Senja di Pelabuhan Golden Horn, Istanbul

Senja di Pelabuhan Golden Horn, Istanbul sungguh lah indah menawan hati, kiranya ada kesempatan untuk mengunjungi tempat ini, alangkah bahagia nya... ;p

Kesibukan di Bosphorus Cruise

Kesibukan di Bosphorus Cruise, Sebuah Pasar Seni di Istanbul yang ramai akan Pengunjung hilir mudik, sesembari mencuci mata melihat keindahan di kanan kiri nya...

TAV Ataturk, Istanbul

Suasana sepanjang jalan menuju Bandar Udara Intenasional TAV Ataturk, Istanbul. Menjelang malam aura eksotis dari cahaya lampu-lampu kendaraan membuat semakin meriah nya kesan selamat datang di kota seribu menara itu...

Panorama Gothik Kota Praha

Panorama Gothik Kota Praha yang begitu mempesona, banyak bangunan-bangunan yang memiliki desain arsitektur yang berseni tinggi berada di kota ini, dari Praha to Istanbul semakin lengkap seolah kita melarutkan diri dalam tatanan kelas tinggi yang sudah pasti begitu memukau...

Jembatan Maria Valeria, Budapest

Jembatan Maria Valeria, Budapest. hmmm... Kekaguman semakin lengkap ketika sesosok malaikat berambut pirang menemani menikmati indahnya kota ini...

2014/02/17

I've tried :(

Bukanlah akhir dari keputusan mu yang membuat ku patah hingga berkeping...

Bukan pula ketakutan ku... untuk malu dan mengakui kegagalan dalam usaha-usaha pencapaian harapan...

Mengapa aku harus takut, jika rasa takut dan berani hanyalah soal sedikit rasa dan keyakinan yang Tuhan pinjamkan kepadaku...?

Bagaimana aku seharusnya bereaksi jika Tuhan menentukan waktu, orang-orang dan tempat yang berbeda untuk kita...?

Bagaimana aku seharusnya bereaksi ketika seseorang tiba-tiba datang dan mengatakan bahwa ia yang paling berhak atas dirimu dan masa depan mu...?

Bagaimana aku seharusnya bereaksi ketika seseorang tiba-tiba datang dan mempersilahkan ku pergi, seolah-olah karena tugas ku sebagai pengantar telah selesai...?

Bagaimana aku seharusnya bereaksi ketika tidak ada satu kata pun ucapan selamat tinggal yang kutemukan di jalan-jalan itu...?

Bagaimana aku seharusnya memahami tentang hal-hal ideal yang kupelajari, namun tak dapat kusimpulkan dalam bahasa dan keilmuan apapun...?

Bagaimana aku seharusnya menjelaskan pada masa kini dan masa depanku...?

Apa yang membuat kita berbeda hingga kemudian perbedaan itu sendiri yang memisahkan...?

Butuh lebih dari kesabaran dan keikhlasan untuk menerima dan mempersilahkan jalan bagi kalian berdua...

Aku disini berjalan sendiri...

Berjalan sendiri pada tepian lautan pertanyaan-pertanyaan...

Lautan pertanyaan yang bahkan ketika kutemukan jawaban nya pun, mungkin itu takkan bermakna dan berguna lagi...

Selamat berbahagia... :)



 

2013/12/14

Metacognition

Metacognition is defined as "cognition about cognition", or "knowing about knowing". It can take many forms; it includes knowledge about when and how to use particular strategies for learning or for problem solving.There are generally two components of metacognition: knowledge about cognition, and regulation of cognition.

Metamemory, defined as knowing about memory and mnemonic strategies, is an especially important form of metacognition. Differences in metacognitive processing across cultures have not been widely studied, but could provide better outcomes in cross-cultural learning between teachers and students.

Some evolutionary psychologists hypothesize that metacognition is used as a survival tool, which would make metacognition the same across cultures. Writings on metacognition can be traced back at least as far as De Anima and the Parva Naturalia of the Greek philosopher Aristotle.

 J. H. Flavell first used the word "metacognition".He describes it in these words:

    Metacognition refers to one’s knowledge concerning one's own cognitive processes and products or anything related to them, e.g., the learning-relevant properties of information or data. For example, I am engaging in metacognition if I notice that I am having more trouble learning A than B; [or] if it strikes me that I should double check C before accepting it as fact.
    —J. H. Flavell (1976, p. 232).

