LG KP500 is working as a modem in Ubuntu!

Last few months I was missing the smooth internet of Ubuntu. I could not connect my LG Cookie mobile as a modem, so I had to stuck into XP. Today I logged into Ubuntu (9.04) without any hope and guess what, I am writing this post from Ubuntu.
I dont know how the mobile is connected as modem, may be I have installed some package earlier or may be because I have upgraded the mobile firmware.
But my mobile is detected as VX4400/VX6000 :P

maroof@marahmed:~$ lsusb
Bus 003 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
Bus 002 Device 003: ID 1004:6000 LG Electronics, Inc. VX4400/VX6000 Cellphone
Bus 002 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub
Bus 001 Device 001: ID 1d6b:0001 Linux Foundation 1.1 root hub

The packages you must need are wvdial and ppp (and may be your mobile driver. I guess I have installed the VX4400 driver, can't remember). This article says it all about configuration. Thanks BDOSN :D.

But still it didn't worked until I changed the DNS server IPs in /etc/ppp/resolve.conf file. I have used the OpenDNS IPs. You can use any free DNS server IP. But the internet speed seems slower :(. May have to tweak something. Good luck and happy browsing.

Now I think Greasemonkey is worthy

I got this link on lifehacker. Until yesterday I wondered why people are fan of greasemonkey. Now I know,

http://www.daniels.net.nz/2009/05/31/block-facebook-quizzes-from-your-news-feed/

My experience with Mint 6.0 xfce

A couple of weeks back in installed Linux mint in my already dual boot laptop (xp pro and Ubuntu 8.10) so it became triple boot. My XP was turtle fast, ubuntu was rabbit fast but i wanted something like kutta fast. so i went for the XFCE version. after installing i had very few chance to use it but during that time my experience wasn't very good. Most problems occurred with firefox. Sometimes the whole desktop was taken by the window hiding the taskbar, so i had to move to another desktop to do something. This was so annoying. At last I decided to remove it and stick to ubuntu (slow and steady wins the race :D). But that required to configure grub again. after a lot of searching i found that after login in to ubuntu,
$sudo grub-install '(hd0)'
is enough to replace the grub of mint. Then you can format the partition of mint with gparted or fdisk.

Installed Ubuntu 8.10

I have ordered the Ubuntu 8.10 CD online and it shipped within one month. WOW. I like everything free :P. I got the CD today evening and installed it by just clicking 3 times and writing 2 words and its marvelous.
I could have installed it months ago by downloading the iso image but the only fear in my mind was i wont be able to connect to the Internet through my phone modem, but surprisingly it not only worked right away but also connects to the Internet much quicker than in XP. The speed is also seems better (moner bhool :D).
I am overwhelmed !!

ha ha ha !! i didn't know

Double clicking on the tab bar of firefox (or other modern! browsers) !!!! :P

Buying digital camera in Bangladesh

I badly need a digital camera (but I dont know why, may be hudai).
My choice of compact digital cameras:
1. Panasonic Lumix DMC-TZ5 (for its zoom)
2. Canon PowerShot SD880 IS (for its excellent build and canon rocks)
3. Panasonic Lumix DMC-FX35 (for its wide lens and picture quality)
4. Canon PowerShot SD1100 IS (for its usability and value)
5. Canon PowerShot A590 IS (for its price and manual control)

Now I doubt if TZ5 is available in Bangladesh. The price may be much more higher. (my budget is less than 20000 Tk). So "No" vote to number one.
The second one is available and the price is about 26000 tk is Canon showroom. (have to check outside market). So "No" vote wins again.
I would be real happy if I can get the FX35 in local market (and also hope the price will be around 15000 Tk). I went to Bashundhara city today but could not check on Panasonic models as the market was about to close. If price difference is not much then I will go for the FX37.
The next option is SD1100. about 20000 Tk in shoroom and about 16000 Tk outside.
But I think I will choose A590 for its manual control and price (16000 Tk in showroom and 11000 Tk in outside), moreover I would like to use CHDK.

