Hub

Hub is a multiple ports of the repeater, as a hub for the center, network equipment of a certain line produced fault, does not affect other lines of work. So on in the local area network has been widely used. Most of the time it in star and extensible network topology structure, RJ45 interface with various mainframe with connected (there are also BNC interfaces), on according to different stories have many types. On according to the input signal processing in the way, can be divided into passive on, active on, intelligent on.

Passive on:

It is the most times one kind, wrong signals do any treatment, the transmission distance for medium without expansion, and to signal to a certain extent. Connections in this on each computer, can receive from the same on all other computer signal,

Active on:

Active and passive on on the difference is that it can to signal amplifier or regenerate, so it will extend the two between hosts the effective transmission distance,

Intelligent on:

Intelligent on besides having active on all the function, besides the network management and routing functions. In intelligent on network, not every machine to receive signals, only and signal the destination address can receive the same address port computer. Some intelligent on can select the best route, this to the network has very good management.

According to other methods have many types, such as 10M and 100M, 10/100M adaptive on etc, there cannot be introduced. Anyhow, the present market price for less than that. Try to try to win sb's favor of a bit.

If we often contact network, to construct a LAN infrastructure as a hub should not strange, but for behind all aspects of hub knowledge, we also know?

A, hubs definition

Hubs belongs to a data communication system the basic equipment, it and twisted-pair cable etc transmission medium is same, it is a kind of does not need any software support or need very little management software management hardware device. It is widely applied to various occasions. Hubs working in a local area network (LAN) environment, applied in the OSI reference model layer 1, so it is called the physical equipment. Hubs internal adopted appliances interconnected, when maintenance LAN environment is logical bus or annular structure, completely can use hubs establish a physical star or tree network structure. In this respect, the role of equivalent hub ports Repeaters. In fact, hub is actually a kind of Repeaters, and its difference only is hubs can provide more port services, so hubs also called multi-port Repeaters.

Ordinary hubs external surface structure is very simple. Such as D - Link the simplest 10BASE ~ T EthernetHub hub is a cuboid, on the ac power socket and switch, a AUI interface and a BNC interface, positive most position distribution line 17 RJ - 45 interface. In front of the right there with each RJ - 45 interface corresponding LED lights and the LED indicator interface state. High-grade hubs in appearance, and modern router or switching router have no much difference. Especially modern two-speed adaptive Ethernet hub, due to general with can implement internal 10 MB/s and 100Mb/s network segment between communicating exchange module, make this kind of hubs can completely in the hub for node segment, realizing each node of communication between the exchange, sometimes you will also such switched hubs simply called switches, all these make first use hubs users difficult to distinguish them correctly. But according to the backplane interface type discrimination hub, is a simple method.

Second, hubs characteristics of the work

According to IEEE 802.3 agreement, hub function is randomly selected a port equipment, and let it exclusive full bandwidth, and hub linked equipment (switches and routers or server) in communication. Can see from this, hub at work, has the following two characteristics. First is on just a ports amplification equipment, work when a port receives data signals, because the signal from the source port to on transmission process has the attenuation, and so on will this signal is shaped amplification, make be attenuation of signal regeneration (restoration) to send state, followed by forwarding to all other in working ports. From on way of working, it can be seen in the network only play amplification and retransmission function, its purpose is to expand the network transmission in scope and does not have the directional teleport ability, signal is - a standard of a Shared equipment. Therefore some called Hub for "silly on" or "dumb on".

Next is only with its top allied on equipment (such as the upper on, switch or server), namely the communication between different ports not directly communicate, but rather through top allied equipment again information broadcast to all ports. Therefore, even in the same on the different communication between two interfaces, must be through two-step operation: the first step is to upload the top allied equipment; information The second step is to top allied equipment then the information broadcast to all ports.

However, with the development of technology and the change of demand, at present on the function of many on the widening, no longer suffer this kind of influence of working mechanism. The network is composed by on a Shared network, but also can only on in half-duplex next work.

Mainly used for sharing network on formation, is from the server directly to solve the most economic plan. Desktop In switched network, connected directly with switches on, will switch port of data sent to the desktop. Use on networking flexible, it's in the star of a network of nodes connected node, the workstation centralized, not conceded problems affecting the whole network of workstation, and the normal operation of the user to join and exit is also free.

Three, hubs classification

There are many types of hub.

1. According to the structure and function of classification

According to the structure and function of classification, hubs can be divided into not management of hubs, stack type hubs and chassis hubs three categories.

(1) not management of hubs

The simplest hubs via Ethernet network connection, and provide the central bus in a star form together. These are called not management of hubs, only for very small diem 12 nodes on the network (in rare cases, can be more a few). Not management of hubs no management software or agreement to provide network management functions, the hubs can be passive, also can be active, active hubs use more.

(2) stack type hubs

Stacked type hubs are slightly more complex hubs. Stacked type hubs most prominent feature is 8 forwarder directly connected to each other. Such simply add hubs and its connection to has been installed on the hubs can be expanded network, this method not only cost is low, and simple.

