query: what layer of the osi model do vlans use

pos: Virtual LAN 3 networks on a single physical infrastructure. VLANs are data link layer (OSI layer 2) constructs, analogous to Internet Protocol (IP) subnets, which are network layer (OSI layer 3) constructs. In an environment employing VLANs, a one-to-one relationship often exists between VLANs and IP subnets, although it is possible to have multiple subnets on one VLAN. Without VLAN capability, users are assigned to networks based on geography and are limited by physical topologies and distances. VLANs can logically group networks to decouple the users' network location from their physical location. By using VLANs, one can control traffic patterns and react

pos: Multiprotocol Label Switching 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

neg: Virtual LAN domains across one physical medium. A VLAN can also serve to restrict access to network resources without regard to physical topology of the network. VLANs operate at the data link layer of the OSI model. Administrators often configure a VLAN to map directly to an IP network, or subnet, which gives the appearance of involving the network layer. Generally, VLANs within the same organization will be assigned different non-overlapping network address ranges. This is not a requirement of VLANs. There is no issue with separate VLANs using identical overlapping address ranges (e.g. two VLANs each use the private network ).

neg: Internet protocol suite own addressing systems (e.g. Ethernet) an address mapping protocol is needed. Such protocols can be considered to be below IP but above the existing link system. While the IETF does not use the terminology, this is a subnetwork dependent convergence facility according to an extension to the OSI model, the internal organization of the network layer (IONL). ICMP & IGMP operate on top of IP but do not transport data like UDP or TCP. Again, this functionality exists as layer management extensions to the OSI model, in its "Management Framework" (OSIRM MF) The SSL/TLS library operates above the transport layer

neg: Internet protocol suite use the best-effort UDP transport. Different authors have interpreted the TCP/IP model differently, and disagree whether the link layer, or the entire TCP/IP model, covers OSI layer 1 (physical layer) issues, or whether a hardware layer is assumed below the link layer. Several authors have attempted to incorporate the OSI model's layers 1 and 2 into the TCP/IP model, since these are commonly referred to in modern standards (for example, by IEEE and ITU). This often results in a model with five layers, where the link layer or network access layer is split into the OSI model's layers 1 and

neg: Computer network suite provides a diverse set of networking capabilities. The protocols have a flat addressing scheme. They operate mostly at levels 1 and 2 of the OSI model. For example, MAC bridging (IEEE 802.1D) deals with the routing of Ethernet packets using a Spanning Tree Protocol. IEEE 802.1Q describes VLANs, and IEEE 802.1X defines a port-based Network Access Control protocol, which forms the basis for the authentication mechanisms used in VLANs (but it is also found in WLANs) – it is what the home user sees when the user has to enter a "wireless access key". Ethernet, sometimes simply called "LAN",

neg: Hacking: The Art of Exploitation book but do some programming themselves. Exploitation is taking the computer's code or set of rules and changing them so the computer does what you want it to do. Finding ways or holes in the system to change is an important part of exploitation. This chapter covers exploit techniques such as memory corruption, Buffer Overflows and format strings, especially using Perl and Bash shellcode. OSI Model In communication among computers through networking the OSI Model is used. The OSI Model is a model that provides the standards that computers use to communicate. There are seven layers in the OSI Model

neg: OSI model is the distinction between the application-entity and the application. For example, a reservation website might have two application-entities: one using HTTP to communicate with its users, and one for a remote database protocol to record reservations. Neither of these protocols have anything to do with reservations. That logic is in the application itself. The application layer per se has no means to determine the availability of resources in the network. Cross-layer functions are services that are not tied to a given layer, but may affect more than one layer. Examples include the following: Neither the OSI Reference Model nor OSI

neg: AX.25 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),

neg: Link aggregation 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

neg: Audio over Ethernet systems based on the lowest layer in the OSI model where the protocol exists. Layer 1 protocols use Ethernet wiring and signaling components but do not use the Ethernet frame structure. Layer 1 protocols often use their own media access control (MAC) rather than the one native to Ethernet, which generally creates compatibility issues and thus requires a dedicated network for the protocol. Layer 2 protocols encapsulate audio data in standard Ethernet packets. Most can make use of standard Ethernet hubs and switches though some require that the network (or at least a VLAN) be dedicated to the audio distribution

