| |
| <!DOCTYPE html> |
| <html lang="en"> |
| <head> |
| <meta charset="utf-8"> |
| <meta name="viewport" content="width=device-width, initial-scale=1"> |
| <meta name="description" content=""> |
| <meta name="author" content=""> |
| |
| <title>PSA UDP Multicast / Apache Celix</title> |
| |
| |
| <link rel="icon" href="/assets/img/favicon.ico"> |
| |
| |
| <link href="/assets/css/bootstrap.min.css" rel="stylesheet"> |
| |
| |
| <link href="/assets/css/style.css" rel="stylesheet"> |
| |
| <style> |
| |
| |
| .card-body img { |
| max-width: 100%; |
| width: 100%; |
| height: auto; |
| } |
| |
| |
| .card-body img + em { |
| text-decoration: underline; |
| } |
| </style> |
| |
| |
| <script> |
| var _paq = window._paq = window._paq || []; |
| |
| _paq.push(['disableCookies']); |
| |
| _paq.push(['trackPageView']); |
| _paq.push(['enableLinkTracking']); |
| (function() { |
| var u="https://analytics.apache.org/"; |
| _paq.push(['setTrackerUrl', u+'matomo.php']); |
| _paq.push(['setSiteId', '9']); |
| var d=document, g=d.createElement('script'), s=d.getElementsByTagName('script')[0]; |
| g.async=true; g.src=u+'matomo.js'; s.parentNode.insertBefore(g,s); |
| })(); |
| </script> |
| |
| |
| </head> |
| <body class="light-grey"> |
| |
| <a href="https://github.com/apache/celix" class="github-ribbon"> |
| <img src="/assets/img/forkme_right_red_aa0000.png" alt="Fork me on GitHub"> |
| </a> |
| |
| |
| <nav class="navbar navbar-expand-lg navbar-dark bg-primary fixed-top"> |
| <div class="container"> |
| <a class="navbar-brand" href="/"> |
| <img src="/assets/img/celix-white.svg" height="40" class="d-inline-block align-top" alt="Celix Logo"> |
| </a> |
| <button class="navbar-toggler" type="button" data-toggle="collapse" data-target="#navbarResponsive" aria-controls="navbarResponsive" aria-expanded="false" aria-label="Toggle navigation"> |
| <span class="navbar-toggler-icon"></span> |
| </button> |
| <div class="collapse navbar-collapse" id="navbarResponsive"> |
| <ul class="navbar-nav ml-auto"> |
| <li class="nav-item"> |
| <a class="nav-link" href="/">Home</a> |
| </li> |
| <li class="nav-item"> |
| <a class="nav-link" href="/download.cgi">Download</a> |
| </li> |
| <li class="nav-item dropdown active"> |
| <a class="nav-link dropdown-toggle" href="#" id="ddDocs" role="button" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false"> |
| Docs |
| </a> |
| <div class="dropdown-menu" aria-labelledby="ddDocs"> |
| <a class="dropdown-item" href="/docs/2.4.0/docs.html">2.4.0 (latest)</a> |
| <a class="dropdown-item" href="/docs/2.3.0/docs.html">2.3.0</a> |
| <a class="dropdown-item" href="/docs/2.2.1/docs.html">2.2.1</a> |
| <a class="dropdown-item" href="/docs/2.1.0/docs.html">2.1.0</a> |
| </div> |
| </li> |
| <li class="nav-item dropdown"> |
| <a class="nav-link dropdown-toggle" href="#" id="ddContributing" role="button" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false"> |
| Contributing |
| </a> |
| <div class="dropdown-menu" aria-labelledby="ddContributing"> |
| <a class="dropdown-item" href="/contributing/youatcelix.html">You at Celix</a> |
| <a class="dropdown-item" href="/contributing/submitting-patches.html">Submitting patches</a> |
| <a class="dropdown-item" href="/contributing/source-and-builds.html">Source code and builds</a> |
| <hr> |
| <a class="dropdown-item" href="/contributing/releasing.html">Releasing</a> |
| <a class="dropdown-item" href="/contributing/volunteers.html">Volunteers</a> |
| <a class="dropdown-item" href="https://whimsy.apache.org/board/minutes/Celix.html">Board Reports</a> |
| </div> |
| </li> |
| <li class="nav-item dropdown"> |
