query: what is a switch that works at more than one layer of the osi model called

pos: Network switch Network switch A network switch (also called switching hub, bridging hub, officially MAC bridge) is a computer networking device that connects devices together on a computer network by using packet switching to receive, process, and forward data to the destination device. A network switch is a multiport network bridge that uses hardware addresses to process and forward data at the data link layer (layer 2) of the OSI model. Some switches can also process data at the network layer (layer 3) by additionally incorporating routing functionality. Such switches are commonly known as layer-3 switches or multilayer switches. Switches for Ethernet

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: Network topology networks, a USB hub in USB networks. A network bridge connects and filters traffic between two network segments at the data link layer (layer 2) of the OSI model to form a single network. This breaks the network's collision domain but maintains a unified broadcast domain. Network segmentation breaks down a large, congested network into an aggregation of smaller, more efficient networks. Bridges come in three basic types: A network switch is a device that forwards and filters OSI layer 2 datagrams (frames) between ports based on the destination MAC address in each frame. A switch is distinct from a

neg: Switching loop their time to live (TTL) value expires, as no TTL concept exists at Layer 2. In practice, the packet will circulate until it is dropped, e.g. due to resource exhaustion. Switching loop A Switching loop or bridge loop occurs in computer networks when there is more than one Layer 2 (OSI model) path between two endpoints (e.g. multiple connections between two network switches or two ports on the same switch connected to each other). The loop creates broadcast storms as broadcasts and multicasts are forwarded by switches out every port, the switch or switches will repeatedly rebroadcast the broadcast messages

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: Switching loop Switching loop A Switching loop or bridge loop occurs in computer networks when there is more than one Layer 2 (OSI model) path between two endpoints (e.g. multiple connections between two network switches or two ports on the same switch connected to each other). The loop creates broadcast storms as broadcasts and multicasts are forwarded by switches out every port, the switch or switches will repeatedly rebroadcast the broadcast messages flooding the network. Since the Layer 2 header does not support a "time to live" (TTL) value, if a frame is sent into a looped topology, it can loop forever.

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: Multilayer switch Multilayer switch A multilayer switch (MLS) is a computer networking device that switches on OSI layer 2 like an ordinary network switch and provides extra functions on higher OSI layers. Switching technologies are crucial to network design, as they allow traffic to be sent only where it is needed in most cases, using fast, hardware-based methods. Switching uses different kinds of network switches. A standard switch is known as a "layer 2 switch" and is commonly found in nearly any LAN. "Layer 3" or "layer 4" switches require advanced technology (see managed switch) and are more expensive, and thus are

neg: Multilayer switch if one machine is not up, the router will not send traffic to it. Multilayer switch A multilayer switch (MLS) is a computer networking device that switches on OSI layer 2 like an ordinary network switch and provides extra functions on higher OSI layers. Switching technologies are crucial to network design, as they allow traffic to be sent only where it is needed in most cases, using fast, hardware-based methods. Switching uses different kinds of network switches. A standard switch is known as a "layer 2 switch" and is commonly found in nearly any LAN. "Layer 3" or "layer 4"

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: 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: 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: 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: 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: 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: 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: Digital subscriber line access multiplexer 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

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: 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: 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: 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: Packet processing including the ability to change one layer without impacting the others and as a model for understanding how a network OS works. As long as the interconnection between layers is maintained, vendors can enhance the implementation of an individual layer without impact on other layers. In parallel with the development of the OSI model, a research network was being implemented by the United States Defense Advanced Research Projects Agency (DARPA). The internetworking protocol developed to support the network, called ARPAnet, was called TCP or Transmission Control Program. As research and development progressed and the size of the network grew, it

neg: Encapsulation (networking) while at the same time each layer communicates with its corresponding layer on the receiving node. These are known as adjacent-layer interaction and same-layer interaction, respectively. In discussions of encapsulation, the more abstract layer is often called the upper layer protocol while the more specific layer is called the lower layer protocol. Sometimes, however, the terms upper layer protocols and lower layer protocols are used to describe the layers above and below IP, respectively. Encapsulation is a characteristic feature of most networking models, including both the OSI model and TCP/IP suite of protocols. Encapsulation (networking) In computer networking, encapsulation is

