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38-408: The SNAP and LSAP fields are added to the packets at the transmitting node in order to allow the receiving node to pass each received frame to an appropriate device driver which understands the given protocol . The OSI model uses a Service Access Point (SAP) to define the communication between layers (like Network, Transport, Session, and the other layers of the seven-layer model), that

76-417: A coordination problem : it emerges from situations in which all parties realize mutual gains, but only by making mutually consistent decisions. Examples : Private standards are developed by private entities such as companies, non-governmental organizations or private sector multi-stakeholder initiatives, also referred to as multistakeholder governance . Not all technical standards are created equal. In

114-527: A MAC station to communicate with upper layers via different protocols. Standard Network layer protocols have been assigned reserved LLC addresses, as recorded in ISO/IEC TR 11802-1. One half of the LLC address space is reserved for such assignment. Other protocols are accommodated in two ways. One way is by local assignment of LSAPs, for which the other half of the LLC address space is available. The second way

152-609: A SNAP packet is usually AA AA 03; however, SNAP can be used with other PDU types as well. On Ethernet , the 8 octets occupied by the LLC and SNAP headers reduce the size of the available payload for protocols such as the Internet Protocol to 1492 bytes, compared to the use of the Ethernet II framing ; therefore, for protocols that have EtherType values, packets are usually transmitted with Ethernet II headers rather than with LLC and SNAP headers. On other network types,

190-434: A government (i.e., through legislation ), business contract, etc. The standardization process may be by edict or may involve the formal consensus of technical experts. The primary types of technical standards are: Technical standards are defined as: Technical standards may exist as: When a geographically defined community must solve a community-wide coordination problem , it can adopt an existing standard or produce

228-515: A large user base, doing some well established thing that between them is mutually incompatible. Establishing national/regional/international standards is one way of preventing or overcoming this problem. To further support this, the WTO Technical Barriers to Trade (TBT) Committee published the "Six Principles" guiding members in the development of international standards. The existence of a published standard does not imply that it

266-412: A new one. The main geographic levels are: National/Regional/International standards is one way of overcoming technical barriers in inter-local or inter-regional commerce caused by differences among technical regulations and standards developed independently and separately by each local, local standards organisation , or local company. Technical barriers arise when different groups come together, each with

304-621: A number of papers in relation to the proliferation of private food safety standards in the agri-food industry, mostly driven by standard harmonization under the multistakeholder governance of the Global Food Safety Initiative (GFSI). With concerns around private standards and technical barriers to trade (TBT), and unable to adhere to the TBT Committee's Six Principles for the development of international standards because private standards are non-consensus,

342-569: A response) in SSAP and DSAP. The SNAP extension allows using EtherType values or private protocol ID spaces in all IEEE 802 networks. It can be used both in datagram and in connection-oriented network services. Ethernet ( IEEE 802.3 ) networks are an exception; the IEEE 802.3x-1997 standard explicitly allowed using of the Ethernet II framing , where the 16-bit field after the MAC addresses does not carry

380-562: A single international standard ; ISO 9001 (quality), ISO 14001 (environment), ISO 45001 (occupational health and safety), ISO 27001 (information security) and ISO 22301 (business continuity). Another example of a sector working with a single international standard is ISO 13485 (medical devices), which is adopted by the International Medical Device Regulators Forum (IMDRF). In 2020, Fairtrade International , and in 2021, Programme for

418-404: Is always useful or correct. For example, if an item complies with a certain standard, there is not necessarily assurance that it is fit for any particular use. The people who use the item or service (engineers, trade unions, etc.) or specify it (building codes, government, industry, etc.) have the responsibility to consider the available standards, specify the correct one, enforce compliance, and use

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456-454: Is an extension of the 802.2 LLC specified in the IEEE 802 Overview and Architecture document. The 5-octet SNAP header follows the 802.2 LLC header if the destination SAP (DSAP) and the source SAP (SSAP) contain hexadecimal values of AA or AB: The SNAP header consists of a 3-octet IEEE organizationally unique identifier (OUI) followed by a 2-octet protocol ID. If the OUI is zero, the protocol ID

494-579: Is assigned an LLC Class according to which service types it supports: Any 802.2 LLC PDU has the following format: When Subnetwork Access Protocol (SNAP) extension is used, it is located at the start of the Information field: The 802.2 header includes two eight-bit address fields, called service access points (SAP) or collectively LSAP in the OSI terminology: Although the LSAP fields are 8 bits long,

532-581: Is compulsory for all IEEE 802 networks with the exception of Ethernet . It is also used in Fiber Distributed Data Interface (FDDI) which is not part of the IEEE 802 family. The IEEE 802.2 sublayer adds some control information to the message created by the upper layer and passed to the LLC for transmission to another node on the same data link. The resulting packet is generally referred to as LLC protocol data unit (PDU) and

