Networking- Networking Adapter Card
Networking can group several computers together. But there are advantages and disadvantages to networking. Advantages of networking in general are:
Ø Expensive resources such as printers and storage devices can be shared
Ø A user can use load and edit files that they have created on any station, provided that the station has the software required to use the files or share files
Ø You can use a network to send electronic mail or to access huge databases such as the World Wide Web or a database of all the products a company sells by sharing internet access
Ø Share hardware devices among multiple computers
Also, there are disadvantages that networking offer, these are:
Ø The cabling, interface cards, file servers, etc. that are required to set a network are expensive
Ø If one computer, cable or interface breaks the whole network may stop operating and you may not be able to use any of the computers until the fault is repaired. In practice this rarely happens. The exact effect of a failure will depend on the topology of the network.
Ø Viruses stored on a computer on a network can spread to other computers over the network
Ø The files stored on computer networks can be accessed, stolen and edited more easily that files stored on a non-networked computer could be. Appropriate security measures must be implemented to prevent this.
The advantages and disadvantages stated apply for the user and organisation. For a user, sharing of files and viruses are what makes networking unattractive. Since for every user, somehow there are files that they do not want others to see. But if they are in a network it cannot be helped. For an organisation, the advantages are most certainly welcome, although there are a few drawbacks, the over-all view for the network is positive. The drawbacks can be addressed separately should it occur. And even if organisation files can be stolen, this can also be addressed by setting up firewalls and other security measures.
By employing close to 100 computers, a server-based network is most applicable. This type of networking can be employed in filing and printing, application, mail, fax and communications. It has a central administration, which also offers greater security. It has centralized backup and offers data redundancy and can support many users.
Network topology refers to the layout used to wire the computers together. Regardless of what type of network is used, any topology can be applied. In bus topology, computers are connected to a single cable that connects all computers, this type of topology is the cheapest of all as it requires the smallest amount of cabling, but if the cable breaks anywhere then none of the computers can access the network. In a mesh topology, any computer can be connected to any other computer, and this topology is very reliable because if one link fails the messages will be directed to another link, and example of this topology is the Internet. The star topology offers communication to all other computers via a central computer, and if one cable breaks only the computer connected to that computer will be affected, but if the central computer fails the whole network will break down. For the ring topology, each computer if connected to two computers that are adjacent to it, and the last computer is linked to the first so that it forms a ring, but if one cable breaks then none of the computers can gain access to the network.
As an additional, there are another three types of topology, these are (Wilson, 2001): Star Bus topology, it is composed of several star topologies linked with a linear bus, and with this type of topology no single computer can take the whole network down, just like in star topology, only the computers connected to the hub that failed are affected; Star Ring topology, which is also known as star wired ring because the hub itself is wired as a ring, this means that physically it is a star, but a logical ring, just like in the ring topology, computers are given equal access to the network media through the passing of the token. A single computer failure cannot stop the entire network, but if the hub fails, the ring that the hub controls also fails; Hybrid Mesh its most important aspect is that a mesh if fault tolerant.
The choice of network adapter depends on network architecture. But there a lots of types of adapters. For a network that has units close to 100, it is best to use the star topology for the network. Because in this type of topology, the organisation will only maintain the central computer that connects every computer together, and this way they can closely monitor the security of their network, also this type of topology is considered to be the most scalable and reconfigurable topology (Wilson, 2001).
In choosing the network adapter, the organisation has to consider the advantages and disadvantages of each type of topology as was discussed above. The types of adapters are basically based on the form factor (plug-in card or plug-in module), the interface (PCI, ISA, PC card, CardBus, MCA), and connectivity (cable or wireless). The form factor is the physical size and shape of a device. It is used to describe the device itself, whether it’s plug-in, integrated or rack-mount. Interface it the connection standard that is used to connect with other devices. And, connectivity is the way the network is connected; it can either be cable or wireless (with or without cable connections between devices). If the connection used is cable, the network is not allowed the complete networking freedom that wireless connection can provide. Brands include IBM, Intel, 3Com, SMC, NetGear, Compaq, and others.