So the final "Ha" vote goes to
if available,
Panasonic Lumix DMC-FX35
else
Canon PowerShot A590 IS

Currently I am using my Sony Ericsson K550i with modded Super Cam driver. Images are not that much bad I guess (dont forget to vote :P).

AutoHotKey

I have been a novice to LifeHacker and everybody praises autohotkey there. The features are very much alluring to me. This is the tool I should make most use of. But alas I still could not make any use of it. If I can make use of it then everybody in my team will be so happy to get rid of sending the hidden numbers(!).
OK now here is the problem:
I have to copy a number from outlook (Ctrl+c)
Move to the next window (Alt+Tab)
Select the existing text of a input field (Ctrl+A)
Paste the copied text there (Ctrl+v)
Submit the form (Enter)
Take a screen shot of the window (Alt+PrintScreen)
Move back to Outlook (Alt+tab)
Press reply of the current mail (Ctrl+r)
Paste the screen shot from the clipboard (Ctrl+v)
Send the mail (Ctrl+Enter)
Done.:P

Now I have made a script to do that. But its not working. When i run the script the Windows behave strangely and sometimes I had to restart the computer :(. Here is my script,

^h::
Send ^c!{tab}^a^v{enter}!{PrintScreen}!{tab}^r^v^{enter}
return


I think I have to use more advanced tricks like checking if the window is active or not. Gedu amare bacha...

using ClearType

I have been using a LCD (i mean notebook) for about six months now, but have not heard about clear type font ! It is disabled in XP as default. Today i have found a article in pcworld about it and it makes me feel like "how stupid i was and bill gates still is:p"

forcing file save dialog in web browser

Sometimes we want to download a file from the web browser in stead of opening the contents of the file. If the file is a text or xml file then the default operation for the browser is to open it. Then we have to save the file by File->Save As. But what will happen if you want to invoke the save dialog box of the browser if you click the link. then you have to manually force the response header to tell the browser that this is not a known MIME type. you can set
content-type="application/octet-stream"

most of the browser will invoke the default save dialog. but the MSIE will not. halai poora foul. To invoke it from IE you have to add another varialble to the response header.
content-disposition="attachment"

these codes can be added from html. but most of the times the file is generated in the server end. so here is the java code which reads a
file from the server and passes the file contents to the client through the response header.

FacesContext fc = FacesContext.getNewInstance();
HttpServletResponse response = (

HttpServletResponse) fc.getExternalContext().getResponse();
OutputStream out = null;
InputStream in = null;

response.setContentType("application/x-mydownload");
response.setHeader("content-disposition=", "attachment;filename=\"myFile.txt\"");
try {
out = response.getOutputStream();
in = new FileInputStream(new File("inputfile.txt");
int i = 0;
while((i=in.read()) != -1) {
out.write((byte)i);
}
out.flush();
out.close();
fc.responseComplete(); //this is important
} catch (IOException e) {
System.out.println("exception occured: "+ e.getMessage());
} finally {
try{
if(in != null) {
in.close();
} catch(Exception ex) {
ex.printStackTrace();
}
}
}

HAWpaPER

Congestion Control: A study on BECN and MaxNet

Maroof Ahmed
100605077F
Department of Computer Science and Engineering (CSE)
Bangladesh University of Engineering and Technology (BUET)

Abstract
Congestion is one of the main barriers of proper utilization of packet switched network. Many important researches are done on congestion control mechanisms and still going on. In this paper I will try to focus on a couple of those researches. One is the Backward Explicit Congestion Notification (BECN) technique and the other one is the MaxNet, which ensures MaxMin fairness for reduced transmission rate of sources.

Introduction
Congestion is a very common thing in a packet switched network. The switches have to maintain some of queue for transmitting data. It has to process the data of the input queue and put them in proper the output queue. If the arrival rate at the input queue is more than the processing rate than congestion occurs.