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: 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: 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: Protocol data unit 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

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: 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: 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: 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: 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: 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: 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: 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: Network packet 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

neg: DNP3 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

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: Communication protocol conforming to the various layer specifications. In the OSI model, communicating systems are assumed to be connected by an underlying physical medium providing a basic (and unspecified) transmission mechanism. The layers above it are numbered (from one to seven); the n layer is referred to as (n)-layer. Each layer provides service to the layer above it (or at the top to the application process) using the services of the layer immediately below it. The layers communicate with each other by means of an interface, called a "service access point". Corresponding layers at each system are called "peer entities". To communicate,

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: Bridging (networking) using a layer 2 forwarding method. There are four forwarding methods a bridge can use, of which the second through fourth methods were performance-increasing methods when used on "switch" products with the same input and output port bandwidths: Bridging (networking) A network bridge is a computer networking device that creates a single aggregate network from multiple communication networks or network segments. This function is called network bridging. Bridging is distinct from routing. Routing allows multiple networks to communicate independently and yet remain separate, whereas bridging connects two separate networks as if they were a single network. In the OSI model,

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: Computer network a unified broadcast domain. Network segmentation breaks down a large, congested network into an aggregation of smaller, more efficient networks. Bridges come in three basic types: A network switch is a device that forwards and filters OSI layer 2 datagrams (frames) between ports based on the destination MAC address in each frame. A switch is distinct from a hub in that it only forwards the frames to the physical ports involved in the communication rather than all ports connected. It can be thought of as a multi-port bridge. It learns to associate physical ports to MAC addresses by examining the

neg: DECnet (areas, level 1 and level 2 routers), VMScluster support (cluster alias) and host services (CTERM). CTERM allowed a user on one computer to log into another computer remotely, performing the same function that Telnet does in the TCP/IP protocol stack. Digital also released a product called the PATHWORKS client, and more commonly known as the PATHWORKS 32 client, that implemented much of DECnet Phase IV for DOS, and 16 and 32 bit Microsoft Windows platforms (all the way through to Windows Server 2003). Phase IV implemented an 8 layer architecture similar to the OSI (7 layer) model especially at the

neg: Bridging (networking) Bridging (networking) A network bridge is a computer networking device that creates a single aggregate network from multiple communication networks or network segments. This function is called network bridging. Bridging is distinct from routing. Routing allows multiple networks to communicate independently and yet remain separate, whereas bridging connects two separate networks as if they were a single network. In the OSI model, bridging is performed in the data link layer (layer 2). If one or more segments of the bridged network are wireless, the device is known as a wireless bridge and the function as wireless bridging. There are four

neg: 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: 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: 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: Network layer model has a layer called the Internet layer, located above the link layer. In many textbooks and other secondary references, the TCP/IP Internet layer is equated with the OSI network layer. However, this comparison is misleading, as the allowed characteristics of protocols (e.g., whether they are connection-oriented or connection-less) placed into these layers are different in the two models. The TCP/IP Internet layer is in fact only a subset of functionality of the network layer. It describes only one type of network architecture, the Internet. The following are examples of protocols operating at the network layer. Network layer In the

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: 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: 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: 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: 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: Packet processing cumulative investment capabilities to move the state of networking forward. In the 1970s, two organizations, the International Organization for Standardization (ISO) and the International Telegraph and Telephone Consultative Committee (CCITT, now called the International Telecommunication Union (ITU-T) each initiated projects with the goal of developing international networking standards. In 1983, these efforts were merged and in 1984 the standard, called The Basic Reference Model for Open Systems Interconnection, was published by ISO and as standard X.200 by the ITU-T. The OSI Model is a 7 layer model describing how a network operating system works. A layered model has many benefits