A. Demetriou, in his theory, one of the neo-Piagetian theories of cognitive development, used the term hypercognition to refer to self-monitoring, self-representation, and self-regulation processes, which are regarded as integral components of the human mind. Moreover, with his colleagues, he showed that these processes participate in general intelligence, together with processing efficiency and reasoning, which have traditionally been considered to compose fluid intelligence.

Metacognition also thinks about one's own thinking process such as study skills, memory capabilities, and the ability to monitor learning. This concept needs to be explicitly taught along with content instruction. Metacognitive knowledge is about our own cognitive processes and our understanding of how to regulate those processes to maximize learning. Some types of metacognitive knowledge would include: 1. Person knowledge (declarative knowledge) which is understanding one's own capabilities. 2. Task knowledge (procedural knowledge) which is how one perceives the difficulty of a task which is the content, length, and the type of assignment. 3. Strategic knowledge (conditional knowledge) which is one's own capability for using strategies to learn information. Young children are not particularly good at this; it is not until upper elementary where students start to develop the understanding of strategies that will be effective.

Different fields define metacognition very differently. Metacognition variously refers to the study of memory-monitoring and self-regulation, meta-reasoning, consciousness/awareness and auto-consciousness/self-awareness. In practice these capacities are used to regulate one's own cognition, to maximize one's potential to think, learn and to the evaluation of proper ethical/moral rules.

In the domain of experimental psychology, an influential distinction in metacognition (proposed by T. O. Nelson & L. Narens) is between Monitoring—making judgments about the strength of one's memories—and Control—using those judgments to guide behavior (in particular, to guide study choices). Dunlosky, Serra, and Baker (2007) covered this distinction in a review of metamemory research that focused on how findings from this domain can be applied to other areas of applied research.

In the domain of cognitive neuroscience, metacognitive monitoring and control has been viewed as a function of the prefrontal cortex, which receives (monitors) sensory signals from other cortical regions and through feedback loops implements control (see chapters by Schwartz & Bacon and Shimamura, in Dunlosky & Bjork, 2008).

Metacognition is studied in the domain of artificial intelligence and modelling. Therefore, it is the domain of interest of emergent systemics. It has been used, albeit off the original definition, to describe one's own knowledge that we will die. Writers in the 1990s involved with the musical "grunge" scene often used the term to describe self-awareness of mortality.[citation needed]
 
* Components
Metacognition is classified into three components:
 
Metacognitive knowledge (also called metacognitive awareness) is what individuals know about themselves and others as cognitive processors.Metacognitive regulation is the regulation of cognition and learning experiences through a set of activities that help people control their learning. Metacognitive experiences are those experiences that have something to do with the current, on-going cognitive endeavor.

Metacognition refers to a level of thinking that involves active control over the process of thinking that is used in learning situations. Planning the way to approach a learning task, monitoring comprehension, and evaluating the progress towards the completion of a task: these are skills that are metacognitive in their nature.

Metacognition includes at least three different types of metacognitive awareness when considering metacognitive knowledge:
 
Declarative Knowledge: refers to knowledge about oneself as a learner and about what factors can influence one's performance. Declarative knowledge can also be referred to as "world knowledge".
 
Procedural Knowledge: refers to knowledge about doing things. This type of knowledge is displayed as heuristics and strategies.A high degree of procedural knowledge can allow individuals to perform tasks more automatically. This is achieved through a large variety of strategies that can be accessed more efficiently.
 
Conditional knowledge: refers to knowing when and why to use declarative and procedural knowledge.It allows students to allocate their resources when using strategies. This in turn allows the strategies to become more effective.

Similar to metacognitive knowledge, metacognitive regulation or "regulation of cognition" contains three skills that are essential.
 
Planning: refers to the appropriate selection of strategies and the correct allocation of resources that affect task performance.

Monitoring: refers to one's awareness of comprehension and task performance 

Evaluating: refers to appraising the final product of a task and the efficiency at which the task was performed. This can include re-evaluating strategies that were used.