(3) chassis hubs

Chassis hub is a modular equipment, in its bottom circuit can insert multiple types of modules. Some hub with redundant slab and power supply. Meanwhile, some module allows users do not have to close the whole hubs can be replace those failure module. A hub of the floor to insert module prepared more buses, these insert module can be adapted to different sections, such as Ethernet, fast Ethernet, Distributed Fiber Data with (FDDl) and Asynchronous' Mode (ATM). Some hubs also contain Bridges and routers or exchange module. Active chassis hubs are possible heavy timing of modules, used and amplification of data signals associated.

2. According to the type of LAN classification

From LAN Angle to distinguish, hubs can be divided into five different types.

(1) single relay segment hubs

The simplest hubs, which are used in the simplest relay type LAN segment of the network hub, and stacked Ethernet hub or token-ring multi-station visit parts (maus) and similar.

(2) more network segment hubs

From single relay segment hubs directly derived from, adopt hub, the backplane network segment with multiple relay hub. Its main advantage is the user distribution can be in multiple relay segment in order to reduce each segment of the network information flow load, network segment information between flow general requirement independent Bridges or router.

(3) port switched hubs

This set is in more bowlder network segment hubs based on user port and multiple backplane network segment the connection between the process automation, and by increasing port switching matrix (PSM) to realize the hub. PSM can provide an automatic tools, used for any foreign user port connected to any relay hub backplane network segment. Port switched hub main advantage is, may realize the mobile, increase and modified automation features.

(4) network interconnection hubs

Port switched hub, and pay attention to port exchange network connections hubs in multiple backplane network segment between can provide some types of integrated connection, this function through a comprehensive Bridges and routers or LAN switches to complete. At present, this kind of hubs are usually adopts cabinet form.

(5) switched hubs

At present, the boundary between the hub and the switch has become blurred. Switched hub have a core switched backboard, using an pure exchange system in place of the traditional Shared media relay segment. Such products have been listed, and mixed (relay/swap) hub, probably in for years to control the market. It should be noted that this kind of hub and the switch between the characteristics of almost no difference between.

Four, LAN hubs choice

With the development of technology, in the local area network especially -- some large and medium-sized LAN, hub has gradually exit application, and be switches instead. At present, hubs are mainly applied in some small networks or the edges of large and medium-sized network. Here in small and medium-sized LAN applications for characteristics and introduced the selection method.

1. With speed for the standard

Hubs speed selection, mainly depends on the following three factors.

(1) top allied equipment bandwidth

If the top allied equipment allowed to run 100Mbit/s, nature can buy lOOMbit/s hubs, Otherwise lOMbit/s hubs should be an ideal choice for network connection, because is the equipment of less, but teletraffic not a huge network, it lOMbit/s hubs can meet the application requirements.

(2) provide connection port number

Because join in all the sites are made.the strove with the same uplink bus, so connection port number, and the more easy to cause conflict. Meanwhile, sent to hubs any port data will be sent to all with connected to the hub ports, port number excessive will reduce the equipment utilization. According to practical experience, a lOMbit/s hubs managed by computer number is unfavorable exceed 15, lOOMbit/s is unfavorable exceed 25. If more than, should use switchboard to replace hubs.

(3) application requirements

Transmitted content does not involve audio and image, throughput relatively hours, choose 10Mbit/s can. If large quantities, and have transmission may involve multimedia applications (note hubs are not fit to transport time sensitivity signals, such as speech signal), ought to choose the 100Mbit/s or 10/100Mbit/s adaptive hubs. 10/100Mbit/s adaptive hubs price general than 100Mbit/s high.

2. To expand could meet the standard

When a hub of port provide when insufficient, generally have the following two expand subscribers purpose method.

(1) stack

Stack is insufficient to solve a single hub port of a kind of method, but because stacked together multiple hubs or work in the same environment, so the stack of layer also cannot too much. However, many hub on market with its stacked layers of more than other brands and selling point, if encounter this kind of circumstance, want to differentiate between: on the one hand can be stacked layers, the more general descriptions hubs stability higher; On the other hand can be stacked layers, each user more actual can enjoy the bandwidth is smaller.

(2) level and even

Even in the network level is increasing the number of users another method, but the function of the use of generally are conditions, namely on must provide can even port, this class for "port on ChangBiao Uplink" or "MDI".frequently, with this port with other on even on level. If no offers special port and we should undertake level even when connecting two hub twisted-pair cable in manufacture time we should undertake the wrong line.

3. To provide for network management function whether standard

Early on belongs to a kind of low-end products, and be management. In recent years, with the development of technology, some hubs in technology introduced switch function, can realize to network management module by increasing hub simple management (SNMP), with convenient use. But it should be pointed out that, although with is to provide support for the SNMP, different vendor's module is to cannot be mixed use, at the same time the same manufacturer of different products and module are different.

4) to shape dimension for reference

If the network system is relatively simple, no building between the integrated wiring, and network within the user is less, such as a family, one or more adjacent office, then there is no need to consider on the overall size. But sometimes it isn't, for example to make it convenient to multiple on centralized, buying on already bought before, when the choose and buy on cabinet must be considering its shape dimension, or on cannot install on the frame. On market now cabinet in the design generally follow the 19 inch industrial standard, it may install most 5 mouth, eight mouths, 16 and 24 of mouth on the mouth. However, in order to prevent accidental, when the choose and buy must notice whether it accords with 19 inches regulated, so in the cabinet of safety, centrally manage.