Copyleft 2005, Binnur Kurt. Objectives

Transcription

1 1 ing Fundamentals Copyleft 2005, Binnur Kurt Objectives Define basic networking terms Describe some commonly used network applications Describe the main purposes and functions of computer networking Describe the history and purposes of the OSI reference model 9 1

2 Objectives (Cont.) Discuss the functions of each of the seven layers of the OSI reference model and provide examples of each Describe the basic process of communication between the layers of the OSI reference model Describe the functions of the TCP/protocol stack and provide examples of each layer s function Compare the TCP/IP protocol stack to the OSI reference model 10 Basic ing Terminology NIC Media Protocol NOS Connectivity devices LAN MAN WAN topology Logical topology 11 2

3 WWW Request-Response Web Browser Web Server 12 Sending Server Server Client A Client B 13 3

4 Defining Components of the Home Office Mobile Users Internet Branch Office Main Office 14 Computer s Branch Office Home Office Remote ISDN Floor 2 Floor 1 Campus Server Farm 15 4

5 The OSI Reference Model Session Data Link 16 Why a Layered Model? Session Data Link Reduces complexity Standardizes interfaces Facilitates modular engineering Ensures interoperable technology Accelerates evolution Simplifies teaching and learning 17 5

6 The Seven Layers of the OSI Model Session Data Link Processes to s Provides network services to application processes (such as electronic mail, file transfer, and terminal emulation) 18 The Seven Layers of the OSI Model 7 Process to s Session Data Link Data Representation Ensures data is readable by receiving system Formats data Structures data Negotiates data transfer syntax for application layer 19 6

7 The Seven Layers of the OSI Model 7 Process to s 6 Data Representation Session Data Link Interhost Communication Establishes, manages, and terminates sessions between applications 20 The Seven Layers of the OSI Model 7 Process to s 6 Data Representation Session Data Link Interhost Communication End-to-End Connections Handles transportation issues between hosts Ensures data transport reliability Establishes, maintains and terminates virtual circuits Provides reliability through fault detection and recovery information flow control 21 7

8 The Seven Layers of the OSI Model 7 Process to s 6 Data Representation Session Data Link Interhost Communication End-to-End Connections Data Delivery Provides connectivity and path selection between two host systems Routes data packets Selects best path to deliver data 22 The Seven Layers of the OSI Model 7 Process to s 6 Data Representation Session Data Link Interhost Communication End-to-End Connections Data Delivery Access to Media Defines how data is formatted for transmission and how access to the network is controlled 23 8

9 The Seven Layers of the OSI Model 7 Process to s Session Data Link Data Representation Interhost Communication End-to-End Connections Data Delivery Access to Media Binary Transmission Defines the electrical, mechanical, procedural, and functional specifications for activating, maintaining, and deactivating the physical link. 24 Data Encapsulation Sender Session Nt Data Link L2 L3 L3 L4 L4 L4 L5 L5 L5 L5 L6 L6 L6 L6 L6 Bits L7 L7 L7 L7 L7 L7 User Data User Data User Data User Data User Data User Data User Data FCS = header 25 9

10 Data De-Encapsulation Receiver Session Data Link L2 L3 L3 L4 L4 L4 L5 L5 L5 L5 L6 L6 L6 L6 L6 Bits L7 L7 L7 L7 L7 L7 User Data User Data User Data User Data User Data User Data User Data FCS = header 26 Peer-to-Peer Communication Sender Receiver Session Data Link Segments Packets Frames Bits Session Data Link 27 10

11 TCP/IP Model Internet Access 28 TCP/IP Protocol Stack vs. OSI Model TCP/IP Protocol Stack OSI Model Internet Access Protocols s Session Data Link Layers Data Flow Layers 29 11

12 Summary There are a number of basic computer network terms, including NIC, media, protocol, physical topology, and logical topology, that are fundamental to an understanding of networks. applications are software programs that run between computers that are connected together on a network. Some common network applications include HTTP, POP3, FTP, Telnet, and SNMP. 30 Summary (Cont.) There are many different ways in which a computer network can be constructed to meet the requirements of an organization, but user components are generally ygrouped into the categories of main office, remote locations, and mobile users. The ISO created and released the OSI reference model in 1984 to provide vendors with a set of standards to ensure greater compatibility and interoperability between various types of network technologies

13 Summary (Cont.) The OSI reference model reduces complexity, standardizes interfaces, facilitates modular engineering, ensures interoperable technology, accelerates evolution, and simplifies teaching and learning. Each layer of the OSI model has a set of unique functions. The seven layers of the OSI model are the application, presentation, session, transport, network, datalink, and physical layers. Encapsulation is the process in which data is wrapped in a particular protocol header before network transit. 32 Summary (Cont.) The TCP/IP protocol stack has four layers: the application layer, transport layer, internet layer, and network access layer. There are both similarities and differences between the TCP/IP protocol stack and the OSI reference model

14 Repeater 34 Hub (Multiport Repeater) 35 14

15 Interface Card 36 Bridge Segment 1 Corporate Internet Segment

16 Switch 38 Firewalls Massachusetts New Hampshire Allow Access to HQ California Vermont No Access to HQ Allow Access to HQ AAA Server Permit access from MA Permit packets from NH Permit packets from VT Deny all other packets Corporate Headquarters 39 16

