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Ahmed Saeed: I am a Postdoc @MIT_CSAIL, Ph.D @GeorgiaTech, Husband, Father, Egyptian, Human. I make networks more predicable and servers more scalable (he/him).

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Sharing the Network: From Circuit Switching to Packet Switching (The Hitchhiker's Guide to Computer Networks)

October 08, 2020

Prelude ... From Circuit Switching to Packet Switching The simplest approach for two people to communicate over long distances is to connect them through a dedicate physical wire. However, how would we scale that model to a million people that individually want to be able to communicate with everyone else? One approach is to extend wires between all pairs of users, requiring hundreds of billions of wires. This is definitely not a good way to design a network. So what's wrong with that design? First, it is unlikely that every single person in that network will want to talk to everyone else at the same time. This means that we can use fewer wires. Second, not all connections are created equal. Longer wires cost a lot more money than short ones. Our design should have short wires whenever possible. Also it will be nice if the cost of extending long wires is shared between multiple users at the same time. Let's revisit our connection strategy. Rather than extending wires betwe...

My PhD coping mechanism (or how speaking my mind out loud helps me maintain my sanity)

May 01, 2018

Getting a PhD can easily become a lonely where students get depressed, feel out of place, thrown away alone with a mild to a sever sense of the imposter syndrome. There is no wonder that "graduate students are more than six times as likely to experience depression and anxiety as compared to the general population" . Almost all my friends in graduate school face some sort of mental health struggle. This prompted me to write a post on my personal approach to dealing with my own issues and they all have to do with talking. Personally, I find it very hard to talk to strangers, so I focus all my talking to people I know. I talk to different people because defeating imposter syndrome, self doubt, angry thoughts, and most importantly the depression spiral requires multiple perspectives, especially with the highly logical PhD student. Talking with advisors One of the challenges of being a graduate student is feeling at loss when it comes to assessing my own progress, strength...

The Hitchhiker's Guide to Computer Networks

July 18, 2020

Introduction One of the few reliable things that didn't crumble under the pressure of quarantining and working from home is our digital infrastructure. It remains largely unaffected as we conduct most of our business activities online. This is no accident. It is the result of 40+ years of continuous research to make that infrastructure faster, cheaper, and more reliable. My goal writing this series is to shed some light on the different hidden aspects of our digital infrastructure. In doing so, I hope that I will help the reader get a behind the scene's view of what we take for granted when we are watching HD videos, buying our groceries online, and chatting online with people on the other side of the planet. A typical Internet user pays for their Internet and online services (Netflix, Amazon Prime, Spotify, iCloud) with some expectations of the quality of experience they will receive. Users also expect that the way they interact with the digital world will keep improving. Th...

The evolution of Internet routing

April 03, 2018

If you ask "how do I get a video from Netflix to my TV screen?" you will probably get a variety of answers depending on whom you ask. Here are a TL;DR of the answers you are most likely to get: the home setting answer "your access point gets the video from the Netflix over the Internet and sends it over wifi to your TV" the smart apps and video encoding answer "the Netflix app creates an HTTP request specifying your account and some chunks of the video you are about to watch and the Netflix server replies with HTTP responses that contain the chunks" the Internet Protocol (IP) answer "your smart TV creates packets addressed to the Netflix server by its IP address. Based on the IP address, the packets are first sent to the access point which sends it over fiber or telephone landlines to the Internet Service Provider (ISP), like AT&T, the ISP then sends it to other networks which eventually deliver it to Netflix (the ISP can also directly deliv...

Video on Demand: Part 1 (The Hitchhiker's Guide to Computer Networks)

August 03, 2020

Data from the 2019 Global Internet Phenomena Report Video is the dominant type of traffic on the Internet. In 2019, video on demand constituted 60% of the total global Internet traffic. The image to the right shows the huge gap between the bandwidth demand of video streaming and the second highest application which is web traffic (think email, blogs, and news). This means that if you are in the computer networks business, you are pretty much in the business of video delivery. So the biggest question here, what is the best way to deliver video? The "best" in this context can mean a couple of different things. It can mean delivering the best quality video for the user. Video quality does not only refer to whether a video is in HD or UHD but also whether it freezes and hangs or not. The "best" way to deliver video can also mean the most cost efficient way. If we can save 1% of the cost of delivering all videos on the Internet, we can save tens of millions of dollars i...

