Linux Multicast FAQ 10-May-1995 Disclaimer - I make no guarantees of the accuracy of any of this. There are people out there who know much more about it than I do; I'm just collecting information. See also http://www.cs.virginia.edu/~mke2e/multicast.html Index Q1. What is multicast anyway? Q2. What can one do with multicast? Q3. What versions of Linux support multicast ? Q4. How can I find out more about mbone ? Q5. How can I connect my local subnet to the global mbone ? Q5a. Does mrouted exist for linux? Q6. What do I need to do to implement multicast in Linux? Q7. What conferencing tools are available for Linux, and where can I get them? Q8. What stops multicast saturating the planet with video junkmail? ============================================================================ Question 1. What is multicast anyway? Loosely speaking, multicast is a scheme for using ip addresses 224.0.0.0 through 239.255.255.255 to send the same data to several machines simultaneously. Addresses between 224.0.0.0 and 224.0.0.255 are reserved for maintenance protocols and aren't forwarded off your subnet. RFC-1060 assigns some ip addresses, which may be found by typing "host -l mcast.net". See http://andrew.triumf.ca/pub/mbone/mcast-hosts.txt Question 2. What can one do with multicast? One can install the mbone conferencing tools and listen in to mbone broadcasts. There are other uses too, such as a proposed accurate time-of-day multicast. Question 3. What versions of Linux support multicast ? Kernels greater than about 1.1.80. Question 4. How can I find out more about mbone ? ftp://ftp.isi.edu/mbone/faq.txt http://www.research.att.com/mbone-faq.html ftp://ee.lbl.gov/conferencing http://www.unige.ch/seinf/mbone.html http://andrew.triumf.ca/pub/mbone There are mailing lists for mbone. See one of the general FAQs above on how to subscribe to the correct list for your area. There is a linux mailing list in the UK, linux-multicast@www.linux.org.uk. To subscribe send mail to linux-multicast-request@www.linux.org.uk Question 5. How can I connect my local subnet to the global mbone ? You need a multicast capable router, maybe Cisco or Proteon, or a system such as Sun or SGI running mrouted. Read the general mbone FAQs. mrouted is coming for Linux 1.3.22 (credits Alan Cox). It wasn't there before as the mrouted code was heavily embedded in the BSD kernel. The mrouted version for SunOS tends to be the most recent. Please obtain at least version 3.3 (with pruning). Latest is now 3.8 - don't install 3.5 Question 5a. Does mrouted exist for linux? James MacKinnon : source and binaries for mrouted-3.81 (didn't hack out the snmp support though) are available in: ftp://ftp.phys.ualberta.ca/pub/linux/ in the file: mrouted-3.81-linux.tgz no mods to /usr/include/... files are necessary (the netinet includes are provided locally). Either use the precompiled binaries or re-build as you wish. I have it running on linux kernels v1.3.53 and v1.3.57 "Amancio Hasty Jr." said: You can install FreeBSD on a small partition and still use your linux ip multicast apps . And if you have problems with running linux apps on FreeBSD just send me a note. Question 6. What do I need to do to implement multicast in Linux? Build a kernel with MULTICAST enabled. Do "route add 224.0.0.0 netmask 240.0.0.0 dev eth0" . (Thanks, Alan) Current net-tools route should be doing it as a net route implicitly. "route add -net 224.0.0.0 netmask 240.0.0.0 dev eth0" should work for all cases (older versions). (You may need to relink route with the later kernel includes.) ping -t 1 -c 2 224.0.0.1 should show up your local multicast-capable hosts. Question 7. What conferencing tools are available for Linux, and where can I get them? ivs - INRIA Videoconferencing tool 3.* binary Receives ivs broadcasts from other platforms. Supports sound using /dev/audio and /dev/mixer. Allows audio transmission. nv - Video tool from Xerox PARC. Supports X11 grab and FAST ScreenMachine II frame grabber. Needs libtcl, libtk. nv3.3b+smII.linux.bin.tar.gz Linux port by Frank Mueller vic - Video Conference tool from LBL. Needs libBLT, libtcl, libtk. Koji OKAMURA's vic binary requires -N and -d arguments, eg. vic -N user -d :0.0 remotehost/port sd - LBL session directory. Easiest way to launch other tools. sd listens to multicast messages on the net and builds a list of available conferences. Just click on "open". vat - LBL audio tool. 1st release, some problems with multicast, volume control not working. wb - LBL whiteboard tool. Allows conference participants to draw on a common object-oriented graphic window. Objects may be moved or erased without affecting objects underneath. Allows an automatic slideshow of short PostScript files (default less than 32k, settable with "-P" option or X resource wb.MaxPostScriptSize), plus import of plain text. sd_listen - Mbone session directory; listens for multicasts of addresses, descrptions of mbone broadcasts. Compatible with LBL "sd". nevot - Networking audio. Source available; needs to be ported. Misc. URLs: http://www.cs.virginia.edu/~mke2e/multicast.html Linux Multicast Homepage ftp://ftp.funet.fi/pub/unix/networking/multicast/LINUX/ file://gaia.cs.umass.edu/pub/hgschulz/nevot/ ftp://ftp.jain.ad.jp/pub/linux/ Koji OKAMURA - nv and vic http://www.inria.fr/rodeo/ivs.html - INRIA Videoconferencing System ftp://ee.lbl.gov/conferencing - LBL site http://www.hrz.uni-giessen.de/~l018/nig.html - nv with SMII (Frank Mueller) Question 8. What stops multicast saturating the planet with video junkmail? A (1). The TTL parameter. Use it! Read the mbone FAQs. Use pruning. A (2). Bandwidth limits on video (default 128kbps). A (3). Not much. A (4). Severe flaming on the rem-conf mailing list. Linux Multicast FAQ by Andrew Daviel 17-May-1995 updated 7-Dec-1995 http://andrew.triumf.ca/~andrew This list is compiled from information on the mbone@isi.edu mailing list and the comp.os.linux.networking newsgroup, plus the product of some web surfing. I don't guarantee to see all questions on the newsgroup. Pleas email me with contributions and corrections at Andrew Daviel This FAQ should be available on http://andrew.triumf.ca/pub/linux/multicast-FAQ --- To read the page with Bulgarian translation - http://www.fatcow.com/edu/multicast-faq-bl (translated October 2011)