neg: Transport layer Transport layer In computer networking, the transport layer is a conceptual division of methods in the layered architecture of protocols in the network stack in the Internet Protocol Suite and the Open Systems Interconnection (OSI) reference model. The protocols of this layer provide host-to-host communication services for applications. It provides services such as connection-oriented communication, reliability, flow control, and multiplexing. The details of implementation and semantics of the transport layer of the TCP/IP model, which is the foundation of the Internet, and the OSI model of general networking are different. The protocols in use today in this layer for the

neg: Deep packet inspection has served ISP's well has been to only operate at layer 4 and below of the OSI model. This is because simply deciding where packets go and routing them is comparably very easy to handle securely. This traditional model still allows ISP's to accomplish required tasks safely such as restricting bandwidth depending on the amount of bandwidth that is used (layer 4 and below) rather than per protocol or application type (layer 7). There is a very strong and often ignored argument that ISP action above layer 4 of the OSI model provides what are known in the security community

neg: Link layer 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,

neg: OSI model specific protocols. The concept of a seven-layer model was provided by the work of Charles Bachman at Honeywell Information Services. Various aspects of OSI design evolved from experiences with the ARPANET, NPLNET, EIN, CYCLADES network and the work in IFIP WG6.1. The new design was documented in ISO 7498 and its various addenda. In this model, a networking system was divided into layers. Within each layer, one or more entities implement its functionality. Each entity interacted directly only with the layer immediately beneath it, and provided facilities for use by the layer above it. Protocols enable an entity in one

neg: Audio over Ethernet 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

neg: Transport Layer Security and begins the secured connection, which is encrypted and decrypted with the session key until the connection closes. If any one of the above steps fails, then the TLS handshake fails and the connection is not created. TLS and SSL do not fit neatly into any single layer of the OSI model or the TCP/IP model. TLS runs "on top of some reliable transport protocol (e.g., TCP)," which would imply that it is above the transport layer. It serves encryption to higher layers, which is normally the function of the presentation layer. However, applications generally use TLS as if it

neg: Internet protocol suite been compared with the OSI model in books and classrooms, which often results in confusion because the two models use different assumptions and goals, including the relative importance of strict layering. This abstraction also allows upper layers to provide services that the lower layers do not provide. While the original OSI model was extended to include connectionless services (OSIRM CL), IP is not designed to be reliable and is a best effort delivery protocol. This means that all transport layer implementations must choose whether or how to provide reliability. UDP provides data integrity via a checksum but does not guarantee

neg: Hacking: The Art of Exploitation 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

neg: Virtual private network coexistence of multiple local area network (LAN) broadcast domains, interconnected via trunks using the IEEE 802.1Q trunking protocol. Other trunking protocols have been used but have become obsolete, including Inter-Switch Link (ISL), IEEE 802.10 (originally a security protocol but a subset was introduced for trunking), and ATM LAN Emulation (LANE). Developed by Institute of Electrical and Electronics Engineers, Virtual LANs (VLANs) allow multiple tagged LANs to share common trunking. VLANs frequently comprise only customer-owned facilities. Whereas VPLS as described in the above section (OSI Layer 1 services) supports emulation of both point-to-point and point-to-multipoint topologies, the method discussed here extends

neg: Internet protocol suite 2. The IETF protocol development effort is not concerned with strict layering. Some of its protocols may not fit cleanly into the OSI model, although RFCs sometimes refer to it and often use the old OSI layer numbers. The IETF has repeatedly stated that Internet protocol and architecture development is not intended to be OSI-compliant. RFC 3439, addressing Internet architecture, contains a section entitled: "Layering Considered Harmful". For example, the session and presentation layers of the OSI suite are considered to be included to the application layer of the TCP/IP suite. The functionality of the session layer can be found