The role of the network Adapter card is to: prepare data from the computer for the network cable, send the data to another computer and control the flow of data between the computer and the cabling system. In choosing the NIC, one must: match the computer’s internal bus architecture and have the right cable connector for the cable being used. In improving the network card performance one can employ (Wilson, 2001):
Ø Direct Memory Access (DMA) with this data is moved directly from the network adapter card’s buffer to computer memory.
Ø Shared Adapter Memory, this will make the adapter memory card to contain memory, which is shared by the computer and the computer identifies RAM on the card if it were actually installed on the computer.
Ø Shared System Memory, the network adapter selects a portion of the computer’s memory for its use and it is the most common.
Ø Bus Mastering, the adapter card takes temporary control of the computer’s bus, freeing the CPU for other tasks, moves data directly to the computer’s system memory, is available on EISA and MCA, and can improve network performance by 20% to 70%.
Ø RAM buffering: RAM on the adapter card acts as a buffer that holds data until the CPU can process it, and this keeps the card from being a bottleneck.
Ø On-board microprocessor enables the adapter card to process its own data without the need of the CPU.
There are also lots of types of interfaces this include (NVC CS, 2003):
Ø ISA (Industry Standard Architecture) is a standard bus architecture that is associated with IBM AT motherboard. It allows 16 bit at a time to flow between the motherboard circuitry and an expansion slot card and its associated device(s).
Ø MCA (Micro Channel Architecture) was developed by IBM for its line of PS/2 desktop computers; MCA is an interface between a computer (or multiple computers) and its expansion cards and their associated devices. MCA was a distinct break from previous bus architecture such as ISA. The pin connections in MCA are smaller than other bus interfaces. For this and other reasons, MCA does not support other bus architectures. Although MCA offers a number of improvements over other bus architectures, its proprietary, non-standard aspects did not encourage other manufacturers to adopt it. It has influenced other bus designs and it is still in use in PS/2 and in some minicomputer systems.
Ø EISA (Extended Industry Standard Architecture) is a standard bus architecture that extends the ISA standard to a 32-bit interface. It was developed in part as an open alternative to the proprietary Micro Channel Architecture (MCA) that IBM introduced in its PS/2 computers. EISA data transfer can reach a peak of 33 megabytes per second.
Ø VESA (Video Electronics Standards Association Local Bus) Local Bus is a standard interface between your computer and its expansion slots that provide faster data flow between the devices controlled by the expansion cards and your computer’s microprocessors. A “local bus” is a physical path on which data flows at almost the speed of the microprocessor, increasing total system performance. VESA Local Bus is particularly effective in systems with advanced video cards and supports 32-bit data flow at 50 MHz. A VESA Local Bus is implemented by adding a supplemental slot and card that aligns with and augments as ISA expansion card.
Ø PCI (Peripheral Component Interconnect) is an interconnection system between a microprocessor and attached devices in which expansion slots are spaced closely for high-speed operation. Using PCI, a computer can support both new PCI cards while similar to the VESA Local Bus. However, PCI 2.0 is no longer a local bus and is designed to be independent of microprocessor design. PCI is designed to be synchronized with the clock speed of the microprocessor, in the range of 20 to 33 MHz. PCI is now installed on most new desktop computers, not only those based on Intel’s Pentium processor but also those based on the Power PC.
PCI transmits 32 bits at a time in a 124-pin connection (the extra pins are for power supply and grounding) and 64 bits in a 188-pin connection in an expanded implementation. PCI uses all active paths to transmit both address and data signals, sending the address on one clock cycle and data on the next. Burst data can be sent starting with an address on the first cycle and a sequence of data transmissions on a certain number of successive cycles.
The price for the above adapters can be as low as below 0 up to an expensive range of 00 – 00 or even higher. All types of adapters, regardless of its brand have this price range.