570-452: Is possible to use diverse framings on a single network. It is possible to do it even for the same upper layer protocol, but in such a case the nodes using unlike framings cannot directly communicate with each other. Following the destination and source SAP fields is a control field . IEEE 802.2 was conceptually derived from HDLC , and has the same three types of PDUs : To carry data in the most-often used unacknowledged connectionless mode

608-793: Is the original name of the ISO/IEC 8802-2 standard which defines logical link control (LLC) as the upper portion of the data link layer of the OSI Model . The original standard developed by the Institute of Electrical and Electronics Engineers (IEEE) in collaboration with the American National Standards Institute (ANSI) was adopted by the International Organization for Standardization (ISO) in 1998, but it remains an integral part of

646-423: Is the registered EtherType value for the protocol running on top of SNAP. If the OUI is an OUI for a particular organization, the protocol ID is a value assigned by that organization to the protocol running on top of SNAP. SNAP is usually used with Unnumbered Information 802.2 protocol data units (PDUs), with a control field value of 3, and the LSAP values are usually hexadecimal AA, so the 802.2 LLC header for

684-407: Is to identify which protocol should process an incoming message. Within a given layer, programs can exchange data by a mutually agreed-upon protocol mechanism. A pair of programs that do not support a common protocol cannot communicate with each other. Thus for multiple protocols to coexist within a layer, it is necessary to determine which protocol is invoked to process a service data unit delivered by

722-666: Is to use a particular reserved LLC address value that has been assigned for use in conjunction with the Sub-network Access Protocol (SNAP) is called the SNAP address. The SNAP address identifies, at each MAC SAP, a single LSAP. Thus, each protocol using SNAP must employ a protocol identifier. Thus, the Subnetwork Access Protocol (SNAP) is a mechanism for multiplexing, on networks using IEEE 802.2 LLC , more protocols than can be distinguished by

760-646: Is usually a formal document that establishes uniform engineering or technical criteria, methods, processes, and practices. In contrast, a custom, convention, company product, corporate standard, and so forth that becomes generally accepted and dominant is often called a de facto standard. A technical standard may be developed privately or unilaterally, for example by a corporation, regulatory body, military, etc. Standards can also be developed by groups such as trade unions and trade associations. Standards organizations often have more diverse input and usually develop voluntary standards: these might become mandatory if adopted by

798-666: The Internet standard RFC 1042 is usually used for encapsulating IPv4 traffic in 802.2 LLC frames with SNAP headers on FDDI and on IEEE 802 networks other than Ethernet . Ethernet networks typically use Ethernet II framing with EtherType 0x800 for IP and 0x806 for ARP. The IPX protocol used by Novell NetWare networks supports an additional Ethernet frame type, 802.3 raw , ultimately supporting four frame types on Ethernet (802.3 raw, 802.2 LLC , 802.2 SNAP , and Ethernet II ) and two frame types on FDDI and other (non-Ethernet) IEEE 802 networks (802.2 LLC and 802.2 SNAP). It

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836-583: The WTO does not rule out the possibility that the actions of private standard-setting bodies may be subject to WTO law. BSI Group compared private food safety standards with "plugs and sockets", explaining the food sector is full of "confusion and complexity". Also, "the multiplicity of standards and assurance schemes has created a fragmented and inefficient supply chain structure imposing unnecessary costs on businesses that have no choice but to pass on to consumers". BSI provide examples of other sectors working with

874-401: The 8-bit 802.2 Service Access Point (SAP) fields. SNAP supports identifying protocols by Ethernet type field values; it also supports vendor-private protocol identifier spaces. It is used with IEEE 802.3 , IEEE 802.4 , IEEE 802.5 , IEEE 802.11 and other IEEE 802 physical network layers , as well as with non-IEEE 802 physical network layers such as FDDI that use 802.2 LLC. The SNAP

912-468: The Endorsement of Forest Certification (PEFC) issued position statements defending their use of private standards in response to reports from The Institute for Multi-Stakeholder Initiative Integrity (MSI Integrity) and Greenpeace. Private standards typically require a financial contribution in terms of an annual fee from the organizations who adopt the standard. Corporations are encouraged to join

950-410: The LLC and SNAP headers are required in order to multiplex different protocols on the link layer, as the MAC layer doesn't itself have an EtherType field, so there's no alternative framing that would have a larger available payload. One might ask, "why is a separate sub-network header necessary?". The answer is that it was to augment a decision made during the layout of the LLC header. At the time that