neg: OSI model 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

neg: OSI model 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

neg: OSI model 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

neg: Meter-Bus 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

neg: Wake-on-LAN NIC signals the computer's power supply or motherboard to initiate system wake-up, in the same way that pressing the power button would do. The magic packet is sent on the data link layer (layer 2 in the OSI model) and when sent, is broadcast to all attached devices on a given network, using the network broadcast address; the IP-address (layer 3 in the OSI model) is not used. Because Wake-on-LAN is built upon broadcast technology, it can generally only be used within the current network subnet. There are some exceptions, though, and Wake-on-LAN can operate across any network in practice,

neg: OSI model 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

neg: Session layer 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

neg: Session layer 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

neg: CAN bus 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

neg: Network tap simple physical apparatus into two outputs, one for the "pass-through", one for the "monitor". This can be called a "passive" tap. Other taps use no power or electronics for the "pass-through", but do use power and electronics for the "monitor" port. These can also be referred to as "passive". Some taps operate at the physical layer of the OSI model rather than the data link layer. For example, they work with multi-mode fiber rather than 1000BASE-SX. This means that they can work with most data link network technologies that use that physical media, such as ATM and some forms of

neg: Asynchronous transfer mode three lowest layers of the ISO-OSI reference model: network layer, data link layer, and physical layer. ATM is a core protocol used over the SONET/SDH backbone of the public switched telephone network (PSTN) and Integrated Services Digital Network (ISDN), but its use is declining in favour of all IP. ATM provides functionality that is similar to both circuit switching and packet switching networks: ATM uses asynchronous time-division multiplexing, and encodes data into small, fixed-sized packets (ISO-OSI frames) called "cells." This differs from approaches such as the Internet Protocol or Ethernet that use variable sized packets and frames. ATM uses a

neg: Denial-of-service attack 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

neg: Broadcast, unknown-unicast and multicast traffic to divert unknown-unicast traffic to specific trunk interfaces in order to split broadcast coming from different VLANs or to use specific trunk interfaces for multiple VLANs. The use of VXLAN as overlay technology allows providing data link layer connectivity services between endpoints that may be deployed across network layer network domains. Since those endpoints are logically part of the same data link layer domain, they must be capable of sending and receiving data link layer multi-destination frames (BUM traffic). BUM traffic can be exchanged across network layer network boundaries by encapsulating it into VXLAN packets addressed to a multicast group,

neg: Layer 8 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

neg: Layer 8 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

neg: OSI protocols 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

neg: OSI model 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

neg: Load balancing (computing) 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

neg: TV Network Protocol traced back to the Highways Agency HDLC standard. It is the property of TfL and is independent of any supplier. As of late of 2011 there are at least eight manufacturers who have a partial or full TVNP interface, including: TVNP layers are broadly based on the OSI model. TVNP Layer 2 and 3 correspond to OSI Layers 2 and 3. When used over RS232 only, TVNP Layer 1 corresponds to OSI Layer 1. TVNP Layer 4 is equivalent to OSI Layer 7. Structuring the TVNP in such a way means that as future needs and provisions change, aspects of

neg: Repeater has continued in telephony and data communications. In computer networking, because repeaters work with the actual physical signal, and do not attempt to interpret the data being transmitted, they operate on the physical layer, the first layer of the OSI model. This is used to increase the range of telephone signals in a telephone line. They are most frequently used in trunklines that carry long distance calls. In an analog telephone line consisting of a pair of wires, it consists of an amplifier circuit made of transistors which use power from a DC current source to increase the power of

neg: Presentation layer 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.

neg: Network layer 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

neg: ISO Development Environment 19, 1992. The Open Source version is still available, even if only for historic interest. The software was ported to a wide set of Unix and Linux variants. The ISODE stack was an implementation of layers 3 to 6 of the OSI model. While the ISODE implementation could be configured to use one of several X.25 (CONS) or connectionless lower layer protocols, many ISODE deployments were based on RFC1006, the implementation of OSI transport protocol TP0 as a layer atop TCP, in order to use IP-based networks which were becoming increasingly common. The stack also implemented an ASN.1 compiler. The

neg: Ethernet 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.

