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. A network is basically the interconnection of related parts, grouping them together in common functionality. It is a system of lines or channels that cross or interconnect various points, called nodes. These nodes can be stations on a rail network, or cities connected by roads. We make us of networks everyday, the telephone network being another example. Computer networks are the same in principle to that of all other networks, in that they interconnect computers and other peripherals, as opposed to cites or stations. LANs Computers, when interconnected in this way, in the same geographical region, are called Local Area Networks (LANs). These networks usually belong to a single company or organisation, and occupy the same building or campus. The diagram below shows a company LAN that has mini LANs in each department with their own server machine. Each mini LAN is connected to a central hub/switch, which also facilitates the connection of the main server. In a situation such as this, each department would have their own hardware and software requirements controlled by their own local server. This prevents the main server and the network over all, from becoming congested, thus improving performance. The technique is known as sub-netting. WANs Wide Area Networks (WANs) are the interconnection of multiple networks spread over a much wider graphical region. This can be across a city, country, continent or even the entire globe. In order to facilitate the connection of these smaller networks to each other, the use of a communication infrastructure is sought. A telecommunications company like Mercury or BT, to mention only two, provides the services for such connections, albeit at a price. Communication Infrastructures There are various technologies available, each varying in performance and cost. PSTN The cheapest by far is the public systems telephone network (PSTN). This is the same media that carries telephone conversations, and in terms of performance, though workable for the home user, is not a viable commercial solution. It has a bandwidth of 56Kbps using compression techniques, however, due to various environmental factors like line quality and control features, this capacity is theoretical. Access to this medium is acquired through the use of a device called a modem. A modem connects the PC to the phone line and acts as an analogue to digital converter. IDSN ISDN (Integrated Services Digital Network) is a faster more reliable solution, that makes use of a fibre optic transmission media (cable). The key features of ISDN are: · High bit-rate - an ISDN channel has throughput of 64Kbps · All digital interfaces - no need for analogue to digital conversion equipment (modems) · Very fast call set-up time as opposed to 30 seconds for modem connections · Supports digitised voice and digital data. ISDN comes in two flavours to UK subscribers. ISDN2 - This solution offers 2x64Kpbs channels (called B channels) and one 16Kpbs channel used or control purposes. Under certain circumstances it is possible to use the control channel (called the D Channel) to carry data, providing a total of 144Kpbs ISDN30 - This solution provides 30B channels, allowing for a total cable capacity of 2Mbps, depending on the amount of channels in use at any one time. As each channel is brought into use the greater the capacity, but also the greater the cost. xDSL The latest in digital solutions, come in the form the xDSL (x Digital Subscriber Line) range, and is a more likely solution for the business user. xDSL, like ISDN, it is an always-on system eliminating the need for dial-up. xDSL comes in several flavours. Depending on location and requirements, one of the following should be considered:
CableAt 512Kbps cable boasts even greater speeds than some of xDSL applications. This type of Internet connectivity uses coaxial cable, the same cable that carriers TV pictures into the home. The PC is connected to the cable box via a length of cable going into the PC's network card (for home users).
When these services are enlisted, it is important to understand, that although the connection behaves like it is a dedicated link between the two entities, it, in fact is not. The data is routed through many switching boxes and over many different cable segments, before it reaches its
destination (see PPTP diagram)
.
?Why Have Networks
Why can't we simply do our business on a day to say basis on standalone machines, without
enlisted the services of networks? The answer to that question is simple, networks provide so many benefits, that they simply cannot be ignored. Granted, their design, implementation and cost, do afford us barriers, but these barriers are far from being insurmountable. In fact, with correctly skilled professionals in place, the barriers are really not barriers at all. The only real obstacle is actually cost. However, the benefits far outweigh the consequences imposed by cost.
Consider the benefits:
· Data Sharing - Groups of users are able to exchange information routinely and quickly from one individual to another. This could be a detailed report created by an employee in the UK and accessed by another in New York, saving considerable amounts of time and money.
· Application Sharing - Groups of users can get access to the set of applications installed to the server. This eliminates the need to install programs on multiple machines. Also, the server is able to keep track of how many users are accessing any program, and can prohibit access to users as licensing permits.
