BIT 368 UNIT_3 (1).pdf

COMPIUTER HARDWARE & NETWORKS BIT 368 Unit 3 Rev Dr. K. O. Peasah Benjamin Odoi-Lartey Jan 2014 kopeasah.cos.knust.edu.gh// 0244223434  NETWORK MODELS (OSI and TCP/IP Models)  What is an OSI Model? A commun...

COMPIUTER HARDWARE & NETWORKS BIT 368 Unit 3 Rev Dr. K. O. Peasah Benjamin Odoi-Lartey Jan 2014 kopeasah.cos.knust.edu.gh// 0244223434  NETWORK MODELS (OSI and TCP/IP Models)  What is an OSI Model? A communication subsystem is a complex piece of Hardware and software. Early attempts for implementing the software for such subsystems were based on a single, complex, unstructured program with many interacting components. The resultant software was very difficult to test and modify. To overcome such problem, the ISO has developed a layered approach. In a layered approach, networking concept is divided into several layers, and each layer is assigned a particular task. Therefore, we can say that networking tasks depend upon the layers. 3  What is an OSI Model? The open systems interconnection (OSI) model is a conceptual model created by the International Organization for Standardization that enables diverse communication systems to communicate using standard Protocols. In plain English, the OSI provides a standard for different computer systems to be able to communicate with each other. The OSI Model can be seen as a universal language for computer networking. It is based on the concept of splitting up a 29/06/23 OSI Model 29/06/23  Layered Architecture The basic elements of layered architecture are services, protocols, and interfaces. Service: It is a set of actions that a layer provides to the higher layer. Protocol: It defines a set of rules that a layer uses to exchange the information with a peer entity. These rules mainly concern both the contents and order of the messages used. Interface: It is a way through which the message is transferred from one layer to another layer. In a layer n architecture, layer n on one machine will have a communication with layer n on another machine, and the rules used in a conversation are known as a layer-n protocol. 6  A Five (5) – Layered Architecture 7  OSI - Model OSI stands for Open System Interconnection is a reference model that describes how information from a software application in one computer moves through a physical medium to the software application in another computer. OSI consists of seven layers, and each layer performs a particular network function. The OSI model was developed by the International Organization for Standardization (ISO) in 1984, and it is now considered as an architectural model for inter-computer communications. The OSI model divides the whole task into seven smaller and manageable tasks. Each layer is assigned a particular task. Each layer is self-contained so that the task assigned to each layer can be performed 8 independently.  OSI Model Layers Functions and Characteristics 9  The Physical Layer defines the electrical and physical specifications for devices. In particular, it defines the relationship between a device and a physical medium. This includes the layout of a pin, voltages, cable specification, hubs, repeaters, network adapters, host bus adapters, and more. 29/06/23  The major functions and services performed by the Physical Layer are: Establishment and termination of a connection to a communication medium. Participation in the process whereby the communication resources are effectively shared among multiple users. For example, flow control. Modulation, or conversion between the representation of digital data in user equipment and the corresponding signals transmitted over a communications channel. These are signals operating over the physical cabling (such as copper and optical fiber) or over a radio link. 29/06/23  The same applies to local-area networks, such as Ethernet, token ring, FDDI (Fiber Distributed Data Interface), ITU-T (International Telecommunication Union Telecommunication Standardization Sector) G.hn and IEEE802.1I. Personal area networks such as Bluetooth and IEEE 802.15.4. 29/06/23  The Data Link Layer provides the functional and procedural means to transfer data between network entities and to detect and possibly correct errors that may occur in the Physical Layer. Originally, this layer was intended for point-to-point and point-to-multipoint media, characteristic of wide-area media in the telephone system. The data link layer is divided into two sub-layers by IEEE. 29/06/23  One is Media Access Control (MAC) and another is Logical Link Control (LLC). Mac is a lower sub-layer, and it defines the way the media access transfer, such as CSMA/CD/CA(Carrier Sense Multiple Access/Collision Detection/Collision Avoidance) LLC provides data transmission methods in different networks. It will re-package the date and add a new header. 29/06/23  The Network Layer provides the functional and procedural means of transferring variable length data sequences from a source to a destination via one or more networks while maintaining the quality of service requested by the Transport Layer. 29/06/23  The Network Layer performs network routing functions, perform fragmentation and reassembly, report delivery errors. Routers operate at this layer—sending data throughout the extended network and making the Internet possible. 29/06/23  The Transport Layer provides transparent transfer of data between end users, providing reliable data transfer services to the upper layers. The Transport Layer controls the reliability of a given link through flow control, segmentation/desegmentation, and error control. 