Similarly, maintaining motivation to see a task to completion is also a metacognitive skill. The ability to become aware of distracting stimuli – both internal and external – and sustain effort over time also involves metacognitive or executive functions. The theory that metacognition has a critical role to play in successful learning means it is important that it be demonstrated by both students and teachers.

Students who demonstrate a wide range of metacognitive skills perform better on exams and complete work more efficiently. They are self-regulated learners who utilize the "right tool for the job" and modify learning strategies and skills based on their awareness of effectiveness. Individuals with a high level of metacognitive knowledge and skill identify blocks to learning as early as possible and change "tools" or strategies to ensure goal attainment. Swanson (1990) found that metacognitive knowledge can compensate for IQ and lack of prior knowledge when comparing fifth and sixth grade students' problem solving. Students with a high-metacognition were reported to have used fewer strategies, but solved problems more effectively than low-metacognition students, regardless of IQ or prior knowledge.

Metacognologists are aware of their own strengths and weaknesses, the nature of the task at hand, and available "tools" or skills. A broader repertoire of "tools" also assists in goal attainment. When "tools" are general, generic, and context independent, they are more likely to be useful in different types of learning situations.

Another distinction in metacognition is executive management and strategic knowledge. Executive management processes involve planning, monitoring, evaluating and revising one's own thinking processes and products. Strategic knowledge involves knowing what (factual or declarative knowledge), knowing when and why (conditional or contextual knowledge) and knowing how (procedural or methodological knowledge). Both executive management and strategic knowledge metacognition are needed to self-regulate one's own thinking and learning.

Finally, there is no distinction between domain-general and domain-specific metacognitive skills. This means that metacognitive skills are domain-general in nature and there are no specific skills for certain subject areas. The metacognitive skills that are used to review an essay are the same as those that are used to verify an answer to a math question.

Metacognitive experience is responsible for creating an identity that matters to an individual. The creation of the identity with meta-cognitive experience is linked to the identity-based motivation (IBM) model. The identity-based motivation model implies that "identities matter because they provide a basis for meaning making and for action." A person decides also if the identity matters in two ways with meta-cognitive experience. First, a current or possible identity is either "part of the self and so worth pursuing" or the individual thinks that the identity is part of their self, yet it is conflicting with more important identities and the individual will decide if the identity is or is not worth pursuing. Second, it also helps an individual decide if an identity should be pursued or abandoned.

Usually, abandoning identity has been linked to meta-cognitive difficulty. Based on the identity-based motivation model there are naive theories describing difficulty as a way to continue to pursue an identity. The incremental theory of ability states that if "effort matters then difficulty is likely to be interpreted as meaning that more effort is needed." Here is an example, a woman who loves to play clarinet has come upon a hard piece. She knows that how much effort she puts into learning this piece is beneficial. The piece had difficulty so she knew the effort was needed. The identity the woman wants to pursue is to be a good clarinet player, having a metacognitive experience difficulty pushed her to learn the difficult piece to continue to identify with her identity. The entity theory of ability represents the opposite. This theory states that if "effort does not matter then difficulty is likely to be interpreted as meaning that ability is lacking so effort should be suspended." Based on the example of the woman playing the clarinet, if she did not want to identify herself as a good clarinet player, she would not have put in any effort to learn the difficult piece which is an example of using metacognitive experience difficulty to abandon an identity.
 
* Relation to sapience

Metacognologists believe that the ability to consciously think about thinking is unique to sapient species and indeed is one of the definitions of sapience.[citation needed] There is evidence that rhesus monkeys and apes can make accurate judgments about the strengths of their memories of fact and monitor their own uncertainty,while attempts to demonstrate metacognition in birds have been inconclusive. A 2007 study has provided some evidence for metacognition in rats, but further analysis suggested that they may have been following simple operant conditioning principles, or a behavioral economic model.

* Metacognitive strategies

Metacognitive-like processes are especially ubiquitous when it comes to the discussion of self-regulated learning. Being engaged in metacognition is a salient feature of good self-regulated learners[citation needed]. Groups reinforcing collective discussion of metacognition is a salient feature of self-critical and self-regulating social groups[citation needed]. The activities of strategy selection and application include those concerned with an ongoing attempt to plan, check, monitor, select, revise, evaluate, etc.

