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Software Testing And Ospf
OSPF Routers in the same broadcast domain or at each end of a point-to-point telecommunications link form adjacencies when they have detected each other. This detection occurs when a router identifies itself in a hello OSPF protocol packet. This is called a two-way state and is the most basic relationship. The routers in an Ethernet or frame relay network select a designated router (DR) and a backup designated router (BDR) which act as a hub to reduce traffic between routers. OSPF uses both unicast and multicast to send "hello packets" and link state updates. As a link state routing protocol, OSPF establishes and maintains neighbor relationships in order to exchange routing updates with other routers. The neighbor relationship table is called an adjacency database in OSPF. Provided that OSPF is configured correctly, OSPF forms neighbor relationships only with the routers directly connected to it. In order to form a neighbor relationship between two routers, the interfaces used to form the relationship must be in the same area. An interface can only belong to a single area. (A neighbor state simulation shows how neighbor state changes from Down to Full Adjacency progressively with exchanging Hello, DD, Request, Update, and Ack packets). An OSPF domain is divided into areas that are labeled with 32-bit area identifiers. The area identifiers are commonly, but not always, written in the dot-decimal notation of an IPv4 address. However, they are not IP addresses and may duplicate, without conflict, any IPv4 address. The area identifiers for IPv6 implementations of OSPF (OSPFv3) also use 32-bit identifiers written in the same notation. While most OSPF implementations will right-justify an area number written in a format other than dotted decimal format (e.g., area 1), it is wise to always use dotted-decimal formats. Most implementations expand area 1 to the area identifier 0.0.0.1, but some have been known to expand it as 1.0.0.0. Areas are logical groupings of hosts and networks, including their routers having interfaces connected to any of the included networks. Each area maintains a separate link state database whose information may be summarized towards the rest of the network by the connecting router. Thus, the topology of an area is unknown outside of the area. This reduces the amount of routing traffic between parts of an autonomous system. (An ABR simulation shows how an ABR lets areas know each others’ network addresses by flooding Summary LSA.) Several special area types are defined. Computer software, or just software, is the collection of computer programs and related data that provide the instructions telling a computer what to do. We can also say software refers to one or more computer programs and data held in the storage of the computer for some purposes. Program software performs the function of the program it implements, either by directly providing instructions to the computer hardware or by serving as input to another piece of software. The term was coined to contrast to the old term hardware (meaning physical devices). In contrast to hardware, software is intangible, meaning it "cannot be touched".[1] Software is also sometimes used in a more narrow sense, meaning application software only. Sometimes the term includes data that has not traditionally been associated with computers, such as film, tapes, and records.[2] Examples of computer software include: Application software includes end-user applications of computers such as word processors or video games, and ERP software for groups of users. Middleware controls and co-ordinates distributed systems. Programming languages define the syntax and semantics of computer programs. For example, many mature banking applications were written in the COBOL language, originally invented in 1959. Newer applications are often written in more modern programming languages. System software includes operating systems, which govern computing resources. Today[when?] large[quantify] applications running on remote machines such as Websites are considered[by whom?] to be system software, because[citation needed] the end-user interface is generally through a graphical user interface, such as a web browser. Testware is software for testing hardware or a software package. Firmware is low-level software often stored on electrically programmable memory devices. Firmware is given its name because it is treated like hardware and run ("executed") by other software programs. Shrinkware is the older name given to consumer-purchased software, because it was often sold in retail stores in a shrink-wrapped box. Device drivers control parts of computers such as disk drives, printers, CD drives, or computer monitors. Programming tools help conduct computing tasks in any category listed above. For programmers, these could be tools for debugging or reverse engineering older legacy systems in order to check source code compatibility. Software Testing software testing training It is the process used to help identify the correctness, completeness, security, and quality of developed computer . Testing is a process of technical investigation, performed on behalf of stakeholders, that is intended to reveal quality-related information about the product with respect to the context in which it is intended to operate. This includes, but is not limited to, the process of executing a program with the intent of finding errors. Quality is not an absolute; it is value to some person. With that in mind, testing can never completely establish the correctness of arbitrary computer software; testing furnishes a criticism or comparison that compares the state and behaviour of the product against a specification. An important point is that software testing should be distinguished from the separate discipline of Software Quality Assurance (SQA), which encompasses all business process areas, not just testing. Discovering the design defects in software, is equally difficult, for the same reason of complexity. Because software and any digital systems are not continuous, testing boundary values are not sufficient to guarantee correctness. All the possible values need to be tested and verified, but complete testing is infeasible. Exhaustively testing a simple program to add only two integer inputs of 32-bits (yielding 2^64 distinct test cases) would take hundreds of years, even if tests were performed at a rate of thousands per second. Obviously, for a realistic software module, the complexity can be far beyond the example mentioned here. If inputs from the real world are involved, the problem will get worse, because timing and