29/06/23 29/06/23  The Session Layer controls the dialogues (connections) between computers. It establishes, manages, and terminates the connections between the local and remote applications. It provides for full-duplex, half-duplex, or simplex operation, and establishes checkpointing, adjournment, termination, and restart procedures. 29/06/23  The OSI model made this layer responsible for the graceful close of sessions, which is a property of the Transmission Control Protocol, and also for session checkpointing and recovery, which is not usually used in the Internet Protocol Suite. The Session Layer is commonly implemented explicitly in application environments that use remote procedure calls. 29/06/23  The Presentation Layer establishes a context between Application Layer entities, in which the higher-layer entities can use different syntax and semantics, as long as the presentation service understands both and the mapping between them. This layer provides independence from differences in data representation (e.g., encryption) by translating from application to network format, and vice versa. This layer formats and encrypts data to be sent across a network, providing freedom from compatibility problems. It is sometimes called the syntax layer. 29/06/23  The application layer is the OSI layer closest to the end user, which means that both the OSI application layer and the user interact directly with the software application. Application layer functions typically include: identifying communication partners, determining resource availability, synchronizing communication. 29/06/23  Identifying communication partners Determines the identity and availability of communication partners for an application with data to transmit. Determining resource availability Decide whether sufficient network or the requested communication exist. Synchronizing communication All communication between applications requires cooperation that is managed by the application layer. 29/06/23  TCP/IP Introduction The Internet Protocol Suite (commonly known as TCP/IP) is the set of communications protocols used for the Internet and other similar networks. It is named from two of the most important protocols in it: the Transmission Control Protocol (TCP) and the Internet Protocol (IP), which were the first two networking protocols defined in this standard. The TCP/IP model was developed prior to the OSI model. The TCP/IP model is not exactly similar to the OSI model. 24  TCP/IP Model The TCP/IP model consists of five layers: the application layer, transport layer, network layer, data link layer and physical layer. The first four layers provide physical standards, network interface, internetworking, and transport functions that correspond to the first four layers of the OSI model, and these four layers are represented in TCP/IP model by a single layer called the application layer. TCP/IP is a hierarchical protocol made up of interactive modules, and each of them provides specific functionality. Here, hierarchical means that each upper-layer protocol is supported by two or more lower-level protocols. 25 29/06/23  TCP/IP Layers Components 27  OSI Model vrs TCP/IP Model Layers OSI TCP/IP Application Layer Application Layer Presentation Layer TELNET, FTP, SMTP, POP3, SNMP, NNTP, DNS,NIS, NFS, HTTP,... Session Layer Transport Layer Transport Layer TCP , UDP ,... Network Layer Internet Layer IP , ICMP, ARP, RARP,... Data Link Layer Link Layer FDDI, Ethernet, ISDN, X.25,... Physical Layer 28  IP Addressing What is IP? IP stands for Internet Protocol and specifies the format of packets, also called datagram and the addressing scheme. IP is usually combine with higher-level protocol called TCP which establishes a virtual connection between a destination and a source IP functions like the postal system which allows you to address a package and drop it in the system with no direct link between source and destination 29  Purpose of IP The Internet Protocol defines the basic unit of data transfer (IP Datagram) IP protocol performs the routing function in a network IP includes a set of rules that processes the idea of unreliable packet delivery 30  IP Services IP supports the following services One-to-One (Unicast) One-to-All (Broadcast) One-to-Many (Multicas) 31  Orientation of IP IP is a Network Layer Protocol IP can be used with several transport protocols 32  IP Address What is IP Address? An IP Address is a unique global address for a network interface. It is a 32 bit long identifier Each octect is separated by a dot and for easy reading by humans is also written in decimal notation It encodes a network number (network prefix) and a (host number) 33  IP Address Format The 32-bit IP address is separated into four 8-bit octets, allowing each octet to have a value ranging from 0 to 255. The address is logically separated into two distinct components; network ID and Host ID. IP addresses can be displayed in three formats  Binary Notation  11000000.10101000.00000001.01100100  Hexadecimal Notation  C0.A8.01.64  Dotted Decimal Notation  192.168.1.100 34 IP Address Format Originally IP addresses were divided into five different categories called classes. These divided IP classes are class A, class B, class C, class D, and class E. Out of these, classes A, B, and C are the most important. Each address class defines a different number of bits for its network prefix (network address) and host number (host address). The starting address bits decide from which class an address belongs. 29/06/23  IP Address Format Network Address: The network address specifies the unique number which is assigned to your network. In the above figure, the network address takes two bytes of IP address. Host Address: A host address is a specific address number assigned to each host machine. With the help of the host address, each machine is identified in your network. The network address will be the same for each host in a network, but they must vary in host address. 