In connecting your network components, there are three primary cable types that could be used: the coaxial cable; the twisted pair, which can be Unshielded Twisted Pair or Shielded Twisted Pair; and the fibre-optic. The Coaxial cable consists of a solid or stranded copper core surrounded by insulation, braided shield and an insulating jacket. The braided shield prevents noise and crosstalk; it is more resistant to interference and attenuation than twisted pair cabling. The plenum (fire resistant) graded cable can be used in false ceilings of office space or under the floor. It can also transmit data, voice, and video and it offers moderate security, which is better than UTP or STP. Although this is the case, there are limitations of the benefits of coaxial cable, these are: length of trunk segment may be up to 607 feet; a maximum of 30 workstations is allowed per trunk; there may be no more than 1024 workstations per network; entire network trunk length can’t exceed 3035 feet (925 meters); the minimum cable length between workstations is 20 inches; and the Ethernet 5-4-3 rule for connecting segments is 5 trunk segments can be connected, with 4 repeaters or concentrators, with no more than 3 populated segments (on coaxial cable). (Wilson, 2001)
The twisted pair cable consists of two insulated wire twisted around each other. The twisting cancels out electrical noise from adjacent pairs (crosstalk) and external sources. It uses RJ-45 telephone type connectors (larger than telephone and consists of eight wires vs. Telephone’s 4 wires). Also, twisted pair cable is generally inexpensive and easy to install. The two types of twisted pair cable are: Unshielded Twisted Pair (UTP) and Shielded Twisted Pair (STP). UTP can only be used for a maximum cable length of 100 metres, but it is the cheapest cable to use. The STP uses a woven copper braid jacket and a higher quality protective jacket. Also uses foil wrap between and around the wire pairs. It is much less susceptible to interference and supports higher transmission rates than UTP. Shielding makes it somewhat harder to install. It can only be used for 100 metres, but it is harder to tap. It is usually used in Apple Talk and Token Ring networks. Fibre-optic cable is the most expensive cable that can be used and the hardest to install. It consists of small core of glass or plastic surrounded by a cladding layer and jacket. The fibres are unidirectional (light travels in one direction) so two fibres are used, one for sending and one for receiving. Kevlar fibres are placed between the two fibres for strength. It is very good at high speed, long distance data transmission, and is not subject to electrical transmission. It offers the best security because it cannot be tapped. It can transmit data at 100Mbps and way up to 2Gbps. It can be used for up to 2000 metres without the use of a repeater. It also supports data, voice and video. Although, it would need specialized knowledge to install. (Wilson, 2001)
If the organisation is only going to network four computers, it is advisable to do what they initially plan to do. But if they are going to add more computers to the network, it may cause trouble. UTP is particularly susceptible to crosstalk, which is when signals from one line get mixed up with signal from another, and it can also be easily tapped because there is no shielding. Although is can hold up to 1023 stations without bridging, the workstations should not exceed 328 feet from the concentrator port and the minimum cable length between workstations is 8 feet (Wilson, 2001). If the organisation really needs to network computers to share a single printer, this should be done for computers that are close, that way the users will know if there are any printing jobs pending before they try to print. The organisation can use the star topology. This way, a single computer that fails will not bring down the network. This suggestions may not be as economical as what was initially planned, but this type is much more efficient and easier to maintain especially if the organisation is planning to add more units to the network.
The important thing is that the organisation knows the factors that need to be considered before cabling. They should first consider the installation logistics, shielding, crosstalk, transmission speed, attenuation, and most especially the cost. They should also remember that the longer the distance the more expensive the cabling will be.
Reference:
Meakin, P. (1999). “Networks: Advantages and Disadvantages.” Cheshire, Washington: Cedar Education.
Meakin, P. (1999). “ Networks: Topology.” Cheshire, Washington: Cedar Education.
NetGear. (2003). “Easy guide to choosing a network card.” Santa Clara, California: Headquarters Netgear, Inc.
NVC CS. (2003). “Input-Output Organization.” Falls Church, Virginia: Virginia Polytechnic Institute and State University.
Wilson, Grant. (2001). “Networking Essentials Notes.” Edmonton, Canada: MCSE Networking Notes.
Credit:ivythesis.typepad.com
0 comments:
Post a Comment