| <a class="nav-link dropdown-toggle" href="#" id="ddSupport" role="button" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false"> |
| Support |
| </a> |
| <div class="dropdown-menu" aria-labelledby="ddSupport"> |
| <a class="dropdown-item" href="/support/mailing-list.html">Mailing Lists</a> |
| <a class="dropdown-item" href="/support/issue-tracking.html">Issue Tracking</a> |
| </div> |
| </li> |
| <li class="nav-item dropdown"> |
| <a class="nav-link dropdown-toggle" href="#" id="ddFoundation" role="button" data-toggle="dropdown" aria-haspopup="true" aria-expanded="false"> |
| ASF |
| </a> |
| <div class="dropdown-menu" aria-labelledby="ddFoundation"> |
| <a class="dropdown-item" href="https://www.apache.org/">ASF Home</a> |
| <a class="dropdown-item" href="https://www.apache.org/foundation/how-it-works.html">How it works</a> |
| <a class="dropdown-item" href="https://www.apache.org/licenses/">License</a> |
| <a class="dropdown-item" href="https://www.apache.org/foundation/sponsorship.html">Sponsorship</a> |
| <a class="dropdown-item" href="https://www.apache.org/foundation/thanks.html">Thanks</a> |
| <a class="dropdown-item" href="https://www.apache.org/security/">Security</a> |
| <a class="dropdown-item" href="https://www.apache.org/foundation/policies/conduct">Code of Conduct</a> |
| </div> |
| </li> |
| </ul> |
| </div> |
| </div> |
| </nav> |
| |
| |
| <div class="section"> |
| <div class="container"> |
| <div class="row py-4"> |
| <div class="col-sm-12 card"> |
| <div class="card-body pt-5"> |
| |
| |
| |
| |
| |
| |
| |
| |
| <a href="/docs/2.3.0/docs.html" title="back to documentation"><< back to documentation</a> |
| |
| |
| |
| <!-- |
| Licensed to the Apache Software Foundation (ASF) under one or more |
| contributor license agreements. See the NOTICE file distributed with |
| this work for additional information regarding copyright ownership. |
| The ASF licenses this file to You under the Apache License, Version 2.0 |
| (the "License"); you may not use this file except in compliance with |
| the License. You may obtain a copy of the License at |
| |
| http://www.apache.org/licenses/LICENSE-2.0 |
| |
| Unless required by applicable law or agreed to in writing, software |
| distributed under the License is distributed on an "AS IS" BASIS, |
| WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. |
| See the License for the specific language governing permissions and |
| limitations under the License. |
| --> |
| <h1 id="pubsub-admin-udp-multicast">PUBSUB-Admin UDP Multicast</h1> |
| <hr> |
| <h2 id="description">Description</h2> |
| <p>This description is particular for the UDP-Multicast PUB-SUB.</p> |
| <p>The UDP multicast pubsub admin is used to transfer user data transparent via UDP multicast. UDP packets can contain approximately<br> |
| 64kB . To overcome this limit the admin has a protocol on top of UDP which fragments the data to be send and these<br> |
| fragments are reassembled at the reception side.</p> |
| <h3 id="ip-addresses">IP Addresses</h3> |
| <p>To use UDP-multicast 2 IP addresses are needed:</p> |
| <ol> |
| <li>IP address which is bound to an (ethernet) interface</li> |
| <li>The multicast address (in the range 224.X.X.X - 239.X.X.X)</li> |
| </ol> |
| <p>When the PubSubAdmin starts it determines the bound IP address. This is done in the order:</p> |
| <ol> |
| <li>The first IP number bound to the interface which is set by the “PSA_INTERFACE” property</li> |
| <li>The interfaces are iterated and the first IP number found is used. (typically this is 127.0.0.1 (localhost)</li> |
| </ol> |
| <p>The multicast IP address is determined in the order:</p> |
| <ol> |
| <li>If the <code>PSA_IP</code> property is defined, this IP will be used as multicast.</li> |