Metacognition is 'stable' in that learners' initial decisions derive from the pertinent fact about their cognition through years of learning experience. Simultaneously, it is also 'situated' in the sense that it depends on learners' familiarity with the task, motivation, emotion, and so forth. Individuals need to regulate their thoughts about the strategy they are using and adjust it based on the situation to which the strategy is being applied. At a professional level, this has led to emphasis on the development of reflective practice, particularly in the education and health-care professions.

Recently, the notion has been applied to the study of second language learners in the field of TESOL and applied linguistics in general (e.g., Wenden, 1987; Zhang, 2001, 2010). This new development has been much related to Flavell (1979), where the notion of metacognition is elaborated within a tripartite theoretical framework. Learner metacognition is defined and investigated by examining their person knowledge, task knowledge and strategy knowledge.

Wenden (1991) has proposed and used this framework and Zhang (2001) has adopted this approach and investigated second language learners' metacognition or metacognitive knowledge. In addition to exploring the relationships between learner metacognition and performance, researchers are also interested in the effects of metacognitively-oriented strategic instruction on reading comprehension (e.g., Garner, 1994, in first language contexts, and Chamot, 2005; Zhang, 2010). The efforts are aimed at developing learner autonomy, interdependence and self-regulation.

Metacognition helps people to perform many cognitive tasks more effectively.[1] Strategies for promoting metacognition include self-questioning (e.g. "What do I already know about this topic? How have I solved problems like this before?"), thinking aloud while performing a task, and making graphic representations (e.g. concept maps, flow charts, semantic webs) of one's thoughts and knowledge. Carr, 2002, argues that the physical act of writing plays a large part in the development of metacognitive skills.

Strategy Evaluation matrices (SEM) can help to improve the knowledge of cognition component of metacogntion. The SEM works by identifying the declarative (Column 1), procedural (Column 2) and conditional (Column 3 and 4) knowledge about specific strategies. The SEM can help individuals identify the strength and weaknesses about certain strategies as well as introduce them to new strategies that they can add to their repertoire.

A regulation checklist (RC) is a useful strategy for improving the regulation of cognition aspect of one’s metacognition. RCs help individuals to implement a sequence of thoughts that allow them to go over their own metacogntion.[32] King (1991) found that fifth-grade students who used a regulation checklist outperformed control students when looking at a variety of questions including written problem solving, asking strategic questions, and elaborating information.

Metacognitive strategies training can consist of coaching the students in thinking skills that will allow them to monitor their own learning. Examples of strategies that can be taught to students are word analysis skills, active reading strategies, listening skills, organizational skills and creating mnemonic devices.

* Meta-Strategic Knowledge
“Meta-Strategic Knowledge” (MSK) is a sub-component of metacognition that is defined as general knowledge about higher order thinking strategies. MSK had been defined as “general knowledge about the cognitive procedures that are being manipulated”. The knowledge involved in MSK consists of “making generalizations and drawing rules regarding a thinking strategy” and of “naming” the thinking strategy.

The important conscious act of a meta-strategic strategy is the “conscious” awareness that one is performing a form of higher order thinking. MSK is an awareness of the type of thinking strategies being used in specific instances and it consists of the following abilities: making generalizations and drawing rules regarding a thinking strategy, naming the thinking strategy, explaining when, why and how such a thinking strategy should be used, when it should not be used, what are the disadvantages of not using appropriate strategies, and what task characteristics call for the use of the strategy.[36]

MSK deals with the broader picture of the conceptual problem. It creates rules to describe and understand the physical world around the people who utilize these processes called Higher-order thinking. This is the capability of the individual to take apart complex problems in order to understand the components in problem. These are the building blocks to understanding the “big picture” (of the main problem) through reflection and problem solving.[37]

* Characteristics of Theory of Mind: Understanding the mind and the "mental world": 
False beliefs: understanding that a belief is only one of many and can be false.
Appearance–reality distinctions: something may look one way but may be something else.
Visual perspective taking: the views of physical objects differ based on perspective.
Introspection: children's awareness and understanding of their own thoughts.

