Lan Technology
LAN technologies
ETHERNET
Ethernet was developed by DIX (Digital, Intel and Xerox) has developed in 1970. In 1980, the IEEE 802.3 standard was published. Two years later, the version 2 was introduced, the basis for today's Ethernet networks. The method of access (for example, the pipe is inaccessible) Carrier Sense Multiple Access / Collision Detection (CSMA / CD). Heard in a CSMA / CD network stations to see if the network is overloaded when the power is free, the station transmits data. Whento listen to two stations, and both define the network is available, it will begin sending data simultaneously and a collision occurs. If the collision is detected and the detection stations was created after a waiting time from a random back-off algorithm for transmission. In today's fast-growing high-bandwidth network environments that will soon become a big problem, stations must wait more often before they can transmit data and more collisions. The solution is tothe network into multiple collision domains, that the devices can be used for this purpose is explained, will be in a network diagram for each of the components of the net.
An Ethernet network is a transmission system, this means that when a station transmits data every other station receives the data. The frame contains an address in the frame header is the only station with that address to make the frame and not to give the higher level protocolsprocessed.
Broadcast Domain
All devices in this field to receive broadcast frames received from any other device within the domain. Broadcast domains are typically limited by routers because routers do not forward broadcast frames. Broadcast frames are frames specifically addressed to all nodes on the LAN, the network will grow as a problem.
REPEATERS
A repeater is a simple device with whichextend LAN segments over long distances. They do not affect the broadcast or collision domains, they are not aware of any high-level protocols and frame formats, you only regenerate / amplify the signal. Repeaters operate at the physical layer of the OSI model. An important rule to expand the use of repeaters in a network is the 5-4-3 rule that the maximum distance between two hosts on the same network can be up to 5 segments, 4 repeaters and only 3 of segments definedpopulated, as shown in the following logical network:
HUBS / Concentration
Hubs, also known as concentrators or multiport repeaters, are used in networks in star / hierarchical to connect multiple stations / cable segments. There are two main types of hubs: passive and active. An active hub takes the incoming frames, amplifies the signal and sends it to all other ports, a passive hub simply splits the signal and sends it. AnotherType of hubs can be managed, if the single port configuration and traffic monitoring, intelligent hubs will or managed.
Hubs operate at the physical layer of the OSI model and protocols are transparent in the sense that they are not aware of the higher level protocols such as IP, IPX or MAC addressing. Have no control of transmission or collision domains, but extends it as follows:
BRIDGES
Bridges are more intelligent than a hub, working on the Data Link Layer of the OSI model.
They are used to increase network performance by segmenting networks into collision domains. Bridges are also protocol transparent, are not aware of the higher-layer protocols. Maintain a table of MAC addresses of all nodes, and which segment is located.
A bridge involves an incoming frame, it reads the MAC address of the database and tips for deciding whatshould be made to the frame when the position is given the destination MAC address in the database, the frame is forwarded to the appropriate port. If the destination port is the same as the port to which the frame arrived, it is discarded. If the location is not known, the frame will be flooded out all ports / segments.
As shown below, bridges control collision domains, they do not control broadcast domains:
SWITCHES
To improve the performance of network switches have been developed even further, the switches are very similar to the bridges, but also maintain a table of MAC addresses per port switch to make decisions that work in the OSI model and protocol transparent.
Some of the main differences are:
- A switch has multiple ports of a bridge
- Bridge switch in the switch software and switch hardware (chips)
- Pass to provide more variance of speed, aeach port can be 10 Mb / s or 100 Mb / s or more are assigned.
As shown below, control switch collision domains, they do not control broadcast domains *:
* Non-control broadcast domains unless they are used Virtual Local Area Networks (VLANs), and the most modern switches support VLANs. The following diagram shows a router configured with two VLANs. As in the diagram above each port is a collision domain, but as you canshown separately in this scheme, the network in two broadcast domains with VLANs. If the network protocol in the network uses the TCP / IP would be the VLAN each his own (sub) network address, such as VLAN 1 could Class C 192.168.110.xe 192.168.220.x. VLAN 2 will
The switches are able to use software to create virtual LANs, a logical grouping of network devices, where members can be on different physical segments. A VLAN can be based on port ID, MACAddresses, protocols or applications. For example, in the network diagram of the switch port 1-12 and port VLAN 1 could be assigned 13-24 to VLAN 2, which could in two different broadcast domains, or Station 1, 2 and 3 with IPX / SPX , while station 4, 5 and 6 could use the TCP / IP.
An example of a large network with VLANs could be an office building with a switch on each of three floors and a main switch connects to all be together. An administrator maybe able to keep a list of MAC addresses and assign stations to different floors to a single VLAN, for example, you create a VLAN (broadcast domain) for each department within the company. Switches to share their information on the MAC address table with other switches, the way to a destination can be found quickly.
ROUTER
Routers are used to connect multiple (sub-) networks and route information between networks using an optimal path("Path") for the destination. Speakers on the network layer (layer 3) of the OSI model and in contradiction to hubs, bridges and switches, routers are protocol-aware. Examples of these protocols: IP, IPX and AppleTalk. Routers make forwarding decisions on a table with the network addresses and corresponding ports are based, this table as the route table is unknown. Common use of routers is to connect to two different types of networks (such as Ethernet and Token Ring) orInterconnect LANs into a WAN. The concept of path will be covered in detail the technical routing protocols.
As shown below, router control collision domains and broadcast domains:
GATEWAY
A gateway (such as a network component) is a device that interconnects networks with different network protocols and architectures and translating between networks. Gateway devices are very intelligent, usually operate onthe transport layer and above the (Session, Presentation, Application). A gateway can be used to use IPX / SPX client to a gateway with TCP / IP uplink to an Internet connection. TCP / IP protocol would be IPX / SPX are converted. Another common use of a gateway is an Ethernet network to connect to an IBM SNA mainframe environment.
NIC
A NIC (Network Interface Card) in an expansion card is used for a computer, a physical connection to the network. The NICInterface defines the physical layer (Layer 1) of the OSI model, the physical address (also called burn-in address and well known: the MAC address) of the drivers for the card and the card is in control Date Link Layer MAC sublayer. The reason for the physical address of the data link layer is defined so that the physical layer uses only one bit.
Half Duplex
Half-duplex means that only one host can communicate at any time, twoHosts communicate with each other alternately transmitted. This is the default on non-switched LAN.
Full-duplex
In full-duplex communication with both hosts can transmit simultaneously, so that theoretically can be transmitted twice as much data on the same connection.
To work for full-duplex mode, certain conditions must be met:
- Network adapters, hubs, etc. must be supported,
- The collision detection and loopback functions are disabled.
InIndeed, the compounds are capable, full-duplex version of Cross-optical link to connect to a port on a switch, where collisions can occur, because each pair has its own end (segment).
Danos tu comentario
Post a Comment