· Device Sharing - Groups of users are able to take advantage of printers, scanners, fax machines and other devices that can be attached to a network. Companies can buy much fewer devices and spend more on each one, so that better capabilities, and higher levels of service are available. Also, it means that costly devices will be utilised more in a shared environment, thus justifying their high costs.
· Communication - E-Mail allows users to communicate via text massages, making communication between users fast, easy, and efficient. · Centralisation - All data is stored centrally. This can include items like reports, help guides, templates and curriculum material like assessments and tutorials in an education environment.
· Compatibility - Since software applications are installed and maintained centrally, it means that users will have access to a standard set of tools and will eliminate diverse formats. Upgrades carried out by administrators need only be performed once on the server and the new software is available to all on the network
· Security - Each user can only gain access to a network by virtue of an account. Each machine will display a screen asking the user for a username and password before gaining access to the network and its resources. Also, the ability to apply permissions on shared items and data items, prohibits users from gaining unauthorised access to sensitive materials or devices that they are not permitted to use. Accounts can also be configured to force users to change their password at regular time intervals, and prevent them from logging onto certain machines or at certain times.
· Internet Access - With the proper equipment and software in place, it is possible to connect a network to the Internet either as part of the Internet, or to simply allow users to access the Internet from their place of work. This is advantageous, since it gives users a much wider base for acquiring information and other resources like drivers and software utilities etc.
Consider the benefits:
· Data Sharing - Groups of users are able to exchange information routinely and quickly from one individual to another. This could be a detailed report created by an employee in the UK and accessed by another in New York, saving considerable amounts of time and money.
· Application Sharing - Groups of users can get access to the set of applications installed to the server. This eliminates the need to install programs on multiple machines. Also, the server is able to keep track of how many users are accessing any program, and can prohibit access to users as licensing permits.
· Device Sharing - Groups of users are able to take advantage of printers, scanners, fax machines and other devices that can be attached to a network. Companies can buy much fewer devices and spend more on each one, so that better capabilities, and higher levels of service are available. Also, it means that costly devices will be utilised more in a shared environment, thus justifying their high costs.
· Communication - E-Mail allows users to communicate via text massages, making communication between users fast, easy, and efficient. · Centralisation - All data is stored centrally. This can include items like reports, help guides, templates and curriculum material like assessments and tutorials in an education environment.
· Compatibility - Since software applications are installed and maintained centrally, it means that users will have access to a standard set of tools and will eliminate diverse formats. Upgrades carried out by administrators need only be performed once on the server and the new software is available to all on the network
· Security - Each user can only gain access to a network by virtue of an account. Each machine will display a screen asking the user for a username and password before gaining access to the network and its resources. Also, the ability to apply permissions on shared items and data items, prohibits users from gaining unauthorised access to sensitive materials or devices that they are not permitted to use. Accounts can also be configured to force users to change their password at regular time intervals, and prevent them from logging onto certain machines or at certain times.
· Internet Access - With the proper equipment and software in place, it is possible to connect a network to the Internet either as part of the Internet, or to simply allow users to access the Internet from their place of work. This is advantageous, since it gives users a much wider base for acquiring information and other resources like drivers and software utilities etc.
Network Types
Networks fall into two major types: peer-to-peer and client/server (sometimes called server-based).
Peer-to-Peer Networking
This is a simple network configuration that requires some basic know-how to set up. Each of the interconnected machines share dual capability and responsibility on the network. That is to say, that each machine serves a dual purpose or role, i.e. they are both clients and servers to some extent.
The server capability of the machines is very basic. The services provided by each, is no more than the ability to share resources like files, folders, disk drives and printers. They even have the ability to share Internet access.
However, the server functionality of these machines stops there. They cannot grant any of the benefits mentioned previously, since these are functions provided only by a dedicated server operating system.
Because all machines on the network have equal status, hence the term peers, there is no centralised control over shared resources. Sharing is endorsed or repealed by each machine's user. Passwords can be assigned to each individual shared resource whether it is a file, folder, drive or peripheral, again done by the user.
Although this solution is workable on small networks, it introduces the possibility that users may have to know and remember the passwords assigned to every resource, and then re-learn them if the user of a particular machine decides to change them! Due to this flexibility and individual discretion, institutionalised chaos is the norm for peer-to-peer networks.