* Mental Illness and Metacognition 
  Sparks of Interest

In the context of mental health, metacognition can be loosely defined as the process that "reinforces one's subjective sense of being a self and allows for becoming aware that some of one's thoughts and feelings are symptoms of an illness.[38]" The interest in metacognition emerged out of a concern for an individual’s ability to understand their own mental status compared to others as well as the ability to cope with the source of their distress. These insights into an individual's mental health status can have a profound affect on the over-all prognosis and recovery. Metacognition brings many unique insights into the normal daily functioning of a human being. It also demonstrates that a lack of these insights compromises ‘normal’ functioning. This leads to less healthy functioning. In the Autism spectrum, there is a profound inability to feel empathy towards the minds of other human beings. In people who identify as alcoholics, there is a belief that the need to control cognitions is an independent predictor of alcohol use over anxiety. Alcohol may be used as a coping strategy for controlling unwanted thoughts and emotions formed by negative perceptions. This is sometimes referred to as self medication.

* Implications
Well’s and Matthew’s theory proposes that when faced with an undesired choice, an individual can operate in two distinct modes: ‘object’ and ‘Metacognitive.’ Object mode interprets perceived stimuli as truth, where Metacognitive mode understands thoughts as cues that have to be weighted and evaluated. They are not as easily trusted. There are targeted interventions unique of each patient, that gives rise to the belief that assistance in increasing metacognition in people diagnosed with schizophrenia is possible through tailored psychotherapy. With a customized therapy in place clients then have the potential to develop greater ability to engage in complex self-reflection. This can ultimately be pivotal in the patient's recovery process. In the Obsessive Compulsive Disorder spectrum, cognitive formulations have greater attention to intrusive thoughts related to the disorder. "Cognitive Self-Consciousness" are the tendencies to focus attention on thought. Patients with OCD exemplify varying degrees of these ‘intrusive thoughts.’ Patients also suffering from Generalized Anxiety Disorder also show negative thought process in their cognition.

With any metacognition strategy, the general consensus is to believe that they are good. But in all actuality some may be very harmful. Cognitive-Attentional Syndrome (CAS) characterizes a Metacognitive model of emotion disorder. CAS is consistent with the constant with the attention strategy of excessively focusing on the source of a threat. This ultimately develops through the client’s own beliefs. Metacognitive therapy attempts to correct this change in the CAS. One of the techniques in this model is called Attention Training (ATT). It was designed to diminish the worry and anxiety by a sense of control and cognitive awareness. Also ATT trains clients to detect threats, test how controllable reality appears to be.

* Works of art as metacognitive artifacts
The concept of metacognition has also been applied to reader-response criticism. Narrative works of art, including novels, movies and musical compositions, can be characterized as metacognitive artifacts which are designed by the artist to anticipate and regulate the beliefs and cognitive processes of the recipient, for instance, how and in which order events and their causes and identities are revealed to the reader of a detective story. As Menakhem Perry has pointed out, mere order has profound effects on the aesthetical meaning of a text. Narrative works of art contain a representation of their own ideal reception process. They are something of a tool with which the creators of the work wish to attain certain aesthetical and even moral effects.

Courtesy of: http://en.wikipedia.org/wiki/Metacognition

2013/12/12

Job Description for Network Engineering

Network engineers are responsible for installing, maintaining and supporting computer communication networks within an organisation or between organisations. Their goal is to ensure the smooth operation of communication networks in order to provide maximum performance and availability for their users, such as staff, clients, customers and suppliers.

Network engineers may work internally as part of an organisation’s IT support team or externally as part of an IT networking consultancy firm working with a number of clients.

Other job titles used to refer to this kind of work include network support, support engineer, IT support engineer, helpdesk support, network administrator, first-line support, second-line support, security engineer and network architect.

Typical work activities

The work is influenced by the size and type of the employing organisation. In a large investment bank for example, a network engineer may have specific responsibility for one area of the system. In a small company, the engineer may be troubleshooter for almost any IT-related problem that arises.

* There are different types of network, such as:
 
  1. LANs - local area networks, linking a limited area such as a home, office or small group of buildings.
  2. MANs - metropolitan area networks, linking a large area such as a campus or city
  3. WANs - wide area networks, which link nationally or internationally
  4. GANs - global area networks, combining all of the above with satellite mobile-communication technologies.

