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Remote Operations Service Element Protocol

Remote operations service element protocol

In the OSI Model, the remote operations service element protocol (ROSE) is an application layer protocol that (a) provides remote operation capabilities, (b) allows interaction between entities in a distributed application, and (c) upon receiving a remote operations service request, allows the receiving entity to attempt the operation and report the results of the attempt to the requesting entity. OSI application protocols such as X.400 and X.500 were defined using ROSE. See also remote procedure call and ASN.1. Category:ITU-T recommendations

OSI model

The Open Systems Interconnection Reference Model (OSI Model or OSI Reference Model for short) is a layered abstract description for communications and computer network protocol design, developed as part of the Open Systems Interconnect initiative. It is also called the OSI seven layers model.

Purpose

The OSI model divides the functions of a protocol into a series of layers. Each layer has the property that it only uses the functions of the layer below, and only exports functionality to the layer above. A system that implements protocol behavior consisting of a series of these layers is known as a 'protocol stack' or 'stack'. Protocol stacks can be implemented either in hardware or software, or a mixture of both. Typically, only the lower layers are implemented in hardware, with the higher layers being implemented in software. This OSI model is roughly adhered to in the computing and networking industry. Its main feature is in the interface between layers which dictates the specifications on how one layer interacts with another. This means that a layer written by one manufacturer can operate with a layer from another (assuming that the specification is interpreted correctly.) These specifications are typically known as Request for Comments or "RFC"s in the TCP/IP community. They are ISO standards in the OSI community. Usually, the implementation of a protocol is layered in a similar way to the protocol design, with the possible exception of a 'fast path' where the most common transaction allowed by the system may be implemented as a single component encompassing aspects of several layers. This logical separation of layers makes reasoning about the behavior of protocol stacks much easier, allowing the design of elaborate but highly reliable protocol stacks. Each layer performs services for the next higher layer, and makes requests of the next lower layer. As previously stated, an implementation of several OSI layers is often referred to as a stack (as in TCP/IP stack). The OSI reference model is a hierarchical structure of seven layers that defines the requirements for communications between two computers. The model was defined by the International Organization for Standardization. It was conceived to allow interoperability across the various platforms offered by vendors. The model allows all network elements to operate together, regardless of who built them. By the late 1970's, ISO was recommending the implementation of the OSI model as a networking standard. Of course, by that time, TCP/IP had been in use for years. TCP/IP was fundamental to ARPANET and the other networks that evolved into the Internet. (For significant differences between TCP/IP and ARPANET, see RFC 871). Only a subset of the whole OSI model is used today. It is widely believed that much of the specification is too complicated and its full functionality has taken too long to implement, although there are many people that strongly support the OSI model. On the other hand, many feel that the best thing about the whole ISO networking effort is that it failed before it could do too much damage.

Description of layers

ARPANET

Layer 1: Physical layer

The physical layer defines all the electrical and physical specifications for devices. This includes the layout of pins, voltages, and cable specifications. Hubs and repeaters are physical-layer devices. The major functions and services performed by the physical layer are:
- establishment and termination of a connection to a communications medium.
- participation in the process whereby the communication resources are effectively shared among multiple users. For example, contention resolution and 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 -- copper and fibre optic, for example. SCSI operates at this level.

Layer 2: Data link layer

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. The addressing scheme is physical which means that the addresses (MAC address) are hard-coded into the network cards at the time of manufacture. The addressing scheme is flat. Note: The best known example of this is Ethernet. Other examples of data link protocols are HDLC and ADCCP for point-to-point or packet-switched networks and LLC and Aloha for local area networks. This is the layer at which bridges and switches operate. Connectivity is provided only among locally attached network nodes.

Layer 3: Network layer

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. The Network layer performs network routing, flow control, segmentation/desegmentation, and error control functions. Routers operate at this layer -- sending data throughout the extended network and making the Internet possible (there also exist layer 3 (or IP) switches). This is a logical addressing scheme - values are chosen by the network engineer. The addressing scheme is hierarchical. This layer can be of least significance in case of Broadcasting Networking.

Layer 4: Transport layer

The transport layer provides transparent transfer of data between end users, thus relieving the upper layers from any concern with providing reliable and cost-effective data transfer. The transport layer controls the reliability of a given link. Some protocols are stateful and connection oriented. This means that the transport layer can keep track of the packets and retransmit those that fail. The best known example of a layer 4 protocol is TCP.

Layer 5: Session layer

The session layer provides the mechanism for managing the dialogue between end-user application processes (By dialog we mean that whose turn it is to transmit). It provides for either duplex or half-duplex operation and establishes checkpointing, adjournment, termination, and restart procedures (keeping a track so as to restart from the very same point where they had left in case of a crash). This layer is responsible for setting up and tearing down TCP/IP sessions.

