A New beginning coming to an end

Searching for information in online database, goggling through the web, learning how to use network simulator, writing and hours of simulation.

I Like to Cite

I found a website which offers a free online service to keep track your academic papers. One unique features it allows to paste the url of the document and it will automatically extract all the important information such as authors and title for your safe reference. In addition, it allows to search academic papers based on tags which have been labeled by other users. The website can be found here -> http://www.citeulike.org/.

New simulatior

I have changed to a new simulator which is supposed to be easier and user friendly. The end.

Stuck again

I'm stuck in programming how transmit a packet which has been pick out by the scheduler. At that moment, the mobile device is already disconected from the base station. What shall I do with the packet which has no destination ( the mobile device is connecting to other base station). According to FMIPv6, the packet would be reroute to new base station. For simplicity, I just drop the packets or placed in a queue until I figure out on how to reroute the packet to the new base station.

Spot the Difference

1. Weighted Round Robin

2. Drop tail queue

Both of them have the same:-

• Buffer size
• Output link bandwidth

However, the implementation still have some flaws. Still in progress...

XGraph

The above graph shows the throughput at CBR receivers. A total of six traffic generators and and six receiver was used for the simulation. Three out of six application managed to received with the average of 55kbps which has been buffered in queue that has higher weight. The other three receivers did not receive any packets since most of the packets are drop. The packets are drop at the queue which has lower weight. In addition, there is a bottleneck link between the transmitter and the receiver which cause the packets to queued up in the buffer before it is schedule to transmit. The graph was plotted using Xgraph 12.1.

Six plus six

A MIRAI-SF Animator showing a simulation scenario which consists of six packet generators and six packet receiver.

Wired Network

The above screenshots are MIRAI-SF animator simulating the wired network. I'm testing my source code within the wired network.Please observed the bottleneck link between rt2 and sw2. The blue bar represents the packet drops when the buffer is full.

No Transmission

I was trying to simulate packet transmission without using the wifi accees point in the FMIPv6 simulation to test Weighted round robin packet scheduler. The result was the mobile node did not receive any packets from the correspondent node. I suspect this got to with the softradio class which handle the switching between 3G node b and wifi access point.I found WRR packet scheduler only good for constant size packet.

IPv6 Addressing

I reviewed some concepts on IPv6 Addressing so that I can make changes to Mirai-SF network simulator MNDL simulation script. I refer to Computer Networking (A Top Down Approach Featuring the Itnernet) by Keith W Ross & James F Kurose (Author) and the TCP/IP Guide website on IPv6 addressing topic. MIRAI-SF network simulator MNDL script uses real IPv6 addressing and subnetting to create topology of network.

Screenshot of an Animator

A screenshot of a default simulation MNDL script for FMIPv6 using MIRAI-SF network simulator version 3.1. This is similar to NAM for NS which animates the trace file of a simulation. The wired links have higher bandwidth than wireless link. As a reuslt, the mobile device received less packets than being sent by the correspondent node.

Duration of the Traffic Source

I made some changes to the MNDL simulation script. The duration of the traffic source has been increased since I noticed earlier that the receiving node did not receive any packets during the simulation run. In addition, I added a method to drop packet whenever the buffer is full.

MIRAI-SF4.2 is available now

I just visited the MIRAI-SF website and found out that there is a new release of MIRAI-SF4.2 network simulator. You need to register your particulara and it can be downloaded at here.

Configuring Simulation

Yesterday, I spent the whole day configuring the simulation script. In MIRAI=SF network simulator it is called a MNDL script. In every network simulation, it has a topology of network node. Each node consists of communication stack which is similar to OSI layers. ns network simulator uses TCL script to configure the simulation scenario.

Today,I just found out there is a problem with packet classification. I already make some changes and added few conditions that I did not covered last time.

Basic concept

I just found out that my text book for computer networking contains all the basic concept for packet scheduling and all the different type of delay definition. I wish I had refer to this book earlier. Arghhh!

