Lecture slides 4 cs303 distributed systems lecture 4. We have chosen to use the neutral term identifier rather than name because we want to be able to distinguish between various kinds of entities used to designate. Naming names play a critical role in all computer systems to access resources, uniquely identify entities, or refer to locations to access an entity, you have resolve the name and. C b id 1 000 000 t i 5 000 d t kcambridge area 1,000,000 entries, 5,000 updates a week given a name e. A naming system should support the use of multiple copies of the same object in a usertransparent manner. Cpsc662 distributed computing naming 2 entities, names, addresses. Can we use addresses of access points as regular name for the associated entity. Naming distributed software systems 2 naming entities a name in a distributed system is a string of bits or characters that is used to refer to an entity types of names address. An increasing number of systems have mobile components. An increasing number of systems have mobile components, which implies new problems of naming and resolving names.
Dtu informatics department of informatics and mathematical. Presently, our most common exposure to distributed systems that exemplify some degree of transparency is through distributed file systems. Distributed software systems 21 scaling techniques 2 1. Local os local os local os machine a machine b machine c network distributed. Name a name is a string composed of a set of symbols chosen from a finite alphabet. There are few methods like forwarding pointers, hierarchical approaches, home based approaches and pointer caches but each has its own short comings. Wed like remote files to look and feel just like local ones. Fundamental concepts underlying distributed computing designing and writing moderatesized distributed applications prerequisites. Naming most computer systems in particular operating systems manage wide collections of entities such as. Naming naming entities naming essence names are used to denote entities in a distributed system. Distributed systems goals by the end of the course, students will be able to.
Middleware and distributed systems naming and directory services. Ecs follows the composition over inheritance principle that allows greater flexibility in defining entities where every object in a games scene is an entity e. A distributed system is a system whose components are located on different networked computers, which communicate and coordinate their actions by passing messages to one another. Distributed systems, spring 2003 1 naming distributed systems, spring 2003 2 naming entities locating mobile entities removing unreferenced entities topics to be covered distributed systems, spring 2003 3 naming entities definitions name resolution name spaces examples dns, x. We now describe the design of fnr and how it is different from existing distributed systems. Distributed naming in a factored operating system by nathan beckmann submitted to the department of electrical engineering and computer science on september 3, 2010, in partial ful llment of the requirements for the degree of master of science in electrical engineering and. Naming versus locating entities flat nametoaddress in a lan. Three generations of distributed systems early distributed systems emerged in the late 1970s and early 1980s because of the usage of local area networking technologies system typically consisted of 10 to 100 nodes connected by a lan, with limited internet connectivity and supported services e. Naming name service management and offering of relations between names and entities identi.
Business firms and other organizations rely on information systems to carry out and manage their operations, interact with their customers and suppliers, and compete in the marketplace. Laszlo boszormenyi distributed systems naming 2 names, addresses, identifiers naming is about mapping between names, addresses, identifiers and the referred entities names a bit or characterstring referring to an entity. Department of informatics and mathematical modelling characterization of distributed systems 1. Naming and directoriies middleware and distributed systems mvl 2008 naming communication and resource sharing demands an identi. Directory node has a number of outgoing edges, each labeled with a name. Each domain has an associated directory node that keeps track of the entities in that domain. Name the server resolved to an address where the server can be reached 3. Naming in distributed systems is modelled as a string translation problem. A collection of independent computers that appears to its users as a single coherent system two aspects. In this chapter, we concentrate on three different, important ways that names are used in distributed systems. Distributed file system dfs a distributed implementation of the classical timesharing model of a file system, where multiple users share files and storage resources a dfs manages set of dispersed storage devices. For instance a company may have many branches operating at. To operate on an entity, we need to access it at anaccess point. In a distributed system, replicas of an object are generally created to improve performance and reliability.
Distributed software systems 2 naming entities a name in a distributed system is a string of bits or characters that is used to refer to an entity types of names address. Entities, names, addresses an entity in a distributed system can be pretty much anything. This chapter presents some common examples of data processing and computing systems and discusses in particular the aspects of parallelism and distribution of control and data. Understanding naming in distributed systems springerlink. Traditional distributed systems often have a three layer naming. Naming naming entities naming entities names, identi. Naming in distributed systems unique identifiers uids e. Types of systems discussed in this course include computational clouds, grid computing, storage systems, peertopeer networks and web. Information system, an integrated set of components for collecting, storing, and processing data and for providing information, knowledge, and digital products. How this distribution is done plays a key role in the efficiency and scalability of the naming system. Explain how a domain is used to implement a hierarchical naming scheme in distributed systems. Access points are entities that are named by means of anaddress. Name the access protocol resolved to the implementation of a communication protocol 2.
Naming, organization of names and name resolution are key issue in any distributed systems. Sanjeev setia distributed software systems cs 707 distributed software systems 2 about this class distributed systems are ubiquitous focus. Distributed systems 17 scale in distributed systems observation many developers of modern distributed systems easily use the adjective scalable without making clear why their system actually scales. A file system is responsible for the organization, storage, retrieval, naming, sharing, and. Architectural models, fundamental models theoretical foundation for distributed system. An entity in a distributed system can be practically anything. Names in a distributed system are organised as a name space. Distributed computing is a field of computer science that studies distributed systems. Middleware and distributed systems naming and directory. In order to access the named resources, there must be a method for resolving the naming. Define a distributed system and give examples of several different distributed systems paradigms.
We start with centralized systems because they are the most intuitive and easy to understand and define. Names in distributed systems n1 university of cambridge. The names that ap plications use may have the same structure, or not. Naming entities names are used to denote entities in a distributed system, e. In general, if two name spaces exist ns1, ns2 to mount a foreign entity in a distributed system, we require at least the following information. Distributed systems, spring 2004 3 naming entities definitions name resolution name spaces examples dns, x.
