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The picture below is schematically simplified LAN of a high-tech company.
Quoted from Ethernet FAQ.
A hub is a common wiring point for star-topology networks, and is a common synonym for concentrator (though the latter generally has additional features or capabilities). Arcnet, 10BaseT Ethernet and 10BaseF Ethernet and many proprietary network topologies use hubs to connect multiple cable runs in a star-wired network topology into a single network. Token-Ring MSAUs (Multi-Station Access Units) can also be considered a type of hub, but don't let a token-ring bigot hear that. Hubs have multiple ports to attach the different cable runs. Some hubs (such as 10BaseT and active Arcnet) include electronics to regenerate and retime the signal between each hub port. Others (such as 10BaseF or passive Arcnet) simply act as signal splitters, similar to the multi-tap cable-TV splitters you might use on your home antenna coax (of course, 10BaseF uses mirrors to split the signals between cables). Token- Ring MSAUs use relays (mechanical or electronic) to reroute the network signals to each active device in series, while all other hubs redistribute received signals out all ports simultaneously, just as a 10Base2 multi-port repeater would.End of Quote.
The HUB has two main relationships within the LAN - with the router and with the Patch Panel. By supporting SNMP it may provide needing dependancies about those relationships.
A HUB has a 1-to-1 connection to a PatchPanel slot. PatchPanel
A patch panel provides an easy one-one-dimensioned connection between the
Terminal Outlet and the HUB, allowing to present a picture of connection
between different hub slots and points within the building.
Until recently the patch panels were only a piece of electricity which didn't
support any information exchange protocol and thus could not supply
about any connections it experiences.
But not long time ago a company
called RIT began constructing of Smart
PatchPanels (TM) which are enhanced with an agent, which looks over
the panels used, is able to get a picture of the existing connections and
then through SNMP provide this picture to
the central database. RIT also presents the software (for MS Windows XX X.x)
A PatchPanel is 1-to-1 connected to the TO.
A terminal outlet(TO) is simply a socket in a building wall or a cubic into which the computer's Network Adapter is plugged in. It is connected by a wire to a patch panel and through it - to the HUB. Each TO has a label, which defines its location in a unique way. A map of TO-s in the building should be supplied by their installator. In Intel Haifa such installator is Binat Ltd. Also a computer database, connecting each TO with a cubic it resides in is recommended. A cubic may have several TO.
A workstation is just the computer that is connected to the TO. We define here not the computer itself but its user. Notice that there may be several computers connected to the same TO (through a Dyna MiniHub, up to eight) and as well one user may own several computers. It is unlikely, though, that a computer will have many owners, everyone has at least a terminal. On the other hand a computer may have no owners.
Name service is a software service that provides each computer with a name
in the Network, for example - www.iil.intel.com. In LAN, usually, and in
the current case the computer name is defined by first word 'www'
(words are parts separated by dots) is its specific name, while the other
three words 'iil.intel.com' define the Internet domain it belongs to.
We won't investigate the topic of Name services here deeply, but if you
are interested in it we refer you to this link.
Notice that usually a computer has a unique name, but sometimes for aliasing
purposes same name may be used by several computers and a computer may have no name.
IP number is a four numbers combination which uniquely defines a computer both in the Internet and the LAN. The IP numbe looks like this: 143.185.1.11. Here, as Intel Haifa is a large LAN, first two numbers define the Internet domain, and the last two one - the way to the computer. Very important is the third number - it defines a "subdomain" - a segment within a LAN, while each segment is also a section in the HUB! Notice that no two computers may have same IP, whereas a computer may have two IP's. The IPs are given either authomatically through DHCP service, or manually by the Network Administrator.
The description of routers is quoted from ACC terminal adapters vs. routers:
In contrast, a router is a packet-forwarding device which, by design, examines all incoming data packets for source and destination addresses, and then determines whether the router has information regarding a route or path for forwarding the data packets to specified destinations. Unlike a Terminal Adapter, a router can either communicate over a point-to-point topology or a multipoint topology. Routers allow multiple workstations on one network to selectively communicate to individual stations on another network, passing all data information simultaneously through a common data port.End of Quote The Router has two main relationships within the LAN - with the HUB and with the IP service. By supporting SNMP it may provide needing dependancies about those relationships.
Of course, not all of the existing relationships may be real-time sampled by existing scripts through SNMP and NAME/IP services. Those relationships are then either collected manually by inspecting the LAN and then typed in the computer. Since LAN is a very dynamic thing, such an inspection should be a regular action and as well the technicians performing changes in LAN that are not observed by programmed mechanism should update the network administration about those changes. Other parts of the databases are collected by non-LAN mechanisms, through filling in of computer forms etc. Currently such databases provide relationships between a computer name and its owner and between a PatchPanel and a HUB slot. Also some equipment which is of old type and does not support SNMP had to be put down manually. More about them in the Database concepts page.
Well, the whole purpose of the project is to prove the concept of the efficiency of storing of the data in a central database located on a main LAN machine - an ENMS server. Please refer to this page on the issue.