Redo and make changes

The packet scheduler that coded by me is wrong. I have wrong idea of how the packet scheduler works. What I need to now is to refer to some reference to polish my understanding of a packet scheduler and basic network.

update on 08/12/2006:

I only have to change the a scheduler process code which only activate for a duration of time.The scheduler have an array list of which queue need to be serve. Every loop the scheduler will remove packet from a different packet. In short, it term of packet scheduler code not many changes I have to make. My code is not yet complicated. There is still room for improvement. However I still need worry about:-

1) The code for traffic generator that simulates background traffic.
2) I have not start on working congestion control.
3) I need to add some behaviour like dropping packet for the packet scheduler.

Scheduler is like a traffic light on the intersection and array list is a procedural list for the traffic light to signal a green light for each of the intersection in clockwise rotation.

How to monitor each other progress?

Last night, Kimin and I had a mutual agreement to monitor each other progress in our final project. Since the year 2007 is around the corner, we agreed to use the blog as a medium to monitor our project's progress. We hope through this method it will boost our motivation to finish off the project as soon as possible. Let see how the pact (i.e a new word that I learned to today from Kimin) will turn out. Click here to check out Kimin's UHF RFID Tag Antenna Design Blog.

Malam kelmarin, saya dan Kimin telah berjanji untuk memantau kemajuan projek masing-masing agar kami dapat menyelesaikan projek kami hi hujung tahnun ini. Kami telah berpakat untuk mencatat segala kemajuan di dalam blog untuk setiap minggu. Kami berharap dengan adanya pendekatan sebegini dapat memberi sedikit motivasi kepada diri masing-masing.

Rate Queuing

I already coded a simple packet scheduler with rate based queuing. However, there is still room for improvement due to some flaws in the code that I did not notice. In the RFC 4594 gave a analogy of rate based queuing.

a rate-based queuing system is a combination of a set ofqueues and a scheduler that empties each at a specified rate. An example of a rate-based queuing system is a road intersection with a stoplight. The stoplight acts as a scheduler, giving each lane a certain opportunity to pass traffic through the intersection.

Saya telah menprogramkan 'packet scheduler' yang mempunyai 'rate-based queuing'. Walau bagaimanapun program tersebut boleh diperbaiki kerana masih terdapat kesalahan yang belum dikenal pasti. Di dalam dokumen standard RFC 4594, memberi satu contoh tentang 'rate-based queuing' seperti tercatat di atas. 'Scheduer' digambarkan sebagai sebuah lampu isyarat yang memberi isyarat kepada setiap persimpangan jalan.

Top Ten Errors in Java

I found an article on Top Ten Errors Java Programmers Make in www.javacoffeebreak.com. The author lists the top ten the Java programmers make during coding.The number one mistake is Null pointers.I agreed with the author because I always get the NullPointerException during source code compilation.

Seperti tercatit di atas, saya juga sering mengalami kesilapan NullPointerException. Menurut penulis aritkel itu, adalah satu tanggungjawab 'programmer' untuk memastikan aturcara program bebas dari kesilapan Null Pointer ini.

How to Schedule a Process?

I would like to code so that a packet scheduler can dequeue between two queues. The scheduler must dequeue packet from first at constant interval time. In between those interval, I would like the scheduler to dequeue from the second queue.

I know that most network simulator such as NS-2 and other kind of simulators implement the scheduling method. So I going to implement one in MIRAI-SF network simulator. I did manage to implement where there is one queue. Right now, I'm scratching my head to implement the scheduler with two queues.. Blur

'Packet Scheduler' boleh ibaratkan sebagai seorang polis trafik di jalan yang mempunyai tiga laluan kemudian menjadi satu laluan. Setiap laluan mempunyai tahap kepentingan masing-masing. Sebagai contoh, laluan pertama ada khas untuk kenderaan yg bergerak laju yang biasa digunakan oleh Orang Kaya dan ambulan. Laluan kedua pula biasa digunakan kenderaan yg bergerak pada kelajuan biasa. Laluan ketiga pula digunakan oleh kenderaan yang dipandu oleh orang tua. Tugas 'polis trafik' ini memberi keutamaaan laluan pertama agar kenderaan itu sampai pada destinasi tepat pada waktunya. Jika tidak, kesesakan lalu lintas akan berlaku di laluan pertama dan menyebabkan kenderaan seperti ambulan lambat sampai ke hospital. Sebenarnya, packet itu adalah kenderaan dan scheduler tu adalah polis.