Network Topologies: Advantages And Disadvantages

Network topology is the layout pattern (or structure) of the interconnection of the various elements (software and hardware) of the network.

There are two types of topologies

* The physical topology

* Logical Topology

 In this particular lesson, we will focus our attention on the physical topology

II-Physical Topology

I I-1 Definition

The physical topology refers to the physical design of the network, its physical layout or the geometric arrangement of the nodes and the links

There are five basic physical topologies:

*The bus topology

*  The star topology

* The ring topology

* The mesh topology

* The tree topology

a)      The Bus topology

Diagram

As we can see from the diagram, here each node is connected to a single cable which is the bus, also referred to as the backbone.

The T-connectors is used by computers to connect to the main cable.

Explanation

In this network organization, any device which wants to communicate sends the broadcast message to all the devices (through the main cable), but only the intended receiver actually accepts and processes the message. A terminator connected at each end of the main cable eliminates any incoming signal to avoid the reverberation problem.

Advantages

·         It is  topology is not  expensive

·         Easy to setup

 Disadvantages

·          The entire network shuts down if there is any break on the main cable

·         It is very difficult to diagnose a problem when the network shuts down.

b)      The Star Topology

Diagram

It is the most commonly used topology in the LAN.  All the computers are connected at the central point which can be a switch or a hub.

Explanation

In this network organization, any device which wants to communicate sends the broadcast message to the central point which will either forward it to the intended computer (case of the switch) or to all the computers (case of hub).

Advantages

·         It very easy to setup

·         The adding, the removing or the malfunctioning of a computer does not affect the rest of the network

·         It easy to diagnose and maintain

Disadvantages       

·          If the central point has a problem, all the computer are disconnected

·         It requires more cables and extra devices and is therefore expensive

c)      The tree topology

Diagram

 

This is the network pattern that combines the characteristics of a bus and star topology.

Advantages

·          It allows for the expansion of an existing network

·         It is supported by several software and hardware vendors

Disadvantages

·         If the backbone  line breaks, the entire segment goes down

·         It is difficult to configure and wire

d)      The Ring topology

Diagram

This is a network topology whereby all devices are connected to one another in the shape of closed loop (ring) so that each device is directly connected to two others devices, one on either side.

Explanation

Messages flow in one direction. Since there is only one path way between two nodes and the message is conveyed through a token ring.

Advantages

·          The transfer of data is fairly simple since it travels only in one direction.

·         No data collision

·         Very high transmission rates are possible

·         Extra computer can be added without any little disturbance of the network, but it must shut down.

Disadvantages

·         If a single link fails, the entire network is disrupted.
(This problem is solved by adding a second ring)

·         The downfall of a single node causes the downfall of the whole network

·         Data must pass through every computer until it reaches the destination

·         Difficult to troubleshoot

 Line topology - This rare topology works by connecting every host to the host located to the right of it. Most networking professionals do not even regard this as an actual topology, as it is very expensive (due to its cabling requirements) and due to the fact that it is much more practical to connect the hosts on either end to form a ring topology, which is much cheaper and more efficient.

Diagram

e) The Mesh topology

Diagram

 It is view as the combination of the above (bus, star, ring)

Advantages

·         If any cable fails, there are many other ways for two nodes to communicate

·         Mesh topology are installed where fault tolerance is important

Disadvantages

·         It is very expensive to wire up

·         It is difficult to install

TAU International Grants Scholarships For The Food Security Program

Deadline: 22 May 2015
The Tel Aviv University is calling students to participate in the Food Safety and Security programme. The primary objective of the courses is to meet the growing need for a new generation of well-rounded academics and policy makers, who have expertise in a specific field, with broad knowledge of biology, public health, law, and international development.
The programme provides students with a multidisciplinary understanding of global food security issues. Leading experts from Israel and around the world will teach intensive theoretical and lab courses.
Courses Offered

• Introduction to Food Security (3 credits)
• Food Security and Public Health (2 credits)
• Plant signaling in changing environments (2 credits)
• Food Security Policy and Economics (2 credits)
• Bioethics (2 credits)
• Plant Molecular Breeding (3 credits) – it is a lab course.

