Comparison of the OSI and TCPIP ref models

Comparison of the OSI and TCP/IP ref. models Ajith G. S: http: //poposir. orgfree. com

Comparison of the OSI and TCP/IP ref. models Ajith G. S: http: //poposir. orgfree. com

Comparison of the OSI and TCP/IP ref. models • • • Similarities The OSI and TCP/IP reference models have much in common. Both are based on the concept of a stack of independent protocols. Both models are based on packet switching technology The application, transport and network layers are similar. Ajith G. S: http: //poposir. orgfree. com

Comparison of the OSI and TCP/IP ref. models • • • Three concepts are central to the OSI Model Services- What the layer does Interfaces- How to access a layer Protocols- Can use any protocols it wants • TCP/IP did not clearly distinguish between the three. OSI model clearly distinguish between services, interfaces and protocols. Ajith G. S: http: //poposir. orgfree. com

Comparison of the OSI and TCP/IP ref. models OSI MODEL TCP/IP MODEL Layered Architecture This is a theoretical model Implementation of OSI model It has 7 Layers It has 4 Layers OSI provides layer functioning and also defines the functions of all layers. It is more based on protocols The protocols are hidden and can easily replaces as technology changes Replacing protocols is not easy Network layer provides both connection oriented and connectionless service Provides connectionless service Transport layer provides connection oriented service Provides both connection oriented and connectionless service Defines services, interfaces and protocols very clearly and make clear distinction between them It is not clearly separated its services, interfaces and protocols. Model was developed before the development of protocols Protocols were developed first and then the model was developed

Critique of OSI Model & Protocols Ajith G. S: http: //poposir. orgfree. com

A Critique of OSI Model & Protocols • • • The disadvantages includes: Bad Timing Bad Technology Bad Implementations Bad Politics Ajith G. S: http: //poposir. orgfree. com

A Critique of OSI Model & Protocols • • Bad timing The time at which a standard is established is absolutely critical to its success. TCP/IP protocols were already in widespread use by research universities by the time the OSI protocols appeared. they did not want to support a second protocol stack Ajith G. S: http: //poposir. orgfree. com

A Critique of OSI Model & Protocols • • • Bad technology Two of the layers (session and presentation) are nearly empty, whereas two other ones (data link and network) are overfull. Service definitions and protocols, is extraordinarily complex. They are also difficult to implement for operation. Some functions, such as addressing, flow control, and error control, reappear again and again in each layer. Ajith G. S: http: //poposir. orgfree. com

A Critique of OSI Model & Protocols • • • Bad Implementation The initial implementations were slow. People were not ready to associate with OSI with poor quality In contrast, one of the first implementations of TCP/IP was part of Berkeley UNIX and was quite good. People began using it quickly, which led to an larger community. Bad Politics First, the TCP/IP model does not clearly distinguish the concepts of services, interfaces, and protocols. Good software engineering can able to implement, but ISO does not able to implement. ISO OSI-7 layer model was creatred : European telecommunication European community Ajith G. S: http: //poposir. orgfree. com

A Critique of TCI/IP Model Ajith G. S: http: //poposir. orgfree. com

A Critique of TCP/IP Model • • The model does not clearly distinguish the concepts of service, interface, and protocol. TCPI/IP model is not at all general and is poorly suited to describing any protocol stack other than TCPI/IP. Host to network layer is not actually a layer. It is an interface TCP/IP model does not distinguish between the physical and data link layers. The physical layer has to do with the transmission of data. The data link layer's job is to delimit the start and end of frames and get them from one side to the other A proper model should include both as separate layers. The TCP/IP model does not do this. . Ajith G. S: http: //poposir. orgfree. com

Novel Netware • • • Net. Ware is a network operating system (NOS) that provides transparent remote file access and other distributed network services, Novell Net. Ware is the most popular network system in the PC world. Net. Ware was developed by Novell, Inc. and introduced in the early 1980 s. Network and transport protocols similar to TCP/IP Based on a client-server architecture. Clients (sometimes called workstations) request services, such as file and printer access, from servers. Ajith G. S: http: //poposir. orgfree. com

Novell Netware • • Novel Netware Protocol Suite Novell provides a suite of protocols developed specifically for Net. Ware. • The five main protocols used by Net. Ware are: 1. Media Access Protocol. 2. Internetwork Packet Exchange/Sequenced Packet Exchange (IPX/SPX). 3. Routing Information Protocol (RIP). 4. Service Advertising Protocol (SAP). 5. Net. Ware Core Protocol (NCP). Ajith G. S: http: //poposir. orgfree. com

Novell Netware Ajith G. S: http: //poposir. orgfree. com

Novel Netware • • • Media Access Protocols: The Net. Ware suite of protocols supports several media-access protocols. These protocols adds the header to the packets and responsible for bit level error checking Ajith G. S: http: //poposir. orgfree. com

Novell Netware • • • IPX(Internetwork Packet Exchange protocol): A protocol that routes outgoing data packets across a network. When a device to be communicated is located on a different network, IPX routes the information to the destination It is a connectionless, unreliable protocol that is equivalent to the IP Novell IPX network addresses must be unique. These addresses are represented in hexadecimal format and consist of two parts: a network number and a node number. The IPX network number, assigned by the network administrator 32 bits long. The node number, which usually MAC address 48 bits long. It makes rout selection based on the information compiled by the Routing Information Protocol (RIP). Ajith G. S: http: //poposir. orgfree. com

Novell Netware • • SPX(Sequenced Packet Exchange protocol): A connection-oriented transport protocol that monitors network transmissions to ensure successful delivery of packets. SPX can track data transmissions consisting of a series of separate packets. SPX also requests acknowledgments from the communications partner, ensuring successful data delivery. If an acknowledgment request brings no response within a specified time, SPX retransmits the request. Net. BIOS. An emulator that allows workstations to run applications that support IBM Net. BIOS calls. Net. BIOS is the IBM standard protocol for applications developed to run peer-to-peer communications on token ring networks. Ajith G. S: http: //poposir. orgfree. com

Novell Netware • • Routing Information Protocol (RIP): Exchange of routing information on a Net. Ware network. A protocol that automates the process of updating routing tables. Routing is the process of moving network packets between separate networks. With RIP, when one router learns about changes in its routes, it broadcasts this information to neighboring routers so they can update their routing tables. As a result, if a network component fails the other network components can inform each other of alternate routes. When the faulty component is repaired, the network changes back to the previous condition. Ajith G. S: http: //poposir. orgfree. com

Novell Netware • • • Service Advertisement Protocol (SAP): A protocol that lets Net. Ware servers advertise their services by name and type. Advertisements are sent via SAP every 60 seconds. A workstation can broadcast a request to find all services available or a specific service closest to the client. Using these SAP packets, clients on the network are able to obtain the address of any servers they can access Ajith G. S: http: //poposir. orgfree. com

Novell Netware • • Net. Ware Core Protocol (NCP): It defines the connection control and service request encoding that make it possible for clients and servers to interact. This is the protocol that provides transport and session services. Net. Ware security is also provided within this protocol. Ajith G. S: http: //poposir. orgfree. com