988-723: The LLC header was being designed, it was thought that a single octet (256 possible values) in the header would be enough to specify all the protocol values that vendors would want to register. As the values began to be reserved, it was discovered that the LLC header would soon run out of open values. The hexadecimal AA and AB values were reserved, and an additional header—the SNAP header—was developed; it can support all EtherType values and multiple spaces of private protocol values. IP datagrams and ARP datagrams are transmitted over IEEE 802 networks using LLC and SNAP headers, except on Ethernet/IEEE 802.3, where they are transmitted with Ethernet II headers. IEEE 802.2#LSAP values IEEE 802.2

1026-890: The U-format is used. It is identified by the value '11' in lower two bits of the single-byte control field. Technical standard A technical standard is an established norm or requirement for a repeatable technical task which is applied to a common and repeated use of rules, conditions, guidelines or characteristics for products or related processes and production methods, and related management systems practices. A technical standard includes definition of terms; classification of components; delineation of procedures; specification of dimensions, materials, performance, designs, or operations; measurement of quality and quantity in describing materials, processes, products, systems, services, or practices; test methods and sampling procedures; or descriptions of fit and measurements of size or strength. It

1064-552: The additional information added by the LLC sublayer is the LLC HEADER . The LLC Header consist of DSAP ( Destination Service Access Point ), SSAP ( Source Service Access Point ) and the Control field. The two 8-bit fields DSAP and SSAP allow multiplexing of various upper layer protocols above LLC. However, many protocols use the Subnetwork Access Protocol (SNAP) extension which allows using EtherType values to specify

1102-443: The board of governance of the standard owner which enables reciprocity. Meaning corporations have permission to exert influence over the requirements in the standard, and in return the same corporations promote the standards in their supply chains which generates revenue and profit for the standard owner. Financial incentives with private standards can result in a perverse incentive , where some private standards are created solely with

1140-461: The development of a technical standard, private standards adopt a non-consensus process in comparison to voluntary consensus standards. This is explained in the paper International standards and private standards . The International Trade Centre published a literature review series with technical papers on the impacts of private standards and the Food and Agriculture Organization (FAO) published

1178-427: The family of IEEE 802 standards for local and metropolitan networks. LLC is a software component that provides a uniform interface to the user of the data link service, usually the network layer . LLC may offer three types of services: The LLC uses the services of the media access control (MAC), which is dependent on the specific transmission medium ( Ethernet , Token Ring , FDDI , 802.11 , etc.). Using LLC

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1216-411: The item correctly. Validation of suitability is necessary. Standards often get reviewed, revised and updated on a regular basis. It is critical that the most current version of a published standard be used or referenced. The originator or standard writing body often has the current versions listed on its web site. In social sciences , including economics , a standard is useful if it is a solution to

1254-472: The length of the frame followed by the IEEE 802.2 LLC header, but the EtherType value followed by the upper layer data. With this framing only datagram services are supported on the data link layer . Although IPv4 has been assigned an LSAP value of 6 (0x06) and ARP has been assigned an LSAP value of 152 (0x98), IPv4 is almost never directly encapsulated in 802.2 LLC frames without SNAP headers. Instead,

1292-450: The low-order bit is reserved for special purposes, leaving only 128 values available for most purposes. The low-order bit of the DSAP indicates whether it contains an individual or a group address: The low-order bit of the SSAP indicates whether the packet is a command or response packet: The remaining 7 bits of the SSAP specify the LSAP (always an individual address) from which the packet

1330-652: The lower layer. The most common reference to SAP, including a Source Service Access Point (SSAP) and a Destination Service Access Point (DSAP) refers to the boundary between the Data Link Layer and the Network Layer. It is common to think of SAP only in terms of its use at Layer 2, specifically in its Logical Link Control (LLC) sub-layer as defined in the IEEE 802.2 standards. Link Service Access Point (LSAP) includes both Destination Service Access Point (DSAP) and Source Service Access Point (SSAP). It enables

1368-528: The protocol being transported atop IEEE 802.2. It also allows vendors to define their own protocol value spaces. The 8 or 16 bit HDLC -style Control field serves to distinguish communication mode, to specify a specific operation and to facilitate connection control and flow control (in connection mode) or acknowledgements (in acknowledged connectionless mode). IEEE 802.2 provides two connectionless and one connection-oriented operational modes: The use of multicasts and broadcasts reduces network traffic when

1406-454: The same information needs to be propagated to all stations of the network. However the Type 1 service provides no guarantees regarding the order of the received frames compared to the order in which they have been sent; the sender does not even get an acknowledgment that the frames have been received. Each device conforming to the IEEE 802.2 standard must support service type 1. Each network node

1444-405: Was transmitted. LSAP numbers are globally assigned by the IEEE to uniquely identify well established international standards. The protocols or families of protocols which have assigned one or more SAPs may operate directly on top of 802.2 LLC. Other protocols may use the Subnetwork Access Protocol (SNAP) with IEEE 802.2 which is indicated by the hexadecimal value 0xAA (or 0xAB, if the source of

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