neg: Xerox Network Systems practically all networking systems in use into the 1990s. XNS was used unchanged by 3Com's 3+Share and Ungermann-Bass's Net/One. It was also used, with modifications, as the basis for Novell NetWare, and Banyan VINES. XNS was used as the basis for the AppleNet system, but this never commercialized; a number of XNS's solutions to common problems were used in AppleNet's replacement, AppleTalk. In comparison to the OSI model's 7 layers, XNS is a five-layer system, like the later Internet protocol suite. The Physical and Data Link layers of the OSI model correspond to the Physical layer (layer 0) in XNS,

neg: Cross-layer optimization 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

neg: X.25 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

neg: OSI model seven-layer protocol model as defined in ISO 7498, rather than refinements in such things as the internal organization of the network layer document. The presumably strict layering of the OSI model as it is usually described does not present contradictions in TCP/IP, as it is permissible that protocol usage does not follow the hierarchy implied in a layered model. Such examples exist in some routing protocols (for example OSPF), or in the description of tunneling protocols, which provide a link layer for an application, although the tunnel host protocol might well be a transport or even an application-layer protocol in

neg: Application layer 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

neg: OSI model host to interact with a corresponding entity at the same layer in another host. Service definitions abstractly describe the functionality provided to an (N)-layer by an (N-1) layer, where N was one of the seven layers of protocols operating in the local host. The OSI standards documents are available from the ITU-T as the X.200-series of recommendations. Some of the protocol specifications were also available as part of the ITU-T X series. The equivalent ISO and ISO/IEC standards for the OSI model were available from ISO. Not all are free of charge. The recommendation X.200 describes seven layers, labeled 1

neg: PHY (chip) offerings from Intel and ICS. PHY (chip) PHY is an abbreviation for the physical layer of the OSI model and refers to the circuitry required to implement physical layer functions. A PHY connects a link layer device (often called MAC as an acronym for medium access control) to a physical medium such as an optical fiber or copper cable. A PHY device typically includes both Physical Coding Sublayer (PCS) and Physical Medium Dependent (PMD) layer functionality. The Ethernet PHY is a component that operates at the physical layer of the OSI network model. It implements the Ethernet physical layer portion

neg: Multiplexing 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

neg: PHY (chip) PHY (chip) PHY is an abbreviation for the physical layer of the OSI model and refers to the circuitry required to implement physical layer functions. A PHY connects a link layer device (often called MAC as an acronym for medium access control) to a physical medium such as an optical fiber or copper cable. A PHY device typically includes both Physical Coding Sublayer (PCS) and Physical Medium Dependent (PMD) layer functionality. The Ethernet PHY is a component that operates at the physical layer of the OSI network model. It implements the Ethernet physical layer portion of the 1000BASE-T, 100BASE-TX, and

neg: IPX/SPX IPX/SPX IPX/SPX stands for Internetwork Packet Exchange/Sequenced Packet Exchange. IPX and SPX are networking protocols used primarily on networks using the Novell NetWare operating systems. IPX and SPX are derived from Xerox Network Systems' IDP and SPP protocols, respectively. IPX is a network layer protocol (layer 3 of the OSI Model), while SPX is a transport layer protocol (layer 4 of the OSI Model). The SPX layer sits on top of the IPX layer and provides connection-oriented services between two nodes on the network. SPX is used primarily by client–server applications. IPX and SPX both provide connection services similar to

neg: OSI model protocols specify any programming interfaces, other than deliberately abstract service specifications. Protocol specifications precisely define the interfaces between different computers, but the software interfaces inside computers, known as network sockets are implementation-specific. For example, Microsoft Windows' Winsock, and Unix's Berkeley sockets and System V Transport Layer Interface, are interfaces between applications (layer 5 and above) and the transport (layer 4). NDIS and ODI are interfaces between the media (layer 2) and the network protocol (layer 3). Interface standards, except for the physical layer to media, are approximate implementations of OSI service specifications. The design of protocols in the TCP/IP model

