which layer of the osi model is responsible for end-to-end data transmission and error recovery
The data link layer
304509
signal timing and frequency for wireless devices. Bit rate control is done at the physical layer and may define transmission mode as simplex, half duplex, and full duplex. The components of a physical layer can be described in terms of a network topology. Bluetooth, Ethernet, and USB all have specifications for a physical layer. The data link layer provides node-to-node data transfer—a link between two directly connected nodes. It detects and possibly corrects errors that may occur in the physical layer. It defines the protocol to establish and terminate a connection between two physically connected devices. It also defines the
OSI model
3994218
which the digital signals are transmitted. It can be twisted pair, coaxial cable, optical fiber, wireless, or other transmission media. The data link layer packages raw bits from the physical layer into frames (logical, structured packets for data). It is specified in [http://www.itu.int/rec/T-REC-X.212/en/ ITU-T Rec. X.212 <nowiki>[ISO/IEC 8886]</nowiki>], ITU-T Rec. X.222 and others. This layer is responsible for transferring frames from one host to another. It might perform error checking. This layer further consists of two sublayers : MAC and LLC. This level is in charge of transferring data between systems in a network, using network-layer addresses of machines to
OSI protocols
598581
DAB to terrestrial broadcast to avoid interference. DAB historically had a number of country specific transmission modes (I, II, III and IV). In January 2017, an updated DAB specification (2.1.1) removed Modes II, III and IV, leaving only Mode I. From an OSI model protocol stack viewpoint, the technologies used on DAB inhabit the following layers: the audio codec inhabits the presentation layer. Below that is the data link layer, in charge of statistical time division multiplexing and frame synchronization. Finally, the physical layer contains the error-correction coding, OFDM modulation, and dealing with the over-the-air transmission and reception of data.
Digital audio broadcasting
2180387
AX.25 AX.25 (Amateur X.25) is a data link layer protocol originally derived from layer 2 of the X.25 protocol suite and designed for use by amateur radio operators. It is used extensively on amateur packet radio networks. AX.25 v2.0 and later occupies the data link layer, the second layer of the OSI model. It is responsible for establishing link-layer connections, transferring data encapsulated in frames between nodes, and detecting errors introduced by the communications channel. As AX.25 is a pre-OSI-model protocol, the original specification was not written to cleanly separate into OSI layers. This was rectified with version 2.0 (1984),
AX.25
881015
Network layer In the seven-layer OSI model of computer networking, the network layer is layer 3. The network layer is responsible for packet forwarding including routing through intermediate routers. The network layer provides the means of transferring variable-length network packets from a source to a destination host via one or more networks. Within the service layering semantics of the OSI network architecture, the network layer responds to service requests from the transport layer and issues service requests to the data link layer. Functions of the network layer include: The TCP/IP model describes the protocols used by the Internet. The TCP/IP
Network layer
304510
protocol for flow control between them. IEEE 802 divides the data link layer into two sublayers: The MAC and LLC layers of IEEE 802 networks such as 802.3 Ethernet, 802.11 Wi-Fi, and 802.15.4 ZigBee operate at the data link layer. The Point-to-Point Protocol (PPP) is a data link layer protocol that can operate over several different physical layers, such as synchronous and asynchronous serial lines. The ITU-T G.hn standard, which provides high-speed local area networking over existing wires (power lines, phone lines and coaxial cables), includes a complete data link layer that provides both error correction and flow control by
OSI model
117376
of its history, Ethernet data transfer rates have been increased from the original 2.94 megabits per second (Mbit/s) to the latest 400 gigabits per second (Gbit/s). The comprise several wiring and signaling variants of the OSI physical layer in use with Ethernet. Systems communicating over Ethernet divide a stream of data into shorter pieces called frames. Each frame contains source and destination addresses, and error-checking data so that damaged frames can be detected and discarded; most often, higher-layer protocols trigger retransmission of lost frames. As per the OSI model, Ethernet provides services up to and including the data link layer.
Ethernet
1288912
Logical link control In the IEEE 802 reference model of computer networking, the logical link control (LLC) data communication protocol layer is the upper sublayer of the data link layer (layer 2) of the seven-layer OSI model. The LLC sublayer provides multiplexing mechanisms that make it possible for several network protocols (e.g. IP, IPX, Decnet and Appletalk) to coexist within a multipoint network and to be transported over the same network medium. It can also provide flow control and automatic repeat request (ARQ) error management mechanisms. The LLC sublayer acts as an interface between the media access control (MAC) sublayer
Logical link control
8015679
scope of the Internet protocol suite, MoCA is a protocol that provides the link layer. In the 7-layer OSI model, it provides definitions within the data link layer (layer 2) and the physical layer (layer 1). DLNA approved of MoCA as a layer 2 protocol. MoCA 1.1 provides 175 Mbit/s net throughputs (275 Mbit/s PHY rate) and operates in the 500 to 1500 MHz frequency range. MoCA 2.0 offers actual throughputs (MAC rate) up to 1 Gbps. Operating frequency range is 500 to 1650 MHz. Packet error rate is 1 packet error in 100 million. MoCA 2.0 also offers lower
Multimedia over Coax Alliance
538759
protocols used). Although X.25 predates the OSI Reference Model (OSIRM), the physical Layer of the OSI model corresponds to the X.25 "physical layer", the data link layer to the X.25 "data link layer", and the network layer to the X.25 "packet layer". The X.25 "data link layer", LAPB, provides a reliable data path across a data link (or multiple parallel data links, multilink) which may not be reliable itself. The X.25 "packet layer" provides the virtual call mechanisms, running over X.25 LAPB. The "packet layer" includes mechanisms to maintain virtual calls and to signal data errors in the event that
X.25
518268
frame synchronization sequence. In the OSI model of computer networking, a frame is the protocol data unit at the data link layer. Frames are the result of the final layer of encapsulation before the data is transmitted over the physical layer. A frame is "the unit of transmission in a link layer protocol, and consists of a link layer header followed by a packet." Each frame is separated from the next by an interframe gap. A frame is a series of bits generally composed of frame synchronization bits, the packet payload, and a frame check sequence. Examples are Ethernet frames,
Frame (networking)
519004
or channel access method, for example, TDM into time-division multiple access (TDMA) and statistical multiplexing into carrier-sense multiple access (CSMA). A multiple access method makes it possible for several transmitters connected to the same physical medium to share its capacity. Multiplexing is provided by the Physical Layer of the OSI model, while multiple access also involves a media access control protocol, which is part of the Data Link Layer. The Transport layer in the OSI model, as well as TCP/IP model, provides statistical multiplexing of several application layer data flows to/from the same computer. Code-division multiplexing (CDM) is a technique
Multiplexing
849751
connecting network nodes. The bitstream may be grouped into code words or symbols and converted to a physical signal that is transmitted over a transmission medium. The physical layer provides an electrical, mechanical, and procedural interface to the transmission medium. The shapes and properties of the electrical connectors, the frequencies to broadcast on, the line code to use and similar low-level parameters, are specified here. Within the semantics of the OSI model, the physical layer translates logical communications requests from the data link layer into hardware-specific operations to cause transmission or reception of electronic signals. In a local area network
Physical layer
304509
signal timing and frequency for wireless devices. Bit rate control is done at the physical layer and may define transmission mode as simplex, half duplex, and full duplex. The components of a physical layer can be described in terms of a network topology. Bluetooth, Ethernet, and USB all have specifications for a physical layer. The data link layer provides node-to-node data transfer—a link between two directly connected nodes. It detects and possibly corrects errors that may occur in the physical layer. It defines the protocol to establish and terminate a connection between two physically connected devices. It also defines the
OSI model
7186056
computer network include electrical cable, optical fiber, and radio waves. In the OSI model, these are defined at layers 1 and 2 — the physical layer and the data link layer. A widely adopted "family" of transmission media used in local area network (LAN) technology is collectively known as Ethernet. The media and protocol standards that enable communication between networked devices over Ethernet are defined by IEEE 802.3. Ethernet transmits data over both copper and fiber cables. Wireless LAN standards use radio waves, others use infrared signals as a transmission medium. Power line communication uses a building's power cabling to
Computer network
538764
of proprietary intelligent communications devices, such as those for IBM System Network Architecture (SNA). Error recovery procedures at the packet layer assume that the data link layer is responsible for retransmitting data received in error. Packet layer error handling focuses on resynchronizing the information flow in calls, as well as clearing calls that have gone into unrecoverable states: X.25 supports two types of virtual circuits; virtual calls (VC) and permanent virtual circuits (PVC). Virtual calls are established on an as-needed basis. For example, a VC is established when a call is placed and torn down after the call is complete.
