What is the difference between a passive star and an active repeater in fiber optic network?

There are two important components of a fiber optic network namely passive star coupler and active repeaters. 

Passive Star in Fiber Optic Network

- Passive star couplers are single mode fiber optic couplers with reflective properties.  

- These couplers are used for optical local area networking at very high speeds. 

- These couplers are made from very simple components such as mirrors and 3 db couplers. 

- Besides this, these star couplers save a lot of optical fiber when compared to its trans-missive counterpart. 

- They are free of any multi-paths so as to avoid any interference. 

- A fiber optic network may consist of any number of passive star couplers and each of them is capable of connecting a number of users. 

- The input and output from every passive star coupler is given to the output and input of an active coupler. 

- The round trip transmission tile is stored by the active star coupler. 

- When it receives a signal from a passive star coupler, it stops the output to that coupler for the duration of the signal.

- It also inhibits the incoming data from all the other passive star couplers for the round trip transmission delay plus signal duration. 

- The purpose of a star coupler is to take one input signal and then splitting it in to a number of output signals. 

- In telecommunications industry and fiber optics communication, this coupler is used in network applications being a passive optical device. 

- If an input signal is introduced to one of the input ports, it is distributed to all of the output ports of the coupler. 

- As per the construction of the passive star coupler, the number of ports it will have is given by the power of 2. 

- For example, in a two port coupler or in a directional coupler or splitter, there are 2 input ports and 2 output ports.

- In a four port coupler, there are 4 i/p ports and 4 o/p ports and so on. 

- The digital equipment corporation also sold a device by the name of star coupler which was used for interconnecting the links and computers through coaxial cable instead of using optical fibers. 

Active Repeater in Fiber Optic Network 

- Active repeater is an important telecommunications device used for re transmitting the signal it receives to a higher level and with higher basically to the other side of an obstacle so that long distances can be covered. 

- Repeater is an electro-mechanical device that helps in regenerating the telegraphy signals. 

- It may be defined as an analog device for amplifying the input signal, reshaping it, re-timing it for re-transmission. 

- A re-generator is a repeater that can perform the re-timing operation. 

- Repeaters just tend to amplify the physical signal without interpreting the data transmitted by the signal. 

- The 1^st layer i.e., the physical layer is where the repeaters operate. 

- Repeaters are employed for boosting the signals in optical fiber lines as well as in twisted pair and coaxial cables. 

- When a signal travels through a channel, it gets attenuated with the distance and time because of the energy loss (dielectric losses, conductor resistance etc.). 

- When light travels in optical fibers, it scattered and absorbed and hence is attenuated. 

- Therefore, in long fiber lines, repeaters are installed at proper intervals for regenerating and strengthening the signal. 

Repeater in optical communication performs the following functions:

Ø  Takes the input signal

Ø  Converts it in to electrical signal

Ø  Regenerates it.

Ø  Converts it in to optical signal

Ø  Re-transmits it

- These repeaters are usually employed in submarine as well as transcontinental communication cables as the loss is unacceptable in these cases.  

How does penetration testing tool emphasize on network security?

The term “penetration testing” is not unheard these days and perhaps many of us are familiar with this type of testing. In this piece of writing we have discussed how the penetration testing tools emphasize up on the network security. 

About Penetration Testing

- Penetration testing is yet another testing methodology that has been adopted for testing the security of a computer network or system against the malicious attacks. 

- It provides a way to evaluate the security level of the computer network by bombarding the network with false simulated attacks as malicious attacks from the outside as well as inside attackers. 

- The aliens, foreigners or outside attackers do not hold any authorized access to the computer system or network but the inside attackers do have that access, but it is limited to a certain level.

- The whole process of the penetration testing is dependent on an active analysis. 

- This active analysis carries out an assessment of all the potential vulnerabilities of the computer network or system that are merely a consequence of its poor security level as well as configuration level. 

- Apart from this, the known and unknown flaws form both the hardware as well as software system contribute to these vulnerabilities rather than only operational weaknesses. 

- Therefore they are to be blamed equally.

- This active analysis is successful only if it is carried out from the view point of a malicious attacker and is concerned about the active exploitation of the recognized vulnerabilities.

About Network Security

- The network security depends up on the effectiveness of the testing. 

- And the testing in turn is affected by the effectiveness of the tools that are employed in the testing.

- The tools indeed affect the network security, since if the tools are reliable and efficient in finding vulnerabilities, obviously there will be more improvement in the security mechanisms.

Reasons why Penetration Testing holds good for Network Security

There are several other reasons why the penetration testing tools holds good for the network security:

- They are effective for the determination of the feasibility of the similar vectors of attack.

-  Help in the identification of the vulnerabilities which possess a very high risk when the exploitation of a combination of low level risks is done following a particular sequence.

-  Prove quite effective in the determination of the vulnerabilities that cannot be detected with the help of application vulnerability scanning software or automated testing processes.

-  Assist in the assessment of the measure of the operational and business impacts of the attacks on the computer network or system.

- Successfully test the effectiveness of the network defenders in detecting and responding to the attacks.

- Provide the evidence in support of the investments that need to be made in the security field of the computer system or network.

Hubs and their types

Hubs have become an integral part of various network and business systems. Hub, sometimes referred to as a concentrator or repeater Hub, refers to a networking component which acts as a convergence point of a Network, allowing the transfer of data packets.

Characteristics of Hubs :
- Hub is a small plastic box which takes its power from an ordinary wall outlet.
- Multiple computers are joined through a hub.
- On this network segment, all computers can communicate directly with each other.
- A hub includes a series of ports that each accept a network cable.
- Hubs are the layer 1 devices while switches and routers are layer 2 and layer 3 devices respectively.
- Hubs do not read any of the data passing through them and are not aware of their source or destination. Essentially, a hub simply receives incoming packets, possibly amplifies the electrical signal, and broadcasts these packets out to all devices on the network - including the one that originally sent the packet.

Types of Hubs :
- Passive Hubs : They do not amplify the electrical signal of incoming packets before broadcasting them out to the network. Their contribution in enhancing the performance is very less. It does not help in any way in the troubleshooting operations. Most of the passive hubs are easily obtainable at a lesser cost.
- Active Hubs : They amplify the incoming signals. An active hub is sometimes referred to as multiport repeater. An active hub takes a larger role in Ethernet communications with the help of technology called store & forward. If the data received being weak but readable, the active hub restores the signal before rebroadcasting the same. An active hub provides information n devices on the network which are not yet fully functional.
- Intelligent Hubs : This hub typically behaves like a stack. It is built in such a way that multiple units can be placed one on top of the other to conserve space. It has the ability to manage the network from one central location. With the help of an intelligent hub, one can easily identify, diagnose problems and even come up with remedial solutions.