In this article, we will try to understand and compare different aspects of centralized, decentralized and distributed systems. Naming names play a critical role in all computer systems to access resources, uniquely identify entities, or refer to locations to access an entity, you have to resolve the name and find the entity name resolution in a distributed system, the naming system itself is implemented across multiple machines. Pdf this paper addresses the problem of naming and identification in distributed systems. Naming is about mapping between names, addresses, identifiers and the referred entities. Comparison centralized, decentralized and distributed. Naming in distributed systems tamu computer science people. Cse 5306 distributed systems naming cse services uta. Connect to a remote machine and interactively send or fetch an arbitrary.
It describes an architecture centered on objects, names and contexts which support different naming policies. It stores information on the entity it is representing and it can store the state of entities in the case of file systems. Feb 23, 2018 about naming concepts in distributed systems. Names are used to denote entities in a distributed system hosts, printers, files, processes, users. Early distributed systems emerged in the late 1970s and early 1980s because of the usage of local area networking technologies system typically consisted of 10 to 100 nodes connected by a lan, with limited internet connectivity and supported services e. Yudel luke, or yudel luke, 3 acacia drive which directory to use. This paper addresses the problem of naming and identification in distributed systems. Finding the entity a name refers to is said resolving a name name resolution naming system the portion of the system devoted to name resolution the issue of naming in distributed systems naming is an issue in computational systems in general features of distributed system makes naming even more di cult openness location mobility. Most data processing systems are of a distributed nature, and most computer systems can be considered as being distributed under certain aspects. Traditional distributed systems often have a three layer naming scheme. Naming in distributed systems has a rich history and literature and the basics are well understood. Naming and directoriies middleware and distributed systems mvl 2011 naming communication and resource sharing demands an identi. Can be humanfriendly or not and location dependent or not. Overall storage space managed by a dfs is composed of different, remotely located, smaller storage spaces.
A name in a distributed system is a string of bits or characters that is used to refer to an entity. Naming services in distributed systems in general provide clients with values of attributes of named objects name space the collection of valid names recognised by a name service a precise specification is required, giving the structure of names e. Viewing names as strings and name resolution mechanisms as syntax directed translators provides a formal handle on the loosely understood concepts associated with naming. Note alocationindependentname for an entity e, is independent from the addresses of the access points offered by e. Most modern systems and applications are distributed for a variety of reasons, including resource sharing, faulttolerance, performance, etc. Distributed software systems 22 transparency in distributed systems access transparency.
To operate on an entity, we need to access it at an access point access points are entities that are named by means of an address an entity may have more than one access. In distributed settings, the naming system is often provided. Distributed algorithms have arisen in a wide spectrum of applications, including telecommunications, distributed information processing, scientific computing, real time process control, etc. Day 05 part 02 naming and location transparency in. The issue of naming in distributed systems naming is an issue in computational systems in general features of distributed system makes naming even more di cult openness location mobility distribution of the naming systems the issue of naming system distribution scalability e ciency andrea omicini universit a di bologna 7 naming a. Geographically partitioned distributed naming database. One more problem is the management of the naming system. Naming systems a naming system is simply a middleware that assists in name resolution naming systems are classified into three classes based on the type of names used. To access an entity, you have resolve the name and find the entity. Computer science distributed ebook notes lecture notes distributed system syllabus covered in the ebooks uniti characterization of distributed systems. Examples example telephone as access point to a person. It is important to understand those schemes because it is likely that one of these can be adopted. A name is a string of bits used to refer to an entity. Naming naming entities naming entities dcu school of.
The ohio state university raj jain 24 15 name resolution cont each computer has a name resolver routine, e. Typical examples include resources such as hosts, printers, disks, and files. In a distributed system, the implementation of a naming system is itself often distributed across multiple machines. Parse components from left to right separated by homepaulsrcgpsgui. Entitycomponent system ecs is an architectural pattern that is mostly used in game development. That is, if not necessary, a user should not be aware that multiple copies of an object are in use.
Names are structured entities, often being a con catenation of several fields. Each domain can be subdivided into multiple smaller subdomains. The components interact with one another in order to achieve a common goal. View notes lecture slides 4 from cs 303 at international institute of information technology. The issue of naming in distributed systems naming is an issue in computational systems in general features of distributed system makes naming even more di cult openness location mobility distribution of the naming systems the issue of naming system distribution scalability e ciency andrea omicini universit a di bologna 6 naming a. These entities are referred to by users of the system and other entities by various kinds of names.
Pdf naming and identification in distributed systems. If we consider naming and binding in file systems, we have the user and programmer. Name services werner nutt 2 naming concepts names strings used to identify objects files, computers, people, processes, objects textual names human readable used to identify individual services, people email address. Electronic version is current, paper directories are an official cache frequency of update some years ago. At the end of the document are references to a set of extant naming schemes. It becomes increasingly difficult to assure the uniqueness of names. Distributed systems, prentice hall, 2002, chapter 4 some terminology. Distributed software systems 1 introduction to distributed computing prof. Msit peertopeer computing northwestern university names, identifiers and addresses names are used to denote entities in a distributed system hosts, printers, files, processes, users. Pdf distributed systems are by now commonplace, yet remain an often difficult area of research.
Leaf node represents the name entity and has the property that it has no outgoing edge. Names are used to share resources, uniquely identify entities and refer to. His current research focuses primarily on computer security, especially in operating systems, networks, and large widearea distributed systems. The telephone number then becomes the address of the person.803 968 1427 1085 1231 1587 1276 755 1384 257 1040 863 1585 591 337 844 234 144 1013 739 881 1157 1023 1083 920 542 762 196 53 596 1247 1330 1056 473