X.25
5219407
ensures that slots will not be wasted (whereas TDM can waste slots). The transmission capacity of the link will be shared by only those users who have packets. Static TDM and other circuit switching is carried out at the physical layer in the OSI model and TCP/IP model, while statistical multiplexing is carried out at the data link layer and above. In statistical multiplexing, each packet or frame contains a channel/data stream identification number, or (in the case of datagram communication) complete destination address information. Examples of statistical multiplexing are: In digital audio and video broadcasting, for example, a statistical
Statistical time-division multiplexing
1066758
Node-to-node data transfer In telecommunications, node-to-node data transfer is the movement of data from one node of a network to the next. In the OSI model it is handled by the lowest two layers, the data link layer and the physical layer. In most communication systems, the transmitting point applies source coding, followed by channel coding, and lastly, line coding. This produces the baseband signal. The presence of filters may perform pulse shaping. Some systems then use modulation to multiplex many baseband signals into a broadband signal. The receiver un-does these transformations in reverse order: demodulation, trellis decoding, error detection
Node-to-node data transfer
3513689
LAPB Link Access Procedure, Balanced (LAPB) implements the data link layer as defined in the X.25 protocol suite. LAPB is a bit-oriented protocol derived from HDLC that ensures that frames are error free and in the right sequence. LAPB is specified in ITU-T Recommendation X.25 and ISO/IEC 7776. It can be used as a Data Link Layer protocol implementing the connection-mode data link service in the OSI Reference Model as defined by ITU-T Recommendation X.222. LAPB is used to manage communication and packet framing between data terminal equipment (DTE) and the data circuit-terminating equipment (DCE) devices in the X.25 protocol
LAPB
1664425
Medium access control In IEEE 802 LAN/MAN standards, the medium access control (MAC) sublayer (also known as the media access control sublayer) and the logical link control (LLC) sublayer together make up the data link layer. Within that data link layer, the LLC provides flow control and multiplexing for the logical link (i.e. EtherType, 802.1Q VLAN tag etc), while the MAC provides flow control and multiplexing for the transmission medium. These two sublayers together correspond to layer 2 of the OSI model. For compatibility reasons, LLC is optional for implementations of IEEE 802.3 (the frames are then "raw"), but compulsory
Medium access control
19406600
VARAN VARAN (Versatile Automation Random Access Network) is a Fieldbus Ethernet-based industrial communication system. VARAN is a wired data network technology for local data networks (LAN) with the main application in the field of automation technology. It enables the exchange of data in the form of data frames between all LAN connected devices (controllers, input/output devices, drives, etc.). VARAN includes the definitions for types of cables and connectors, describes the physical signalling and specifies packet formats and protocols. From the perspective of the OSI model, VARAN specifies both the physical layer (OSI Layer 1) and the data link layer (OSI
VARAN
1348347
a strict hierarchical sequence of encapsulation requirements, as is attributed to OSI protocols. Data link layer The data layer, or layer 2, is the second layer of the seven-layer OSI model of computer networking. This layer is the protocol layer that transfers data between adjacent network nodes in a wide area network (WAN) or between nodes on the same local area network (LAN) segment. The data link layer provides the functional and procedural means to transfer data between network entities and might provide the means to detect and possibly correct errors that may occur in the physical layer. The data
Data link layer
519060
with media access control methods and protocols. Some networks are able to dynamically change their logical topology through configuration changes to their routers and switches. The transmission media (often referred to in the literature as the "physical media") used to link devices to form a computer network include electrical cable (Ethernet, HomePNA, power line communication, G.hn), optical fiber (fiber-optic communication), and radio waves (wireless networking). In the OSI model, these are defined at layers 1 and 2 — the physical layer and the data link layer. A widely adopted "family" of transmission media used in local area network (LAN) technology
Network topology
7186084
spans a city or a large campus. A wide area network (WAN) is a computer network that covers a large geographic area such as a city, country, or spans even intercontinental distances. A WAN uses a communications channel that combines many types of media such as telephone lines, cables, and air waves. A WAN often makes use of transmission facilities provided by common carriers, such as telephone companies. WAN technologies generally function at the lower three layers of the OSI reference model: the physical layer, the data link layer, and the network layer. An enterprise private network is a network
Computer network
512814
network efficiency. An Ethernet switch operates at the data link layer (layer 2) of the OSI model to create a separate collision domain for each switch port. Each device connected to a switch port can transfer data to any of the other ports at any time and the transmissions will not interfere. Because broadcasts are still being forwarded to all connected devices by the switch, the newly formed network segment continues to be a broadcast domain. Switches may also operate at higher layers of the OSI model, including the network layer and above. A device that also operates at these
Network switch
543731
a continuous bit stream. In the seven-layer OSI model of computer networking, "packet" strictly refers to a protocol data unit at layer 3, the network layer. The correct term for a data unit at layer 2, the data link layer, is a "frame", and at Layer 4, the transport layer, the correct term is "segment" or "datagram". For TCP/IP communication over Ethernet, a TCP segment is carried in one or more IP packets, which are each carried in one or more Ethernet frames. The basis of the packet concept is the postal letter: the header is like the envelope, the
Network packet
1765642
the number of stuff bits inserted. ISO 11898 series specifies physical and data link layer (levels 1 and 2 of the ISO/OSI model) of serial communication technology called Controller Area Network that supports distributed real-time control and multiplexing for use within road vehicles. There are several CAN physical layer and other standards: ISO 11898-1:2015 specifies the data link layer (DLL) and physical signalling of the controller area network (CAN). This document describes the general architecture of CAN in terms of hierarchical layers according to the ISO reference model for open systems interconnection (OSI) established in ISO/IEC 7498-1 and provides the
CAN bus
15334706
wide area network connection. Despite the different semantics of layering in TCP/IP and OSI, the link layer is sometimes described as a combination of the data link layer (layer 2) and the physical layer (layer 1) in the OSI model. However, the layers of TCP/IP are descriptions of operating scopes (application, host-to-host, network, link) and not detailed "prescriptions" of operating procedures, data semantics, or networking technologies. RFC 1122 exemplifies that local area network protocols such as Ethernet and IEEE 802, and framing protocols such as Point-to-Point Protocol (PPP) belong to the link layer. Local area networking standards such as Ethernet