* The type of network will affect the engineer's responsibilities. Typical tasks usually include:
  1. Installing, supporting and maintaining new server hardware and software infrastructure
  2. Managing email, anti-spam and virus protection
  3. Setting up user accounts, permissions and passwords
  4. Monitoring network usage
  5. Ensuring the most cost-effective and efficient use of servers
  6. Suggesting and providing IT solutions to business and management problems
  7. Ensuring that all IT equipment complies with industry standards
  8. Analysing and resolving faults, ranging from a major system crash to a forgotten password
  9. Undertaking routine preventative measures and implementing, maintaining and monitoring network security, particularly if the network connects to the internet
  10. Providing training and technical support for users with varying levels of IT knowledge and competence
  11. Supervising other staff, such as help-desk technicians
  12. Working closely with other departments/organisations and collaborating with other IT staff
  13. Planning and implementing future IT developments and undertaking project work
  14. Managing the website and keeping internal networks running
  15. Monitoring the use of the web by employees.
Posts entitled 'technical support' usually include responsibility for other IT equipment, such as printers and scanners 

Courtesy of : http://www.prospects.ac.uk/network_engineer_job_description.htm

2013/12/10

Arsitektur jaringan komputer

Model arsitektur menyediakan pendekatan dalam bentuk modular fungsional pada desain sebuah jaringan. Selain hirarki, modul digunakan untuk mengatur kumpulan perangkat server (server farm), manajemen jaringan, jaringan-jaringan kampus, Jaringan berskala WAN dan Internet.

* Model jaringan berbentuk hirarki   
  
Menurut  CCDA 640-864 Official Cert Guide (2011,p40), model berbentuk hirarki (Hierarchical model), memungkinkan kita untuk merancang internetworks, yang mengkombinasikan fungsi –fungsi, disesuaikan pada hirarki organisasi. Seperti menyederhanakan sebuah tugas-tugas desain untuk membangun jaringan, serta memenuhi kebutuhan saat ini dan dapat tumbuh untuk memenuhi kebutuhan masa depan.

Model hirarki menggunakan lapisan-lapisan (layers) untuk menyederhanakan tugas-tugas pada internetworking. Setiap lapisan fokus pada fungsi spesifik, memungkinkan Anda untuk memilih sistem dan fitur yang tepat, untuk setiap lapisan. Model hirarki berlaku baik untuk terminologi desain LAN dan WAN.

* Manfaat model hirarki
 
Manfaat menggunakan model hirarki untuk desain jaringan meliputi:
1.Penghematan biaya
2.Memudahkan pemahaman perancangan
3.Mudah mengembangkan jaringan karena berbasis modular
4.Memudahkan perawatan (maintenance), dalam melakukan isolasi pemulihan jaringan    

Manajer jaringan dapat dengan mudah mengerti dan menentukan awal perubahan (transisi) dalam jaringan, yang membantu mengidentifikasi sebuah kegagalan, karena akan lebih sulit memecahkan masalah, jika desain secara hirarki atau pembagian segment tidak digunakan.

* Desain jaringan berbentuk hirarki

Pada gambar 3.3 menunjukkan secara umum, desain hirarki yang diterapkan pada terminologi LAN, dan dibagi menjadi tiga lapisan (layers), menurut CCDA 640-864 Official Cert Guide: (2011,p41) :


Gambar 2.5: Model hirarki terdiri dari: Core, Distribution, and Access
Sumber: CCDA 640-864 Official Cert Guide: (2011,p41)

Adapun lapisan-lapisan yang membagi hirarki jaringan komputer berdasarkan CCDA 640-864 Official Cert Guide: (2011,p41) adalah:1.Core Layer (Lapisan Core)

Core layer (lapisan inti) adalah lapisan yang menangani switching berkecepatan tinggi dan sangat penting, karena menunjukkan karakteristik jaringan, bagi sebuah corporate atau perusahaan.

Ciri-ciri jaringan lapisan core (core layer):

a.Fast Transport
b.Kehandalan tinggi
c.Adanya redundansi
d.Toleransi kesalahan
e.Latensi rendah dan pengelolaan yang baik
f.Terbatas dan diameter yang konsisten
g.QOS (Quality Of Service)

Ketika jaringan menggunakan perangkat router, jumlah lompatan (hop) antara router yang satu dengan yang lainnya disebut diameter. Sebagai catatan, sangat dibutuhkan sebuah diameter yang konsisten diantara hirarki jaringan. Perjalanan dari satu stasiun (node) ke  stasiun (node) yang lain diantara backbone, harus memiliki jumlah hop yang sama. Jarak dari stasiun akhir (node) ke server dalam backbone juga harus konsisten.