29/06/23  IP Address Format 37  IP Address Class Ranges 38  Class A IP Address  Class A addresses are assigned to networks with a very large number of hosts  Class A address uses only the first higher order octet (byte) to identify the network prefix, and the remaining three octets (bytes) are used to define the individual host addresses.  The class A address ranges between 0.0.0.0 to 127.255.255.255.  The first bit of the first octet is always set to 0 (zero), and next 7 bits determine the network address, and the remaining 24 bits determine the host address.  So the first octet ranges from 0 to 127 (00000000 to 01111111). 39  Class B IP Address Class B addresses are assigned to medium-sized to large-sized networks The two high-order bits in a class B address are always set to binary 1 0. The next 14 bits complete the network ID The remaining 16 bits represent the host ID. So the first octet ranges from 128 to 191 (10000000 to 10111111). 40  Class C IP Address Class C addresses are used for small networks. The class C address ranges between 192.0.0.0 to 223.255.255.255. The three high-order bits in a class C address are always set to binary 1 1 0. The next 21 bits complete the network ID. The remaining 8 bits represent the host ID. Its first octet ranges from 192 to 223 (11000000 to 11011111). 41  Class D and E IP Address Class D addresses are reserved for IP multicast addresses. The four high-order bits in class D addresses are always set to binary 1 1 1 0. The remaining bits are for the address that interested hosts recognize. The class D address ranges between 224.0.0.0 to 239.255.255.255 In multicasting, data is not assigned to any particular host machine, so it is not require to find the host address from the IP address, and also, there is no subnet mask present in class D. Class E is an experimental address that is reserved for future use. The high-order bits in class E address are set to 1111 42  Class Ranges of Network IDs The network ID cannot begin with the number 127. The number 127 in a class A address is reserved for internal loopback functions All bits within the network ID cannot be set to 1. All 1’s in the network ID are reserved for use as an IP broadcast address 43  Public vs Private IP Address Public IP Address This address is considered as any valid address assigned to any user to be routable on the public Internet. The organization responsible for registering such IP address ranges are called Internet Service Providers (ISP) Private IP Address Any number or address assigned to a device on a private TCP/IP Local Area Network that is accessible only within the Local Area Network 44  Class A: 16777216 addresses in total. Class B: 65536 addresses in total. Class C: 256 addresses in total. 29/06/23 46  Converting Private to Public Address Network Address Translation This technique involves mapping an IP address to another by changing the header of IP packets while in transit via a router. NAT allows one, unique IP address to represent an entire group of computer. 47  Converting Private to Public Address Port Address Translation (PAT) This is another technique used to convert private IP address to public but with different port number assignment. The packet will contain the port number that assign to the device that wants to access the Internet and through this port number 48  SUBNETTING Subnetting is a technique or practice that enables the network administrator to further divide the host part of the address into two or more subnets. In this case a part of the host address is reserved to identify the particular subnet. This is easier to see if we show the IP address in binary format 49  Subnet Mask A subnet mask is a 32-bit number created by setting host bits to all 0s and setting network bits to all 1s Subnet masks are frequently express in dotted decimal notation. Note Subnet mask is not an IP address. Each host on at TCP/IP network requires a subnet mast even on a single segment network. Read more from the link below https://networklessons.com/cisco/ccna-routing-switching-icnd1-100-105/what-is-subnetting 50  Journey to IP Versions IPv(1-3): were not formally assigned IPv4: TCP/IP, 32bit IP address currently used on the Internet. IPv5: Internet Stream Protocol (SP) Experimental Protocol Never introduced for public use IPv6: Designed to replace IPv4, 128bit IP address containing some major improvements and new features such as security. 51  Features of IPv4 Connectionless Protocol and best effort based Simplicity It is simpler and easy to implement and remember It requires less memory Familiarity Millions of devices are already knowing it Existing infrastructure already supports it 52  Shortcomings of IPv4 IPv4 specification didn’t identify any security mechanism Millions of class A addresses are wasted Many class B addresses also wasted Not so many organizations are so small to have a class C block Class E address were reserved for future purposes 53  IPv4 Supporting Devices PCs Servers Modems Routers Printers Cameras Smart Phones Tablets and Gaming Systems Just about anything else connecting to the Internet 54  Benefits of IPv6 55  Why IPv6 IPv6 provides a platform on new Internet functionality that will be needed in the immediate future and provide flexibility for the future growth and expansion 56  NETWORK SECURITY switch ports can be grouped based on: - type of applications - access privilege - place-restricted applications and resources in a secured VLAN. more security enhancements can be added by using router access lists, defined by: - station addresses - application types - protocol types 57  THANK YOU 5 29/06/23