In this paper at first I have discussed about what congestion is and what techniques can be followed to control congestion. Then I have studied about a popular congestion control mechanism BECN for ATM Network. And then another internet congestion control mechanism MaxNet is discussed. At last the concluding remarks are given.

What is Congestion?
Congestion is an important issue in packet-switched network. Congestion in the network may occur if the load on the network- the number of packets sent to the network- is greater than the capacity of the network- the number of packets a network can handle. Congestion control refers to the mechanisms and techniques to control the congestions and keep the load below the capacity [1].

Congestion Control Mechanisms
Congestion can be prevented, before it happens or it may be removed after it is detected. In general we can divide congestion control mechanism into two broad categories: open loop congestion control (prevention) and closed looped congestion control (removal).

In open loop congestion controls there are some popular policies that can be applied to prevent congestion before it happens. In these mechanisms congestion control is handled by either the source or the destination. Some policies are retransmission policy, window policy, acknowledgment policy, discarding policy, admission policy etc.

Closed loop congestion control mechanism try to alleviate congestion after it happens. Several mechanisms have been used by different protocols. Some popular mechanisms are back pressure, choke point, implicit signaling, explicit signaling, backward signaling, forward signaling etc.

Congestion Control for ATM Network
Congestion control in an ATM network is achieved by exchange of feedback information, carried by the data cell headers or resource management cells. Two feed back congestion control schemes have been proposed to the ATM Forum [2]: rate-based flow control and credit-based flow control.

Rate based schemes make use of feedback information from the network to adjust the rate that the source of each virtual connection (VC) can send cells to the network. BECN has advantages of fast response and fault tolerant against some end system abnormalities. Unlike FECN in which end system does most processing, BECN requires more switch hardware in order not only to generate BECN RM cells but also to filter the information on congestion to prevent over reactive in sending the RM cells.

Credit based flow control schemes operate a link-by-link control by using the information contained in a credit cell (a special RM cell) returned from the receiver to the sender on each link. It adjusts the number of cells to be sent to the receiver to meet the its ability to accept new cells hence avoiding buffer overflow.

BECN
Backward explicit congestion notification (BECN) is a congestion avoidance technique. BECN provides a simple and effective traffic management for ATM LAN.

In the LAN all the attached stations share a single resource the shared medium. to transmit, will a station contends for access to the shared medium via the medium excess (MAC) protocol . If the network is heavily loaded it will apply back pressure, through the (MAC) protocol, to stations requesting access. Once a station has successfully gained access to the shared and now you medium it may transmit it’s data without fear of causing network congestion since all stations can receive from at the data rate of the shared medium. The most frequently discussed traffic management approach in ATM network is to determine the traffic characteristics of the source and to allocate resources accordingly you when the call is admitted to the network. this approach is best suited if the traffic is voice or compressed video, that means traffic sources can be accurately characterized in advance of transmission.

In ATM switch there is a queue to hold the incoming traffic. If the queue exceeds a certain threshold value, then it sends congestion notification cells back to the sources of the virtual channels currently submitting traffic to it. The sources that receive BECN cells on a particular virtual channel, it must reduce its transmission rate for the indicated virtual channel. if no BECN cells are received on a particular virtual channel for a certain period of time a source may gradually restore its transmission rate on that virtual channel [3].

In the pictorial representation of BECN in ATM network (Fig 1) we can understand it better. The sources (S) are sending packets to transmitter (T). After a transmission delay the packets reach at receiver (R). If the length of the destination queue exceeds a certain threshold value the Filter (F) generates BECN cells. With no filtering one BECN cell is generated for each incoming cell and returned to the source transmitter of the incoming cell.

:p

Fig 1: BECN in ATM Network

MaxNet
In the Internet all the bottlenecked links contribute in the aggregated congestion signal that controls source rate. But MaxNet is such an architecture [5] that uses only one link, the most severely bottlenecked link, to control the source rate. It produces MaxMin fairness for sources with general homogeneous utility function.

