roman10
From the monthly archives: November 2011
This is a follow up of the previous post IP/TCP/UDP Checksum Calculation part 1 theory, and part 2 implementation.
This post gives an example using libnetfiler_queue library and the checksum code we implemented in part 2 to illustrate how to use the checksum code and verify that our code [...]
This is a follow up of the previous post, how to calculate IP/TCP/UDP checksum part 1 — theory.
IP Header Checksum Calculation Implementation
To calculate the IP checksum, one can use the code below,
/* set ip checksum of a given ip header*/
void compute_ip_checksum(struct iphdr* iphdrp){
iphdrp->check = 0; [...]
This is the first part of How to Calculate IP/TCP/UDP Checksum. The 2 parts followed are Part 2 Implementation and Part 3 Usage Example and Validation.
This part focuses on the algorithms. We’ll go through IP/TCP/UDP one by one.
IP Header Checksum Calculation
IP checksum is a 16-bit field in IP [...]
This is a follow up post of the Android UDP Client and Server communication programming. TCP and UDP are the two main transport layer protocols used in today’s Internet. TCP aims to provide connection-oriented, reliable end-to-end communication service.
Similar to UDP, TCP programming in Android also uses the APIs provided in java.net [...]
UDP and TCP are the two main transport protocols used in today’s Internet. This post illustrates how to program UDP client and server in Android.
Android UDP communication uses the APIs provided in java.net package, which are also available in Java standard edition etc.
To program a UDP server, one can use the [...]
Android has made video recording very simply by providing a few high level classes, including Camera, SurfaceView and MediaRecorder. This tutorial illustrates the Video Recording API by providing a workable example as shown in the screenshots.
Figure 1. Screenshots of Android Video Capturing Sample Program
The Camera class allows us to [...]
Please jump to “0. Android NDK” if you want pure technical stuff; please jump to end of the post to download the sample code if you want to figure out everything yourself.
Recently I am doing a project that decodes a video using ffmpeg and render it on Android using Bitmap. At [...]
Please read the previous post here first to get some background information about RED.
0. Download ns2, Compile it and Install it.
This is a preparation step. It’s not the focus of this post, please refer to reference 1 for details. Note that since we’re going to modify NS2, we’ll need [...]
1. TCP and its Algorithms (Slow-Start, Congestion Avoidance, Fast Retransmit and Fast Recovery)
TCP is a complex transport layer protocol containing four interwined algorithms: Slow-start, congestion avoidance, fast retransmit and fast recovery.
In Slow-start phase, TCP increases the congestion window each time an acknowledgement is received, by number of packets acknowledged. This strategy [...]
1. Why Active Queue Management (AQM) Mechanism
Network bandwidth is shared by users. Users want to get as much bandwidth as possible. However, there’s always limited bandwidth. When the bandwidth cannot satisfy what everyone is trying to get, congestion might occur. That’s why there’re congestion avoidance algorithms implemented in TCP at the users’ end. [...]
40% Discount on My Book — Android NDK Cookbook
Android NDK Cookbook ebook 40% discount with promotion code MREANC40 at Packt Publishing The promotion code is valid until 15th June.Categories
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