crc - How long should a checksum be? -


tcp segments include checksum field of 16-bits , ip datagrams , udp packets. @ link layer, crc checksum 4 bits (for 802.3 , 802.4).

on extreme part of spectrum, computing parity bit might yield lot of false-positive, packet looks valid in fact not, because number of bits have been altered. on other hand, having 16-bit checksum when 4 bits suffice waste of memory/bandwidth/money.

how evaluate how many bits checksum should be?

ps: i have taken internet stack example, applies protocol/software really.

ps2: not sure forum use.

first, quick nomenclature correction - checksums , crcs 2 different approaches trying solve same problem: detect bit errors occurred during data transmission in noisy channels. in general crcs more powerful detecting errors @ expense of more complexity.

selecting right error detection scheme requires knowledge channel (e.g. error probability) , noise characteristics (e.g. impulsive, bursty). there papers out there problem analyzed in detail , guidance given in how select error detection method. suggest trying introductory presentation starting point:

http://www.ece.cmu.edu/~koopman/pubs/koopmancrcwebinar9may2012.pdf

it give better understanding of complexity of beautiful area , provide links other learning materials.


Comments

Post a Comment

Popular posts from this blog

jquery - How can I dynamically add a browser tab? -

since using iframes house external pages are, accounts "not preferred method" , disallowed sites (flickr, one), want dynamically generate browser tabs. e.g., when user submits form, want dynamically generate tab on browser in response submitted. e.g., might want add new tab url like: http://www.bigsurgarrapata.com/contact how in jquery? you want form target attribute action attribute. http://www.w3schools.com/tags/att_form_target.asp browsers have ultimate control on result of target attribute open new tab value of _blank. <form action="contact_submit.php" target="_blank" method="post">
Read more

keyboard - C++ GetAsyncKeyState alternative -

i using windows.h library's getasynckeystate function define key pushed on keyboard . here program returns int value of pushed key example. #include <iostream> #include <windows.h> using namespace std; int main (){ char i; for(i=8;i<190;i++){ if(getasynckeystate(i)== -32767){ cout<<int (i)<<endl; } } return 0; } but trying make opengl simple game , function appeared slow . there function not need cycle 180 times , if statement . thanks you're trying make opengl game, you're going use glfw. if that's case can away using glfwgetkey() such: if (glfwgetkey(glfw_key_up) == glfw_press) {...} if (glfwgetkey(glfw_key_down) == glfw_press) {...} that method nicely explained in tutorial 6 opengl-tutorial.org . should start first tutorial of beginners tutorials , later intermediate tutorials . if you're going make win32 window can listen wm_keydown or wm_keyup messages , virtua...
Read more

android - java.net.UnknownHostException(Unable to resolve host “URL”: No address associated with hostname) -

i developing app testing asp.net webservice in android.for simple webservice adding 2 numbers used.where numbers passed parameters.the result in dialogue.the webserver works in local. when application runs following result exception.i provided internet permission in manifest. java.net.unknownhostexception(unable resolve host “ http://url.com/ ”: no address associated hostname) my code given below main activity public static string rslt=""; /** called when activity first created. */ @override public void oncreate(bundle savedinstancestate) { super.oncreate(savedinstancestate); setcontentview(r.layout.activity_main); button b1=(button)findviewbyid(r.id.button1); final alertdialog ad=new alertdialog.builder(this).create(); b1.setonclicklistener(new onclicklistener() { @override public void onclick(view arg0) { // todo auto-generated method stub try { ...
Read more