Layer 6: Presentation layer

The presentation layer relieves the Application layer of concern regarding syntactical differences in data representation within the end-user systems. MIME encoding, data compression, encryption, and similar manipulation of the presentation of data is done at this layer. An example of a presentation service would be the conversion of an EBCDIC-coded text file to an ASCII-coded file or serializing objects and other data structures into and out of XML.

Layer 7: Application layer

The application layer interfaces directly to and performs common application services for the application processes. The common application services provide semantic conversion between associated application processes. Examples of common application services include the virtual file, virtual terminal (for example, Telnet), transfer and Manipulation protocol" (JTM, standard ISO/IEC 8832).

Interfaces

In addition to standards for individual protocols in transmission, there are also interface standards for different layers to talk to the ones above or below (usually operating-system-specific). For example, Microsoft Windows's Winsock and Unix's Berkeley sockets and System V Streams are interfaces between applications (layers 5 and above) and the transport (layer 4). NDIS and ODI are interfaces between the media (layer 2) and the network protocol (layer 3).

Table of examples

Parallel

ODI

Humor

The 7 layer model has often been extended in a humorous manner, to refer to non-technical issues or problems. A common joke is the 9 layer model, with layers 8 and 9 being the "financial" and "political" layers. Network technicians will sometimes refer euphemistically to "layer-eight problems," meaning problems with an end user and not with the network. The OSI model has also on occasion been jokingly called the "Taco Bell model", since the restaurant chain has been known for their 7 layer burrito. Dick Lewis uses an [http://www.lewistech.com/rlewis/Resources/james.aspx analogy of James Bond delivering classified messages] to illustrate the seven-layer model.

See also


- DoD model
- List of network protocols
- OSI protocols Category:Computer networks Category:ITU-T recommendations ko:OSI 모델 ja:OSI参照モデル

Protocol

Protocol may mean:
- Protocol (treaty), a treaty or international agreement that supplements a previous one
- Protocol (politics), a logbook or other artifact of a political meeting between persons from different nations
- Protocol (diplomacy), the etiquette of diplomacy and affairs of state
- Communications protocol, a set of rules governing communication between electronic devices
- Protocol (computing), a set of rules governing communication within and between computer networks
- Protocol (object-oriented programming), what or how unrelated objects use to communicate with each other in object-oriented computer programs
- Medical protocol, a set of guidelines for medical treatment
- Clinical protocol, the method used in a clinical trial of a drug or medical treatment
- Protocol (guidelines), a set of guidelines for use in various circumstances

See also


- The Protocols of the Elders of Zion. ms:Protokol ja:プロトコル

Operation

The word operation can mean any of several things:
- The method, act, process, or effect of using a device or system. See military operation, manufacturing operations, anomalous operation.
- In medicine, a surgical procedure to diagnose, cure or palliate a certain disease.
- In mathematics, an operation is an action applied to (one or more, but usually finitely many) numbers or other mathematical entities (e.g., vectors) to produce a well-defined result. Examples include addition, multiplication, root extraction, and comparison. See unary operation, binary operation, arity.
- In computer programming, a program step, usually specified by a part of an instruction word, that is undertaken or executed by a computer. Logical operations such as And, Or and Not are also operations typically performed by devices known as logic gates.
- In music a basic operation is one which may be performed on a set of pitches or pitch classes, including transposition, inversion, and multiplication. These may be combined to form compound operations, and inversion may be more accurately thought of as the compound operation transpositional inversion. See: transformation, permutation, counterpoint.
- If something happens by operation of law, then it occurs automatically based on circumstances not intended by the affected parties.
- The tactical shooting PC game Operation Flashpoint.
- The game of physical skill, Operation.
- In business, an organizational unit or set of procedures and processes that lead to business outcomes. See Business Operations
- In law enforcement a sting operation can be used to catch a law breaker in the act. ja:手術