Security can also be a major concern, because users may give passwords to other unauthorised users, allowing them to access areas of the network that the company does not permit. Furthermore, due to lack of centralisation, it is impossible for users to know and remember what data lives on what machine, and there are no restrictions to prevent them from over-writing the wrong files with older versions of the file. This of course cripples attempts to organise proper backups.
It may appear that peer-to-peer networks are hardly worthwhile. However, they offer some powerful incentives, particularly for smaller organisations. Networks of this type are the cheapest and easiest to install, requiring only Windows95, a network card for each machine and some cabling. Once connected, users can start to share information immediately and get access to devices.
As a result, networks of this type are not scalable and a limit of no more than 10 machines is the general rule.
Advantages
· Easy to install and configure.
· No dedicated server required.
· Users control their own resources.
· Inexpensive to purchase and operate.
· No specialist software required.
· No dedicated administrator to run the network required.
Disadvantages
· Difficult to employ security.
· Too many passwords for shared resources.
· Backups difficult to manage.
· No centralisation.
· Limited users.
Client/Server Networks
Server based networks, or client/server networks as they are properly called, has a machine at the heart of its operations called the server. A server is a machine that provides services over a network by responding to client requests. Servers rarely have individuals operating it, and even then, it is usually to install, configure or manage its capabilities. The server's essential role on the network is to be continuously available to handle the many requests generated by its clients.
Server-based networks provide centralised control of the entire network environment. The computer systems used for this role are generally more powerful than end-user machines, incorporating faster CPUs, more memory, larger disk drives and other drive types installed, like a tape drive for backup purposes. These are required, because servers are dedicated to handling multiple simultaneous requests from their client communities.
Server based networks provide centralised verification of user accounts and passwords. Only valid account name and password combinations are allowed access to the network. Client/Server networks typically require a single login to the network itself, meaning that users need to remember long password lists to access various resources. Concentrations of resources on a single server, mean that they are easier to find, as opposed to the peer-to-peer model, were resources were distributed throughout the network since they were attached to multiple machines. The server being a central data repository, means that not only is data more accessible to users, but it also makes life much easier in terms of performing backups, since the data is in a location know to the administrator.
Server-based networks are easier to scale. Peer-to-peer networks bog down seriously as they grow beyond ten users, and serious slow up with 20 users. On the other hand, client/server networks can handle a few users, up to a thousand users as such networks grow to keep pace with an organisations growth and expansion.
Unlike peer-to-peer networks, client/server networks don't come cheap. The server machine itself may cost several thousands of pounds, along with the software to make it run; another thousand pounds. Because of the complex nature of this kind of networking environment, a dedicated administrator is required to be on site at all times to be involved in the day to day running of the network. Hiring an individual of this nature adds considerably to the cost of client/server networks.
Lastly, because the networks operability is so dependant upon the server, this introduces a single point of failure, if the server goes down the network goes down. There are measures available, that can legislate for such failures, however these techniques add even more cost to this solution.
Advantages
· Centralised user accounts, security and access controls simplify network administration.
· More powerful equipment means more efficient access network resources.
· Single password login, means access to all resources.
· Supports greater numbers of users, or networks where resources are heavily used.
Disadvantages
· More costly to install and maintain.
· Single point of failure, server goes down, the network goes down.
· Complex special-purpose software requires appointment of expert staff, increasing costs.
· Dedicated hardware and software increases costs.
· Centralised user accounts, security and access controls simplify network administration.
· More powerful equipment means more efficient access network resources.
· Single password login, means access to all resources.
· Supports greater numbers of users, or networks where resources are heavily used.
Disadvantages
· More costly to install and maintain.
· Single point of failure, server goes down, the network goes down.
· Complex special-purpose software requires appointment of expert staff, increasing costs.
· Dedicated hardware and software increases costs.
Network Design
Layering (ISO/OSI Seven Layer Network Model)
A vital part of network design is to use a layered reference model. In other words, processes (like creating a program), can be more easily managed if they are broken down into layers or modules, where each of the layers communicate with the layer directly above and beneath itself. This permits designers to work at any stage in the development of a project and to divide the design of the network into more manageable chunks.
In the early/mid 80s the International Standards Organisation provided such a model. The model, called the Open Systems Interconnect Seven Layer Model, aided network designers and vendors in standardising networking protocols and equipment. The model also provides an invaluable tool used to aid students in the understanding of networks and how it all fits together. The following is a very brief description of each layer.
