Wireless network interface card

A wireless network interface controller (WNIC) is a network card which connects to a radio-based computer network, unlike a regular network interface controller (NIC) which connects to a wire-based network such as token ring or ethernet. A WNIC, just like a NIC, works on the Layer 1 and Layer 2 of the OSI Model. A WNIC is an essential component for wireless desktop computer. This card uses an antenna to communicate through microwaves. A WNIC in a desktop computer usually is connected using the PCI bus. Other connectivity options are USB and PC card. Integrated WNIC's are also available, (typically in Mini PCI/PCI Express Mini Card form).

Contents
1 Modes of operation
2 Range

Modes of operation

A WNIC can operate in two modes known as infrastructure mode and ad hoc mode.

In an infrastructure mode network the WNIC needs an access point: all data is transferred using the access point as the central hub. All wireless nodes in an infrastructure mode network connect to an access point. All nodes connecting to the access point must have the same service set identifier (SSID) as the access point, and if the access point is enabled with WEP they must have the same WEP key or other authentication parameters.

In an ad-hoc mode network the WNIC does not require an access point, but rather can directly interface with all other wireless nodes directly. All the nodes in an ad-hoc network must have the same channel and SSID.

WNICs are designed around the IEEE 802.11 standard which sets out low-level specifications for how all wireless networks operate. Earlier interface controllers are usually only compatible with earlier variants of the standard, while newer cards support both current and old standards.

Specifications commonly used in marketing materials for WNICs include:

Wireless data transfer rates (measured in Mbit/s); these range from 2 Mbit/s to 54 Mbit/s.[1]
Wireless transmit power (measured in dBm)
Wireless network standards (may include standards such as 802.11b, 802.11g, 802.11n, etc.) 802.11g offers data transfer speeds equivalent to 802.11a – up to 54 Mbit/s – and the wider 300-foot (91 m) range of 802.11b, and is backward compatible with 802.11b.
Wireless local area network standards view • talk • edit 802.11
Protocol Release[2] Freq.
(GHz) Typ throughput
(Mbit/s)
[citation needed] Max net bitrate
(Mbit/s) Modulation rin.
(m) rout.
(m)
– Jun 1997 2.4 00.9 002 DSSS ~20 ~100
a Sep 1999 5 23 054 OFDM ~35 ~120
b Sep 1999 2.4 04.3 011 DSSS ~38 ~140
g Jun 2003 2.4 19 054 OFDM ~38 ~140
n Nov 2009 2.4
5 130[3] 600[4] OFDM ~70 ~250[5]
y Nov 2008 3.7 23 054 OFDM ~50 ~5000


RANGE

Wireless range may be substantially affected by objects in the way of the signal and by the quality of the antenna. Large electrical appliances, such as a refrigerators, fuse boxes, metal plumbing, and air conditioning units can impede a wireless network signal. The theoretical maximum range is only reached under ideal circumstances and true effective range is typically about half of the theoretical range.[1] Specifically, the maximum throughput speed is only achieved at extremely close range (less than 25 feet (7.6 m) or so); at the outer reaches of a device's effective range, speed may decrease to around 1 Mbit/s before it drops out altogether. The reason is that wireless devices dynamically negotiate the top speed at which they can communicate without dropping too many data packets.

Networking Topologies

An Overview of Computer Network Topology



Network topology is one of the very important topics to learn when it comes to build up computer network. There are many Network Topologies on which network administrator decide to build the network on. Topology is basically defined as layout or design of network, and computers are connected using the design of the topology. These topologies can be either physical or logical design. Physical topology refers to physical design of network which includes devices, cables, location and installation of network where as in logical topology it is the amount of data to be transferred with in the network as apposed in its design.


There are five different Networking Topologies :


a) Bus
b) Star
c) Ring
d) Mesh
e) Tree.


When networks are design using multiple topologies it is called Hybrid Networks, this concept is usually utilized in complex networks were larger number of computer clients are required.


Bus Topology:



Bus topology is one the easiest topologies to install, it does not require lots of cabling. There are two most popular Ethernet cable types which are used in this topology they are 10Base-2 and 10BaseT. Bus topology based networks works with very limited devices. It performs fine as long as computer count remain with in 12 – 15, problems occurs when number of computer increases.
Bus topology uses one common cable (backbone) to connect all devices in the network in linear shape. Network interface cards of all network devices are attached to single communication medium backbone cable. When any computer sends out message in the network it is broadcasted in the entire network but only intended computer accepts the message and process it. Bus topology provide simplicity to the network, however there is big disadvantage of this topology, if main single network cable some how gets damaged, it will shut down the entire network no computer will run on network and no communication can be made among computers until backbone cable is replaced.





