Local Area Network(LAN) A local area network (LAN) is a computer network that interconnects computers within a limited area. Example: a residence, school, laboratory, university campus,office building etc. Ethernet and Wi-Fi are the two most common technologies in use for local area networks.
Ethernet Ethernet is a family of computer networking technologies commonly used in local area networks (LAN), metropolitan area networks (MAN) and wide area networks(wan). It was commercially introduced in 1980 and first standardized in 1983 as IEEE 802.3. It supports higher bit rates and longer link distances. Over time, Ethernet has largely replaced competing wired LAN technologies such as token ring, FDDI and ARCNET.
. 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. As per the OSI model, Ethernet provides services up to and including the data link layer. The original Ethernet uses coaxial cable as a shared medium, while the newer Ethernet variants use twisted pair and fiber optic links in conjunction with hubs or switches. Ethernet data transfer rates vary from the original 2.94 Mbits/s to the latest 400 Gbits/s.
Virtual LAN A virtual local area network (VLAN) is a logical group of workstations, servers and network devices that appear to be on the same LAN despite their geographical distribution. A VLAN allows a network of computers and users to communicate in a simulated environment as if they exist in a single LAN and are sharing a single broadcast and multicast domain. VLANs are implemented to achieve scalability, security and ease of network management. They can quickly adapt to changes in network requirements and relocation of workstations and server nodes. Higher-end switches allow the functionality and implementation of VLANs. The purpose of implementing a VLAN is to improve the performance of a network or apply appropriate security features.
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. The key benefits of implementing VLANs include: Allowing network administrators to apply additional security to network communication Making expansion and relocation of a network or a network device easier Decreasing the latency and traffic load on the network and the network devices, offering increased performance
. VLANs also have some limitations as listed below: High risk of virus issues because one infected system may spread a virus through the whole logical network. Equipment limitations in very large networks because additional routers might be needed to control the workload More effective at controlling latency than a WAN, but less efficient than a LAN
A Token Ring network A token ring network is a local area network (LAN) topology where nodes/stations are arranged in a ring topology. Data passes sequentially between nodes on the network until it returns to the source station. To prevent congestion and collision, a token ring topology uses a token to ensure that only one node/station on the line is allowed to transmit at a time. A token ring LAN is physically wired as a star topology but configured as a ring topology. The token ring LAN system was standardized by the Institute of Electrical and Electronics Engineers as IEEE 802.5.
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. The token ring LAN process undergoes following sequence of events: A token continually circulates inside the token ring LAN To transmit a message, a node inserts a message and destination address inside an empty token. The token is examined by each successive node. The destination node copies the message data and returns the token to the source with the source address and a data receipt message. The source receives the returned token, verifies copied and received data and empties the token. The empty token now changes to circulation mode, and the process continues.
Fiber Distributed Data Interface.(FDDI) FDDI is a set of ANSI and ISO standards for data transmission on fiber optic lines in a local area network (LAN) that can extend in range up to 200 km (124 miles). The FDDI protocol is based on the token ring protocol. In addition to being large geographically, an FDDI local area network can support thousands of users. FDDI is frequently used on the backbone for a wide area network (WAN).
. A FDDI network contains two rings, one as a secondary backup in case the primary ring fails. The primary ring offers up to 100 Mbit/s capacity. When a network has no requirement for the secondary ring to do backup, it can also carry data, extending capacity to 200 Mbit/s.
Metropolitan Area Network A metropolitan area network (MAN) is similar to a LAN but spans an entire city or campus. MANs are formed by connecting multiple LANs. Thus, MANs are larger than LANs but smaller than wide area networks (WAN). MANs are extremely efficient and provide fast communication via high-speed carriers, such as fiber optic cables.
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Distributed Queue Dual Bus ( DQDB ) IEEE defined a MAN standard for covering an entire city. This was called Distributed Queue Data Interface (DQDB) and put up as IEEE standard 802.6. It is a distributed multi-access network that : (i) supports integrated communications using a dual bus and distributed queuing (ii) provides access to LAN and MAN networks (iii) supports connectionless data transfer, connectionoriented data transfer, and voice communications.
A wide area network (WAN) A WAN is a telecommunications network that extends over a large geographical distance. WAN is a computer networking technology used to transmit data over long distances, and between different LANs and MANs. WANs are often established with leased telecommunication circuits. Business, education and government entities use WAN to relay data to staff, students, clients, buyers, and suppliers from various locations across the world. In essence, this mode of telecommunication allows a business to effectively carry out its daily function regardless of location. The Internet may be considered a WAN. Typically, TCP/IP is the protocol used for a WAN in combination with devices such as routers, switches, firewalls and modems.
Switched Multimegabit Data Service(SMDS) Switched Multimegabit Data Service is a wide area networking (WAN) service designed for LAN interconnection through the public telephone network. SMDS is a connectionless service. It is a switching service that provides data transmission in the range between 1.54 Mbit/s to 45 Mbit/s