· Application Layer
This layer interacts with the user to create the message to be sent over the network. It provides the link between the user's application package and the communications system. Services that are supported at this layer include:
· File and print services
· Remote program access (Telnet)
· File transfer programs (FTP)
· Presentation Layer
Ensures that machines with the different data representations can still pass the same meaning from one user to another. This layer also provides facilities like compression/decompression encryption/decryption and terminal emulation.
· Session Layer
Controls communications between applications across the network
· Establish a connection
· Maintain the connection
· Terminate the connection
· Transport Layer
Responsible for the reliable delivery of the transmitted message.
· Network Layer
Adds unique addressing information to packets so that they are routed to the correct receiving station on another network. It is responsible for:
· Determining addresses either on a local network or an internetwork.
· Finding the best route between source and destination addresses.
· Data Link Layer
Responsible for creating, transmitting and receiving data frames. A checksum for error detection is added to the frame and is sent to layer 1 for transmission
· Physical Layer
Concerned with moving data between the stations and the medium that connects the stations. This layer defines the electrical (i.e. voltage) and mechanical (i.e. pin wiring) requirements for connecting to equipment to the medium
All networking related concepts and devices, operate at one or more of these layers, allowing designers to categorise problems and tackle them logi
Topology
A network topology is the physical layout of the network. In networking there are three main topologies in use; Bus, Star and Ring.
Bus
The bus topology is by far the most popular method for connecting computers. All components of the bus topology are connected via a backbone which is a single cable segment connecting all computers in a straight line (theoretically). On bus networks, the signal transmitted by a computer, is propagated along the entire length of the network, and is thus called a broadcast system, because all other nodes hear the transmission.
Star
The star topology is when each network component is connected by a cable segment to a central hub. Some confusion is found with regards to the star topology, with two descriptions being applied. Firstly, it is stated that the signal sent from one computer to another, is received by the hub, and the message directed to the intended node. This method is therefore known as a directed system. Secondly however, some sources say that all nodes connected to the hub hear the transmission with only the intended node actually downloading the packet, thus a broadcast system. The first description is most likely the correct one.
Ring
Ring topology networks are created when a computer is connected directly to the next computer in line, forming a circle of cable. As each computer receives the signal, it acts on it, regenerates it, and passes it along. Signals travel in only one direction on the ring. This topology is used by Token ring networks, see later.
Intranets
Many companies are now turning to intranets as a means of sharing information among company employees. Like all larger networks, it is based on the client /server model, with a server machine at its heart. An intranet is a network that runs principally like the Internet, however, it remains private and is not accessible to the public.
When users access the network, they are greeted with a Web browser interface. That is to say, rather than using the standard Windows desktop, users access files, databases, e-mail, printers and other resources via the Web browser software, just as though they were surfing the Web.
In order for your company to set up an intranet, they will require a server machine as mentioned, which must be configured as a Web server. That is to say, it requires having Web server software installed. This is not a problem for companies using Microsoft WindowsNT, or later, because this software comes complete with Web server software free, called IIS (Internet Information Services).
The server is configured as a Web server, and the company website is uploaded. It is also a requirement to have TCP/IP installed. TCP/IP is a protocol suite that allows computers to communicate and transfer data. TCP/IP is the protocol used by the Internet itself. So the components required for an intranet are:
Server machine, configured as a Web server. Browser software, Internet Explorer TCP/IP protocol suite.
Extranet
Although an intranet is a private network, and not accessible to the public since it is not attached directly to the Internet, it is sometimes required to give outside users access to its services. These users would be an authorised group, perhaps customers, clients, partners or mobile users. These users would access the intranet via the normal Internet by a non-public means and would require to login using a username and password. The login associated with the user, will determine what range of access will be afforded them.
Security of this type is managed by a hardware and software combination that surrounds the company's resources and protects the network, called a firewall. This is a dedicated machine that intercepts all incoming traffic and filters through only traffic that is permitted. Its purpose is to prevent unauthorised external access to the network.
Network Architecture
A network's architecture generally defines its overall structure, including its topology, physical media, and channel access method. The following is a brief summary of the more popular architectures used in networking to day.