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: 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: 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: 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: 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: 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: Denial-of-service attack network-level attacks continue to be of high capacity, they are occurring less frequently. Ali further notes that although network-level attacks are becoming less frequent, data from Cloudflare demonstrates that application-layer attacks are still showing no sign of slowing down. The OSI model (ISO/IEC 7498-1) is a conceptual model that characterizes and standardizes the internal functions of a communication system by partitioning it into abstraction layers. The model is a product of the Open Systems Interconnection project at the International Organization for Standardization (ISO). The model groups similar communication functions into one of seven logical layers. A layer serves the layer

neg: Internet protocol suite (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.

neg: OSI model layer provides independence from data representation by translating between application and network formats. The presentation layer transforms data into the form that the application accepts. This layer formats data to be sent across a network. It is sometimes called the syntax layer. The presentation layer can include compression functions. The Presentation Layer negotiates the Transfer Syntax. The original presentation structure used the Basic Encoding Rules of Abstract Syntax Notation One (ASN.1), with capabilities such as converting an EBCDIC-coded text file to an ASCII-coded file, or serialization of objects and other data structures from and to XML. ASN.1 effectively makes an

neg: Intelligent Network of the OSI seven-layer model. This means that the IN standards only had to define the application layer, which is called the Intelligent Networks Application Part or INAP. The INAP messages are encoded using ASN.1. The interface between the SCP and the SDP is defined in the standards to be an X.500 Directory Access Protocol or DAP. A more lightweight interface called LDAP has emerged from the IETF which is considerably simpler to implement, so many SCPs have implemented that instead. The core CS-1 specifications were adopted and extended by other standards bodies. European flavours were developed by ETSI, American

neg: Dell M1000e the same fabrics (Broadcom) and running the same firmware-version. All the M-series switches are OSI layer 3 capable: so one can also say that these devices are Ethernet switches with built-in router or layer3 functionality. The most important difference between the M-series switches and the Dell PowerConnect "classic" switches (e.g. the 8024 model) is the fact that most interfaces are "internal" interfaces that connect to the blade-servers via the midplane of the enclosure. Also the M-series can't be running outside the enclosure: it will only work when inserted in the enclosure. This is a 20-port switch: 16 internal and 4

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: 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: Autonegotiation mandatory for 1000BASE-T gigabit Ethernet over twisted pair. In the OSI model, autonegotiation resides in the physical layer. In 1995, a standard was released to allow connected network adapters to negotiate the best possible shared mode of operation. The initial autonegotiation standard contained a mechanism for detecting the speed but not the duplex setting of Ethernet peers that did not use autonegotiation. Autonegotiation can be used by devices that are capable of more than one transmission rate, different duplex modes (half duplex and full duplex), and different standards at the same speed (though in practice only one standard at each

neg: Cisco Inter-Switch Link encapsulating the Ethernet frame, whereas with IEEE 802.1Q the tag is internal. This is a key advantage for IEEE 802.1Q as it means tagged frames can be sent over standard Ethernet links. The size of an Ethernet encapsulated ISL frame can be expected to start from 94 bytes and increase up to 1548 bytes because of the overhead (additional fields) the protocol creates via encapsulation. ISL adds a 26-byte header (containing a 15-bit VLAN identifier) and a 4-byte CRC trailer to the frame. ISL functions at the data-link layer of the OSI model. Another related Cisco protocol, "Dynamic Inter-Switch Link

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: N-entity N-entity In telecommunication, a "n"-entity is an active element in the "n"-th layer of the Open Systems Interconnection--Reference Model (OSI-RM) that (a) interacts directly with elements, "i.e.", entities, of the layer immediately above or below the "n"-th layer, (b) is defined by a unique set of rules, "i.e.", syntax, and information formats, including data and control formats, and (c) performs a defined set of functions. The "n" refers to any one of the 7 layers of the OSI-RM. In an existing layered open system, the "n" may refer to any given layer in the system. Layers are conventionally numbered from

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: 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: 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: 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 it calls the next lower layer to send and receive packets that comprise the contents of that path. Two instances at the same layer are visualized as connected by a "horizontal" connection in that layer. The model is a product of the Open Systems Interconnection project at the International Organization for Standardization (ISO). In the late 1970s, one project was administered by the International Organization for Standardization (ISO), while another was undertaken by the International Telegraph and Telephone Consultative Committee (CCITT, from French: Comité Consultatif International Téléphonique et Télégraphique). These two international standards bodies each developed a document that defined

