error and flow controlConnectionless, unreliable (e.g., UDP)4TransportInternetwork packet routingMinimizes subnet congestionResolves differences between subnets3NetworkMovesDataNetwork access control - MAC addressPacket framingError and flow controlThe Open Systems Interconnection Reference Model was developed by the International Organization for Standardization and released in 1984.Layer 1: Realm of Electrical Engineering. Deals with impedance, signals, connectors.Layer 2: Understands a frame, what gets to talk on the network, generates or checks the CRC/checksum. Delivers frames based on the DLC address.Layer 3: Connects networks, unreliable delivery based on the network address, routing.Layer 4: Guaranteed delivery to an application address. TCP is an example. Can also be connectionless (unreliable). UDP is an example.Layer 5: Session-oriented conversations. RPC is an example.Layer 6: ASCII to EBCDIC conversion, video compression, security encryption.Layer 7: Protocol Application — not the user application.The OSI model is the key to interoperability between diverse types of environments connected by devices purchased from a variety of vendors. It is also the key enabling Sniffer Portable to make sense of the electrical pulses that fly by on a network cable or phone line.All layers support the layer above it. When troubleshooting, always start from the bottom up. A problem at a lower layer can create a problem at an upper layer.2Data LinkMoves bits across a physical mediumInterface between network medium and network devicesDefines electrical and mechanical characteristics of LAN1Physical
5The Physical Layer operates depending on the chosen network topology. TCP/IP Structure and Addressing - OSI Model ReviewThe Physical LayerThe Physical Layer only transmits bits to, and receives bits from, the physical medium, and does not “see” the bits as organized into meaningful patterns, such as an address.The Physical Layer operates depending on the chosen network topology.
6A physical address is also referred to as a: TCP/IP Structure and Addressing - OSI Model ReviewPhysical AddressesA physical address is also referred to as a:Hardware addressAdapter addressNetwork interface card (NIC) addressMedium Access Control (MAC) addressA physical address is required for network devices to ultimately deliver information to a given network node.
7TCP/IP Structure and Addressing - OSI Model Review The Data Link LayerWe can categorize physical addresses, for the purposes of networking, into two general types:A LAN address is commonly found in an Ethernet or Token Ring LAN environment.WAN addresses in High-Level Data Link Control (HDLC) or frame relay network protocol addressingDivided into two distinct partsMACThe MAC address of the node – interfaces with lower layersLLCTags and identifies protocols - interfaces with upper layers
8There are two primary types of logical addresses, as follows: TCP/IP Structure and Addressing - OSI Model ReviewLogical AddressesA logical address is generally implemented as a software entity rather than a hardware entity.There are two primary types of logical addresses, as follows:Network addresses, processed at the Network LayerPort or process addresses, processed at the Transport Layer
9The Three-Layer Network Hierarchy Diagram illustrates this concept. TCP/IP Structure and Addressing - OSI Model ReviewThe Network LayerBecause layer protocols designate both a host and a network, they allow us to build hierarchical networks.The Three-Layer Network Hierarchy Diagram illustrates this concept.
10Three-Layer Network Hierarchy TCP/IP Structure and Addressing - OSI Model ReviewThe Network LayerThree-Layer Network Hierarchy
11TCP/IP Structure and Addressing - OSI Model Review The Transport LayerThe Well-Known Port Numbers Table lists some of the more commonly used TCP and User Datagram Protocol (UDP) addresses.DecimalProtocol-Description20212325536769161TCP-FTP DataTCP-FTPTCP-TELNETTCP-SMTPTCP/UDP-DNSUDP-BOOTP/DHCPUDP-TFTPUDP-SNMP
12The Transport Layer provides: TCP/IP Structure and Addressing - OSI Model ReviewThe Transport LayerThe Transport Layer is responsible not only for application addressing, but also for providing reliable communications over the best effort Layer 3 protocols.The Transport Layer provides:Flow controlWindowingData sequencingRecovery
13TCP/IP Structure and Addressing - OSI Model Review Layers 5 through 7The remaining OSI model layers work with the data itself. These layers leave the end-to-end data transport issues to the lower four layers:The Session LayerThe Presentation LayerThe Application Layer
14TCP/IP Structure and Addressing - OSI Model Review The Session LayerThe Session Layer:establishes, manages, and terminates sessions between applications.provides its services to the Presentation Layer.synchronizes dialog between Presentation Layer entities and manages their data exchange.
