Troubleshooting Computers

#Step 1
Identify the problem. Before knowing what needs to be done, you must know what is working properly and what isn't. It is also important to know whether anything has happened that might impact what isn't working (for instance, was something recently added to the system, was there a power spike or did somebody start pulling wires thinking they were trying to fix something?).

#Step 2

Analyze the problem. Once you've determined what isn't working, you can start looking for likely causes of the problem. When troubleshooting a home theater setup, are many things not working or is only one item giving you trouble?

#Step 3

Isolate or locate the problem. Using the analysis in the previous step, you can start eliminating possible trouble spots. For example, if your TV set turns on and the DVD player works fine but the cable or satellite picture doesn't show, you can assume the set is fine and start focusing on what isn't showing properly.

#Step 4

Diagnose the problem. Make sure that the equipment turns on, that all necessary wires are connected and properly seated. Check to make sure you have no unplugged power cords. You'd be surprised how often a problem is caused by something simply being turned off or unplugged.

#Step 5

Resolve the problem. Once you've figured out what isn't working right, fix it. If it's unplugged, plug it in. If something isn't turning on, use a different electric outlet to verify you don't have an electrical problem. If a cable line looks damaged, replace it.

#Step 6

Verify the repair. Once you think you've fixed the problem, make sure the problem is gone. Verify that your equipment is working properly. If all is well, you're done; if there is still a problem (or you've uncovered a new problem in the process) you'll need to start the process again from Step 1. If the trouble is beyond your skill level or all attempts to fix are unsuccessful, you may need to call a professional to fix it.

JUDE 1:3

Jude 1:3 (New American Standard Bible)

Beloved, while I was making every effort to write you about our common salvation, I felt the necessity to write to you appealing that you contend earnestly for the faith which was once for all handed down to the saints.

Different Classes of IP Address

IP Address Classes and Structure

When the IEEE committee sat down to sort out the range of numbers that were going to be used by all computers, they came out with 5 different ranges or, as we call them, "Classes" of IP Addresses and when someone applies for IP Addresses they are given a certain range within a specific "Class" depending on the size of their network.

To keep things as simple as possible, let's first have a look at the 5 different Classes:






In the above table, you can see the 5 Classes. Our first Class is A and our last is E. The first 3 classes ( A, B and C) are used to identify workstations, routers, switches and other devices whereas the last 2 Classes ( D and E) are reserved for special use.

As you would already know an IP Address consists of 32 Bits, which means it's 4 bytes long. The first octec (first 8 Bits or first byte) of an IP Address is enough for us to determine the Class to which it belongs. And, depending on the Class to which the IP Address belongs, we can determine which portion of the IP Address is the Network ID and which is the Node ID.

For example, if I told you that the first octec of an IP Address is "168" then, using the above table, you would notice that it falls within the 128-191 range, which makes it a Class B IP Address.

Understanding the Classes

We are now going to have a closer look at the 5 Classes. If you remember earlier I mentioned that companies are assigned different IP ranges within these classes, depending on the size of their network. For instance, if a company required 1000 IP Addresses it would probably be assigned a range that falls within a Class B network rather than a Class A or C.

The Class A IP Addresses were designed for large networks, Class B for medium size networks and Class C for smaller networks.

Ethernet Cables

Cat 1: Previously used for POTS telephone communications, ISDN and doorbell wiring.

Cat 2: Previously was frequently used on 4 Mbit/s token ring networks.

Cat 3: used for data networks using frequencies up to 16 MHz. Historically popular for 10 Mbit/s Ethernet networks.

Cat 4: Defined up to 20 MHz, and was frequently used on 16 Mbit/s token ring networks.

Cat 5: Defined up to 100 MHz, and was frequently used on 100 Mbit/s Ethernet networks. May be unsuitable for 1000BASE-T gigabit ethernet.Category 5 cable is a currently outdated standard that provides support for up to 100Mhz operation. It can be used for 10/100 Ethernet without worry, however for longer runs of 1000MbE it is recomended to use Cat. 5e or higher.

Cat 5e: Defined up to 100 MHz, and is frequently used for both 100 Mbit/s and 1000BASE-T Gigabit Ethernet networks. Category 5e cable provides support for frequencies up to 100Mhz. Cat. 5e generally provides the best price for performance, however for future proofing Cat. 6 or higher might be a better choice as it usually does not cost much more.

Cat 6: Defined up to 250 MHz, more than double category 5 and 5e. Category 6 is defined up to a frequency of 250Mhz. Allowing 10/100/1000 use with up to 100 meter cable length, along with 10GbE over shorter distances.