Ethernet
Developed by Xerox, Ethernet is the most popular network architecture today. It has many advantages, including ease of installation and lower costs. Ethernet is generally less expensive than most other architectures. Another reason that it is so popular is that it can support the use of many different media types (cable). Ethernet uses a channel access protocol called CSMA/CD (Carrier Sense Multiple Access with Collision detection). Simply put, this protocol oversees the transmission of data across the wire. If a machine is transmitting, it is not possible for another machine to transmit at the same time. It must wait till the medium is free. If it does transmit, the data sets will collide, causing a garbled signal. So the role of Carrier Sense is to be able to detect if the wire is available. Multiple Access permits multiple machines to share the wire, while Collision Detection takes care of any collisions that do occur, and provide the machines involved another chance at transmitting their various data again. Ethernet networks run on a bus topology, or more accurately, a star-bus, which physically is a star, but logically operates like a bus, i.e. a broadcast system. Ethernet operates at speeds of 10Mbps and newer standards support 100Mbps, these are the two categories that divide Ethernet, based on transmission speeds and media use.
10 Mbps Standards
There are four major implementations of 10Mps Ethernet:
· 10Base5: Ethernet using thick coaxial cable with a maximum segment length of 500mtrs
· 10Base2: Ethernet using thin coaxial cable with a maximum segment length of 185mtrs
· 10Base-T: Ethernet over unshielded twisted-pair (UTP) cable with a maximum cable length of 100mtrs
· 10Base-F: Ethernet over fibre-optic cable with a maximum cable length of 2000mtrs 100 Mbps Standards
· 100VG-AnyLan: Emerging Architecture that is a mixture of Token Ring and Ethernet. Uses Fiber and UTP. Cable lengths of 100, 150 and 2000 meters.
· 100Base-T: (fast Ethernet)
This standard has three sub categories.
o 100Base-T4: Four-pair Cat 3, 4 or 5 UTP; Max cable length 100mtrs.
o 100Base-TX: Two-pair Cat 5 UTP. Max cable length 100mtrs.
o 100Base-FX: Two -strand fibre-optic cable. Max cable length 2000mtrs
Token Ring
The Token Ring architecture was developed by IBM in the mid-1980's, providing users with fast, reliable transport. Token Ring is so called, because an empty data frame continually circulates the network, and any node wishing to transmit, would seize the token, and put its data onto the network with the address of the intended node. By using the token passing channel access method, token ring networks ensure that all computers get equal time on the network.
As the frame circulates the network, each node examines the address field of the frame in order to determine whether or not the frame is intended for it. If not, the node allows the frame to pass to the next node. This process continues until the intended node receives the frame, at which point the node takes a copy of the data and releases the frame back onto the network. When it returns to the originating node, the frame is removed and a new frame is generated. The new empty frame is left to circulate the network until a node waiting to transmit seizes it.
Unlike Ethernet, there are no collisions, so data seldom has to be re-sent. Because all computers on the network have equal access to the token, traffic is consistent and token ring handles increases in network size gracefully.
The newest versions of token ring operate at speeds of up to 16Mbps. Because collisions never occur, token ring can handle larger packets sizes than Ethernet. This allows large blocks of data to be transferred. Token ring networks run on a ring topology, or a star-ring topology, i.e. a physical star configuration, but the hub device logically operates like a ring were the token is circulated from port to port in an infinite loop.
Fibre Distribute Data Interface (FDDI)
This architecture is installed in high-demand networks, and is a very reliable solution. FDDI uses the token-passing channel access method while using dual rings for fault tolerance. That is to say, if one cable breaks, the other is used to work around the problem, thus keeping the network alive. FDDI transmits at 100Mbps and can include up to 500 nodes over a distance of 100km (60miles). FDDI networks are wired as a physical ring, it has no hubs, and machines are generally directly connected to each other by means of fibre-optic cabling.
Unlike token ring, machines in this solution are not required to wait for the token to make a full circle before transmitting another token. When a computer possessing the token has more than one data frame to send, it can send additional tokens before the initial frame completes its journey. This allows data to be transmitted around the network more quickly. Also, once the computer has finished sending its token, it can immediately pass the token along. Again, it need not wait for the token to complete its circuit around the network. FDDI network use a ring topology, and occasionally a star-ring.
Unlike token ring networks, FDDI permits administrators to assign priorities to certain nodes, for example a server running time-sensitive data or video.
