Monthly Archives: May 2010

Can you live outside KL but work in KL ?

I try to analyze the data. Are we able to work at KL but live outside KL? Well given that house price in KL is too expensive to buy, more than affordable for rental. But the prices is way lower should you go far out of KL. For example like the place I am living now, Rawang.

But does the cheaper price of houses justify the travelling cost included?

Lets do the math.

For example the current job that I applied, the work days is 6 days a week. That means working on saturday. Lets take out our calculator.

First is travel by car. Assuming you already own one. The cost involve is:

  • Fuel: RM10 daily (back and forth about RM60/week)
  • Toll: RM7.20 daily (back and forth)
  • Parking: RM3 ~ RM6 daily/entry (depend on where the parking lot is)
  • Total daily is: RM20.20 ~ 23.20
  • Total monthly: RM464.60 ~ 533.60 (assuming 23 days work per month)

Second is to travel by public transport

  • Bus: RM2.40 daily (back and forth to Rawang KTM station)
  • Train: RM6.60 daily (back and forth Rawang – KL)
  • Total daily: RM9.00
  • Total monthly: RM207

But if you were to take normal road and find free parking, the cost by traveling with car is just RM10 for fuel. Unless you stuck on long hours jam and risk of empty fuel tank… You’re force to re-fill petrol and it will cost more than RM10 daily. So the monthly cost is around RM230++ but you got to go early to grab the free parking space.

The other things is you can’t predict anything to happen everyday. You could be facing on heavy traffic jam. You also could be facing with problematic KTM train. Both will make you arrive late for work. At least in your own car, you still looks ok. In tin sardine KTM and delayed, you would looks like…. uh! And smell… (especially going back home).

Parking in KL is terrible. If your company got adequate parking at the building, maybe driving your own car wouldnt be a problem. Or you could just paid for monthly parking at any parking lot.

I would say taking public transport is the cheapest way to go. But once reach KL, you need to walk a bit to go to your workplace. It does help if your workplace is closer to any train station. On bright day I will enjoy walking to my office. On a rainy day… Not as much. Need to bring extra shoes… And umbrella of course :)

Utorrent 2.0.1 Slow in Download

Before this I am using UTorrent 1.8.5 and download speed is great. Max out my 2Mbps DSL connection (around 200kbps++). So when new upgrade available, I happily upgrade to new version. Little did I know what it come with…

The download speed is very slow. Rarely reach even 100kbps. Most of the time around 50kbps only. I am tired of waiting… I try to download torrent with more seed. But it still wont go up to the old speed. Now I start to Googling around.

I found the tips in UTorrent own forum.

Go to your Preferences (Options -> Preferences or Ctrl + P)

Then change the value in Advanced.

bt.transp_disposition from the default 31 (default value on mine) to 5 (as suggested by one of the forumer).

After that, the speed of download increase to a bit around 150kbps… But still drop back to 50kbps sometimes. So this one does not solve the problem totally.

Then one more forumer suggested that change the value of net.calc_overhead. From True to False.

The new version of UTorrent is somehow limit the download speed to the rate of limited upload rate. So if your upload rate is 5kbps like what I said, you’ll get 50kbps download speed.

This setting will disable that options. So you will get your full download speed :) Nice!

Or you can just increase the upload speed limit to get more download speed. Or you can always downgrade to older version of UTorrent.

Type of Middleware

RPC

  • Remote Procedure Call
  • Asynchronous and Synchronous
  • Client make call to procedure running in remote system

Message Oriented Middleware

Message sent to client is collected and stored until they’re acted upon

SQL-Oriented Data Access

Between application and database

Embedded Middleware

Communication service between embedded application and real time operating system

Middleware

What is middleware?

Software layer that lies between the operating system and the application on each site of the system

Middleware Functions:

Hiding distribution

Make of many part running in distributed location

Hiding the heterogeneity of various hardware components, operating system and communication protocol

Provide uniform, standard, high level interface to the application developer and integrator

Application can easily be composed, versed, ported and made to interoperate

Supply set of common service

Perform various general purpose functions such as

  • Avoid duplicating effort
  • Facilitate collaboration between application

Corba Stubs and Skeleton

Defining Corba Stubs and Skeleton is defining ORB stubs and skeleton

Basically Stubs is at client, Skeleton is at server.