unpredictable environmental effects and human interactions are all possible input parameters under consideration. Good testing provides measures for all relevant factors. The importance of any particular factor varies from application to application. Any system where human lives are at stake must place extreme emphasis on reliability and integrity. In the typical business system usability and maintainability are the key factors, while for a one-time scientific program neither may be significant. Our testing, to be fully effective, must be geared to measuring each relevant factor and thus forcing quality to become tangible and visible. Tests with the purpose of validating the product works are named clean tests, or positive tests. The drawbacks are that it can only validate that the software works for the specified test cases. A finite number of tests can not validate that the software works for all situations. On the contrary, only one failed test is sufficient enough to show that the software does not work. Dirty tests, or negative tests, refers to the tests aiming at breaking the software, or showing that it does not work. A piece of software must have sufficient exception handling capabilities to survive a significant level of dirty tests. A testable design is a design that can be easily validated, falsified and maintained. Because testing is a rigorous effort and requires significant time and cost, design for testability is also an important design rule for software development. Software reliability has important relations Software testing with many aspects of software, including the structure, and the amount of testing it has been subjected to. Based on an operational profile (an estimate of the relative frequency of use of various inputs to the program, testing can serve as a statistical sampling method to gain failure data for reliability estimation. Software testing is not mature. It still remains an art, because we still cannot make it a science. We are still using the same testing techniques invented 20-30 years ago, some of which are crafted methods or heuristics rather than good engineering methods. Software testing can be costly, but not testing software is even more expensive, especially in places that human lives are at stake. Solving the software-testing problem is no easier than solving the Turing halting problem. We can never be sure that a piece of software is correct. We can never be sure that the specifications are correct. No verification system can verify every correct program. We can never be certain that a verification system is correct either. Conclusions Software testing is an art. Most of the testing methods and practices are not very different from 20 years ago. It is nowhere near maturity, although there are many tools and techniques available to use. Good testing also requires a tester's creativity, experience and intuition, together with proper techniques. Testing is more than just debugging. Testing is not only used to locate defects and correct them. It is also used in validation, verification process, and reliability measurement. Testing is expensive. Automation is a good way to cut down cost and time. Testing efficiency and effectiveness is the criteria for coverage-based testing techniques. Complete testing is infeasible. Complexity is the root of the problem. At some point, software testing has to be stopped and product has to be shipped. The stopping time can be decided by the trade-off of time and budget. Or if the reliability estimate of the software product meets requirement. Testing may not be the most effective method to improve software quality. Alternative methods, such as inspection, and clean-room engineering, may be even better. In a diplomatic context the word protocol refers to a diplomatic document or a rule,guideline etc which guides diplomatic behaviour. Synonyms are procedure and policy.[1] While there is no generally accepted formal definition of "protocol" in computer science, an informal definition, based on the previous, could be "a description of a set of procedures to be followed when communicating". In computer science the word algorithm is a synonym for the word procedure, so a protocol is to communications what an algorithm is to computations.[1][2] Communicating systems use well-defined formats for exchanging messages. Each message has an exact meaning intended to provoke a defined response of the receiver. A protocol therefore describes the syntax, semantics, and synchronization of communication. A programming language describes the same for computations, so there is a close analogy between protocols and programming languages: protocols are to communications what programming languages are to computations.[2] Using a layering scheme to structure a document tree. Diplomatic documents build on each other, thus creating document-trees. The way the sub-documents making up a document-tree are written has an impact on the complexity of the tree. By imposing a development model on the documents, overall readability can be improved and complexity can be reduced. An effective model to this end is the layering scheme or model. In a layering scheme the documents making up the tree are thought to belong to classes, called layers. The distance of a sub-document to its root-document is called its level. The level of a sub-document determines the class it belongs to. The sub-documents belonging to a class all provide similar functionality and, when form follows function, have similar form. The communications protocols in use on the Internet are designed to function in very complex and diverse settings, so they tend to be very complex. Unreliable transmission links add to this by making even basic requirements of protocols harder to achieve. To ease design, communications protocols are also structured using a layering scheme as a basis. Instead of using a single universal protocol to handle all transmission tasks, a set of cooperating protocols fitting the layering scheme is used.[3] The TCP/IP model or Internet layering scheme and its relation to some common protocols. The layering scheme in use on the Internet is called the TCP/IP model. The actual protocols are collectively called the Internet protocol suite. The group responsible for this design is called the Internet Engineering Task Force (IETF). Obviously the number of layers of a layering scheme and the way the layers are defined can have a drastic impact on the protocols involved. This is where the analogies come into play for the TCP/IP model, because the designers of TCP/IP employed the same techniques used to conquer the complexity of programming language compilers (design by analogy) in the implementation of its protocols and its layering scheme.