Link layer
4758209
in detail, the implementation of bit timing, synchronization, encoding/decoding, band rate, bus length and the physical connection of the transceiver to the communication wires. The data link layer standard is responsible for fully specifying how messages are assembled ready for transmission by the physical layer, error handling, message-filtering and bus arbitration and how these standards are to be implemented in hardware. The application layer standard, in general defines how the data communication layers are interfaced to the application that wishes to communicate. It describes message specifications, network management implementations and response to the request from the application of services. Layers
Fieldbus
3571353
This is not useful if the entire stream is not available when the communication is initiated, or when searching it is expensive. DIME is more oriented to streaming, allowing, for example, a receiver to process chunks of the message as they arrive without having to wait for the entire message. DIME was defined the transmission format at the data link layer in the OSI model although it was typically transmitted over HTTP. One difficulty here was that it could form an HTTP message of, essentially, any size (the limit being the size information for each chunk, which was 32 bits
Direct Internet Message Encapsulation
1298244
address of the process-to-process communication. In the OSI model, this function is supported by the session layer. Some transport layer protocols, for example TCP, but not UDP, support virtual circuits, i.e. provide connection-oriented communication over an underlying packet oriented datagram network. A byte-stream is delivered while hiding the packet mode communication for the application processes. This involves connection establishment, dividing of the data stream into packets called segments, segment numbering and reordering of out-of order data. Finally, some transport layer protocols, for example TCP, but not UDP, provide end-to-end reliable communication, i.e. error recovery by means of error detecting code
Transport layer
3994221
manages and terminates the connections between the local and remote application. It provides for full-duplex, and half-duplex or simplex operation, and establishes checkpointing, adjournment, termination, and restart procedures. The OSI model made this layer responsible for graceful close of sessions, which is a property of the Transmission Control Protocol, and also for session checkpointing and recovery, which is not usually used in the Internet Protocol Suite. The session layer is commonly implemented explicitly in application environments that use remote procedure calls. This layer defines and encrypts/decrypts data types from the application layer. Protocols such as MIDI, MPEG, and GIF are
OSI protocols
304518
this layer responsible for graceful close of sessions, which is a property of the Transmission Control Protocol, and also for session checkpointing and recovery, which is not usually used in the Internet Protocol Suite. The session layer is commonly implemented explicitly in application environments that use remote procedure calls. The presentation layer establishes context between application-layer entities, in which the application-layer entities may use different syntax and semantics if the presentation service provides a mapping between them. If a mapping is available, presentation protocol data units are encapsulated into session protocol data units and passed down the protocol stack. This
OSI model
304515
no error recovery, and was designed for use on network layers that provide error-free connections. Class 4 is closest to TCP, although TCP contains functions, such as the graceful close, which OSI assigns to the session layer. Also, all OSI TP connection-mode protocol classes provide expedited data and preservation of record boundaries. Detailed characteristics of TP0-4 classes are shown in the following table: An easy way to visualize the transport layer is to compare it with a post office, which deals with the dispatch and classification of mail and parcels sent. A post office inspects only the outer envelope of
OSI model
500909
above it and is served by the layer below it. For example, a layer that provides error-free communications across a network provides the communications path needed by applications above it, while it calls the next lower layer to send and receive packets that traverse that path. In the OSI model, the definition of its application layer is narrower in scope than is often implemented. The OSI model defines the application layer as being the user interface. The OSI application layer is responsible for displaying data and images to the user in a human-recognizable format and to interface with the presentation
Denial-of-service attack
984021
Presentation layer In the seven-layer OSI model of computer networking, the presentation layer is layer 6 and serves as the data translator for the network. It is sometimes called the syntax layer. The presentation layer is responsible for the delivery and formatting of information to the application layer for further processing or display. It relieves the application layer of concern regarding syntactical differences in data representation within the end-user systems. An example of a presentation service would be the conversion of an EBCDIC-coded text computer file to an ASCII-coded file. The presentation layer is the lowest layer at which application
Presentation layer
304520
application protocol invariant with respect to syntax. The application layer is the OSI layer closest to the end user, which means both the OSI application layer and the user interact directly with the software application. This layer interacts with software applications that implement a communicating component. Such application programs fall outside the scope of the OSI model. Application-layer functions typically include identifying communication partners, determining resource availability, and synchronizing communication. When identifying communication partners, the application layer determines the identity and availability of communication partners for an application with data to transmit. The most important distinction in the application layer
OSI model
1298247
the transport layers of the Internet protocol suite, the OSI protocol suite, NetWare's IPX/SPX, AppleTalk, and Fibre Channel. ISO/IEC 8073/ITU-T Recommendation X.224, "Information Technology - Open Systems Interconnection - Protocol for providing the connection-mode transport service", defines five classes of connection-mode transport protocols designated class 0 (TP0) to class 4 (TP4). Class 0 contains no error recovery, and was designed for use on network layers that provide error-free connections. Class 4 is closest to TCP, although TCP contains functions, such as the graceful close, which OSI assigns to the session layer. All OSI connection-mode protocol classes provide expedited data and
Transport layer
304508
In practice, the availability of a communication service is determined by the interaction between network design and network management protocols. Appropriate choices for both of these are needed to protect against denial of service. The physical layer is responsible for the transmission and reception of unstructured raw data between a device and a physical transmission medium. It converts the digital bits into electrical, radio, or optical signals. Layer specifications define characteristics such as voltage levels, the timing of voltage changes, physical data rates, maximum transmission distances, and physical connectors. This includes the layout of pins, voltages, line impedance, cable specifications,