Students successfully completing the Summer Institute courses will receive academic credit, a Certificate of Participation, and an academic transcript acceptable at universities worldwide. Tuition costs are $900 for the lecture courses, $1200 for the lab course. Scholarships are available, including for those signing up for more than one course.
About TAU International
Tel Aviv University is Israel’s leading center of higher learning, providing an education for 30,000 students ranked among the finest in the world. It is comprised of 126 schools and departments across the spectrum of sciences, humanities and arts.
Eligibility Criteria

1. The programme is open to graduate students from any institution of higher learning worldwide, and for professionals in relevant fields.
2. Students from developing countries are especially encouraged to apply for scholarships.

Apply before the deadline.
For more information, visit TAU International.

Design Lab 2015: A chance for Students around the World to win $10,000 & 6 months paid internship

Deadline: 8 April 2015 (submissions will open on 4 March 2015)

Electrolux invites design students around the world to submit a description of a concept idea, a visual sketch and consumer motivation on the theme Healthy Happy Kids. Innovative ideas for future households – products, services, accessories and consumables in either cooking, fabric care or air purification are to be submitted to participate in the competition. Remember the theme, Children must be included in concept to be selected for the competition.

Prizes

1. First prize: € 10 000 and 6 months paid internship at Electrolux
2. Second prize: € 6 000
3. Third prize: € 4 000
4. People’s Choice: € 2 000

The first prize winner will have to move to the location of the design center for six months internship. The internship will take place the next year after the winner has been chosen, either from January to June (2016) or from September 2016 to February 2017.

Focus Areas

• Cooking
• Fabric Care
• Air Purification

Categories

1. Product
2. Accessory
3. Consumable
4. Service

Eligibility Criteria

• Entrants can be undergraduate and graduate design students currently enrolled at a school or university and graduates from 2014 and later from anywhere in the world.
• Entrants can also be students in architecture and engineering, but the person entering the competition must have conducted some design courses as a part of their studies.
• Entrants must have excellent visual presentation skills.
• All text in the submissions must be in English.
• Only one piece of work can be submitted.
• Submissions must be based on the theme Healthy Happy Kids within one of the focus areas mentioned above.
• Submission can be on one or more of the categories listed above.
• File format: JPG; file size: maximum 5MB; color space: RGB.

Application will demand

1. Personal details
2. Concept description
3. Consumer motivation
4. Images – visual sketches (no text in the images)

For more information, please visit Design Lab 2015.

Women Deliver Young Leaders Program & Scholarships To Attend 2016 Conference

Deadline: 1 March 2015

Women Deliver invites youth under the age of 30 to apply for three-year fellowship program entitled Young Leaders Program. The program is aimed at developing the skills of youth advocates through online learning communities, seed grant funding, and high-level networking and media opportunities. The young leaders should commit up to 10 hours a week during the three-years’ leaders program.

Young Leaders will get opportunity to

1. Attend the Women Deliver 2016 Conference during 16-19 May 2016 in Copenhagen, Denmark with full scholarship
2. Participate in capacity-building e-learning opportunities that cover sexual and reproductive health and rights issues, advocacy, communications, proposal writing, project management, and monitoring and evaluation.
3. Apply for seed grant funding to implement a community-based project. The fellows must fully participate in and complete both e-courses in their entirety to be eligible for seed grant.
4. Make connections with a wide range of people working in the field, including high-level policymakers, donors, and journalists.
5. Join a network of former and current Young Leaders as well as professional mentors to increase advocacy around sexual and reproductive health and rights in their home countries.
6. Attend a two-day youth pre-conference workshop on advocacy around maternal health, with a focus on communications and new technologies, and serve as a youth representative at the conference.

Youth who are not interested in becoming youth leader but willing to attend the conference can apply for scholarship to participate in the conference. Selected participants can get chance to serve as youth representative at the conference and connect with the wide range of policymakers, donors, activists, and journalists in attendance.

A full scholarship to the Women Deliver 2016 Conference includes – conference registration, roundtrip airfare, reimbursement of the cost to acquire a new visa to enter Denmark, $50 for ground transportation to and from the airport within home country and round trip ground transportation between the Copenhagen airport and hotel, overnight accommodation, and $50 per diem, per night stayed at the hotel to attend the conference.