neg: Multilayer switch CodePoint). These 6 bits were used for Type of Service (ToS). The following 4 mappings are normally available in an MLS: Many MLSs implement QoS differentiated services and/or integrated services in hardware. Some MLSs are also able to route between VLANs and/or ports like a common router. The routing is normally as quick as switching (at wirespeed). According to Cisco, Layer 3 switches are basically routers that switch based on Layer 3 information, the basic difference being processing speed and/or the way they do the switching; Layer 3 switches use ASICs/hardware instead of the CPU/software that a router would. Layer

neg: OSI model similar networking models. In 1983, these two documents were merged to form a standard called The Basic Reference Model for Open Systems Interconnection. The standard is usually referred to as the Open Systems Interconnection Reference Model, the OSI Reference Model, or simply the OSI model. It was published in 1984 by both the ISO, as standard ISO 7498, and the renamed CCITT (now called the Telecommunications Standardization Sector of the International Telecommunication Union or ITU-T) as standard X.200. OSI had two major components, an "abstract model" of networking, called the Basic Reference Model or seven-layer model, and a set of

neg: Network architecture networks or nodes in the network, or the usage of specific types of hardware links. The Open Systems Interconnection model (OSI model) is a product of the Open Systems Interconnection effort at the International Organization for Standardization (ISO). OSI defines and codifies the concept of layered network architecture. It is a way of sub-dividing a communications system further into smaller parts called layers. A layer is a collection of similar functions that provide services to the layer above it and receives services from the layer below it. On each layer, an instance provides services to the instances at the layer

neg: Internet protocol suite 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

neg: Circuit-level gateway rules and may be controlled to acknowledged computers only. Circuit-level firewalls conceal the details of the protected network from the external traffic, which is helpful for interdicting access to impostors. But circuit-level firewalls do not clean entity packets. Circuit-level gateways are relatively inexpensive and have the advantage of hiding information about the private network they protect. On the other hand, they do not filter individual packets. Circuit-level gateway A circuit-level gateway is a type of firewall. Circuit-level gateways work at the session layer of the OSI model, or as a "shim-layer" between the application layer and the transport layer of

neg: Abstraction layer graphical objects. Abstraction layer In computing, an abstraction layer or abstraction level is a way of hiding the working details of a subsystem, allowing the separation of concerns to facilitate interoperability and platform independence. Examples of software models that use layers of abstraction include the OSI model for network protocols, OpenGL and other graphics libraries. In computer science, an abstraction layer is a generalization of a conceptual model or algorithm, away from any specific implementation. These generalizations arise from broad similarities that are best encapsulated by models that express similarities present in various specific implementations. The simplification provided by a

neg: Abstraction layer Abstraction layer In computing, an abstraction layer or abstraction level is a way of hiding the working details of a subsystem, allowing the separation of concerns to facilitate interoperability and platform independence. Examples of software models that use layers of abstraction include the OSI model for network protocols, OpenGL and other graphics libraries. In computer science, an abstraction layer is a generalization of a conceptual model or algorithm, away from any specific implementation. These generalizations arise from broad similarities that are best encapsulated by models that express similarities present in various specific implementations. The simplification provided by a good abstraction

neg: Internet protocol suite 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

neg: Manufacturing Message Specification MMS using Internet protocols instead of the bottom four layers of the original stack plus RFC 1006 ("ISO Transport over TCP") in the transport layer. The top three layers use the same OSI protocols as before. In terms of the seven-layer OSI model, the new MMS stack looks like this: With the new stack, MMS has become a globally accepted standard. Manufacturing Message Specification Manufacturing Message Specification (MMS) is an international standard (ISO 9506) dealing with messaging systems for transferring real time process data and supervisory control information between networked devices or computer applications. The standard is developed and maintained

