CODEWITHSUNDEEP
network-programmingmulticast
Jeremy Dunck
Jeremy Dunck

Reputation: 5894

Is 1-to-n multicast on the open internet reliable?

I'm a newbie at networking. I understand the concept of multicast, but was wondering if it's reliable on the open/public internet?

It seems like sort of an edge case that different backbones or ISPs might intentionally break to reduce router load or generally segment the network for practical high-use applications.

Is my fear reasonable?

P.S. Follow-up question here: Best tutorial for application multicasting?

Upvotes: 9

Views: 3694

Answers (6)

manh chau nguyen
manh chau nguyen

Reputation: 29

When you use youtube it's a communication between you and the server, it's unicast though it's over UDP like multicast. Multicast needs to use multicast routers. Internet is not especially provided with this type of routers. Moreover for the provider of video stream service he cannot charge the user because the configuration of the multicast-group is done in the routers, and he has no control of those routers in the Internet. Multicast is often used by the company for video-conferencing, this can be a service from the carrier service provider on his own Mbone or on the company own network.

Upvotes: 0

Steve-o
Steve-o

Reputation: 12866

Yeah, internet-scale multicast routing isn't really a solved problem, nor is there much progress from what I can tell.

The current recommended large scale solution is source-specific multicast, SSM, whereby as a client to request multicast traffic from specific sources rather than wide open listening. This still requires support from all intermediary routers and so may only become more practical with IPv6 which mandates multicast support as opposed to IPv4 which it is optional and frequently disabled.

http://en.wikipedia.org/wiki/Source-specific_multicast

Upvotes: 3

Robert S. Barnes
Robert S. Barnes

Reputation: 40558

It's as useful or reliable as UDP broadcast ( meaning useful on networks you have control of and as reliable as standard UDP ), but uses less resources on your network. If you're going to write a new broadcasting app use multicast instead.

Upvotes: 1

Jonathan
Jonathan

Reputation: 2192

Yeah, internet-scale multicast routing isn't really a solved problem, nor is there much progress from what I can tell.

Upvotes: 2

jackrabbit
jackrabbit

Reputation: 5653

Typically multicast refers to UDP multicast, which is not reliable.

Upvotes: 0

Martin v. Löwis
Martin v. Löwis

Reputation: 127447

IP multicast in the internet doesn't really work. From the Wikipedia article:

For both these reasons, and also reasons of economics, IP Multicast is not in general use in the commercial Internet.

People who desire to participate in the global IP multicast need to attach themselves to the MBONE. The Wikipedia article points out that application-level multicast infrastructures do work, e.g. IRC.

Upvotes: 5

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