15The Presentation Layer: TCP/IP Structure and Addressing - OSI Model ReviewThe Presentation LayerThe Presentation Layer:ensures that information sent by the Application Layer of one system is formatted in a manner in which the destination system’s Application Layer can read it.can translate between multiple data representation formats, if necessary.
16The Application Layer: TCP/IP Structure and Addressing - OSI Model ReviewThe Application LayerThe Application Layer:is the layer closest to the user.provides user application services to application processes outside the OSI model’s scope and does not support the other layers.identifies and establishes the intended communication partners availability, synchronizes cooperating applications, and establishes agreed procedures for application error recovery and data integrity control.determines whether sufficient resources exist for the intended communications.
17Lesson 2.3 – The TCP/IP protocol suite TCP/IP Structure and Addressing - Internet Protocol SuiteThis lesson covers important aspects and protocols of a TCP/IP system.Lesson 2.3 – The TCP/IP protocol suiteTCP/IP suite pre-dates the OSI modelThe TCP/IP model is the defacto model in use on the internetKEY POINTEach TCP/IP architecture layer has a specific purpose.
18TCP/IP Structure and Addressing - Internet Protocol Suite Overview of the TCP/IP Protocol SuiteThe TCP/IP Protocols Diagram shows a detailed picture of the TCP/IP layers.TCP/IP Protocols
19The TCP/IP model layers function as follows: TCP/IP Structure and Addressing - Internet Protocol SuiteOverview of the TCP/IP Protocol SuiteThe TCP/IP model layers function as follows:Network Interface LayerInternetwork LayerTransport LayerApplication Layer
20These low-level protocols define how a host connects to the network. TCP/IP Structure and Addressing - Internet Protocol SuiteNetwork Interface Layer ProtocolsThe Network Interface Layer protocols define rules that determine how a host accesses a LAN.These low-level protocols define how a host connects to the network.
21IP, in its current version 4, provides the following functions: TCP/IP Structure and Addressing - Internet Protocol SuiteInternetwork Layer ProtocolsThe Internetwork Layer protocols define the basic unit of transfer across a network and provide support for a global addressing scheme and routing.IP, in its current version 4, provides the following functions:A global addressing structureService type requestsPacket fragmentationPacket reassembly
22Other protocols at the Internetwork Layer include: TCP/IP Structure and Addressing - Internet Protocol SuiteInternetwork Layer ProtocolsOther protocols at the Internetwork Layer include:Address Resolution Protocol (ARP)/ Reverse ARP (RARP)Internet Control Message Protocol (ICMP)Internet Group Management Protocol (IGMP)
23TCP/IP provides applications two different levels of service: TCP/IP Structure and Addressing - Internet Protocol SuiteTransport Layer ProtocolsThe Transport Layer’s primary function is to provide communication from one application program to another.TCP/IP provides applications two different levels of service:TCPUDP
24TCP/IP Structure and Addressing - Internet Protocol Suite Application Layer ProtocolsAn application passes data to the Transport Layer protocols, which sequence the data into messages, or byte streams, for transport across the network.The TCP/IP protocol suite includes the following Application Layer protocols:TelnetFile Transfer Protocol (FTP)Simple Mail Transfer Protocol (SMTP)Simple Network Management Protocol (SNMP)
25Post Office Protocol 3 (POP3) Hypertext Transfer Protocol (HTTP) TCP/IP Structure and Addressing - Internet Protocol SuiteApplication Layer ProtocolsDNSPost Office Protocol 3 (POP3)Hypertext Transfer Protocol (HTTP)Network News Transfer Protocol (NNTP)UNIX-to-UNIX Copy Program (UUCP) protocol
27Multiplexing Using TCP Port Numbers Multiplexing relies on the use of a concept called a socket. A socket consists of three things:An IP addressA transport protocolA port number
28Overview of TCP/IP Applications - Port Numbers Jessie receives 3 packets:A UDP-based ad applicationA TCP-based wire-transfer applicationA TCP web server application…Jessie needs to know which application to give the data to, but all three packets are from the same Ethernet and IP address. You might think that Jessie could look at whether the packet contains a UDP or a TCP header, but, as you see in the figure, two applications (wire transfer and web) both are using TCP.