17 Summary ing devices are products used to connect networks. Hubs, switches, and routers interconnect devices within LANs, MANs, and WANs. ing devices function at different layers of the OSI model, primarily Layer, 2, and 3. Repeaters reshape, amplify, and retime signals before sending them along the network. 40 Summary (Cont.) The term "hub" (also called a multiport repeater) is used instead of repeater" when referring to the device that serves as a connection point in a network. Hubs work Layer 1 only and make no filtering decisions. Layer 2 LAN switches work at Layer 2, and they make limited MAC hardware address decisions. Routers can make decisions as to the best path for delivery of data on the network

18 Summary (Cont.) Working at Layers 2, 3, and 4, multilayer switches enable implementation of Layer 3 QoS and security functionality and perform many of the same functions as routers do, but in hardware. Voice gateways, DSLAMs, and optical devices are newer types of network connectivity devices. Firewalls and AAA servers provide security to the network. 42 Topologies Bus Topology Ring Topology Star Topology Extended Star Topology Mesh Topology 43 18

19 Logical Topologies 2 Internet A Main Server D B C Main Switch Workgroup Switch E0 E G E1 1 E2 F Repeater H Bridge I J 44 Bus Topology 45 19

20 Star Topology 46 Extended-Star Topology 47 20

21 Ring Topology 48 Dual-Ring Topology Two links connected to the same networking device 49 21

22 Full-Mesh Topology 50 Partial-Mesh Topology 51 22

23 Summary A physical topology describes the plan for wiring the physical devices, while a logical topology describes how information flows through a network. In a physical bus topology, a single cable connects all the devices. The most commonly used architecture in Ethernet LANs is the physical star topology, with each host in the network connected to the central device with its own cable. 52 Summary (Cont.) When a star network is expanded to include additional networking devices that are connected to the main networking device, it is called an extended-star topology. In a ring topology, all the hosts are connected in the form of a ring or circle. A full-mesh topology connects all devices to each other, while in a partial-mesh topology, at least one device has multiple connections to others

24 Communications Protocol rking Fundamental Host TCP Host Networ 54 TCP/IP Protocol Stack Session Data-link OSI Reference Model FTP, Telnet, SMTP TCP IP OSPF ARP, RARP, SNAP LLC IGRP Many Implementations RIP TCP/IP Protocol Stack DNS, SNMP NetBIOS INT, IS-IS ICMP 55 24

25 TCP Characteristics Connection-Oriented Protocol Full-Duplex Operation Error Checking Sequencing Acknowledgments Flow Control Packet Recovery 56 UDP Characteristics Minimal Service Unreliable Not-Guaranteed Direct Access to Datagrams 57 25

26 Layer Overview Data Link File Transfer TFTP * FTP * NFS SMTP Remote Login Telnet * rlogin * Management SNMP * Name Management DNS* *Used by the router 58 Summary Protocols define a standard set of rules for communicating between devices. TCP/IP is a suite of protocols arranged as a stack. TCP is a connection-oriented protocol that provides flow control and reliable data delivery services. UDP provides minimal, non-guaranteed, transport services. The transport layer supports multiple application protocols

27 and Host Addresses Host Dotted-Decimal Notation An IP address is a 32-bit binary number: The 32-bit binary number can be divided into four octets: Each octet (or byte) can be represented in decimal: The address can be written in dotted-decimal notation:

28 IP Address Classes No. of bit 7 24 Class A: 0 no. Host no. No. of bit Class B: 1 0 no. Host no. No. of bit Class C: no. Host no. No. of bit Class D:* Address No. of bit Class E:** Address *Class D addresses are used for multicast groups. There is no need to allocate octets or bits to separate network and host addresses. **Class E addresses are reserved for research use only. 62 IP Address Class Components Class A: Class B: Class C: 1 Byte 8 Bits N N N 1 Byte 8 Bits H N N 1 Byte 8 Bits H H N 1 Byte 8 Bits N = number assigned by ARIN H = Host number assigned by administrator H H H 63 28

29 IP Address Range IP Address Class Class A Class B Class C Class D Class E IP Address Range (First octet decimal value) ( ) * ( ) ( ) ( ) ( ) Determine the class based on the decimal value of the first octet. *127 ( ) is a Class A address reserved for loopback testing and cannot be assigned to a network. 64 Addresses 8 Bits 1 Byte N NETWORK 8 Bits 1 Byte N 32 Bits 8 Bits 1 Byte HOST 8 Bits 1 Byte Address (host bits = all zeros) H H 65 29

30 Broadcast Address 8 Bits 1 Byte N NETWORK 8 Bits 1 Byte 32 Bits HOST Address (host bits = all zeros) N N N 8 Bits 1 Byte H 8 Bits 1 Byte H H H Broadcast Address (host bits = all ones) 66 Private IP Addresses Class A B C RFC 1918 Internal Address Range to to to

31 IPv4 Address Allocation Class C 12.5% Class B 25% Other Classes 12.5% Class A 50% With Class A and B addresses virtually exhausted, Class C addresses (12.5 percent of the total space) are left to assign to new networks