| <li>If the <code>PSA_MC_PREFIX</code> property, is defined, this property is used as the first 2 numbers of the multicast address extended with the last 2 numbers of the bound IP.</li> |
| <li>If the <code>PSA_MC_PREFIX</code> property is not defined <code>224.100</code> is used.</li> |
| </ol> |
| <h3 id="discovery">Discovery</h3> |
| <p>When a publisher request for a topic a TopicSender is created by a ServiceFactory. This TopicSender uses the multicast address as described above with a random chosen portnumber. The combination of the multicast-IP address with the portnumber and protocol(udp) is the endpoint.<br> |
| This endpoint is published by the PubSubDiscovery within its topic in ETCD (i.e. udp://224.100.10.20:40123).</p> |
| <p>A subscriber, interested in the topic, is informed by the the TopologyManager that there is a new endpoint. The TopicReceiver at the subscriber side creates a listening socket based on this endpoint.</p> |
| <p>Now a data-connection is created and data send by the publisher will be received by the subscriber.</p> |
| <hr> |
| <h2 id="properties">Properties</h2> |
| <table border="1"> |
| <tr><th>Property</th><th>Description</th></tr> |
| <tr><td>PSA_INTERFACE</td><td>Interface which has to be used for multicast communication</td></tr> |
| <tr><td>PSA_IP</td><td>Multicast IP address used by the bundle</td></tr> |
| <tr><td>PSA_MC_PREFIX</td><td>First 2 digits of the MC IP address </td></tr> |
| </table> |
| <hr> |
| <h2 id="shortcomings">Shortcomings</h2> |
| <ol> |
| <li>Per topic a random portnr is used for creating an endpoint. It is theoretical possible that for 2 topic the same endpoint is created.</li> |
| <li>For every message a 32 bit random message ID is generated to discriminate segments of different messages which could be sent at the same time. It is theoretically possible that there are 2 equal message ID’s at the same time. But since the message ID is valid only during the transmission of a message (maximum some milliseconds with large messages) this is not very plausible.</li> |
| <li>When sending large messages, these messages are segmented and sent after each other. This could cause UDP-buffer overflows in the kernel. A solution could be to add a delay between sending of the segments but this will introduce extra latency.</li> |
| <li>A Hash is created, using the message definition, to identify the message type. When 2 messages generate the same hash something will terribly go wrong. A check should be added to prevent this (or another way to identify the message type). This problem is also valid for the other admins.</li> |
| </ol> |
| |
| |
| </div> |
| </div> |
| </div> |
| </div> |
| </div> |
| |
| |
| <footer class="py-3 bg-secondary"> |
| <div class="container"> |
| <div class="row"> |
| <div class="col-md-8 text-center"> |
| <p class="m-0 text-white"> |
| Copyright © 2024 The Apache Software Foundation, Licensed under |
| the <a href="https://www.apache.org/licenses/LICENSE-2.0">Apache License, Version 2.0</a>. |
| <br> |
| Apache Celix, Celix, Apache, the Apache feather logo and the Apache Celix logo are trademarks of The Apache Software Foundation. |
| </p> |
| </div> |
| <div class="col-md-4 text-center"> |
| <a href="https://www.apache.org/events/current-event.html" target="_blank"> |
| <img src="https://www.apache.org/events/current-event-234x60.png" title="Apache Event" width="234" height="60" border="0"> |
| </a> |
| </div> |
| </div> |
| </div> |
| </footer> |
| |
| |
| <script src="/assets/js/jquery.min.js"></script> |
| <script src="/assets/js/bootstrap.bundle.min.js"></script> |
| |
| |
| </body> |
| </html> |