Remote Access
Running a network affords us another tremendous benefit, remote access. Remote access allows company personnel to log into the network from any location, providing they have a modem and a telephone connection. It is even possible to connect to the company LAN by using cellular communications techniques. This requires a mobile phone with an in-built modem connected to the users laptop. The phone-to-laptop connection can be done via a cable or infrared interface. The Nokia 7110 is a good example. This type of connection is currently very slow, and it is recommended for sending and receiving e-mails only.
If remote access is required from a permanent location, e.g. home users, then a faster technology can be installed, like ISDN, ADSL etc. This will allow teleworkers (those who work from home) to connect to the network and us its resources as though they were directly connected at an office location in the company's premises. This technique is known as Virtual Private Networking (VPN).
Special software is required to facilitate this process called VPN software. This is installed on the users remote system and not only manages the connection, but ensures that the connection remains private. Even though the user is using a public communications medium (the Internet), their transmissions are shielded from others. This is done using a protocol called PPTP (point-to-point tunnelling protocol). This protocol gives the data security, by encapsulating the data in encrypted packets, in effect building a tunnel that the data passes through, shielding it from other users. This is what puts the term "Private" in VPN
If remote access is required from a permanent location, e.g. home users, then a faster technology can be installed, like ISDN, ADSL etc. This will allow teleworkers (those who work from home) to connect to the network and us its resources as though they were directly connected at an office location in the company's premises. This technique is known as Virtual Private Networking (VPN).
Special software is required to facilitate this process called VPN software. This is installed on the users remote system and not only manages the connection, but ensures that the connection remains private. Even though the user is using a public communications medium (the Internet), their transmissions are shielded from others. This is done using a protocol called PPTP (point-to-point tunnelling protocol). This protocol gives the data security, by encapsulating the data in encrypted packets, in effect building a tunnel that the data passes through, shielding it from other users. This is what puts the term "Private" in VPN
"Prevention is better than cure"
.
Today, there are many programs available to assist with network management. These programs can help identify conditions that may lead to problems, prevent network failures, and troubleshoot problems when they occur.
Monitoring Applications
One program, "Netcracker", is a design application that allows network creators to design a simulated version of their network before putting the real thing together. Another example is "ConfigMaker", by Cisco. This program allows the designer to configure network components by using proper operating system syntax and then tests the implementation as a simulation. These programs are priced in the thousands rather than the hundreds. However, this is justified by the amount of time that can be saved by eradicating problems before network installation. While these programs allow us to build and monitor networks, they are not a comprehensive solution, and monitoring software should be used in order to continually check the on-going status of the network. There are many software monitoring packages available. Sun Microsystems have an entire range, from small LAN management to Enterprise Network management packages. "Solstice Site ManagerTM 2.3" is one example: a state-of-the-art method for managing sites of up to 100 nodes. It simplifies management of network resources to keep the network running at peak efficiency.
Causes
There are many factors that can inhibit the performance of a network, leading to a situation called "bottlenecking". - a sharp and notable reduction in performance. This can be caused by equipment not capable for the demands that are being placed on the network. Equipment like network cards, hubs, repeaters etc. Also, the bandwidth of the cable may not be sufficient for traffic demands. Users can cause slowdown by playing resource hungry games across the LAN, or engaging in heavy Internet downloads, like MP3 files and video. The problems can also be caused by poor LAN organisation, where all nodes populate a single segment, and therefore a single collision domain. In other words, the network is like a small room packed with lots of people all talking at the one time, leading to chaos.
Baselines
It is recommended that a baseline be established that will assist the network administrator in monitoring performance. A baseline defines a point of reference against which to measure network performance and behaviour when problems occur. In other words, it has to be established what is "normal" for your network, before it can be determined what is "abnormal". A baseline can be established by using performance-monitoring software. There may be no need to buy expensive management software. Users running Windows servers are provided with integrated management tools at no extra charge. They do not provide the same range or capability of the higher end solutions, but they are still powerful tools. These tools allow the administrator to view various logs that maintain error, security and system information. Other tools can track processor, disk and memory usage and analyse protocol performance.
Solutions
Trends gathered by these tools can indicate the problems previously mentioned, and can help the administrator prescribe solutions to the problem.
Possible solutions include:
- Moving to a faster technology by upgrading cable, Interface cards and components (switches, hubs and bridges).
