Network topology

1. Different network topologies

Mesh Topology
Devices are connected with many redundant interconnections between network nodes. In a true mesh topology every node has a connection to every other node in the network.

Star Topology
All devices are connected to a central hub. Nodes communicate across the network by passing data through the hub.

Bus Topology
All devices are connected to a central cable, called the bus or backbone.

Ring Topology
All devices are connected to one another in the shape of a closed loop, so that each device is connected directly to two other devices, one on either side of it.

Tree Topology
A hybrid topology. Groups of star-configured networks are connected to a linear bus backbone.


2. What is:

UTP

Speed: 10,100,1000 Mbps
Maximum Distance: 100m
Cost: inexpensive

-Short for unshielded twisted pair, a popular type of cable that consists of two unshielded wires twisted around each other.

-UTP cables are not shielded. This lack of shielding results in a high degree of flexibility as well as rugged durability. UTP cables are found in many ethernet networks and telephone systems. For indoor telephone applications.

-UTP is often grouped into sets of 25 pairs according to a standard 25-pair color code originally developed by AT&T. A typical subset of these AD1L colors (white/blue, blue/white, white/orange, orange/white) shows up in most UTP cables.

-UTP cabling is often used in data networks for short and medium length connections because of its relatively lower costs compared to fiber and coaxial cabling.

STP

Speed: 10, 100 Mbps
Maximum Distance: 100m
Cost: expensive

-STP cabling includes metal shielding over each individual pair of copper wires. This type of shielding protects cable from external EMI (electromagnetic interferences). e.g. the 150 ohm shielded twisted pair cables defined by the IBM Cabling System specifications and used with token ring networks.

Advantages

It is a thin, flexible cable that is easy to string between walls.
Most modern buildings come with CAT 5 UTP already wired into the wall outlets or at least run between the floors.
Because UTP is small, it does not quickly fill up wiring ducts.
UTP costs less per foot than any other type of LAN cable.

Disadvantages

Twisted pair’s susceptibility to the electromagnetic interference greatly depends on the pair twisting schemes (usually patented by the manufacturers) staying intact during the installation. As a result, twisted pair cables usually have stringent requirements for maximum pulling tension as well as minimum bend radius.

Firewire

-A very fast external bus standard that supports data transfer rates of up to 400Mbps (in 1394a) and 800Mbps (in 1394b). Products supporting the 1394 standard go under different names, depending on the company. Apple, which originally developed the technology, uses the trademarked name FireWire. Other companies use other names, such as i.link and Lynx, to describe their 1394 products.

-A single 1394 port can be used to connect up 63 external devices. In addition to its high speed, 1394 also supports isochronous data -- delivering data at a guaranteed rate. This makes it ideal for devices that need to transfer high levels of data in real-time, such as video devices.
-Although extremely fast and flexible, 1394 is also expensive. Like USB, 1394 supports both Plug-and-Play and hot plugging, and also provides power to peripheral devices.

Optical Cable

A technology that uses glass (or plastic) threads (fibers) to transmit data. A fiber optic cable consists of a bundle of glass threads, each of which is capable of transmitting messages modulated onto light waves.

Fiber optics has several advantages over traditional metal communications lines:

• Fiber optic cables have a much greater bandwidth than metal cables. This means that they can carry more data.
  
• Fiber optic cables are less susceptible than metal cables to interference.
  
• Fiber optic cables are much thinner and lighter than metal wires.
  
• Data can be transmitted digitally (the natural form for computer data) rather than analogically.
  

The main disadvantage of fiber optics is that the cables are expensive to install. In addition, they are more fragile than wire and are difficult to splice.

Fiber optics is a particularly popular technology for local-area networks. In addition, telephone companies are steadily replacing traditional telephone lines with fiber optic cables. In the future, almost all communications will employ fiber optics.

3. Arrangement of wires: cross over and straight through

UTP and STP

10 Base T / 100 Base T Straight

10BaseT and 100BaseT are most common mode of LAN. You can use UTP category-5 cable for both mode. (You can use UTP category-3 cable for 10BaseT, in which there are only 3 wires inside the cable.) A straight cable is used to connect a computer to a hub. You can use it to connect 2 hubs in the case one of the hub has an uplink port (and you use normal port on the other hub).
Pin ID
side A
side B
1
orange-white
orange-white
2
orange
orange
3
green-white
green-white
4
blue
blue
5
blue-white
blue-white
6
green
green
7
brown-white
brown-white
8
brown
brown

10 Base T / 100 Base T Cross

A cross cable for 10BaseT and 100BaseT is used to connect 2 computers directly (with ONLY the UTP cable). It is also used when you connect 2 hubs with a normal port on both hubs. (In other words, the cross cable is used relatively in a rare case.)
Pin ID
side A
side B
1
orange-white
green-white
2
orange
green
3
green-white
orange-white
4
blue
blue
5
blue-white
blue-white
6
green
orange
7
brown-white
brown-white
8
brown
brown

5. What is Wi-Fi?

Wi-Fi short for wireless fidelity and is meant to be used generically when referring of any type of 802.11 network, whether 802.11b, 802.11a, dual-band, etc. The term is promulgated by the Wi-Fi Alliance.

Any products tested and approved as "Wi-Fi Certified" (a registered trademark) by the Wi-Fi Alliance are certified as interoperable with each other, even if they are from different manufacturers. A user with a "Wi-Fi Certified" product can use any brand of access point with any other brand of client hardware that also is certified. Typically, however, any Wi-Fi product using the same radio frequency (for example, 2.4GHz for 802.11b or 11g, 5GHz for 802.11a) will work with any other, even if not "Wi-Fi Certified."

Formerly, the term "Wi-Fi" was used only in place of the 2.4GHz 802.11b standard, in the same way that "Ethernet" is used in place of IEEE 802.3. The Alliance expanded the generic use of the term in an attempt to stop confusion about wireless LAN interoperability.