[4] Like diplomatic protocols, communications protocols have to be agreed upon by the parties involved. To reach agreement a protocol is developed into a technical standard. International standards are developed by the International Organization for Standardization (ISO). Protocol testing protocol testing training Generally, only the simplest protocols are used alone. Most protocols, especially in the context of communications or networking, are layered together into protocol stacks where the various tasks listed above are divided among different protocols in the stack.Whereas the protocol stack denotes a specific combination of protocols that work together, a reference model is a software architecture that lists each layer and the services each should offer. The classic seven-layer reference model is the OSI model, which is used for conceptualizing protocol stacks and peer entities. This reference model also provides an opportunity to teach more general software engineering concepts like hiding, modularity, and delegation of tasks. This model has endured in spite of the demise of many of its protocols (and protocol stacks) originally sanctioned by the ISO. In the field of telecommunications, a communications protocol is the set of standard rules for data representation, signaling, authentication and error detection required to send information over a communications channel.protocol testing An example of a simple communications protocol adapted to voice communication is the case of a radio dispatcher talking to mobile stations. Communication protocols for digital computer network communication have features intended to ensure reliable interchange of data over an imperfect communication channel. Communication protocol is basically following certain rules so that the system works properly The TCP/IP protocol suite establishes the technical foundation of the Internet. (UDP/IP is part of the the family). Development of the TCP/IP was started by DOD projects and now, most protocols in the suite are developed by the industry non-for-profit organization named Internet Engineering Task Force (IETF) under the Internet Architecture Board (IAB), an organization initially sponsored by the US government and now an open and autonomous organization. The IAB provides the coordination for the R&D underlying the TCP/IP protocols and guides the evolution of the Internet. The TCP/IP protocols are well documented by the Request For Comments (RFC), which are drafted, discussed, circulated and approved by the IETF committees. All documents are open and free and could be found online in the IETF site listed in the reference. In computing, a protocol is a set of rules which is used by computers to communicate with each other across a network. A protocol is a convention or standard that controls or enables the connection, communication, and data transfer between computing endpoints. In its simplest form, a protocol can be defined as the rules governing the syntax, semantics, and synchronization of communication. Protocols may be implemented by hardware, software, or a combination of the two. At the lowest level, a protocol defines the behavior of a hardware connection. A protocol is a formal description of message formats and the rules for exchanging those messages. Common protocols IP (Internet Protocol) UDP (User Datagram Protocol) TCP (Transmission Control Protocol) DHCP (Dynamic Host Configuration Protocol) HTTP (Hypertext Transfer Protocol) FTP (File Transfer Protocol) Telnet (Telnet Remote Protocol) SSH (Secure Shell Remote Protocol) POP3 (Post Office Protocol 3) SMTP (Simple Mail Transfer Protocol) IMAP (Internet Message Access Protocol) L2 - L2 protocol testing L2 - Layer 2 Layer 2 and Layer 3 protocols This is also referred to as the OSI (Open Systems Interconnection) Data Link Layer. It provides the means for synchronizing the bit stream flowing to and from the physical layer and for the detection of errors due to transmission problems e.g. noise and interference. An example of a Data Link protocol would be Ethernet operating on a LAN (Local Area Network). L3 - Layer 3 This is also referred to as the OSI (Open Systems Interconnection) Network Layer. It provides the paths for the transfer of data between systems and across networks. The paths between systems may include switched services and interconnections of multiple subnetworks on route. An example of a protocol operating at the network layer would be IP (Internet Protocol). Network testing network protocol testing Users and network administrators often have different views of their networks. Often, users who share printers and some servers form a workgroup, which usually means they are in the same geographic location and are on the same LAN. A community of interest has less of a connection of being in a local area, and should be thought of as a set of arbitrarily located users who share a set of servers, and possibly also communicate via peer-to-peer technologies. technologies. Network administrators see networks from both physical and logical perspectives. The physical perspective involves geographic locations, physical cabling, and the network elements (e.g., routers, bridges and application layer gateways that interconnect the physical media. Logical networks, called, in the TCP/IP architecture, subnets, map onto one or more physical media. For example, a common practice in a campus of buildings is to make a set of LAN cables in each building appear to be a common subnet, using virtual LAN (VLAN) technology. Both users and administrators will be aware, to varying extents, of the trust and scope characteristics of a network. Network testing Again using TCP/IP architectural terminology, an intranet is a community of interest under private administration usually by an enterprise, and is only accessible by authorized users (e.g. employees).[5] Intranets do not have to be connected to the Internet, but generally have a limited connection. An extranet is an extension of an intranet that allows secure communications to users outside of the intranet (e.g. business partners, customers).[5] Categories of Testing 1.Unit, System, Regression – The Major Categories are The Component Categories for Network-Enabled Products Stress and Reliability Tests include Functional Tests include 2.Load Testing 3.Stress Testing 4.Negative Testing 5.Inopportune Testing 6.Protocol Conformance (Compliance) Testing. 7.Line Speed Testing 8.Performance Testing 9.Robustness (Security) Testing 10.Interoperability Testing 11.Deep-path testing Article Directory: http://www.articledashboard.com |
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