OSI model
273700
without the need to examine the packet itself. This allows one to create end-to-end circuits across any type of transport medium, using any protocol. The primary benefit is to eliminate dependence on a particular OSI model data link layer (layer 2) technology, such as Asynchronous Transfer Mode (ATM), Frame Relay, Synchronous Optical Networking (SONET) or Ethernet, and eliminate the need for multiple layer-2 networks to satisfy different types of traffic. Multiprotocol label switching belongs to the family of packet-switched networks. MPLS operates at a layer that is generally considered to lie between traditional definitions of OSI Layer 2 (data link
Multiprotocol Label Switching
3994219
keep track of destinations and sources. This layer uses routers and switches to manage its traffic (control flow control, error check, routing etc.) So here it takes all routing decisions, it deals with end to end data transmission. The connection-mode and connectionless-mode transport services are specified by [http://www.itu.int/rec/T-REC-X.214/en/ ITU-T Rec. X.214 <nowiki>[</nowiki>ISO/IEC 8072<nowiki>]</nowiki>]; the protocol that provides the connection-mode service is specified by [http://www.itu.int/rec/T-REC-X.224/en/ ITU-T Rec. X.224 <nowiki>[</nowiki>ISO/IEC 8073<nowiki>]</nowiki>], and the protocol that provides the connectionless-mode service is specified by [http://www.itu.int/rec/T-REC-X.234/en/ ITU-T Rec. X.234 <nowiki>[</nowiki>ISO/IEC 8602<nowiki>]</nowiki>]. The transport layer transfers data between source and destination processes. Generally, two connection modes
OSI protocols
2785773
of the OSI model that MTP does not provide, is provided by SCCP or other Level 4 parts (MTP users). "MTP Level 1" is described in ITU-T Recommendation Q.702, and provides the "Signalling Data Link" functional level for narrowband signalling links. For broadband signalling links, ITU-T Recommendation Q.2110 or Q.2111 describe the signalling data link function. MTP1 represents the physical layer. That is, the layer that is responsible for the connection of SS7 Signaling Points into the transmission network over which they communicate with each other. Primarily, this involves the conversion of messaging into electrical signal and the maintenance of
Message Transfer Part
1471215
upon the underlying transport layer protocols to establish host-to-host data transfer channels and manage the data exchange in a client-server or peer-to-peer networking model. Though the TCP/IP application layer does not describe specific rules or data formats that applications must consider when communicating, the original specification (in ) does rely on and recommend the robustness principle for application design. In the OSI model, the definition of the application layer is narrower in scope. The OSI model defines the application layer as the user interface responsible for displaying received information to the user. In contrast, the Internet Protocol Suite does not
Application layer
206800
top layers in the OSI model, i.e. the application layer, the presentation layer and the session layer, are not distinguished separately in the TCP/IP model which only has an application layer above the transport layer. While some pure OSI protocol applications, such as X.400, also combined them, there is no requirement that a TCP/IP protocol stack must impose monolithic architecture above the transport layer. For example, the NFS application protocol runs over the eXternal Data Representation (XDR) presentation protocol, which, in turn, runs over a protocol called Remote Procedure Call (RPC). RPC provides reliable record transmission, so it can safely
Internet protocol suite
206789
information, and IGMP which is used to manage IP Multicast data, are layered on top of IP but perform internetworking functions. This illustrates the differences in the architecture of the TCP/IP stack of the Internet and the OSI model. The TCP/IP model's internet layer corresponds to layer three of the Open Systems Interconnection (OSI) model, where it is referred to as the network layer. The internet layer provides an unreliable datagram transmission facility between hosts located on potentially different IP networks by forwarding the transport layer datagrams to an appropriate next-hop router for further relaying to its destination. With this
Internet protocol suite
304514
transport layer can keep track of the segments and re-transmit those that fail delivery. The transport layer also provides the acknowledgement of the successful data transmission and sends the next data if no errors occurred. The transport layer creates segments out of the message received from the application layer. Segmentation is the process of dividing a long message into smaller messages. OSI defines five classes of connection-mode transport protocols ranging from class 0 (which is also known as TP0 and provides the fewest features) to class 4 (TP4, designed for less reliable networks, similar to the Internet). Class 0 contains
OSI model
15334707
and IEEE 802 specifications use terminology from the seven-layer OSI model rather than the TCP/IP model. The TCP/IP model in general does not consider physical specifications, rather it assumes a working network infrastructure that can deliver media level frames on the link. Therefore, RFC 1122 and RFC 1123, the definition of the TCP/IP model, do not discuss hardware issues and physical data transmission and set no standards for those aspects. Some textbook authors have supported the interpretation that physical data transmission aspects are part of the link layer. Others assumed that physical data transmission standards are not considered communication protocols,
Link layer
849750
Physical layer In the seven-layer OSI model of computer networking, the physical layer or layer 1 is the first and lowest layer. This layer may be implemented by a PHY chip. The physical layer consists of the electronic circuit transmission technologies of a network. It is a fundamental layer underlying the higher level functions in a network. Due to the plethora of available hardware technologies with widely varying characteristics, this is perhaps the most complex layer in the OSI architecture. The physical layer defines the means of transmitting raw bits rather than logical data packets over a physical data link
Physical layer
538938
Protocol (IP) networks. IPsec supports network-level peer authentication, data-origin authentication, data integrity, data confidentiality (encryption), and replay protection. The initial IPv4 suite was developed with few security provisions. As a part of the IPv4 enhancement, IPsec is a layer 3 OSI model or Internet Layer end-to-end security scheme, while some other Internet security systems in widespread use operate above layer 3, such as Transport Layer Security (TLS) and Secure Shell (SSH), both of which operate at the Application layer. IPsec can automatically secure applications at the IP layer. From 1986 to 1991, the NSA sponsored the development of security protocols
IPsec
984026
layer and request services from the session layer. It provides support for common application services, such as: The specific application service element sublayer provides application specific services (protocols), such as Other protocols sometimes considered at this level (though perhaps not strictly adhering to the OSI model) include: Presentation layer In the seven-layer OSI model of computer networking, the presentation layer is layer 6 and serves as the data translator for the network. It is sometimes called the syntax layer. The presentation layer is responsible for the delivery and formatting of information to the application layer for further processing or display.