Membatasi diameter internetwork, menyediakan kinerja yang dapat diprediksi dan kemudahan dalam troubleshooting. Kita dapat menambahkan router yang berjalan pada layer distribusi dan klien LAN  ke dalam model hirarki, tanpa meningkatkan diameter pada lapisan core.


2.Distribution layer (lapisan distribusi)

Lapisan distribusi didalam jaringan adalah titik isolasi di antara lapisan jaringan access dan lapisan core. Lapisan distribusi dapat memiliki banyak aturan, termasuk melaksanakan fungsi-fungsi dibawah ini:

a.Konektivitas berbasis kebijakan (misalnya, memastikan bahwa lalu lintas yang dikirim dari jaringan tertentu  diteruskan ke satu antarmuka, sementara semua lalu lintas lainnya diteruskan keluar antarmuka yang lain adanya access list.

b.Redundansi dan Load balancing
c.Agregasi antara jaringan LAN
d.Agregari antara koneksi WAN
e.Quality Of Service (QOS)
f.Filter keamanan
g.Broadcast atau multicast definisi domain
h.Routing antara Virtual LAN
i.Media Translasi (contoh, antara Ethernet dan Token Ring)
j.Redistribusi antara domain-domain routing (contoh, routing antara dua protokol yang berbeda
k.Sebagai pembatas antara protokol routing yang statik dan dinamis.

3.Access Layer (lapisan akses)


Lapisan akses menyediakan akses pengguna ke segmen-segmen lokal pada jaringan. Fungsi daripada access layer meliputi, yaitu:

a.Layer 2 switching
b.Ketersediaan yang tinggi
c.Keamanan port
d.Inspeksi protokol ARP (Address Resolution Protocol)
e.Spanning Tree
f.Power over ethernet (PoE)
g.Pembatasan rate traffic/policy
h.Virtual access control lists (VACL)
i.Auxiliary VLAN

Pada gambar 2.6 mendeskripsikan layanan switching pada desain jaringan dengan model hirarki:


 Gambar 2.6: Layanan switching pada model hirarki jaringan
Sumber: CCDA 640-864 Official Cert Guide: (2011,p46)

 Pada gambar 2.7 mendeskripsikan layanan routing pada desain jaringan dengan model berhirarki:


Gambar 2.7: Layanan routing pada model hirarki jaringan
Sumber: CCDA 640-864 Official Cert Guide: (2011,p46)


Keuntungan lainnya di dalam penerapan jaringan berbasis hirarki adalah, pemisahan broadcast domain sesuai dengan segment nya masing-masing, sehingga pemanfaatan kapasitas bandwidth dapat di optimalkan.

Gambar 2.8: Jaringan menggunakan perangkat switch yang rata (flat)
Sehingga menghasilkan suatu broadcast domain yang besar
Sumber: CCNA Discovery Learning Guide: (2008, p4)

 
Pada gambar 2.9 dibawah ini menunjukan jaringan yang menggunakan model hirarki, dan terlihat bahwa pembagian broadcast domain di lakukan secara terpisah. 


Gambar 2.9: Jaringan menggunakan hirarki dan pembagian broadcast domain dilakukan secara terpisah
Sumber: CCNA Discovery Learning Guide: (2008, p4)

Menerapkan saluran yang memiliki redundansi (backup) pada lapisan core, bertujuan untuk memberikan jalur alternatif, jika terjadi kegagalan dan kerusakan pada saluran utama. Ketika perangkat-perangkat layer 3 ditempatkan pada layer core, jalur redundansi ini dapat digunakan untuk mengatur load balancing dalam hal menyediakan backup. Melalui penambahan protokol STP (Spanning Tree Protocol) jalur backup akan di matikan terlebih dahulu (disable), terkecuali ketika jalur utama putus, maka secara otomatis jalur backup akan menjadi aktif kembali. 


Gambar 2.10: Redundansi dalam topologi mesh yang berbasis hirarki
Sumber: CCNA Discovery Learning Guide: (2008, p12)
 

Br
Zaid Amin