LOCAL AREA NETWORK (LAN) HIGH PERFORMANCE
Distributed MODEL FIBER INTERFACE (FDDI)
Computer Network is a collection of computers, printers, and other equipment are connected in one unit and form a certain system. Information travels through a wired or wireless computer network that allows users to exchange information (data), print on the same printer and can simultaneously use the same application program.
LAN (Local Area Network) is a privately owned network within a single organisasitertentu, building or campus-sized to several kilometers. LANs are often used for connecting personal computers and workstations in the office or a company for sharing and exchanging information.
With a system of this LAN so multiple PCs that had been working on their own, can eventually work together within certain limits, even with a larger computer system. Cooperation can be done also growing from just a mutual exchange of data to use the equipment connected to one computer system.
LAN become so popular is because in general can be used as office automation paralatan. In Figure 1 appears a LAN network that consists of several PCs that are placed at various places. PC is known as a workstation. Each workstation can be used as a stand-allone (stand-alone computer), but also can be used to access storage or output devices, which in this case referred to as peripherals, which are located far from each other but still within a single network.
LAN network will typically consist of: File servers, serves to control the hard drive and plugging into the network. Utility server, with the existence of this equipment allows for each user on the network could use some equipment, such as modems, and other ploter. Printer servers, serves to divide the lawyer-access of the printer into the network so that it can be used for all users. Gateway, is a useful equipment in the network to communicate with other networks.
Figure 1. LAN Network Model
As the name implies, the LAN can only reach the area is restricted area (local), such as for example in one building, one department or one campus (currently limited understanding means no more than 20 km). And because of its short distance, then the data transmission speed becomes very high.
Demands kebututuhan activity in data communications using a LAN today, required a network that has high performance, high-speed access, wide range, and high reliability.
At this time has been developed efforts to improve the performance of LAN becomes higher. The things that have been developed for high performance LAN is as follows:
FDDI is the Fiber Distributid Data Interface (FDDI), which is a speed networking technology, 100-Mbps jakauannya distance can reach 200 km, using models of token ring.
Is CDDI Copper Data Distributid Iterface FDDI protocol which is the development of more than two pairs of wires.
3. Fast Ethernet
Fast Ethernet is a LAN device to support a capacity of 10 Mbps requires a lot of supporting devices such as repeaters, bridges, routers to obtain a higher transfer rate.
4. Gigabit Ethernet
Gigabit Ethernet is an extension of IEEE 802.3 Ethernet standard. Based on Ethernet protocol to increase speed access to ten times as much achieve the 1000 Mbps or 1 Gbps.
100VG-ANYLAN is an IEEE specification for 100-Mbps Token Ring and Ethernet to the implementation of more than 4-pair UTP cable. MAC layer is not compatible with the IEEE 802.3 MAC Layer.
HPPI (High Performance Parallel Interface) was originally designed as a data channel point to point with a master - slave who uses a dedicated cable without switching. Capacity provided 800 Mbps and 1600 Mbps. In the capacity of 800 Mbps twisted pair cables used 50 to channel 50 bits (32 bit data 18 bit control). Every 40 nanoseconds a word was transferred to a simplex channel with a length of no more than 25 m.
7. Fibre CHANEL
It is a system using a fiber optic network capable of providing very large capacity because it has a very wide bandwidth that can be used for data communication with very high speed.
B. PROBLEM LIMITATION
Given the number of models in high-performance LAN authors in the writing of this paper limit the issues discussed only FDDI, which includes:
1. Understanding FDDI
2. FDDI Transmission Media
3. FDDI Specifications
4. Type FDDI
5. Failure Tolerance FDDI
6. Advantages FDDI
1. Understanding Fiber Distributed Data Interface (FDDI)
Fiber Distributed Data Interface (FDDI) is a speed networking technologies by applying a 100-Mbps token-passing method. FDDI Token Ring technology is different from the old, by applying the dual-ring that uses glass fiber cable.
FDDI mostly used as high-speed backbone technology because of its support for the provision of greater bandwidth than ordinary copper wires.
FDDI uses dual-ring architecture with traffic on each of rings in opposite directions (called counter-rotating). Dual-ring architecture consisting of primary and secondary ring. With this architecture, when there is failure of the primary ring FDDI network can still function by automatically using the secondary ring. Primary ring is the default ring that will be used for data transmission and secondary ring will always be idle, unless needed.
The basic form arstektur FDDI ring:
Figure 2. The basic form of architecture FDDI
FDDI Standards developed by the American National Standards Institute (ANSI) X3T9.5 in the mid-1980s, and adopted by the International Organization for Standardization (ISO).
2. FDDI Transmission Media
FDDI uses fiber glass as the main transmission media, but also can use a copper wire transmission media using specifications Copper Distributed Data Interface (CDDI).
