Does Your Uplink Multicast?

knof asks: "It seems like the big ISPs want to waste bandwidth, because they don't support technologies like multicast, at least here in Germany. As far as I know the only way to get multicast access is to setup a feed to the MBone or to use the DFN (Deutsches ForschungsNetz) if you're a student, which I am not. Is it expensive or difficult for ISPs to make their networks multicast aware? How is the situation in other countries? And are there any ISPs in Germany which are Multicast friendly?" It would be interesting to know how much of the Internet is capable of multicasting. Even here in the US, I don't believe it's getting widely used. Is this changing?

Comments

Multicast

[Tuzanor]

over the internet, multicast is a pretty much a useless feature. A lot of the time it won't even work because a lot of routers have been configured to ignore multicast addresses to save space on the routing tables. If only early on they knew that streaming video/audio was coming...

Considering how many IPs are wasted for multicast, its really no wonder why we're at a shortage right now. Whoever sorted the current IP space needs to be shot in the HEAD (so that his brain may NEVER be brought back). 16 million IPs for loopback? excuse me? out of that whole block the only one that gets any use is 127.0.0.1

Those Class D and E spaces could have given us many usefull IPs...and now...useless.

Re:Multicast on an ISP is bad

[sparetiredesire]

Do you even know what "multicast" is? Multicast is more efficient for multi-party communication. If you sent seperate packets to each of K users you'd use K times the bandwidth on your outgoing link. This is what happens if you use unicast instead.

With multicast you send a single packet, and the network replicates it at the latest possible point. What would you propose as a more efficient means?

For all of us who are Multicast illiterate

[Mustang Matt]

A quick search on google revealed this great article!

Multicast Explanation

Multicasting, the MBone, et al.

[jd]

First, if you ask on the MBONE mailing list for a feed, they'll tell you to go to your ISP, and that if -they- don't support it, well, tough.

Then, if you go to your ISP, and you're VERY lucky, they'll tell you to go to the MBONE mailing list. Most ISPs I've talked to just tell you to go to hell.

The conclusion I came to is that the existing multicast structure that exists (which is all native PIM, or near enough) is controlled and run by a Royal Priesthood, and only The Worthy (and very rich) can pay a tithe great enough to appease the Net Gods.

(UUNET is a great example. Sure, they'll provide multicast! Provided you pay $10,000+, for a high-speed link. For the cheaper nodes? No f* way! Peasents don't deserve such technology!)

Given this attitude, can you SERIOUSLY wonder why the less-knowledgable view technology with suspicion? It's not exactly as though they're being encouraged to see it as a powerful friend.

Getting on with the question of "is it expensive?" The correct answer is "no - unless your admin charges $100,000 per character typed".

For those who want to convince their admins to enable multicasting, but wish to use less force than a Daisy Cutter, here are the simple instructions to set things up:

• Enable multicasting and multicast routing in the kernel. If you wish to use PIM, also enable PIM-1 and/or PIM-2.
  
• Recompile the kernel, install, and reboot.
  
• On reboot, you'll now see additional messages, informing you that multicast routing is present. You'll also see an protocol listed (IGMP), which is used for communicating group information between multicast sites.
  
• So far, so good. For most computers, all you need to is add the multicast group address to the routing table, like so: route add -net 224.0.0.0 netmask 240.0.0.0 dev eth0 (or whatever device you're using)
  
• To check that this is working, ping the network address like so: ping -c 2 224.0.0.1. All multicast-enabled computers on your LAN should respond, with their OWN address, not the multicast group address.
  
• On the machine to be used as a router, you need to do two more steps. You need to enable packet forwarding (which, if it's being used as a router, will already be done. DUH!)
  
• The router will also need EITHER multicast routing enabled in the router software (if the option exists), OR a software router such as PIMD, MROUTED, or GATED 5.0. (I strongly advise AGAINST GATED. It's closed-source, the development cycle was suspicious, the cost is phenominal, and it really does nothing that the other, free (in all senses) software can't do anyway.)
  

And that is it! The sum total of the arcane art of multicasting.

Those who are used to games are probably much more familiar with broadcasting, as very very few games use multicasting. Multicasting would be useful for games, as it would seriously reduce the network load, but as network games are typically server-based, rather than distributed, there's really nothing to multicast, right now.

The Internet backbone is, essentially, entirely multicast-ready. There is no "virtual" network of tunnels, any more, but rather one multicast cloud, which the ISP merely has to belong to. The main reasons ISPs don't join are as follows:

• There's very little software that uses it, so there's nothing to promote it with.
  
• There's next to zero information on it, making tech support a hazardous occupation for mom & pop ventures.
  
• There's very little demand for it, because most services which would be ideal over multicast (eg: streaming audio/video) is all done over unicast. There's therefore absolutely no incentive for users to look any further.
  
• It's impossible for advertisers and servers to exploit financially, as there's no means of telling how many people are accessing the service. There's ONE output stream, regardless of the number of people receiving.
  
• The Internet backbone providers aren't keen on Joe & Jane Q Public using multicasting, as there are very few multicast addresses available. The addressing (for IPv4, anyway) could not support an explosion of interest in multicasting.
  
• Cable companies are not going to provide a service which seriously competes with their own regular TV service. They may be stupid, but they're not crazy.
  
• Microsoft provides only a crippled multicast service with Windows (no multicast routing, and no multicast loopback), so software shops that gear to Microsoft OS' tend not to bother with it.
  
• Because multicasting is done over dynamic addresses, you can't filter it's content, making it utterly repugnant to virtually all governments.
  
• There are no certifications in multicast technology, making it a valueless skill for students or employees to learn. If it can't be quantified or evaluated, employers are generally uninterested.
  
• Multicasting is the Internet's last, best-kept secret. The moment the prawn industry cottons onto the fact that they can stream explicit video to many more people, for far less money on their part, in a way that cannot be blocked without blocking multicasting entirely, is the moment that the entire political, legal and religious scenes become irrelevent. (As if they weren't, already.) This would drive not so much as the final nail into the coffin of control, but it would throw in a 30-tonne stake for good measure.
  
  

  
  THESE are the reasons multicasting isn't in general, wide-spread use, not the cost (there isn't one), and not the complexity (there isn't any).