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: Computer worm worms as malware. Several worms, like XSS worms, have been written to research how worms spread. For example, the effects of changes in social activity or user behavior. One study proposed what seems to be the first computer worm that operates on the second layer of the OSI model (Data link Layer), it utilizes topology information such as Content-addressable memory (CAM) tables and Spanning Tree information stored in switches to propagate and probe for vulnerable nodes until the enterprise network is covered. Computer worm A computer worm is a standalone malware computer program that replicates itself in order to spread

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: 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: Network packet 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

neg: Presentation layer 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

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: Communication protocol original version of RM/OSI, the layers and their functionality are (from highest to lowest layer): In contrast to the TCP/IP layering scheme, which assumes a connectionless network, RM/OSI assumed a connection-oriented network. Connection-oriented networks are more suitable for wide area networks and connectionless networks are more suitable for local area networks. Using connections to communicate implies some form of session and (virtual) circuits, hence the (in the TCP/IP model lacking) session layer. The constituent members of ISO were mostly concerned with wide area networks, so development of RM/OSI concentrated on connection oriented networks and connectionless networks were only mentioned in

neg: Wireless network interface controller and additional capabilities (such as mesh networking, which is known as the IEEE 802.11s standard) for devices with limited functionality. FreeBSD also supports SoftMAC drivers. Wireless network interface controller A wireless network interface controller (WNIC) is a network interface controller which connects to a wireless radio-based computer network, rather than a wired network, such as Token Ring or Ethernet. A WNIC, just like other NICs, works on the Layer 1 and Layer 2 of the OSI Model. This card uses an antenna to communicate via microwave radiation. A WNIC in a desktop computer is traditionally connected using the PCI bus.

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: Service data unit recoding, splitting or transformations on the data, forming one or more layer (n) PDUs. The added headers or trailers and other possible changes are part of the process that makes it possible to get data from a source to a destination. Layer (n) may also generate additional layer (n) PDUSs. Each unit of data that layer that layer (n) gives to layer (n-1) below is in turn handed down as a layer (n-1) SDU. http://www.infocellar.com/networks/osi-model.htm Service data unit In Open Systems Interconnection (OSI) terminology, a service data unit (SDU) is a unit of data that has been passed down from

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: Message Transfer Part is ANSI T1.111. In Europe, national MTP protocols are based on ETSI EN 300-0088-1. The SS7 stack can be separated into four functional levels: Level 1 through Level 3 comprise the "MTP", and Level 4 the "MTP user". "MTP Level 3" is sometimes abbreviated "MTP3"; "MTP Level 2", "MTP2". MTP and SCCP are together referred to as the "Network Service Part (NSP)". There is no one-to-one mapping of MTP Levels 1 through 3 onto the OSI model. Instead, MTP provides the functionality of layers 1, 2 and part of layer 3 in the OSI model. The part of layer 3

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: Wireless network interface controller Wireless network interface controller A wireless network interface controller (WNIC) is a network interface controller which connects to a wireless radio-based computer network, rather than a wired network, such as Token Ring or Ethernet. A WNIC, just like other NICs, works on the Layer 1 and Layer 2 of the OSI Model. This card uses an antenna to communicate via microwave radiation. A WNIC in a desktop computer is traditionally connected using the PCI bus. Other connectivity options are USB and PC card. Integrated WNICs are also available, (typically in Mini PCI/PCI Express Mini Card form). Early wireless network interface

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: 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: 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: 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: Multilayer switch need for video conferencing. Layer 4 information has been used to help make routing decisions for quite a while. For example, extended access lists can filter packets based on layer 4 port numbers. Another example is accounting information gathered by open standards using sFlow provided by companies like Arista Networks or proprietary solutions like NetFlow switching in Cisco's higher-end routers. Some switches can use up to OSI layer 7 packet information; these may be called layer 4–7 switches, content switches, content services switches, web switches or application switches. Content switches are typically used for load balancing among groups of servers.

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: 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