Ring Topology:

Ring topology is one of the old ways of building computer network design and it is pretty much obsolete. FDDI, SONET or Token Ring technologies are used to build ring technology. It is not widely popular in terms of usability but incase if you find it any where it will mostly be in schools or office buildings. In ring network topology computers and other networking devices are attached to each other in such a way that they have devices adjacent to each other (Left and right side). All messages are travelled in the same directory either clockwise or anticlockwise. In case of failure of any device or cable the whole network will be down and communication will not be possible.






Star Topology:

This is the most commonly used network topology design you will come across in LAN computer networks. In Star, all computers are connected to central device called hub, router or switches using Unshielded Twisted Pair (UTP) or Shielded Twisted Pair cables.
In star topology, we require more connecting devices like routers, cables unlike in bus topology where entire network is supported by single backbone. The most practical point of Star topology success is that the entire network does not go down incase of failure of a computer or cable or device, it will only affect the computer whose wire failed rest of the network will be working fine. However, incase of failure of central communication device such as Hub, Router or Switch the entire network will collapse. Star topology is widely used in homes, offices and in buildings because of its commercial success.





Tree Topology:

Just as name suggest, the network design is little confusing and complex to understand at first but if we have better understanding of Star and Bus topologies then Tree is very simple. Tree topology is basically the mixture of many Star topology designs connected together using bus topology. Devices like Hub can be directly connected to Tree bus and each hub performs as root of a tree of the network devices. Tree topology is very dynamic in nature and it holds potential of expandability of networks far better than other topologies like Bus and Star.






Mesh Topology:

Mesh topology is designed over the concept of routing. Basically it uses router to choose the shortest distance for the destination. In topologies like star, bus etc, message is broadcasted to entire network and only intended computer accepts the message, but in mesh the message is only sent to the destination computer which finds its route it self with the help of router. Internet is based on mesh topology. Routers plays important role in mesh topology, routers are responsible to route the message to its destination address or computer. When every device is connected to every other device it is known as full mesh topology and if every device is connected indirectly to each other then it is called partial mesh topology.






Conclusion:

Topologies are essence of computer networks design. Efficent networks can only be built based on the complete knowledge and understanding of above mentioned topologies. Knowledge of every communication device is of equal importance to help you find the best option for your network requirements. Optimum networks can be built with complete knowledge and understanding of computer network devices and how they are designed, any mistake in choosing inappropriate techniques, device etc can only be the waste of time, resources

Network Design and Implementation

Local Area Networks
There is a perception that LAN design is very simple and straightforward, and that a single solution will fit almost any scenario. This is where most LAN-related problems originate. To build a well-balanced LAN, a number of factors must be taken into consideration. Some of them are: desired network size (# of machines), layout, amount of current traffic, future traffic expectations, security requirements. We evaluate all of these factors, among others, which helps us design a flexible solution within budget, and with sufficient room for expansion.





Remote Network Solutions
When a company has several offices, remote connectivity is essential. In most cases, communicating only via email is far from adequate. File sharing, Windows domain-based services, and direct access between workstations are often needed. To achieve this, we build virtual tunnels between your offices, as well as to our own network. Machines in separate locations can now communicate as if they were on the same physical network. And for those working at home or on the road, we provide easy VPN access to the office network.

Centralized Routing
We handle all routing at the core of our network. If you have several locations, we will interconnect them with redundant virtual links. In case one of those links becomes unavailable, our dynamic routing protocols automatically send traffic via the remaining ones. In the meantime, our network engineers are notified of the situation and start working on the problem immediately. Having multiple paths brings peace of mind to our customers and us.

Network Redundancy
For critical applications, a single-sided network may not be adequate. Designing redundant systems is one of our specialties. We can set up router and switch redundancy with failover, up to a full network mesh. In case any one device fails, connectivity is not affected. In addition, we are able to utilize multiple Internet links, if available. They can be used in an active-standby scenario, or an active-active one. Load-balancing solutions play an important role in networking, and we take full advantage of what today’s technology offers.

Network Security

Introduction

Detecting and preventing intrusion with deep packet analysis and forensics

Today's enterprise organizations rely on digital assets that must be protected from unauthorized access or dispersion. The costs of data leakage are well documented and include not only loss of value, intellectual property and customers, but also government sanctions and fines for noncompliance to data privacy regulations. A complete deep packet capture, record and playback solution from Solera Networks ensures that the source of data leaks are quickly identified, stemming the loss of data.

With easy packet level reconstruction of all of the traffic on your network, you now have context for what happened before, during and after every security alert.

A capture appliance from Solera Networks gives all of your securtiy tools, whether they be Intrusion Detection, Intrusion Prevention, or Firewalls, full context into what has happenned on your network.

Network Security »