Note the Key Dates

1. 1 March 2015: Application deadline
2. 1 May 2015: Notification to selected applicants
3. 15 June 2015: Deadline for confirmation from the winners

Eligibility Criteria

• Applicants can be youth under 30 years from anywhere around the world.
• Applicants must have high level of proficiency in English language.
• To become Youth leader, applicants must be passionate about maternal, sexual, and reproductive health and rights.
• For Conference scholarship, applicants must be working to advance the health, rights, and well-being of girls and women in their community and around the world.

Note: Women Deliver will cover the costs of obtaining visa and provide supporting documentation, to enter Denmark.

For more information, please visit Women Deliver Young Leaders Program.

Creation Of New GCE Centre In Agyati-Bafut Sub Division: Principal Jubilates

The Principal of GSS Agyati in Bafut Sub Division, Mezam Division of the North West Region, Mr. Chenwi Emmanuel, is beyond doubt greatly fulfilled with the creation of a new GCE center in his school. Following the creation of the school in 2011, the pioneer batch is soon to sit in for the GCE examination.

Amidst the joyin him, he gladly confessed that his plea and request for the GCE center has proved quite fruitful with its creation. He continued that, if his school has been granted a GCE Center, it is great indication that the school is ripe enough. With pride, he said the school just had a block where GCE materials will be kept. Following the creation of the GCE center, about six security guards have been employed and there is more land for the construction of more classroom blocks since the school is looking forward to having a second cycle next academic year.

The Principal, in delight, saluted the hierarchy for thier great support and for having responded to his plea. With honour, he boosted of the number of staff in his school and the amount of hardwork they put in, adding that the 55 candidates registered for the GCE examination this year are undoubtedly going to make it.

While anxiously waiting for the expected great results that the pioneer batch is to produce for June 2015, Mr. Chenwi Emmanuel happily announced that his school was 'changing level' every other day, now boasting three buildings and a number of classrooms which are sufficient for the current number of students in the school.

The Principal, while jubilating over the absence of poor mismanagement in his school, said he was greatly thankful tot he North West Regional Delegation of Secondary Education for its constant supervision in the school to make sure there were no mismanagement issues by the Parent Teachers Association, PTA. The Principal concluded by saying that the teachers and parents should join him in this struggle of hard work and unity to see to it that their children produce the best results come the 2015 GCE session.

TechChange Summer Fellowship Program 2015 for non-US Citizens

Deadline: 15 February 2015

The TechChange invites non-US citizens based outside of the Unites States (also non-US citizens based in US with student visas or other legal working status) to apply for Summer Fellowship Program. The program is designed for recent graduates and rising college seniors.

The fellows will get an opportunity to participate in practical training in web development along with a unique exposure to a range of applications and organizations using technology to tackle a variety of global challenges. Fellows will be provided $2000 monthly stipend for the fellowship period and support with job placement at the conclusion of the fellowship.

The fellows will spend three months in Tech Change USA, designing and implementing a web development project related to education, technology, and social good. They will be provided training, mentorship and a series of events to support their work. Field trips to organizations working in technology and social change; event series on a range of technology and social change related topics and training in Javascript (Node.js), PHP, Python, Django, Backbone.js, database management, and more will prepare the fellow for her/his future endeavor.

Eligibility Criteria

• Applicants can be non-US citizens based in or outside the USA.
• Applicants must be a current junior, senior, or a recent graduate.
• Applicants should be available to spend 3 months period (8 June – 28 August 2015) in the USA.
• Applicants should have capacity to work at a tech company with a solid foundation in web development or object-oriented programming. At least one year of experience in computer science or web development is must.
• Applicants must have passion to make a difference in the world – interest in international relations, international development, humanitarian work, and social good is a requirement.
• Applicants must be willing to challenge themselves. Self-starting youth with willingness to have a little fun is must.

Note: Applications are being reviewed and selections being made. We suggest you to apply early.

For more information, please visit TechChange Summer Fellowship 2015.

Scramble For Employment: More Than 80.000 Youths To Compete For 4.700 Positions Into The Police Force in Cameroon

 Coni T. Tawong

• What becomes of the 75.300 youths or more who would not be employed?
• Why can government not instead make strong laws and strengthen security (matricule numbers) in the private sector?

Here is what scare youths from the private sector
Treatment of employees by employers in the private sector in Cameroon is very poor due to the fact that the employers have capital. This makes the youths to look up only to the civil service where they see the job security (matricule number) lacking in the private sector.