Presentation layer
206787
stack for transmission or reception over another IP connection. Such a connection, or virtual link, may be established with a transport protocol or even an application scope protocol that serves as a tunnel in the link layer of the protocol stack. Thus, the TCP/IP model does not dictate a strict hierarchical encapsulation sequence. The TCP/IP model's link layer corresponds to the Open Systems Interconnection (OSI) model physical and data link layers, layers one and two of the OSI model. The internet layer has the responsibility of sending packets across potentially multiple networks. Internetworking requires sending data from the source network
Internet protocol suite
5714584
and they are Physical layer, Data-Link layer, Network layer, Transport layer, Session layer, Presentation layer, and Application layer. Each packet that a computer sends out to another computer must go through each layer of the OSI Model. Sockets The standard way to communicate on a network with the use of computer operating systems is a socket. A socket is used by a programmer to create a way to send and receive data using the layers of the OSI. There are two types of sockets: a Stream Socket and a Datagram Socket. Stream Sockets use Transmission Control Protocol (TCP). A Datagram
Hacking: The Art of Exploitation
1271418
of operating scopes (application, host-to-host, network, link) and not detailed "prescriptions" of operating procedures or data semantics. Session layer In the seven-layer OSI model of computer networking, the session layer is layer 5. The session layer provides the mechanism for opening, closing and managing a session between end-user application processes, i.e., a semi-permanent dialogue. Communication sessions consist of requests and responses that occur between applications. Session-layer services are commonly used in application environments that make use of remote procedure calls (RPCs). An example of a session-layer protocol is the OSI protocol suite session-layer protocol, also known as X.225 or ISO
Session layer
11832288
of which consist of routing across the Network layer of the OSI model only. Some approaches utilize both the Network and Data link layer but do not consider the cross layer behaviors. This makes quantifying the QoS parameters difficult and leads to considerations of QoS but does not guarantee QoS. To address this problem, appropriate cross-layer cooperation is required. Adaptive QoS schemes provide QoS information by factoring the impacts of node mobility and lower-layer link parameters into QoS performance. Most QoS approaches tend to focus on only one QoS parameter (e.g., packet loss, end-to-end delay, and bandwidth). For example, while
Adaptive quality of service multi-hop routing
1833912
Transmission Convergence (PTM-TC) protocol(s) stack. The aggregated traffic is then directed to a telco's backbone switch, via an access network (AN), also called a Network Service Provider (NSP), at up to 10 Gbit/s data rates. The DSLAM acts like a network switch since its functionality is at Layer 2 of the OSI model. Therefore, it cannot re-route traffic between multiple IP networks, only between ISP devices and end-user connection points. The DSLAM traffic is switched to a Broadband Remote Access Server where the end-user traffic is then routed across the ISP network to the Internet. Customer-premises equipment that interfaces well
Digital subscriber line access multiplexer
494439
of the current load. This resource allocation approach, while apt for applications that require guaranteed quality of service, is inefficient for applications that are highly dynamic in their load characteristics or which would benefit from a more dynamic resource allocation. Frame Relay networks can dynamically allocate bandwidth at both the physical and logical channel level. As a WAN protocol, Frame Relay is most commonly implemented at Layer 2 (data link layer) of the Open Systems Interconnection (OSI) seven layer model. Two types of circuits exist: permanent virtual circuits (PVCs) which are used to form logical end-to-end links mapped over a
Frame Relay
304525
its own right. OSI model The Open Systems Interconnection model (OSI model) is a conceptual model that characterizes and standardizes the communication functions of a telecommunication or computing system without regard to its underlying internal structure and technology. Its goal is the interoperability of diverse communication systems with standard protocols. The model partitions a communication system into abstraction layers. The original version of the model defined seven layers. A layer serves the layer above it and is served by the layer below it. For example, a layer that provides error-free communications across a network provides the path needed by applications
OSI model
304502
OSI model The Open Systems Interconnection model (OSI model) is a conceptual model that characterizes and standardizes the communication functions of a telecommunication or computing system without regard to its underlying internal structure and technology. Its goal is the interoperability of diverse communication systems with standard protocols. The model partitions a communication system into abstraction layers. The original version of the model defined seven layers. A layer serves the layer above it and is served by the layer below it. For example, a layer that provides error-free communications across a network provides the path needed by applications above it, while
OSI model
206791
addresses. IPv6 production implementations emerged in approximately 2006. The transport layer establishes basic data channels that applications use for task-specific data exchange. The layer establishes host-to-host connectivity, meaning it provides end-to-end message transfer services that are independent of the structure of user data and the logistics of exchanging information for any particular specific purpose and independent of the underlying network. The protocols in this layer may provide error control, segmentation, flow control, congestion control, and application addressing (port numbers). End-to-end message transmission or connecting applications at the transport layer can be categorized as either connection-oriented, implemented in TCP, or connectionless,
Internet protocol suite
5980654
The DNP3 protocol has significant features that make it more robust, efficient, and interoperable than older protocols such as Modbus, at the cost of higher complexity. In terms of the OSI model for networks, DNP3 specifies a layer 2 protocol. It provides multiplexing, data fragmentation, error checking, link control, prioritization, and layer 2 addressing services for user data. It also defines a Transport function (somewhat similar to the function of layer 4) and an Application Layer (layer 7) that defines functions and generic data types suitable for common SCADA applications. The DNP3 frame strongly resembles, but is not identical to
DNP3
1298246
packet loss occasionally can be accepted, for example IP-TV and IP-telephony, and for online computer games. Many non-IP-based networks, such as X.25, Frame Relay and ATM, implement the connection-oriented communication at the network or data link layer rather than the transport layer. In X.25, in telephone network modems and in wireless communication systems, reliable node-to-node communication is implemented at lower protocol layers. The OSI connection-mode transport layer protocol specification defines five classes of transport protocols: "TP0", providing the least error recovery, to "TP4", which is designed for less reliable networks. This list shows some protocols that are commonly placed in
Transport layer
13170105
Packet segmentation In data communications networks, packet segmentation is the process of dividing a data packet into smaller units for transmission over the network. Packet segmentation happens at layer four of the OSI model or the transport layer. Segmentation may be required when: Protocols that perform packet segmentation at the source usually include a mechanism at the destination to reverse the process and reassemble the original packet from individual segments. This process may include automatic repeat-request (ARQ) mechanisms to detect missing segments and to request the source to re-transmit specific segments. In a communication system based on a layered OSI
Packet segmentation
543734
