Saturday, February 28, 2009

Nature of Australia

I have taken these photos in Melbourne, Australia. This is near by Glenory (Suburub) behind my friend’s residence. All the photos are taken by using FujiFilm FinePix S5800 camera.

This photo is taken by Anand Sharma. All other, except this, photos are taken by me.

Friday, February 27, 2009

Why is TCP performance more affected by losses over high-delay and high-speed network paths?

TCP recovers from errors through end to end retransmissions that is the reason why recovery is slower in high delay paths. Further, because it takes longer to reach the peak throughput supported by higher speed links TCP drastically reduces its throughput after each loss.

Thursday, February 26, 2009

Bagalamukhi Ma

Jai Ma Ta Di...

For more Matadi's bhajan and pictures click on LABELS: Deity below

Monday, February 23, 2009

The CSMA/CA access protocol does not detect collision as CSMA/CD does. How does this limitation affect link-layer and transport-layer performance?

In wired network, when two transmitters start simultaneously collision occurs and that can be detected by transmitters. Then they abort their transmission and retry later. However, in wireless networks transmission and reception is done in the same band that makes collision detection difficult. Hence, the WLAN use CSMA/CA to avoid collision. CSMA/CA, is listen before talk mechanism, where transmitters wait for a random interval after the medium becomes idle before starting transmission. The transmitter that starts first seizes the medium and all others back off, there by reducing the change of collisions. However, there may be collision that is not detected by CSMA/CA and corrupted frames not retransmitted by CSMA/CA are considered by the link-layer and transport-layer. Link layer is responsible for flow control, acknowledgement and error recovery. It also species which mechanism are to be used for addressing stations over the transmission medium and for controlling the data exchanged between the sender and receiver. To recover from wireless losses, including undetected collisions, transmitters may need to optionally ask for acknowledgements to retransmit transparently unacknowledged frames at the link layer. Further, in some cases, wireless transmission errors are not related to network congestion but due to corrupted packets that not handed over to TCP. TCP assumes those packets are lost and reduces its congestion window size that leads to throughput degradation.

Friday, February 20, 2009

A trip to Australia

It’s always easy to be with friend in foreign country, especially when you have a friend who is already established in that country. This year I traveled Australia. A friend of mine, Anand, is living there with his family. I didn’t feel any difficulties from the airport to the airport. He came to pick me up in the airport with his car and we traveled a lot in CBD and suburbs. I lived in his place for five days and four nights. 

Photo: Coming back from the conference in the plateform

I felt home away from home. I ate Gundruk and Sadheko Sukuti that I was missing since I left Kathmandu. I even got a chance to eat Thai version of Wai Wai.

Melbourne is beautiful. Over the years I’ve been experiencing high raised apartments and big buildings. But, in Melbourne houses are only one floor in suburbs, most of houses have small front and back yard. Melbourne has a small CBD and that is full of Asians, Indians, and even Nepalese. I saw many Nepalese in Federation square chatting and surfing internet. I even saw the Nepalese sleeping all over the day beside the street in a floating boat. 

Photo: Infront of Eureka Building (picture taken by Archana Shrestha)

I was in the 60th floor of 63 building in Seoul, but this time I experienced Eureka Tower, a 300 meter skyscraper in Melbourne. It costs $16 to go to 88th floor. It has 91 floors and top 10 floors’ windows are 24 carat gold plated glasses. This is the world’s tallest residential building.

Photo: Seeing Melbourne City from the 88th floor of Eureka building

View from the 88th floor of Eureka building

View from the 88th floor of Eureka building

Me and Aanand in his house

An artist near federation squre

Tramp a convinent way to travel in Melbourne

Thursday, February 19, 2009

Bagalamukhi Painting

An Indian Painting of Bagalamukhi.

Wednesday, February 18, 2009

A day in Singapore with Chinese friend

Regardless of work area, I am more in touch with people from my own geographical region. However, I have many friends from many countries. I could say from all the continents where ever people live. 

Near the City Hall in Singapore

This time I got a chance to spend one day (in 2009-02-11) in Singapore with a friend who is a friend of mine in my university. Jin Cheng, a Chinese friend who is pursuing PhD in NTU, one of the best universities in Singapore. He is working in microwave circuit design under the Indian professor who has graduated from IIT. 

Mr. Cheng came to meet me in the Changi airport. No doubt, he is excellent in Chinese which is a well known language in Singapore and around 70% of people are ethical Chinese. Since the very beginning, I heard that it’s not good to do shopping without Chinese fellow in Singapore. I had nothing much to buy but a dual SIM (GSM + CDMA) cell phone for my brother who is working in a telecom company and fan of cell phones, keeps 2 cell phones – CDMA and GSM. I tried to get such a phone in Singapore’s best electronics shopping mall called Lucky Plaza. Unfortunately, I couldn’t find such a phone. Yes, I found one by Samsung company but that had dual SIM slot but both for GSM. I had a bitter experience of hunting phone in several outlets. I also tried in Motorolla’s stall, just front of the gate in the first floor, but the sales person said it’s not possible to buy CDMA in Singapore, coz. in Singapore, they have only GSM network. I surprised, although Singapore is a hub for shopping in Asia, especially for electronics gadgets. I decided to give up and hangout around rather than finding camera and I did the same. I visited China town, City hall, Merlion (mascot of Singapore), The Civilian War Memorial (dedicated to the civilians who lost their lives in the World War II, during the Japanese occupation) etc. 

A famous church in Singapore.

World's heighest rollercoster in inset.

Cheng and me, Merlion in the background.

Although, it was short stay, it was a great lifetime experience to me. Thank you Mr. Cheng for being all the time to walk around Singapore.

War memorial in Singapore.

China Town in Singapore.

Thursday, February 5, 2009

Bagalamukhi Paintings

It's an Indian paintings.

Lab MT - Falling down more than 20 times while learning ski

Day before yesterday I went to ski with entire members of our lab to a ski resort called Oak Valley. We skied for 8 hours including night skiing. Now I am feeling pain all over my body. I fall down more than 20 times. By mistake, I didn’t lock my shoes, so it’s slightly loose that is the reason why I fall down several times. However, it’s a nice experience. I enjoyed a lot. I am worried now not because I have pain in my body but I have to go to Australia for presentation, I didn't prepare for my presentation.

Kazi, Jonayed (Bangaladesh), me, Prof. and doughter, Dawun (Korea), Farruh (Uzbekisthan) and Deoksu (Korea) from left to right

Deoksu, Kazi, me, Key young, Farruh and Jonayed

Deoksu, me and Farruh