How to receive a million packets per second 16 Jun Tweet Last week during a casual conversation I overheard a colleague saying:
Understanding how data is transferred via the network will help you to improve performance through tuning, troubleshooting, or introduction to a new technology. This article will describe the overall operation scheme of the network stack based on data flow and control flow in Linux OS and the hardware layer.
However, here we will describe them as one. Connection-oriented First, a connection is made between two endpoints local and remote and then data is transferred.
Bidirectional Byte Stream Bidirectional data communication is made by using byte stream. In-order Delivery A receiver receives data in the order of sending data from a sender. For that, the order of data is required. To mark the order, bit integer data type is used.
Therefore, the sender TCP buffers unacknowledged data from the receiver. Flow Control A sender sends as much data as a receiver can afford. A receiver sends the maximum number of bytes that it can receive unused buffer size, receive window to the sender.
The sender sends as much data as the size of bytes that the receiver's receive window allows.
Congestion Control The congestion window is used separately from the receive window to prevent network congestion by limiting the volume of data flowing in the network. Different from flow control, congestion control is implemented by the sender only.
Data Transmission As indicated by its name, a network stack has many layers. The following Figure 1 shows the layer types.
There are several layers and the layers are briefly classified into three areas: The user area and the kernel area are called "host" to distinguish them from the device area. It is a more accurate term than the commonly used "LAN card".
Let's take a look at the user area. First, the application creates data to send the "User data" box in Figure 1 and then calls the write system call to send the data. Assume that the socket fd in Figure 1 has been already created.
When the system call is called, the area is switched to the kernel area. POSIX-series operating systems including Linux and Unix expose the socket to the application by using a file descriptor.
The file layer executes a simple examination and calls the socket function by using the socket structure connected to the file structure. The kernel socket has two buffers.
One is the send socket buffer for sending; And the other is the receive socket buffer for receiving. When the write system call is called, the data in the user area is copied to the kernel memory and then added to the end of the send socket buffer.TRAFFIC CONTROL SYSTEM USING RASPBERRY-PI Shabbir Bhusari1, SumitPatil2, Mandar Kalbhor3 Traffic Control, Raspberry Pi, Image Processing, VehicleCounting,OpenCV Real Time Traffic Light Control Using Image Processing" Vol.
2, No. March. Raspberry pi,Webpage. The first measurement system simulates data provided by image processing: upstream traffic flow of each link, the simulated queue from each link, the simulated occupancy of each pertinent zone in the inner junction are given each second to the control system.
Image processing is a better solution to control the state change of the traffic light. It shows that it can decrease the traffic congestion and avoids the time being wasted by a green light on an empty road.
The first measurement system simulates data provided by image processing: upstream traffic flow of each link, the simulated queue from each link, the simulated occupancy of each pertinent zone in the inner junction are given each second to the control system.
This is the Turner-Fairbank Highway Research Center. View Table of Contents. FOREWORD. The objective of the third edition of the Traffic Detector Handbook is to provide a comprehensive reference document to aid the practicing traffic engineer, planner, or technician in selecting, designing, installing, and maintaining traffic sensors for signalized intersections and freeways.
Most modern intersections are designed to use vehicle detection at the stop bars and on the intersection approaches. There are a variety of ways to do this, including inductive loops, microwave radar and video detection (image processing/computer vision).