is possible to layer a transport protocol on top of the packet service that can provide such protection; TCP and UDP are the best examples of layer 4, the Transport Layer, of the seven layered OSI model. The Consultative Committee for Space Data Systems (CCSDS) packet telemetry standard defines the protocol used for the transmission of spacecraft instrument data over the deep-space channel. Under this standard, an image or other data sent from a spacecraft instrument is transmitted using one or more packets. A packet is a block of data with length that can vary between successive packets, ranging from
Network packet
9180498
the V.42 protocol, and LAPD for the ISDN protocol stack. In Frame Relay Local Management Interface (LMI) messages are carried in a variant of LAPF frames. LAPF corresponds to the OSI model Data Link layer. Link Access Procedure for Frame Relay In wide area network computing, Link Access Procedure for Frame Relay (or LAPF) is part of the network's communications protocol which ensures that frames are error free and executed in the right sequence. LAPF is formally defined in the International Telecommunication Union standard Q.922. It was derived from IBM's Synchronous Data Link Control protocol, which is the layer 2
Link Access Procedure for Frame Relay
1487300
between electrical-idle and specific 10b-characters in a defined pattern, negotiating a mutually supported signalling rate (1.5, 3.0, or 6.0 Gbit/s), and finally synchronizing to the far-end device's PHY-layer data stream. During this time, no data is sent from the link-layer. Once link-initialization has completed, the link-layer takes over data-transmission, with the PHY providing only the 8b/10b conversion before bit transmission. After the PHY-layer has established a link, the link layer is responsible for transmission and reception of Frame Information Structures (FISs) over the SATA link. FISs are packets containing control information or payload data. Each packet contains a header (identifying
Serial ATA
1271416
layer of the OSI model is responsible for session checkpointing and recovery. It allows information of different streams, perhaps originating from different sources, to be properly combined or synchronized. An example usage of the session layer is session beans, which are only active as long as the session is active, and are deleted when the session is disconnected. Java developers can use them to store information about the user during a web session. An example application is web conferencing, in which the streams of audio and video must be synchronous to avoid so-called lip sync problems. Flow control ensures that
Session layer
304513
"management annex", ISO 7498/4, belong to the network layer. These include routing protocols, multicast group management, network-layer information and error, and network-layer address assignment. It is the function of the payload that makes these belong to the network layer, not the protocol that carries them. The transport layer provides the functional and procedural means of transferring variable-length data sequences from a source to a destination host, while maintaining the quality of service functions. The transport layer controls the reliability of a given link through flow control, segmentation/desegmentation, and error control. Some protocols are state- and connection-oriented. This means that the
OSI model
304517
3 packets to deliver to the endpoint. L2TP carries PPP frames inside transport segments. Although not developed under the OSI Reference Model and not strictly conforming to the OSI definition of the transport layer, the Transmission Control Protocol (TCP) and the User Datagram Protocol (UDP) of the Internet Protocol Suite are commonly categorized as layer-4 protocols within OSI. The session layer controls the dialogues (connections) between computers. It establishes, manages and terminates the connections between the local and remote application. It provides for full-duplex, half-duplex, or simplex operation, and establishes checkpointing, adjournment, termination, and restart procedures. The OSI model made
OSI model
10165386
arrangement in a Domain Information Model for vital signs data transmission are defined. Beyond this the standard defines a service model for the standardized communication. The common background for assembly and transmission of objects and their attributes are defined in this standard. It's subdivided in a communication model and an information model. The communication model describes the layers 5 to 7 of the OSI 7-layer model. The information model defines the modeling, formatting and the syntax for transmission coding of the objects. All defined parts of this standard family are designed to allow communication according to this principle. The arrangement
ISO/IEEE 11073
3436682
used in many telecommunications networks around the world because IS-IS (an OSI routing protocol) is mandated by the ITU-T as the protocol for management of Synchronous Digital Hierarchy (SDH) elements. From August 1990 to April 1995 the NSFNET backbone supported CLNP in addition to TCP/IP. However, CLNP usage remained low compared to TCP/IP. CLNS is used by ISO Transport Protocol Class 4 (TP4), one of the five transport layer protocols in the OSI suite. TP4 offers error recovery, performs segmentation and reassembly, and supplies multiplexing and demultiplexing of data streams over a single virtual circuit. TP4 sequences PDUs and retransmits
Connectionless-mode Network Service
1298242
Internet all originated in the development of TCP/IP. In the OSI model the transport layer is often referred to as Layer 4, or L4, while numbered layers are not used in TCP/IP. The best-known transport protocol of TCP/IP is the Transmission Control Protocol (TCP), and lent its name to the title of the entire suite. It is used for connection-oriented transmissions, whereas the connectionless User Datagram Protocol (UDP) is used for simpler messaging transmissions. TCP is the more complex protocol, due to its stateful design incorporating reliable transmission and data stream services. Other protocols in this group are the Datagram
Transport layer
2603768
only the lower layers are defined in the standard, interaction with upper layers is intended, possibly using an IEEE 802.2 logical link control sublayer accessing the MAC through a convergence sublayer. Implementations may rely on external devices or be purely embedded, self-functioning devices. The physical layer is the initial layer in the OSI reference model used worldwide. The "physical layer" (PHY) ultimately provides the data transmission service, as well as the interface to the "physical layer management entity", which offers access to every layer management function and maintains a database of information on related personal area networks. Thus, the PHY
IEEE 802.15.4
201455
routers every time the time to live (called hop limit in the IPv6 protocol) is reduced by one. The absence of a checksum in the IPv6 header furthers the end-to-end principle of Internet design, which envisioned that most processing in the network occurs in the leaf nodes. Integrity protection for the data that is encapsulated in the IPv6 packet is assumed to be assured by both the link layer or error detection in higher-layer protocols, namely the Transmission Control Protocol (TCP) and the User Datagram Protocol (UDP) on the transport layer. Thus, while IPv4 allowed UDP datagram headers to have
IPv6
14733913
cause a higher layer to duplicate functionality of a lower layer, a prime example being error recovery on both a per-link basis and an end-to-end basis. Secondly, it is common that a protocol implementation at one layer may require data, state or addressing information that is only present at another layer, thus defeating the point of separating the layers in the first place. For example, TCP uses the ECN field in the IPv4 header as an indication of congestion; IP is a network layer protocol whereas TCP is a transport layer protocol. There are commonly reoccurring problems that occur in
Communication protocol
14249229
FX.25 Forward Error Correction FX.25 is a protocol extension to the AX.25 Link Layer Protocol. FX.25 provides a Forward Error Correction (FEC) capability while maintaining legacy compatibility with non-FEC equipment. FX.25 was created by the Stensat Group in 2005, and was presented as a technical paper at the 2006 TAPR Digital Communications Conference in Tucson, AZ. FX.25 is intended to complement the AX.25 protocol, not replace it. It provides an encapsulation mechanism that does not alter the AX.25 data or functionalities. An error correction capability is introduced at the bottom of Layer 2 in the OSI model. The AX.25 Link