Cat 6a: Defined up to 500 MHz, double that of category 6. Suitable for 10GBase-T. It allows up to 10GbE with a length up to 100m.

Cat 7: Defined up to 600 MHz. This standard specifies four individually-shielded pairs (STP) inside an overall shield. Category 7 is the informal name for "Class F" cabling defined by a different standards body than Cat. 6a and lower. It supports frequencies up to 600Mhz and may support the upcoming 100GbE standard.

Cat 7a: Category 7a is an upcoming standard that allows frequencies up to 1000Mhz. Supported Ethernet bandwidths have not been defined.

JUNIPER NETWORKS: Routers

Juniper Networks, Inc. (NASDAQ: JNPR) is an information technology and computer networking products multinational company, founded in 1996. It is headquartered in Sunnyvale, California, USA. The company designs and sells high-performance Internet Protocol network products and services. Juniper's products include T-series, M-series, E-series, MX-series, and J-series families of routers, EX-series Ethernet switches, WX-series WAN optimization devices, and SRC Session and Resource Control appliances. JUNOS , Juniper's network operating system runs on most of the Juniper products. In 2009, Juniper made its debut on Fortune Magazine's 100 Best Companies to Work for. Juniper ranked 4 in Fortune Magazine's World's Most Admired Companies list in Networking Communications category in 2009.

Canopy Antenna

A typical Canopy setup consists of a cluster of up to 6 co-located standard access points, each with a 60 degree horizontal beamwidth antenna, to achieve 360 degree coverage. The most commonly used APs are now available in 120, 180, or even 360 degrees for site-based coverage, thus decreasing the need for so many APs on a tower. Also included would be one or more backhauls or otherwise out-of-band links (to carry data to/from other network occasions) and a Cluster Management Module (CMM) to provide power and synchronization to each Canopy AP or Backhaul Module(BM).

Customers of the system receive service through subscriber modules (SMs) aimed towards the AP. The SMs should be mounted on the tall point of a building to get a reliable connection else Fresnel zone obstruction will weaken the signal. Under ideal operating conditions connections at distances up to 3.5 miles can be achieved using equipment with integrated antennas. Network operators can opt to install reflector dishes or Stinger antennas, or to use Canopy models that accept external antennas at one or both ends of the link to increase coverage distance.

Most Canopy equipment receives its power using Power over Ethernet, however, none of its standards comply with IEEE 802.3af.

In general, the 900 MHz version is more effective for use in outlying areas because of its ability to penetrate through trees. However, it requires careful installation due to the easy propagation of interference on that band. Other frequencies currently available are the 2.4Ghz, 5.2Ghz, 5.4Ghz, and 5.7Ghz versions.

SWITCH vs ROUTER

SWITCH

ROUTER

A router is a more sophisticated network device than either a switch or a hub. Like hubs and switches, network routers are typically small, box-like pieces of equipment that multiple computers can connect to. Each features a number of "ports" the front or back that provide the connection points for these computers, a connection for electric power, and a number of LED lights to display device status. While routers, hubs and switches all share similiar physical appearance, routers differ substantially in their inner workings.
Traditional routers are designed to join multiple area networks (LANs and WANs). On the Internet or on a large corporate network, for example, routers serve as intermediate destinations for network traffic. These routers receive TCP/IP packets, look inside each packet to identify the source and target IP addresses, then forward these packets as needed to ensure the data reaches its final destination.
Routers for home networks (often called broadband routers) also can join multiple networks. These routers are designed specifically to join the home (LAN) to the Internet (WAN) for the purpose of Internet connection sharing. In contrast, neither hubs nor switches are capable of joining multiple networks or sharing an Internet connection. A home network with only hubs and switches must designate one computer as the gateway to the Internet, and that device must possess two network adapters for sharing, one for the home LAN and one for the Internet WAN. With a router, all home computers connect to the router equally, and it performs the equivalent gateway functions.
Additionally, broadband routers contain several features beyond those of traditional routers. Broadband routers provide DHCP server and proxy support, for example. Most of these routers also offer integrated firewalls. Finally, wired Ethernet broadband routers typically incorporate a built-in Ethernet switch. These routers allow several hubs or switches to be connected to them, as a means to expand the local network to accomodate more Ethernet devices.
In home networking, hubs and switches technically exist only for wired networks. Wi-Fi wireless routers incorporate a built-in access point that is roughly equivalent to a wired switch.