Open systems interconnect

The Open Systems Interconnection (usually abbreviated to OSI) was a new effort in networking started in 1982 by the International Organization for Standardization (ISO), along with the ITU-T. Prior to OSI, networking was completely vendor-developed and proprietary, with protocol standards such as SNA and DECnet. OSI was a new industry effort, attempting to get everyone to agree to common network standards to provide multi-vendor interoperability. It was common for large networks to support multiple network protocol suites, with many devices unable to talk to other devices because of a lack of common protocols between them. The OSI reference model (which actually predates the OSI protocol work, dating to 1977) was the most important advance in the teaching of network concepts. It promoted the idea of a common model of protocol layers, defining interoperability between network devices and software. However, the actual OSI protocol stack that was specified as part of the project was considered by many to be too complicated and to a large extent unimplementable. Taking the "forklift upgrade" approach to networking, it specified eliminating all existing protocols and replacing them with new ones at all layers of the stack. This made implementation difficult, and was resisted by many vendors and users with significant investments in other network technologies. In addition, the OSI protocols were specified by committees filled with differing and sometimes conflicting feature requests, leading to numerous optional features. Because so much was optional, many vendors' implementations simply could not interoperate, negating the whole effort. The OSI approach was eventually eclipsed by the Internet's TCP/IP protocol suite. TCP/IP's pragmatic approach to computer networking and two independent implementations of simplified protocols made it a practical standard. For example, the definition for OSI's X.400 e-mail standards took up several large books, while the Internet e-mail (SMTP) definition took only a few dozen pages in RFC-821. It should be noted, however, that over time there have been numerous RFCs which extended the original SMTP definition, so that its complete documentation finally takes up several large books as well. Many of the protocols and specifications in the OSI stack are long-gone or have been superseded, such as token-bus media, CLNP packet delivery, FTAM file transfer, and X.400 e-mail. Some still survive, often in significantly simplified forms. The X.500 directory structure still remains with significant usage, mainly because the original unwieldy protocol has been stripped away and effectively replaced with LDAP. IS-IS also continues as a network routing protocol used by larger telecommunications companies, having been adapted for use with the Internet Protocol. Many legacy SONET systems still use TARP (TID Address Resolution Protocol - utilizes CLNP and IS-IS) to translate Target Identifier of a SONET node. Often protocols and specifications in the OSI stack remain in use in legacy systems, unless or until such legacy systems are eventually upgraded, replaced or decomissioned. The collapse of the OSI project in 1996 severely damaged the reputation and legitimacy of the organizations involved, especially ISO. The worst part was that OSI's backers took too long to recognize and accommodate the dominance of the TCP/IP protocol suite.

Further reading


- Marshall T. Rose, The Open Book (Prentice-Hall, Englewood Cliffs, 1990)
- David M. Piscitello, A. Lyman Chapin, Open Systems Networking (Addison-Wesley, Reading, 1993)

See also


- CMIS, Common Management Information Services

Reference


- ISO 7498:1984 Open Systems Interconnection - Basic Reference Model Category:ITU-T recommendations

X.500

X.500 is a series of computer networking standards covering electronic directory services. The X.500 series was developed by ITU-T, formerly known as CCITT. The directory services were developed in order to support the requirements of X.400 electronic mail exchange and name lookup. ISO was a partner in developing the standards, incorporating them into the Open Systems Interconnect suite of protocols. ISO/IEC 9594 is the corresponding ISO identification. The protocols defined by X.500 include:
- DAP (Directory Access Protocol)
- DSP (Directory System Protocol)
- DISP (Directory Information Shadowing Protocol)
- DOP (Directory Operational Bindings Management Protocol) X.509, the portion of the standard providing for an authentication framework, is now also widely used outside of the X.500 directory protocols. It specifies a standard format for public-key certificates. Because of the complexity of the protocols, a simplified alternative, known as Lightweight Directory Access Protocol (LDAP), was developed implementing only a subset of the protocols.

List of X.500 series standards

External links


- [http://sec.cs.kent.ac.uk/x500book/ Understanding X.500 - The Directory (Copyright 1994, 1996 D W Chadwick.) ] Category:OSI protocols Category:ISO standards Category:ITU-T recommendations

Remote procedure call

: This article relates to computers. For Rules of Professional Conduct (RPC) relating to U.S. lawyers' ethical rules, see American Bar Association Model Rules of Professional Conduct A remote procedure call (RPC) is a protocol that allows a computer program running on one host to cause code to be executed on another host without the programmer needing to explicitly code for this. When the code in question is written using object-oriented principles, RPC is sometimes referred to as remote invocation or remote method invocation. RPC is an easy and popular paradigm for implementing the client-server model of distributed computing. An RPC is initiated by the caller (client) sending a request message to a remote system (the server) to execute a certain procedure using arguments supplied. A result message is returned to the caller. There are many variations and subtleties in various implementations, resulting in a variety of different (incompatible) RPC protocols. In order to allow servers to be accessed by differing clients, a number of standardized RPC systems have been created. Most of these use an interface description language (IDL) to allow various platforms to call the RPC. The first popular implementation of RPC on Unix was Sun's RPC (sometimes called ONC RPC), which was used as the basis for NFS. Another early Unix implementation was the RPC mechanism in Apollo Computer's Network Computing System (NCS), which after HP's acquisition of Apollo later surfaced as DCE/RPC in the OSF's Distributed Computing Environment (DCE). A decade later Microsoft adopted DCE/RPC as the basis of their Microsoft RPC (MSRPC) mechanism, and implemented DCOM (and ActiveX) atop it. Xerox PARC's ILU, and CORBA, offered a similar RPC paradigm on the Windows and Unix platforms. Java's Java Remote Method Invoke (JRMI) API has replaced earlier Unix implementations of RPC on the Unix platform. .NET Remoting offers low-level RPC facilities for distributed systems implemented on the Windows platform. Web services were the first real attempt to implement RPC between platforms. Using Web services a .NET client can call a remote procedure implemented in Java on a Unix server (and vice versa). Web services use XML as the IDL, and HTTP as the network protocol. The advantage of this system is simplicity and standardization, the IDL is a text file that is widely understood, and HTTP is built into almost all modern operating systems. An example of such an RPC system is SOAP, developed in turn from XML-RPC. However, web services have been criticized as wasteful in terms of bandwidth and processing requirements. An example of a modern RPC system that attempts to avoid both the complexity of CORBA and the inefficiency of web services is ZeroC's Internet Communications Engine (ICE). An alternative approach to RPC is Representational State Transfer REST. Category:Operating system technology ja:RPC