FX.25 Forward Error Correction
8640682
users in the network, set user based policies and generate reports by username. According to Bruce Schneier and RSA: Since the OSI layer numbers are commonly used to discuss networking topics, a troubleshooter may describe an issue caused by a user to be a "layer 8" issue, similar to the PEBKAC acronym, the ID-Ten-T Error and also PICNIC. Political economic theory holds that the 8th layer is important to understanding the OSI Model. Political policies such as network neutrality, spectrum management, and digital inclusion all shape the technologies comprising layers 1-7 of the OSI Model. An 8th layer has also
Layer 8
6269155
Piggybacking (data transmission) In two-way communication, wherever a frame is received, the receiver waits and does not send the control frame (acknowledgement or ACK) back to the sender immediately. The receiver waits until its network layer passes in the next data packet. The delayed acknowledgement is then attached to this outgoing data frame. This technique of temporarily delaying the acknowledgement so that it can be hooked with next outgoing data frame is known as piggybacking. Piggybacking data is a bit different from Sliding Window Protocol used in the OSI model. In the data frame itself, we incorporate one additional field
Piggybacking (data transmission)
12707945
who add value further up the chain (e.g., service providers, consultants, disaster recovery solution providers, storage providers). Vendor neutral data centres focus on the "bottom" layers in the stack of services provided to data centre customers: space, security, power, environment, and cabling. In terms of the OSI model, they provide Layer 1 services. Vendor-neutral data centre "Vendor neutrality" in the data centre market refers to a specialised and focused business model, in which a data centre provider limits its activities to a fixed set of value layers in order to avoid conflicts of interest. The provider creates an open market
Vendor-neutral data centre
7059109
Gateway address The gateway address (or default gateway) is a router interface connected to the local network that sends packets out of the local network. The gateway has a physical and a logical address. The gateway operates at the network layer (Layer 3) of the OSI Model. The gateway is used when transmitting packets. When packets are sent over a network, the destination IP address is examined. If the destination IP is outside of the network, then the packet goes to the gateway for transmission outside of the network. The gateway is on the same network as end devices. The
Gateway address
8640681
Layer 8 Layer 8 is used to refer to "user" or "political" layer on top of the OSI model of computer networking. The OSI model is a 7-layer abstract model that describes an architecture of data communications for networked computers. The layers build upon each other, allowing for abstraction of specific functions in each one. The top (7th) layer is the Application Layer describing methods and protocols of software applications. It is then held that the user is the 8th layer. Network appliances vendor like Cyberoam claim that Layer 8 allows IT administrators to identify users, control Internet activity of
Layer 8
1288914
higher layer protocols work in an end-to-end fashion, i.e. re-transmission is done from the original source to the final destination, rather than on individual physical segments. For these protocol stacks only the multiplexing capabilities of the LLC sublayer are used. An LLC sublayer was a key component in early packet switching networks such as X.25 networks with the LAPB data link layer protocol, where flow control and error management were carried out in a node-to-node fashion, meaning that if an error was detected in a frame, the frame was retransmitted from one switch to next instead. This extensive handshaking between
Logical link control
304507
to 7. Layer 1 is the lowest layer in this model. At each level "N", two entities at the communicating devices (layer N "peers") exchange protocol data units (PDUs) by means of a layer N "protocol". Each PDU contains a payload, called the service data unit (SDU), along with protocol-related headers or footers. Data processing by two communicating OSI-compatible devices is done as such: Some orthogonal aspects, such as management and security, involve all of the layers (See ITU-T X.800 Recommendation). These services are aimed at improving the CIA triad - confidentiality, integrity, and availability - of the transmitted data.
OSI model
1348344
5 12 12 15 7" numbers sequence is transmitted, which the receiver will see on its end if there are no transmission errors. The receiver knows that the last number received is the error-detecting metadata and that all data before is the message, so the receiver can recalculate the above math and if the metadata matches it can be concluded that the data has been received error-free. Though, if the receiver sees something like a "7 5 12 12 15 7" sequence, it can run the check by calculating 7 + 5 + 12 + 12 + 15 = 51
Data link layer
520396
The letters themselves are SDUs when the bags are opened but become PDUs when the address is read for final delivery. When the addressee finally opens the envelope, the top-level SDU, the letter itself, emerges. Protocol data units of the OSI model are: Given a context pertaining to a specific OSI layer, "PDU" is sometimes used as a synonym for its representation at that layer. Protocol data units for the Internet Protocol Suite are: On TCP/IP over Ethernet, the bit stream on the physical layer is commonly called an Ethernet Packet. ATM's corresponding data link layer PDU is called a
Protocol data unit
1271414
Session layer In the seven-layer OSI model of computer networking, the session layer is layer 5. The session layer provides the mechanism for opening, closing and managing a session between end-user application processes, i.e., a semi-permanent dialogue. Communication sessions consist of requests and responses that occur between applications. Session-layer services are commonly used in application environments that make use of remote procedure calls (RPCs). An example of a session-layer protocol is the OSI protocol suite session-layer protocol, also known as X.225 or ISO 8327. In case of a connection loss this protocol may try to recover the connection. If a
Session layer
11706015
cooperation with Texas Instruments Deutschland GmbH and Techem GmbH. The concept was based on the ISO-OSI Reference Model, in order to realize an open system which could use almost any desired protocol. Since the M-Bus is not a network, and therefore does not - among other things - need a transport or session layer, the levels four to six of the OSI model are empty. Therefore, only the physical, the data link, the network and the application layer are provided with functions. Meter-Bus M-Bus (Meter-Bus) is a European standard (EN 13757-2 physical and link layer, EN 13757-3 application layer) for
Meter-Bus
7966146
application. Layer 3 audio over Ethernet protocols encapsulate audio data in OSI model layer 3 (network layer) packets. By definition it does not limit the choice of protocol to be the most popular layer 3 protocol, the Internet Protocol (IP). In some implementations, the layer 3 audio data packets are further packaged inside OSI model layer 4 (transport layer) packets, most commonly User Datagram Protocol (UDP) or Real-time Transport Protocol (RTP). Use of UDP or RTP to carry audio data enables them to be distributed through standard computer routers, thus a large distribution audio network can be built economically using
Audio over Ethernet
206784
(uses TCP) but below application protocols. Again, there was no intention, on the part of the designers of these protocols, to comply with OSI architecture. The link is treated as a black box. The IETF explicitly does not intend to discuss transmission systems, which is a less academic but practical alternative to the OSI model. The following is a description of each layer in the TCP/IP networking model starting from the lowest level. The link layer has the networking scope of the local network connection to which a host is attached. This regime is called the "link" in TCP/IP literature.