Stubs has no problem meshing perfectly with the skeleton at server.

Even if different programming language

Even if different ORB by different vendor

Why is that ?

Because IDL define the interface so strictly that every programming language and vendor must follow the standard, thus having no problem in compatibility with different language or vendor.

Cryptography System

  • Cryptography is a practice of creating and using encryption system
  • Cryptographic system is a method of hiding data so that only certain people can view
  • Plain text is the original data
  • Ciphertext is the protected data or the encrypted text
  • Encryption is the process or procedure to convert plain text to ciphertext
  • Decryption is the procedure of converting ciphertext to plain text
  • Cryptographic system consist of algorithm + key + key management facilities

2 basic type of cryptographic system

Symmetric

  • Have only one key – private key
  • use the same key to encrypt and decrypt

Asymmetric

  • Have 2 key
  • Public and private

What is ORB interface?

ORB interface is the one that provides access to every ORB service, except:

  • Client invocation (through Stubs or DII)
  • Object activation and call (through object adapter, typically POA)

The services include:

  • Access to Initial Service (Naming Service, Trader Service, Root POA and others)
  • Access to the IFR and construction of DII invocations
  • Object reference operations:
  • Conversion of Object references between Session and Stringifield format
  • Conversion of URL format corbaloc and corbaname object references to invokable references
  • Creation of duplicate object references
  • Releasing storage for object references
  • Policy operation including create_policy
  • valuetype factory operations
  • Thread related operations
  • incl work_pending and perform_work

What is ORB?

ORB is Object Request Broker.

It is a middleware that uses CORBA specification. It take care of all the details involve in routing a request from client to object, and routing response to its destination.

ORB is the custodian of the Interface Repository (IFR), an OMG standardized distributed database containing IDL interface definition.

On the client side:

  • ORB provide interface definition from the IFR
  • Construct invocations for use with the Dynamic Invocation Interface (DII),
  • Convert Object References between session and stringifield format
  • Convert URL-format corbaloc and corbaname object references to session references.

On the server side:

  • Same as above process. Plus,
  • ORB deactivates inactive objects.
  • Re-activates  object whenever request come in.
  • Activate and De-activates in the way that uses resources best.

ORB, wow!

Centralized versus Distributed System

Note: Tomorrow Exam.

Centralized

  • Have non autonomous component
  • Often built using homogeneous technology
  • Multiple users share the resources of a centralized system at all time
  • Have single point of control and failure

Distributed

  • Have autonomous components
  • May be built using heterogeneous technology
  • Distributed system components may be used exclusively
  • Executed in concurrent process
  • Multiple point of failure

Simply said, distributed system is better that centralized system should there be enough resources involved.

Centralized utilized the same resources for multiple user. An example would be Database system where multiple user access the same database on the same server. This also mean that the database have the server as the only point of control, thus translate to single point of failure.  It is either it work, or not.

In distributed system, it have autonomous components where they posses full control over their part all the time. There is also no master components that have total control over the system. Every component is on their own. It define an interfaces to communicate with each other.

Heterogeneous technology means the ability to integrate components on legacy system with newly written program on newer system. They’re able to integrate and communicate even though have different programming language even. Usually the source of the components is compiled into heterogeneous machine code.

Components also can be used (or is used) exclusively by only one user. Looks like disadvantage, but this is the advantages of distributed system where a shared component might get overloaded by too many user or too many request. More so that components can be located so they’re local to the users and other components it may interact with. This improve overall performance.

The components create new thread whenever they start to perform a service for a user or another components. That way the components is always open for another service. Also it have multiple point of failure. It is design to be like that so if one components down, the other component that is not related to it, still available for a service.

Clearly distributed system has an advantage over the centralized system. With all the autonomous, heterogeneous, multi threading and multiple point of failure, it sure have lots of advantages.