FDDI defines two types of fiber cable that can be used, namely Single-Cable-mode single-mode fiber allows only one mode for delivery of light through the fiber. (A mode is a light entering the fiber at a particular point of reflection.), And Multimode - Multimode fiber allows multiple modes of light through fiber cables dirambatkan. The figure below shows the single-mode fiber using a laser light source and multimode fiber using LED cahya sources:
Figure 3. Fiber cable to single mode and multimode
Comparison between Single Mode and Multimode Fiber: Fiber Single-mode ribbon Lepar provide transmission capacity that is larger and long-range fiber cable further than multimode fiber. This is caused by the presence of multiple modes of light propagation in fiber cable that can deliver at different distances. (Depending on the angles in reflection). Given these conditions cause any light coming in the destination at different times. (This is called the dispersion of capital.) Cable single-mode fiber is often used to connect between buildings, while kbel multimode fiber is often used to connect the room or floor in one building. Multimode fiber cable using Light-Emitting Diodes (LEDs) as a tool to produce light, whereas single-mode generally uses a laser beam.
3. FDDI Specifications
FDDI standard specification defined in 4 specifications, namely:
a. Media Access Control (MAC) - MAC specification defines how a transmission medium is accessible, including the definition of the frame format, token handling, addressing, algorithms calculate cyclic redundancy check (CRC), and error recovery mechanisms.
b. Physical Layer Protocol (PHY) - the specification defines the procedures PHY encoding / decoding data, the need for clock, framing and other functions.
c. Physical Medium Dependent (PMD) - tarnsmisi PMD defines the characteristics of media, including glass fiber connections, power level, bit error rates, optical components, and connectors are required.
d. Station Management (SMT) - SMT specification defines FDDI station configuration, ring configurations, and control of the ring, including the addition and reduction of new stations, initialization, kegagaan protection and recovery, scheduling, and collection of statistical data on the FDDI network.
The figure below shows the specification 4 FDDI, and relationships with each other and their relationship with the sublayer is Logical Link Control (LLC):
Figure 4. FDDI Specifications
There are specification and FDDI OSI model, namely the physical specifications and the media-access model of Open Systems Interconnection (OSI) and similar to the IEEE 802.3 Ethernet and IEEE 802.5 Token Ring in relation to the OSI model.
The following figure shows the specification of FDDI and its relationship with the OSI model:
Figure 5. Specification FDDI OSI model
4. Equipment Type FDDI
There are three types of tools / equipment FDDI, namely:
a. Single-Attachment Station (SAS),
Single-Attachment Station (SAS) is a SAS paired only to a FDDI ring through a concentrator, which can be described as follows.
Figure 6. Type SAS FDDI
b. Dual-Attachment Station (DAS)
Dual-Attachment Station (DAS) - Each FDDI DAS has two ports, determined by A and B. The ports that connect the DAS to the dual FDDI ring. Therefore, each port provides a connection to the second ring, both primary and secondary. Watershed can be described as follows.
Figure 7. Type DAS FDDI
c. Concentrator (Dual-Attachment Concentrator [DAC])
FDDI concentrator (also called a dual-attachment concentrator
[DAC]) is a "building" is important from an FDDI network. Concentrator directly attached bath with primary and secondary ring, and convinced that the failure or power failure at any SAS does not make the ring die. This will be very useful when the equipment is installed equipment that is often turned off or turned on, for example, is a PC. The following figure shows the installation of SAS, DAS, and concentrator on the FDDI ring:
Figure 8. FDDI Concentrator Type
5. Failure Tolerance FDDI
FDDI provides several mechanisms to support fault tolerance of FDDI networks, namely:
a. Dual Ring
Dual Ring is the main configuration for fault tolerance for all FDDI network. Dual ring is the main ability of FDDI to handle a failure on its network. If a station on the dual ring fails or dead, or damaged cable, dual-ring configuration is automatically "wrapped" (back to itself) into one ring. When the ring in "wrapped", dual-ring topology becomes a single-ring topology.
Figure 9. Dual Ring
- Ring Station Recovery after a Failure
When a station fails, devices located on both sides will be in "wrap" form a single ring. Network operations will resume back to the station which is still connected to the ring.
- Recovery after a Ring Cable Failure
When a cable failure, the equipment was in second ujungya will do the "wrap". And then the network operational.
- "Recovery" after Multiple faults
When two or more failures occur, FDDI ring is divided into two or more independent rings which of course does not allow a single ring with other rings are interconnected with each other.
- Optical Bypass Switch
An optical bypass switch provides dual-ring operating in a sustainable manner if a device on a dual ring die or fail.
c. Dual Homing
Dual homing provides a redundant configuration for the device is critical to the FDDI network. Essential equipment such as routers or mainframe can use the technique that provides two-homing tambaan similar equipment to support critical operations. In dual-homing situations, critical equipment is connected to two concentrator. One pair of the connection concentrator is expressed as an active connection, and others expressed as a passive partner.
Figure 10. Model Dual-Homing
Passive connections will continue to exist on the backup status of the connection, until the primary sambunan otherwise fail. When this occurs, the passive connection is automatically activated.
The frame format of FDDI can diambarkan like the image below:
Figure 10. FDDI Frame Format
- Preamble - A unique sequence EACH That station prepares for an upcoming frame.
- Start Delimiter - Indicates the beginning of a frame by employing a signaling pattern That
- Differentiates it from the rest of the frame.
- Frame Control - Indicates the size of the address fields, whether the frame contains
- Asynchronous or synchronous data, and other control information.
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