Abstract syntax notation one

In telecommunications and computer networking Abstract Syntax Notation one (ASN.1) is a standard and flexible notation that describes data structures for representing, encoding, transmitting, and decoding data. It provides a set of formal rules for describing the structure of objects that are independent of machine-specific encoding techniques and is a precise, formal notation that removes ambiguities. ASN.1 is a joint ISO and ITU-T standard, originally defined in 1984 as part of CCITT X.409:1984. ASN.1 moved to its own standard, X.208, in 1988 due to wide applicability. The substantially revised 1995 version is covered by the X.680 series. ASN.1 defines the abstract syntax of information but does not restrict the way the information is encoded. Various ASN.1 encoding rules provide the transfer syntax (a concrete representation) of the data values whose abstract syntax is described in ASN.1. The standard ASN.1 encoding rules include BER (Basic Encoding Rules), CER (Canonical Encoding Rules), DER (Distinguished Encoding Rules), PER (Packed Encoding Rules), and XER (XML Encoding Rules). ASN.1 together with specific ASN.1 encoding rules facilitates the exchange of structured data especially between application programs over networks by describing data structures in a way that is independent of machine architecture and implementation language. Application layer protocols such as X.400 electronic mail, X.500 directory services, H.323 (VoIP) and SNMP use ASN.1 to describe the PDUs they exchange. It is also extensively used in the Access and Non-Access Strata of UMTS. There are many other application domains of ASN.1 [http://asn1.elibel.tm.fr/en/uses/index.htm]. Many free and commercial tools for ASN.1 are available [http://asn1.elibel.tm.fr/links/#tools].

Standards

Standards describing the ASN.1 notation ([http://www.itu.int/ITU-T/studygroups/com17/languages/ free download from the ITU-T website]):
- ITU-T Rec. X.680 | ISO/IEC 8824-1
- ITU-T Rec. X.681 | ISO/IEC 8824-2
- ITU-T Rec. X.682 | ISO/IEC 8824-3
- ITU-T Rec. X.683 | ISO/IEC 8824-4 Standards describing the ASN.1 encoding rules ([http://www.itu.int/ITU-T/studygroups/com17/languages/ free download from the ITU-T website]):
- ITU-T Rec. X.690 | ISO/IEC 8825-1 (BER, CER and DER)
- ITU-T Rec. X.691 | ISO/IEC 8825-2 (PER)
- ITU-T Rec. X.693 | ISO/IEC 8825-4 (XER) [http://asn1.elibel.tm.fr/standards/ List of all ASN.1 standards]

See also


- TTCN

References


- Federal Standard 1037C
- MIL-STD-188.
- [http://asn1.elibel.tm.fr/fr/biblio/index.htm Other references]

External links


- [http://www.asn1.org/ The ASN.1 Consortium]
- [http://asn1.elibel.tm.fr/ ASN.1 Information site]
- [http://asn1.elibel.tm.fr/links/ Other links]
- [http://asn1.elibel.tm.fr/en/tools/tutorial/ ASN.1 tutorial] Category:ITU-T recommendations

Category:ITU-T recommendations

ITU-T Recommendations are the names given to telecommunications and computer protocol specification documents published by ITU-T. Many of the recommendations that define OSI are also ISO standards. Standards for Internet protocols are typically developed in the IETF, and standards for mobile telephone systems are developed in ETSI and other forums. See also :Category:Network protocols. Category:Computer and telecommunication standards

353

---- Gebeurtenissen:
- Slag van Mons Seleucus - Constantius II verslaat de usurpator Magnentius.
- Constantius II wordt enig keizer. ---- Geboren: ---- Overleden:
- 10 augustus - Magnentius, tegenkeizer (zelfmoord)
- 18 augustus - Magnus Decentius, Caesar onder Magnentius (zelfmoord). Categorie:4e eeuw ko:353년

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