In a MaxNet network, the congestion signal, qi, communicated to source i, is the maximum of all link prices on the end-to-end transmission path, as illustrated in Figure 2. Let pl be the price at link l and Li be the set of links source i uses. Then

qi = max{pl, l in Li}

:p

Fig 2: MaxNet logical feedback loop


The source, l, maximizing pl is termed the controlling link of the path. If multiple sources achieve the maximum, then one is selected arbitrarily. To determine qi, the packet format must include sufficient bits to communicate the complete congestion price. Each link replaces the congestion price in the packet with its own congestion price if its own price is larger than the one in the packet. The congestion signal is relayed back to the source by the destination host in acknowledgment packets.

The behavior of source i is governed by an explicit demand function, Di(•), such that its transmit rate is
xi = Di(qi)
for a congestion signal qi. The link Active Queue Management (AQM) algorithm is the well studied integrator process:
pl(t + 1) = pl(t) + (yl(t) - cl)ρl
where yl(t) = ∑i:lεLixi(t) is the aggregate arrival rate for link l at time t, ρl is the control gain and cl is the target capacity of link l which is related to its physical capacity Cl by the target utilization
0 < µl < cl =" µlCl."

Conclusion
In the conclusion I can say that more efficient and dedicated congestion mechanism should be developed for better use of network bandwidth. Further research can be done on multilayered and hybrid congestion control mechanisms. In the future I have plan to stimulate the congestion control mechanisms I have discussed here.

References
[1]Forouzan B.A., “Data Communications and Networking”, 7th ed, page-636
[2] Qin Li and Zheng Wang, “A Comparison Study of Congestion Control for ABR Service in ATM Networks”
[3] Peter Newman, “Backward Explicit Congestion Notification for ATM Local Area Networks”
[4] Frank Akujobi, Ioannis Lambadaris, Rupinder Makkar Nabil Seddigh, Biswajit Nandy, “BECN for Congestion Control in TCP/IP Networks: Study and Comparative Evaluation”
[5] Bartek Wydrowski, Moshe Zukerman, “MaxNet: A congestion control architecture”

life goes on

I am back after a long time. In beteen many things happened which changed my life. I got a job as Trainee Software Engineer in Technovista Ltd. I am going to office regularly now. But now I am sad about the road misshap, which claimed two valuable lives of our senior brothers and severly injured another. Though I have never met them, I feel sorry for them as they were very young and about to start their real life. This is so pathetic. May Allah almighty bless their souls.

SS7

Next day I have to face an interview (actually two) in huawei technologies. So I am studying for it. Yesterday I have studied about SS7. this is Control channel signaling system no 7.
The standard defines the procedures and protocol by which network elements in the public switched telephone network (PSTN) exchange information over a digital signaling network to effect wireless (cellular) and wireline call setup, routing and control. This signaling is used to control the calls between PCN (personal communication network) and PSTN (public service telecommunication network). it includes some nodes like ssp(service switching point), scp(service control point) and signal transfer point. the ss7 protocol layers contains 3 MTP (message transfer protocol), SCCP (signaling connection control protocol), TCAP (transaction capabilities application part), ISUP (integrated services digital network user part), OMAP (operations, maintenance and administration part) and MAP (mobile application part).
MTP level-1: same as physical layer of OSI
MTP level-2: same as data link layer of OSI
MTP level-3 + SCCP: same as network layer of OSI, SCCP dose global title translation
ISUP: presentation+session+transport layer of OSI, also part of application and network layer
tacap+omap+map: application layer of OSI


I hope this info will help my other friends who will also face the interview today and tomorrow.

Ready 1 2 3 Start

Hmm
Starting my blog. I am a very simple person from Bangladesh. I think you all know Bangladesh very well now as Prof Dr Yunus got the Nobel peace price this year. I am really proud of this fact.I want to do something for my country, but the circumstances dose not permit me to do whatever I want. So I am just a watcher of the flow of my life.