Which network device is used to connect two network segments on the data link layer?
Learn how LANs, connected by intermediate network devices, work like large networks. Show
Network interconnection device is a widely used term for any hardware that connects different network resources. The key devices that make up a network are switches, routers, bridges, repeaters, and gateways. All the devices have different ranges, based on network requirements and scenarios. The following are interconnection scenarios:
To understand the various devices for network interconnection, we created the following glossary. Repeaters They are used to extend the length of the network. They were created to regenerate and amplify weak signals, thus extending the length of the network. The basic function of a repeater is to restructure and amplify the data signal up to its original level. The important features of these devices are the following:
Hubs A Hub is basically a multi-port repeater, it acts as a multiplexor and connects multiple cables coming from different connections. Hubs cannot filter data, so packets of data are sent to all connected devices; the collision domain of all hosts connected through the Hub remains one. The Hubs lack intelligence to find the best path for data packets, the consequences being inefficiency and waste. Bridge A bridge operates on the data link layer. It is a repeater with additional filtering functionality based on reading the source and destination MAC addresses. It is also used to interconnect two LANs that operate under the same protocol. It has a single input and a single output port, thus making it a 2 port device. Switch A switch is a multiport bridge; it is a data link layer device. The switch is very efficient; it performs error checking before forwarding packets. In other words, the switch divides the collision domain of the hosts, but the broadcast domain remains the same. Router Routers link two or more different networks; these can consist of various types of LAN network segments. A router receives packets and selects the optimal route to forward the packet across the network. Routers create a table of all addresses of the devices, and this is called a routing table. With it, the router sends a transmission from the source to the destination using the best path. The routers work on the network level of the OSI model. Gateway Gateways are multipurpose connection devices for creating junctions between different networks. They are capable of converting the format of the packages from one environment to match the format of another. They function as messaging agents that take data from one system, interpret the data and transfer it to another system. Remember that having a technology partner with the necessary experience and knowledge will help you achieve your business goals. We invite you to visit https://www.kionetworks.com/es-mx/ References: Accenture (2018). The Brave New World of Open Banking https://www.accenture.com/_acnmedia/pdf-77/accenture-brave-new-world-open-banking.pdf accessed September 2019. The data link 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 nodes on a network segment across the physical layer.[2] The data link layer provides the functional and procedural means to transfer data between network entities and may also provide the means to detect and possibly correct errors that can occur in the physical layer. The data link layer is concerned with local delivery of frames between nodes on the same level of the network. Data-link frames, as these protocol data units are called, do not cross the boundaries of a local area network. Inter-network routing and global addressing are higher-layer functions, allowing data-link protocols to focus on local delivery, addressing, and media arbitration. In this way, the data link layer is analogous to a neighborhood traffic cop; it endeavors to arbitrate between parties contending for access to a medium, without concern for their ultimate destination. When devices attempt to use a medium simultaneously, frame collisions occur. Data-link protocols specify how devices detect and recover from such collisions, and may provide mechanisms to reduce or prevent them. Examples of data link protocols are Ethernet, Point-to-Point Protocol (PPP), HDLC and ADCCP. In the Internet Protocol Suite (TCP/IP), the data link layer functionality is contained within the link layer, the lowest layer of the descriptive model, which is assumed to be independent of physical infrastructure. Function[edit]The data link provides for the transfer of data frames between hosts connected to the physical link. Within the semantics of the OSI network architecture, the protocols of the data link layer respond to service requests from the network layer, and perform their function by issuing service requests to the physical layer. That transfer can be reliable or unreliable; many data link protocols do not have acknowledgments of successful frame reception and acceptance, and some data link protocols might not even perform any check for transmission errors. In those cases, higher-level protocols must provide flow control, error checking, acknowledgments, and retransmission. The frame header contains the source and destination addresses that indicate which device originated the frame and which device is expected to receive and process it. In contrast to the hierarchical and routable addresses of the network layer, layer 2 addresses are flat, meaning that no part of the address can be used to identify the logical or physical group to which the address belongs. In some networks, such as IEEE 802 local area networks, the data link layer is described in more detail with media access control (MAC) and logical link control (LLC) sublayers; this means that the IEEE 802.2 LLC protocol can be used with all of the IEEE 802 MAC layers, such as Ethernet, Token Ring, IEEE 802.11, etc., as well as with some non-802 MAC layers such as FDDI. Other data-link-layer protocols, such as HDLC, are specified to include both sublayers, although some other protocols, such as Cisco HDLC, use HDLC's low-level framing as a MAC layer in combination with a different LLC layer. In the ITU-T G.hn standard, which provides a way to create a high-speed (up to 1 Gigabit/s) local area network using existing home wiring (power lines, phone lines and coaxial cables), the data link layer is divided into three sub-layers (application protocol convergence, logical link control and media access control). Sublayers[edit]The data link layer is often divided into two sublayers: logical link control (LLC) and media access control (MAC).[3] Logical link control sublayer[edit]The uppermost sublayer, LLC, multiplexes protocols running at the top of the data link layer, and optionally provides flow control, acknowledgment, and error notification. The LLC provides addressing and control of the data link. It specifies which mechanisms are to be used for addressing stations over the transmission medium and for controlling the data exchanged between the originator and recipient machines. Media access control sublayer[edit]MAC may refer to the sublayer that determines who is allowed to access the media at any one time (e.g. CSMA/CD). Other times it refers to a frame structure delivered based on MAC addresses inside. There are generally two forms of media access control: distributed and centralized.[4] Both of these may be compared to communication between people. In a network made up of people speaking, i.e. a conversation, they will each pause a random amount of time and then attempt to speak again, effectively establishing a long and elaborate game of saying "no, you first". The Media Access Control sublayer also performs frame synchronization, which determines the start and end of each frame of data in the transmission bitstream. It entails one of several methods: timing-based detection, character counting, byte stuffing, and bit stuffing.