• Employers of the private sector in Cameroon are egocentric and generally do not love those who work under them.
• All private institutions in Cameroon are commercially oriented e.g. mission schools, lay private schools, mission hospitals, communication & transport companies etc
• The salaries in the private sector in Cameroon are  very low
• There is no strong Law (though laws exist) that seriously protect the private sector workers
• Workers of the private sector are treated with sentiments, meaning that if your employer gets angy with you, he or she can dismiss you and go unpunished.
• If an employer sees a worker prospers, the prosperous worker will be dismissed.
• Generally, working with the weakened private sector in Cameroon means you are not working as contrasted to the private sector of other countries.

Allegations Of Human Right Abuses & Extortions in Wum by Senior State Counsel

By Coni T. Tawong

A team of officials from the Ministry of Justice is now poised to open investigation at the Wum High Court over allegations of extortions and abuse of human rights of locales by the Senior State Counsel of Menchum Division brought to their knowledge by Hon. Ndong Larry Hills, Social Democratic Front (SDF) member of parliament (MP) for Menchum North Constituency.

The MP Menchum North, in a letter addressed to the Minister of Justice and keeper of the seals alleged that the Senior State Counsel for Wum-Menchum, Mr. Bekondo Brunett has been extorting money from the population as well as taken measures to stiffened court cases in order to receive money from accused individuals. The MP in his petition titled "The Failure of the Judiciary in Menchum" stated clearly taht the Police, Gendarmes and Penitentiary in his constituency are unable to investigate and hold up to investigations as prescribed by law because of the State Counsel's malicious actions. He said the State Counsel has made it a point of duty that all cases, arrests must be brought to him adding that the forces of law and order have been rendered powerless in the Division.

The MP's allegations have been supported by a Senior Gendarme official in Menchum who said he had been nursing similar plans to petition the Senior State Counsel to the powers that be.

The document addressed to the Minister of Justice and Keeper of the Seals had other copies directed to the Presidency, North West Governor, SDO Menchum and the President of Menchum High Court.

In reaction to these allegations, the Senior State Counsel for Wum-Menchum, Mr. Bekondo Brunett has said that nobody will derail him from his assignment to ensure the rule of law, peace and eradicate crime.

He has described the petition as baseless and a tactic by his detractors to paint him black. Talking on his relationship with the population, he said that "I have served this Division in three different capacities. I will continue to work for the good of the people not withstanding the shots from detractors".

The legal department he said is working with the support of all the auxiliaries in Menchum in unison. "I call on the population to fearlessly report all offences perpetrated against them by criminals to the legal department or forces of law and order for investigation and persecution.

According to Mr. Bekondo Brunett, in doing so, there is always opposition and hatred, "consequently intimidation from those quarters whose interests are threatened. If you are strict be ready for all sorts of calumny against you even manipulation all from detractors"

200 Boko Haram Fighters Vanquished In Fierce Battle

Chad said Wednesday it inflicted heavy losses on Nigeria’s Boko Haram, killing “over 200” Islamist militants in a border town that it wrested from the rebels in a ground offensive.

Nine Chadian soldiers were also killed and 21 injured Tuesday in Gamboru as regional forces took the fight against the insurgents on to Nigerian soil for the first time, the Chadian army said.

“This toll is provisional,” the Chadian military said in a statement, adding that troops were still combing the town on Nigeria’s border with Cameroon for lingering rebel elements.

Around 2,000 Chadian troops backed by armoured vehicles poured across the border into Gamboru on Tuesday after the African Union last week backed a regional force to take on the extremists.

The sound of automatic gunfire could be heard Wednesday in the town, which has been abandoned by residents after a barrage of air strikes by Chad in the run-up to its offensive, an AFP journalist reported.

While the operation in Gamboru continued, the town of Fotokol on the other side of the border, in Cameroon, came under fresh attack from the jihadists.

“The guys (Boko Haram) entered this morning. The fighting between them and our soldiers is very intense,” a Cameroonian security source in Fotokol told AFP by telephone.

The Cameroonian troops had managed to repel the attack by mid-morning, after Chadian soldiers crossed back from Nigeria to help defend the town.

In Gamboru, the clashes left scenes of desolation, with bodies lying on the ground, houses destroyed, shops gutted and trucks charred.