neg: Internet protocol suite the File Transfer Protocol (FTP), the Simple Mail Transfer Protocol (SMTP), and the Dynamic Host Configuration Protocol (DHCP). Data coded according to application layer protocols are encapsulated into transport layer protocol units (such as TCP or UDP messages), which in turn use lower layer protocols to effect actual data transfer. The TCP/IP model does not consider the specifics of formatting and presenting data, and does not define additional layers between the application and transport layers as in the OSI model (presentation and session layers). Such functions are the realm of libraries and application programming interfaces. Application layer protocols generally treat

neg: OSI model 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

neg: Physical layer 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

neg: Internet protocol suite 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

neg: Infrared Data Association link around as fast as possible. The mandatory IrLAP (Infrared Link Access Protocol) is the second layer of the IrDA specifications. It lies on top of the IrPHY layer and below the IrLMP layer. It represents the data link layer of the OSI model. The most important specifications are: On the IrLAP layer the communicating devices are divided into a "primary device" and one or more "secondary devices". The primary device controls the secondary devices. Only if the primary device requests a secondary device to send, is it allowed to do so. The mandatory IrLMP (Infrared Link Management Protocol) is

neg: Transport Layer Interface Transport Layer Interface In computer networking, the Transport Layer Interface (TLI) was the networking API provided by AT&T UNIX System V Release 3 (SVR3) in 1987 and continued into Release 4 (SVR4). TLI was the System V counterpart to the BSD sockets programming interface, which was also provided in UNIX System V Release 4 (SVR4). TLI was later standardized as XTI, the X/Open Transport Interface. It was originally expected that the OSI protocols would supersede TCP/IP, thus TLI is designed from an OSI model-oriented viewpoint, corresponding to the OSI transport layer. Otherwise, TLI looks similar, API-wise, to sockets. TLI and

neg: OSI model 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.

neg: X.25 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,

neg: OSI protocols presentation layer formats shared by different applications. This keeps track of how each application talks to another application. Destination and source addresses are linked to specific applications. OSI protocols The Open Systems Interconnection protocols are a family of information exchange standards developed jointly by the ISO and the ITU-T. The standardization process began in 1977. While the seven-layer OSI model is often used as a reference for teaching and documentation, the protocols originally conceived for the model did not gain popularity, and only X.400, X.500, and IS-IS have achieved lasting impact. The goal of an open-standard protocol suite instead has

neg: Data link layer 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

neg: Internetworking or voice chat. Two architectural models are commonly used to describe the protocols and methods used in internetworking. The Open System Interconnection (OSI) reference model was developed under the auspices of the International Organization for Standardization (ISO) and provides a rigorous description for layering protocol functions from the underlying hardware to the software interface concepts in user applications. Internetworking is implemented in the Network Layer (Layer 3) of the model. The Internet Protocol Suite, also called the TCP/IP model of the Internet was not designed to conform to the OSI model and does not refer to it in any of

neg: Application layer Application layer An application layer is an abstraction layer that specifies the shared communications protocols and interface methods used by hosts in a communications network. The application layer abstraction is used in both of the standard models of computer networking: the Internet Protocol Suite (TCP/IP) and the OSI model. Although both models use the same term for their respective highest level layer, the detailed definitions and purposes are different. In TCP/IP, the application layer contains the communications protocols and interface methods used in process-to-process communications across an Internet Protocol (IP) computer network. The application layer only standardizes communication and depends

neg: VARAN 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

neg: Adaptive quality of service multi-hop routing 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

neg: Session (computer science) communication consists of independent requests with responses. An established session is the basic requirement to perform a connection-oriented communication. A session also is the basic step to transmit in connectionless communication modes. However any unidirectional transmission does not define a session. Communication Transport may be implemented as part of protocols and services at the application layer, at the session layer or at the transport layer in the OSI model. In the case of transport protocols that do not implement a formal session layer (e.g., UDP) or where sessions at the application layer are generally very short-lived (e.g., HTTP), sessions are

neg: Physical layer (LAN) or a metropolitan area network (MAN) using Open Systems Interconnection (OSI) architecture, the "physical signaling sublayer" is the portion of the physical layer that The Internet protocol suite, as defined in RFC 1122 and RFC 1123, is a high-level networking description used for the Internet and similar networks. It does not define an equivalent layer that deals exclusively with hardware-level specifications and interfaces, as this model does not concern itself directly with physical interfaces. Several RFCs mention a "physical layer" and "data link layer", but that is in the context of IEEE protocols. RFC 1122 and 1123 do not