- Increasing memory
- Installing additional CPUs
- Subnetting (breaking the network into smaller more manageable chunks using routers).
- Preventing users from running power hungry games or applications across the network.
Acceptable Performance
The philosophy of networking is providing the best service at the cheapest price. It is not difficult to have a high-performance network. All that is required is the best equipment, the best technologies, the best methodologies and the best personnel to tie it all together. However, in the real world this is seldom, if ever the case, due to costs. Therefore, a trade-off is sought, and ideal performance gives way to acceptable performance. As users, we demand the best; we want the fastest access to resources and faster links to the Internet. We want our applications to run better, and we want more bandwidth to run multimedia applications. Cost constraints prevent this from always being possible. In fact, our requirements as users (playing power-hungry games over the LAN) are often sacrificed to support business needs. Organisations are not willing to spend huge amounts of money simply to keep its users happy, preferring systems that suit business needs, and get the job done.
Today, there are many programs available to assist with network management. These programs can help identify conditions that may lead to problems, prevent network failures, and troubleshoot problems when they occur.
Monitoring Applications
One program, "Netcracker", is a design application that allows network creators to design a simulated version of their network before putting the real thing together. Another example is "ConfigMaker", by Cisco. This program allows the designer to configure network components by using proper operating system syntax and then tests the implementation as a simulation. These programs are priced in the thousands rather than the hundreds. However, this is justified by the amount of time that can be saved by eradicating problems before network installation. While these programs allow us to build and monitor networks, they are not a comprehensive solution, and monitoring software should be used in order to continually check the on-going status of the network. There are many software monitoring packages available. Sun Microsystems have an entire range, from small LAN management to Enterprise Network management packages. "Solstice Site ManagerTM 2.3" is one example: a state-of-the-art method for managing sites of up to 100 nodes. It simplifies management of network resources to keep the network running at peak efficiency.
Causes
There are many factors that can inhibit the performance of a network, leading to a situation called "bottlenecking". - a sharp and notable reduction in performance. This can be caused by equipment not capable for the demands that are being placed on the network. Equipment like network cards, hubs, repeaters etc. Also, the bandwidth of the cable may not be sufficient for traffic demands. Users can cause slowdown by playing resource hungry games across the LAN, or engaging in heavy Internet downloads, like MP3 files and video. The problems can also be caused by poor LAN organisation, where all nodes populate a single segment, and therefore a single collision domain. In other words, the network is like a small room packed with lots of people all talking at the one time, leading to chaos.
Baselines
It is recommended that a baseline be established that will assist the network administrator in monitoring performance. A baseline defines a point of reference against which to measure network performance and behaviour when problems occur. In other words, it has to be established what is "normal" for your network, before it can be determined what is "abnormal". A baseline can be established by using performance-monitoring software. There may be no need to buy expensive management software. Users running Windows servers are provided with integrated management tools at no extra charge. They do not provide the same range or capability of the higher end solutions, but they are still powerful tools. These tools allow the administrator to view various logs that maintain error, security and system information. Other tools can track processor, disk and memory usage and analyse protocol performance.
Solutions
Trends gathered by these tools can indicate the problems previously mentioned, and can help the administrator prescribe solutions to the problem.
Possible solutions include:
- Moving to a faster technology by upgrading cable, Interface cards and components (switches, hubs and bridges).
- Increasing memory
- Installing additional CPUs
- Subnetting (breaking the network into smaller more manageable chunks using routers).
- Preventing users from running power hungry games or applications across the network.
Acceptable Performance
The philosophy of networking is providing the best service at the cheapest price. It is not difficult to have a high-performance network. All that is required is the best equipment, the best technologies, the best methodologies and the best personnel to tie it all together. However, in the real world this is seldom, if ever the case, due to costs. Therefore, a trade-off is sought, and ideal performance gives way to acceptable performance. As users, we demand the best; we want the fastest access to resources and faster links to the Internet. We want our applications to run better, and we want more bandwidth to run multimedia applications. Cost constraints prevent this from always being possible. In fact, our requirements as users (playing power-hungry games over the LAN) are often sacrificed to support business needs. Organisations are not willing to spend huge amounts of money simply to keep its users happy, preferring systems that suit business needs, and get the job done.
Best Regards,
. .
3bbdullah Mohammad
alinma bank
Control Cnter - riyadh - ksa