Services[edit]The services provided by the data link layer are:
Error detection and correction[edit]In addition to framing, the data link layer may also detect and recover from transmission errors. For a receiver to detect transmission errors, the sender must add redundant information as an error detection code to the frame sent. When the receiver obtains a frame it verifies whether the received error detection code matches a recomputed error detection code. An error detection code can be defined as a function that computes the r (amount of redundant bits) corresponding to each string of N total number of bits. The simplest error detection code is the parity bit, which allows a receiver to detect transmission errors that have affected a single bit among the transmitted N + r bits. If there are multiple flipped bits then the checking method might not be able to detect this on the receiver side. More advanced methods than parity error detection do exist providing higher grades of quality and features.
A simple example of how this works using metadata is transmitting the word "HELLO", by encoding each letter as its position in the alphabet. Thus, the letter A is coded as 1, B as 2, and so on as shown in the table on the right. Adding up the resulting numbers yields 8 + 5 + 12 + 12 + 15 = 52, and 5 + 2 = 7 calculates the metadata. Finally, the "8 5 12 12 15 7" numbers sequence is transmitted, which the receiver will see on its end if there are no transmission errors. The receiver knows that the last number received is the error-detecting metadata and that all data before is the message, so the receiver can recalculate the above math and if the metadata matches it can be concluded that the data has been received error-free. Though, if the receiver sees something like a "7 5 12 12 15 7" sequence (first element altered by some error), it can run the check by calculating 7 + 5 + 12 + 12 + 15 = 51 and 5 + 1 = 6, and discard the received data as defective since 6 does not equal 7. More sophisticated error detection and correction algorithms are designed to reduce the risk that multiple transmission errors in the data would cancel each other out and go undetected. An algorithm that can even detect if the correct bytes are received but out of order is the cyclic redundancy check or CRC. This algorithm is often used in the data link layer. Protocol examples[edit]
Relation to the TCP/IP model[edit]In the Internet Protocol Suite (TCP/IP), OSI's data link layer functionality is contained within its lowest layer, the link layer. The TCP/IP link layer has the operating scope of the link a host is connected to, and only concerns itself with hardware issues to the point of obtaining hardware (MAC) addresses for locating hosts on the link and transmitting data frames onto the link. The link-layer functionality was described in RFC 1122 and is defined differently than the data link layer of OSI, and encompasses all methods that affect the local link. The TCP/IP model is not a top-down comprehensive design reference for networks. It was formulated for the purpose of illustrating the logical groups and scopes of functions needed in the design of the suite of internetworking protocols of TCP/IP, as needed for the operation of the Internet. In general, direct or strict comparisons of the OSI and TCP/IP models should be avoided, because the layering in TCP/IP is not a principal design criterion and in general, considered to be "harmful" (RFC 3439). In particular, TCP/IP does not dictate a strict hierarchical sequence of encapsulation requirements, as is attributed to OSI protocols. See also[edit]
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Which network device that operates at the data link layer is a repeater used to connect two or more network segments?Bridge. A bridge is a network device that operates at the data link layer device. A bridge is a repeater with the added functionality of filtering content by reading the MAC addresses of the source and destination. It is also used to connect two LANs that use the same protocol.
Which of the following is a data link layer device?Network switches are the most common network devices that exist at the data link layer.
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