neg: Network switch 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

neg: OSI model through intermediate nodes. If the message is too large to be transmitted from one node to another on the data link layer between those nodes, the network may implement message delivery by splitting the message into several fragments at one node, sending the fragments independently, and reassembling the fragments at another node. It may, but does not need to, report delivery errors. Message delivery at the network layer is not necessarily guaranteed to be reliable; a network layer protocol may provide reliable message delivery, but it need not do so. A number of layer-management protocols, a function defined in the

neg: UniPro protocol stack UniPro protocol stack In mobile-telephone technology, the UniPro protocol stack follows the architecture of the classical OSI Reference Model. In UniPro, the OSI Physical Layer is split into two sublayers: Layer 1 (the actual physical layer) and Layer 1.5 (the PHY Adapter layer) which abstracts from differences between alternative Layer 1 technologies. The actual physical layer is a separate specification as the various PHY options are reused in other MIPI Alliance specifications. The UniPro specification itself covers Layers 1.5, 2, 3, 4 and the DME (Device Management Entity). The Application Layer (LA) is out of scope because different uses of

neg: Link layer 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

neg: UniPro protocol stack of the stack. Furthermore, it provides means to control the peer UniPro stack on the Link. UniPro protocol stack In mobile-telephone technology, the UniPro protocol stack follows the architecture of the classical OSI Reference Model. In UniPro, the OSI Physical Layer is split into two sublayers: Layer 1 (the actual physical layer) and Layer 1.5 (the PHY Adapter layer) which abstracts from differences between alternative Layer 1 technologies. The actual physical layer is a separate specification as the various PHY options are reused in other MIPI Alliance specifications. The UniPro specification itself covers Layers 1.5, 2, 3, 4 and the

neg: Deep packet inspection be out of bounds for a particular application. While IDSs are able to detect intrusions, they have very little capability in blocking such an attack. DPIs are used to prevent attacks from viruses and worms at wire speeds. More specifically, DPI can be effective against buffer overflow attacks, denial-of-service attacks (DoS), sophisticated intrusions, and a small percentage of worms that fit within a single packet. DPI-enabled devices have the ability to look at Layer 2 and beyond Layer 3 of the OSI model. In some cases, DPI can be invoked to look through Layer 2-7 of the OSI model. This

neg: IPsec 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

neg: Presentation layer are 'objects' in object-oriented programming, and the exact way that streaming video is transmitted. In many widely used applications and protocols, no distinction is made between the presentation and application layers. For example, HyperText Transfer Protocol (HTTP), generally regarded as an application-layer protocol, has presentation-layer aspects such as the ability to identify character encoding for proper conversion, which is then done in the application layer. Within the service layering semantics of the OSI network architecture, the presentation layer responds to service requests from the application layer and issues service requests to the session layer. In the OSI model: the presentation

neg: Keyword Protocol 2000 Keyword Protocol 2000 Keyword Protocol 2000, abbreviated KWP2000, is a communications protocol used for on-board vehicle diagnostics systems (OBD). This protocol covers the application layer in the OSI model of computer networking. The protocol is standardized by International Organization for Standardization as ISO 14230. KWP2000 also covers the session layer in the OSI model, in terms of starting, maintaining and terminating a communications session. One underlying physical layer used for KWP2000 is identical to ISO 9141, with bidirectional serial communication on a single line called the K-line. In addition, there is an optional L-line for wakeup. The data rate is

neg: X/Open Transport Interface (TCP), Xerox Network Systems (XNS), Systems Network Architecture (SNA), X.25, Asynchronous Transfer Mode (ATM) or any other transport layer provider that function at Layer 4 of the OSI Model. XTI provides similar functionality as the Berkeley sockets interface, however it is protocol independent in contrast to the socket interface which is heavily biased toward the Internet Protocols. It is based on the UNIX System V Transport Layer Interface (TLI)., which is a transport service definition adhering to the Open Systems Interconnection (OSI) model. XTI consists of a cooperating STREAMS module, link library application programming interface (API), header files, and the