Internet protocol suite
6860205
the Basic level of service capability; in this way it is ensured that users with Extended Service capabilities can inter-operate, at a basic level, with users having Basic Service capabilities and vice versa. The ATSMHS is provided by a set of end systems, which collectively comprise the ATS Message Handling System. The systems co-operate to provide users (human or automated) with a data communication service. The AMHS network is composed of interconnected ATS Message Servers that perform message switching at the application layer (Layer 7 in the OSI model). Direct users connect to ATS Message Servers by means of ATS
Aeronautical Message Handling System
8153837
(nearly) the same time, the packet sent by the full-duplex end will be discarded and lost due to an assumed collision and the packet sent by the half duplex device will be delayed or lost due to a CRC error in the frame. The lost packets force the TCP protocol to perform error recovery, but the initial (streamlined) recovery attempts fail because the retransmitted packets are lost in exactly the same way as the original packets. Eventually, the TCP transmission window becomes full and the TCP protocol refuses to transmit any further data until the previously-transmitted data is acknowledged. This,
Duplex mismatch
12130547
Cross-layer optimization Cross-layer optimization is an escape from the pure waterfall-like concept of the OSI communications model with virtually strict boundaries between layers. The cross layer approach transports feedback dynamically via the layer boundaries to enable the compensation for e.g. overload, latency or other mismatch of requirements and resources by any control input to another layer but that layer directly affected by the detected deficiency. In the original OSI networking model, strict boundaries between layers are enforced, where data are kept strictly within a given layer. Cross‑layer optimization removes such strict boundaries to allow communication between layers by permitting one
Cross-layer optimization
5202406
one physical address (i.e. MAC address), or it allows each interface to have its own address. The former requires that both ends of a link use the same aggregation method, but has performance advantages over the latter. Channel bonding is differentiated from load balancing in that load balancing divides traffic between network interfaces on per network socket (OSI model layer 4) basis, while channel bonding implies a division of traffic between physical interfaces at a lower level, either per packet (OSI model Layer 3) or a data link (OSI model Layer 2) basis. Link aggregation addresses two problems with Ethernet
Link aggregation
538750
Internet Protocol (IP) systems instead. X.25 is still used (e.g., in the credit card payment industry) and available in niche applications. X.25 is one of the oldest packet-switched services available. It was developed before the OSI Reference Model. The protocol suite is designed as three conceptual layers, which correspond closely to the lower three layers of the seven-layer OSI model. It also supports functionality not found in the OSI network layer. X.25 was developed in the ITU-T (formerly CCITT) Study Group VII based upon a number of emerging data network projects. Various updates and additions were worked into the standard,
X.25
538909
responsible for reliable delivery of data, rather than the network itself, using unreliable datagrams and associated end-to-end protocol mechanisms. Concepts of this network influenced later ARPANET architecture. DECnet is a suite of network protocols created by Digital Equipment Corporation, originally released in 1975 in order to connect two PDP-11 minicomputers. It evolved into one of the first peer-to-peer network architectures, thus transforming DEC into a networking powerhouse in the 1980s. Initially built with three layers, it later (1982) evolved into a seven-layer OSI-compliant networking protocol. The DECnet protocols were designed entirely by Digital Equipment Corporation. However, DECnet Phase II (and
Packet switching
710995
network interfaces on a network socket (OSI model layer 4) basis, while channel bonding implies a division of traffic between physical interfaces at a lower level, either per packet (OSI model Layer 3) or on a data link (OSI model Layer 2) basis with a protocol like shortest path bridging. One of the most commonly used applications of load balancing is to provide a single Internet service from multiple servers, sometimes known as a server farm. Commonly load-balanced systems include popular web sites, large Internet Relay Chat networks, high-bandwidth File Transfer Protocol sites, Network News Transfer Protocol (NNTP) servers, Domain
Load balancing (computing)
16582939
based on the OSI protocol model to meet the evolving challenges of the smart grid. At the application layer, ETSI TS 104 001 provides a table-oriented data storage based, in part, on the ANSI C12.19 / MC12.19 / 2012 / IEEE Std 1377™ standards for Utility Industry End Device Data Tables and ANSI C12.18 / MC12.18 / IEEE Std 1701™, standard Protocol Specification for ANSI Type 2 Optical Port for its services and payload encapsulation . This standard and command system that provides for not only smart meters and related data but for general purpose extension to other smart grid
Open Smart Grid Protocol
9405308
forward error correction coding and other physical layer overhead. The theoretical maximum throughput for end user is clearly lower than the peak data rate due to higher layer overheads. Even this is never possible to achieve unless the test is done under perfect laboratory conditions. The typical throughput is what users have experienced most of the time when well within the usable range to the base station. The typical throughput is hard to measure, and depends on many protocol issues such as transmission schemes (slower schemes are used at longer distance from the access point due to better redundancy), packet
Comparison of wireless data standards
14956962
are 7 layers, each one is generically called N layer. The N+1 entity ask for transmission services to the N entity. At each level two entities (N-entity) interact by means of the (N) protocol by transmitting Protocol Data Units (PDU). Service Data Unit (SDU) is a specific unit of data that has been passed down from an OSI layer, to a lower layer, and has not yet been encapsulated into a PDU, by the lower layer. It is a set of data that is sent by a user of the services of a given layer, and is transmitted semantically unchanged
Security service (telecommunication)
538902
inefficient. Frame Relay operates principally at layer two of the OSI Model. However, its address field (the Data Link Connection ID, or DLCI) can be used at the OSI network layer, with a minimum set of procedures. Thus, it rids itself of many X.25 layer three encumbrances, but still has the DLCI as an ID beyond a node-to-node layer two link protocol. The simplicity of Frame Relay makes it faster and more efficient than X.25. Because Frame Relay is a data link layer protocol, like X.25 it does not define internal network routing operations. For X.25, its packet IDs—the virtual
Packet switching
15206613
Gibson MaGIC Media-accelerated Global Information Carrier (MaGIC) is an Audio over Ethernet protocol developed by Gibson Guitar Corporation in partnership with 3COM. MaGIC allows bidirectional transmission of multichannel audio data, control data, and instrument power. Revision 1.0 was introduced in 1999; the most current revision 3.0c was released in 2003. MaGIC is used in several guitar products such as Gibson Digital Guitar. In terms of ISO OSI model, MaGIC can use physical and link layer (MAC/LLC) based on 100 Mbit Fast Ethernet signalling specified in IEEE 802.3/IEEE 802.3af and IEEE 802.2, however MaGIC implements proprietary network and application layers which
Gibson MaGIC
15206609
Gibson MaGIC Media-accelerated Global Information Carrier (MaGIC) is an Audio over Ethernet protocol developed by Gibson Guitar Corporation in partnership with 3COM. MaGIC allows bidirectional transmission of multichannel audio data, control data, and instrument power. Revision 1.0 was introduced in 1999; the most current revision 3.0c was released in 2003. MaGIC is used in several guitar products such as Gibson Digital Guitar. In terms of ISO OSI model, MaGIC can use physical and link layer (MAC/LLC) based on 100 Mbit Fast Ethernet signalling specified in IEEE 802.3/IEEE 802.3af and IEEE 802.2, however MaGIC implements proprietary network and application layers which
Gibson MaGIC