“We have routed this band of terrorists,” the commander of the Chadian contingent Ahmat Dari told AFP Tuesday, vowing to “hunt them down everywhere.”

Nigerian defence spokesman Chris Olukolade denied that the presence of foreign troops on Nigerian soil compromised the country’s sovereignty.

“Nigeria’s territorial integrity remains intact,” he said, claiming national forces had “planned and are driving the present onslaught against terrorists from all fronts in Nigeria, not the Chadian forces.”

Source: News Express

Links/ Liens:

Job Opportunities / Opportunités d'emploi

Position title/Fonction	Location/Localisation
Controleur Interne	Douala, Cameroun
Analyste crédit	Douala, Cameroun
Gestionnaire Administration et Paie	Douala, Cameroun
Chargé de recouvrement	Douala, Cameroun
Gestionnaire Marketing	Douala, Cameroun
Gestionnaire conformité	Douala, Cameroun
Gestionnaire Comptable	Douala, Cameroun
Auditeur Interne	Douala, Cameroun
Conseiller Dépôts	Douala, Cameroun
Chef de Caisses	Douala, Cameroun
Superviseur Assistance Commerciale	Douala, Cameroun
Agent de Recouvrement	Douala, Cameroun
Chargé de Clientèle	Douala, Cameroun
Collecteur/rice mobile	Douala, CAMEROUN
Gestionnaire SIG	Douala, CAMEROUN
Agent Logistique	Douala, CAMEROUN
Adjoint Responsable Logistique	Douala, CAMEROUN
Gestionnaire Recrutement et Développement desCarrières	Douala, Cameroon
Branch Manager/Deputy Branch Manager	DOUALA, CAMEROUN
Cashier	DOUALA, CAMEROUN
Client Assistant	DOUALA, CAMEROUN
Client Officer	DOUALA, CAMEROUN
Adjoint Directeur d'Agence	DOUALA, CAMEROUN
Caissière/Caissier	DOUALA, CAMEROUN
Assistant (e) Clientèle	DOUALA, CAMEROUN
Chargé(e) de Clientèle	DOUALA, CAMEROUN

MINEDUB: 3060 teachers to be recruited in 2015

H. E. Yusuf Hadidja Alim & pupils

The Minister of Basic Education, Yusuf Hadidja Alim has announced the recruitment of 3060 teachers and the construction of 1300 classrooms in 2015.

Basic Education Minister made the announcement on Friday 29th January 2015 when receiving New Year wishes from employees, friends and well-wishers of the basic education family in the country.
Speaking during the ceremony, the Minister expressed gratitude to the different partners that contributed to the success of projects in her Ministry, throughout 2014.

She further loaded the restless efforts of the Secretary General, Professor Ivo Leke Tambo and all of the staff who took all to their hands to ensure effective execution of the projects in 2014, which ranged from the development and validation of the national textbook policy and teaching materials, reform of the Certificate of Primary Education and First school leaving certificates.

The Minister also used the occasion to caution the staff to be punctual, to process cases expeditiously, to fight against corruption and ensure efficient use of funds and facilities at their disposal.

The Secretary of State to the Minister of Basic Education (MINEDUB), Benoit Ndong Soumhet in his part said the ministry is declined to tackle major axes of its ministry this year 2015.

Long before the presentation of New Year wishes to the Minister, a consultation meeting of heads of central board of the Ministry held a lecture on "Improving educational performance of teachers for better grades." It was intended to check the level of implementation of educational programs, their coverage, and situation of schools in conflict areas.

Fight Against Boko Haram: Yaoundé and N'Djamena Pool their Forces

The President of the Republic of Cameroon, His Excellency Paul BIYA hereby announces that within the framework of the excellent friendship and good neighbourhood ties existing between Cameroon and Chad, His Excellency Mister Idriss DEBY ITNO, President of the Republic of Chad, has decided to send an important contingent of Chadian Armed Forces to support the Cameroonian Armed Forces who are fighting against the repeated attacks of the Boko Haram Islamic sect with courage, determination and bravery acknowledged by all.

The President of the Republic warmly welcomes this gesture of brotherhood and solidarity enshrined in the constant commitment of both Head of States in favour of the stability, peace and security of their countries and their respective peoples.