neg: Link layer however it was developed within the OSI reference stack, where it is a Layer 2 protocol. It is not an Internet standard. The link layer of the TCP/IP model is often compared directly with the combination of the data link layer and the physical layer in the Open Systems Interconnection (OSI) protocol stack. Although they are congruent to some degree in technical coverage of protocols, they are not identical. The link layer in TCP/IP is still wider in scope and in principle a different concept and terminology of classification. This may be observed when certain protocols, such as the Address

neg: Subnetwork Access Protocol order to allow the receiving node to pass each received frame to an appropriate device driver which understands given protocol. The Open Systems Interconnect (OSI) model uses a SAP to define the communication between layers (like Network, Transport, Session, and the other layers of the Seven-Layered Model), that 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

neg: Multilayer switch NAT with port and transaction awareness, usually performs a form of port translation for sending incoming packets to one or more machines that are hidden behind a single IP address. The "layer 4" refers to the layer 4 or transport layer of the OSI model. The router operates on the transport layer and makes decisions on where to send the packets. Modern load balancing routers can use different rules to make decisions on where to route traffic. This can be based on least load, or fastest response times, or simply balancing requests out. This is also a redundancy method, so

neg: Link layer and are not part of the TCP/IP model. These authors assume a hardware layer or physical layer below the link layer, and several of them adopt the OSI term data link layer instead of link layer in a modified description of layering. In the predecessor to the TCP/IP model, the "ARPAnet Reference Model" (RFC 908, 1982), aspects of the link layer are referred to by several poorly defined terms, such as "network-access layer", "network-access protocol", as well as "network layer", while the next higher layer is called "internetwork layer". In some modern text books, "network-interface layer", "host-to-network layer" and "network-access

neg: Packet switching 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

neg: Multicast address Multicast address A multicast address is a logical identifier for a group of hosts in a computer network that are available to process datagrams or frames intended to be multicast for a designated network service. Multicast addressing can be used in the link layer (layer 2 in the OSI model), such as Ethernet multicast, and at the internet layer (layer 3 for OSI) for Internet Protocol Version 4 (IPv4) or Version 6 (IPv6) multicast. IPv4 multicast addresses are defined by the most-significant bit pattern of "1110". This originates from the classful network design of the early Internet when this group

neg: Layer 8 been referenced to physical (real-world) controllers containing an external hardware device which interacts with an OSI model network. An example of this is ALI in Profibus. A network guru T-shirt from the 1980s shows Layer 8 as the "financial" layer, and Layer 9 as the "political" layer. The design was credited to Evi Nemeth. In the TCP/IP model, the 4-layer model of the Internet, the 5th layer is analogously sometimes described as the "political layer" (and the 6th as the "religious layer"). This appears in RFC 2321, which is a humorous April Fools' Day RFC published in 1998. Layer 8

neg: Interface Message Processor on the ARPANET was the one at the University of Maryland. "BBN Report 1822" specifies the method for connecting a host computer to an IMP. This connection and protocol is generally referred to as "1822", the report number. The initial version of the 1822 protocol was developed in 1969: since it predates the OSI model by a decade, 1822 does not map cleanly into the OSI layers. However, it is accurate to say that the 1822 protocol incorporates the physical layer, the data link layer, and the network layer. The interface visible to the host system passes network layer addresses

neg: OSI protocols OSI protocols The Open Systems Interconnection protocols are a family of information exchange standards developed jointly by the ISO and the ITU-T. The standardization process began in 1977. While the seven-layer OSI model is often used as a reference for teaching and documentation, the protocols originally conceived for the model did not gain popularity, and only X.400, X.500, and IS-IS have achieved lasting impact. The goal of an open-standard protocol suite instead has been met by the Internet protocol suite, maintained by the Internet Engineering Task Force (IETF). The OSI protocol stack is structured into seven conceptual layers. The layers