Extending wpa_supplicant for kernel mac80211 control

April 03, 2018

wpa_supplicant is a popular cross platform tool for wifi network configuration. On linux kernel, wpa_supplicant can use NetLink ( nl80211 ) to pass commands and arguments to the configuration API of IEEE 802.11 (cfg80211). In this post, I will go through the different edits needed to pass arguments from userspace to mac80211 through wpa_supplicant. I will use my work on WiFi augmentation which allows wpa_supplicant to configure mac80211 to control its medium access control behavior. wpa_supplicant has two main components: wpa_supplicant daemon and the wpa_cli client program. The edits I will present will be in both the daemon and the client. My edits assumes the existence of some functions in kernel that the user of wpa_supplicant is attempting to invoke. The edit starts with the wpa_cli (client) code. The wpa_cli code maintains an array of all commands it can process mapped to callback functions that should be executed on the invocation of that command. The array can be foun...

Sun Campus Ambassador - Alexandira University

November 12, 2008

It is finally official. Say Hello! to the new Sun Campus Ambassador(CA.). It has been 4 months now since I first heard of the position. It was the first day of Wikimania; I talked with the people at the Sun Microsystems booth. It turned out the one of them was the regional manager of Education and Research. He was the one that told me all about the CA position. It was really a long journey, CV sent, first phone interview, second phone interview and a lot of e-mails coming and going ever since. I hope that I’ll be able to do my job as it should be done- Of course I'll need your help to do that. I welcome feedback and at any time. I am really happy with the activities going all over our department and I hope that it could be of great help to everyone and that I would be a good part of what's going on. For any feedbacks or questions concerning the CA position or activities you are welcomed to comment here or send me an e-mail.

Getting over stone age of the internet: discovering agriculture and building homes

November 01, 2009

If you look at the current internet, giving its age and the type of problems it's facing, you can see clearly that we're still in the middle of, what I'd like to call it, the stone age of the internet. We're talking about a technology that's only 30 years old, it has yet a lot of potentials to be discovered and drawbacks and problems to be solved. The problem I want to expose here is privacy. I'd like to compare the real stone age (5000 years B.C.) to the internet stone age (1985 to 2009). The stone age: During the stone age humans lived in the forests and took cover in caves from the rain, they lived in tribes that shared the same interest and cared for each other's interests. Communication between those tribes was almost impossible and they probably fought over everything (territory, food, women, etc). They slept right there in the open thinking that they are well protected that way. Invented some traps and protection systems to protect them and maybe c...

Attaching a WiFi Dongle to an AR Drone 2.0 (a.k.a. Compiling Drivers for ARM Based Devices)

December 04, 2013

Correction (4/24/2014): for your driver to work the AR Drone 2.0 you have to compile the kernel version provided by Parrot which can be found here https://devzone.parrot.com/projects/show/oss-ardrone2 One of the down sides of "out of the box" AR Drone 2.0 is that you can't control multiple drones from the same machine. Another down side is that you can't attach USB devices except flash memories and some other predefined devices due to the limited nature of the busybox deployed on the drone. To over come the first down side without manipulating the WiFi configurations of the built-in WiFi card (i.e. you don't want to mess up your new drone), you will need to overcome the second problem (i.e. install a WiFi dongle and its driver manually). In this tutorial, I try to walk you through the steps to do just that. I assume that you are working a Linux machine (seriously we are not going to compile drivers on Windows). Ubuntu is preferable ! Because the Drone has a...

Sun SPOT

July 25, 2008

Have you ever dreamed of having a project that produced a chip that did something real, something that you can make then use in the real world, instead of the digital projects that come from wonderland were people use some switches to play a game! Well, I had that dream. I love to program chips to make stuff like telling me when someone turns the light on in some room and to react to it according to some program I've already put in it. Though our beloved FPGA can do a lot of really great stuff but it's programming is frustrating. VHDL is one great-extremely-low-level language and it can teach us a lot about digital design but again if I want something to use something in a robotics project would I choose VHDL over Java?! I guess not. Sun has done it people. A programmable device that could be programmed directly using J2ME technologies. With high processing power and a lot of cool features that could be put in real use easily, I think it's everything that a programmable boa...

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