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And what's the difference to broadcast, as in "broadcast adress x.x.x.255"? -- Abdull 08:38, 30 May 2005 (UTC)
Others can correct if I am wrong. I suppose you can think of multicast as a controlled or selective way of broadcasting over a wide area network (not just within the loca area network).
The broadcast address in a IP subnet (which x.x.x.255 is one example) can only be used to talk to all hosts the local broadcast domain (eg on a Ethernet LAN). This address maps directly to broadcast address like Ethernet's ff:ff:ff:ff:ff:ff address. Any packets to this address does not go outside the IP subnet.
This is in contrast to multicast, which allows sending packets to all nodes which subscribe to a particular multicast ip address/
--sdf
I'm currently writing on a chapter about how broadcasting (tv/radio stations) evolved to multicasting on the internet, also describing things like broadcast domains in a rather simple matter. I'd rewrite it to fit in this article if that's appreciated... -def
Routers are layer 3 devices that do not use spanning tree protocol.
1. Broadcast is a special multicast group. That is an all hosts group. In IPv4 there are actually two distinct forms of a broadcast address. The first is the limited local broadcast address of the form 255.255.255.255. When an IP datagram is sent to this destination, it is sent to all hosts on the local network. Datagrams to this destination will not be forwarded by a router. The second form is the directed broadcast address and the actual destination IP address depends on the network being referred to. Generally speaking we say that the network bits are set to the network address of the destination network and the host bits are set to all binary 1's. For for example, if you want to send a broadcast to all hosts on the 192.0.2.0/24 network, you set use the network bits to the network address, which in this case is just the first three octets (192.0.2) and the host bits, the last octet to 255, resulting in final destination address of 192.0.2.255. What would be the directed broadcast address for 192.0.2.0/25? 192.0.2.127.
2. I'm not sure what is meant by "pose as the sender" comment. I think they are essentially saying that if you let everyone in the group share the same key, then how do you know who the actual sender is. This is actually a separate problem and the original author I think is a little confused. That part needs to be ripped out and changed completely.
3. Web conferencing, instant messaging and IRC are hardly multicast technologies as the term multicast is commonly used. Again, I think someone is confused. Those need to be ripped out.
I will plan on doing a major update of this article shortly.
Multicast and the protocols surrounding multicast snooping and routing have been widely implemented in almost every network vendors equipment (accept for the more entry level devices). Multicast scales very well across the LAN/WAN (if the network supports it). A 5mbps MPEG stream could be sent to ever user on a network while only using 1 x 5mbps worth of bandwidth on any one link.
The reason that the internet doesn't support multicast (don't forget the MBONE) is not because of the protocols as much as it would require a massive configuration change and upgrades globally to implement the protocols. Which mean that every phone company, ISP, cable company, DSL and Cable modem manufacturer would have to be on board and agree to make the changes at the same time. Never going to happen.
That is why, in part, the Internet 2 came to be. The I2 (like the original internet) connects universities, k-12 and government agencies together on high bandwidth connections. The entire I2 is multicast enabled. This means that if a video is being multicast from NYU, someone can watch at Berkley, Bowling Green.
Multicast is also a term used on a Warcraft 3 map known as Defense of the Ancients. It is a passive spell used by the Ogre Magi that gives him a chance to, as the term suggests, multicast his spells onto targets.
If this is really information someone is looking for, it definitly belongs into a seperate entry.
I don't know what the intention of this edit is, but I think the original version made more sense. Revert? -- lynX 11:23, 24 January 2007 (UTC)
In the "Routing Schemes" figure, it's unclear whether the labels ("anycast", "broadcast", etc.) correspond to the illustration above or to the one below (below is what's intended, I believe). This is especially confusing if the figure is read from top to bottom. DRE 19:01, 30 May 2007 (UTC)
What is Windows Media Player multicast?-- Hhielscher 19:57, 17 November 2006 (UTC)
A friend proposed to me a simple multicast scheme in which the sender lists the unicast addresses of all destinations, and then intermediate routers split the packets. This eliminates the need to maintain receiver groups, at the expense of scalability - but it would be nice for small applications, on the order of a few dozen receivers. Can anyone refer me to research on this topic? Is there any reason this scheme is unworkable? Thanks. Dcoetzee 23:08, 13 October 2009 (UTC)
I was somewhat proud of recent edits to the first paragraph. I think it is a bit confusing to use the term Multicast addressing bolded or partially bolded in the lead as there is a separate article called Multicast address. Kbrose ( talk · contribs) has reverted this edit with the following comment: No, in networking it does not refer to the message but the addressing and routing process, perhaps in television it's the message. This is news to me. Anyone else have input or a reference on this? -- Kvng ( talk) 06:15, 26 August 2010 (UTC)
Here is a link for use of term in TV.
Kbrose ( talk) 16:19, 26 August 2010 (UTC)
The article suggests that IP multicast is used in internet television. This is doubtful, because Internet routers do not have enough state to remember the multicast information for all television channels (as explained later in the article). Perhaps it's just wishful thinking? — Preceding unsigned comment added by 173.66.54.78 ( talk) 17:23, 15 May 2012 (UTC)
They don’t have to remember all the channels; only the ones in actual use. Like for Usenet, there would be a directory function that maps user requests to multicast addresses. 71.38.204.2 ( talk) 18:26, 15 November 2017 (UTC)
"IP Multicast is widely deployed..." -- I think this is misleading, Fabiovh ( talk) 14:27, 23 February 2009 (UTC)
Would anybody care to add an overview of reliable multicast?
The article says: "... applying that to IP Multicast traffic would enable any of the receivers to pose as the sender. This is clearly unacceptable".
How is it possilbe to pose as the sender? Can anyone please explain why is it unacceptable in a language that will be understood by someone who's not a cryptography expert?-- Amir E. Aharoni 07:47, August 29, 2005 (UTC)
This article is lacking substantially in several parts. Just to point out something on multicast (group) security, what makes this all so challenging is finding efficient algorithms for (1) key management (for assuring confidentiality within dynamic groups) and (2) source authentication. What the paragraph about security issues is talking about is the problem of using symmetric keys for authentication which only allows GROUP authentication (vs. source authentication). The cited sentence should rather say something like "Use of symmetric keys for authentication would enable any of the receivers to IMPERSONATE the sender.". Asymmetric cryptography on the other hand in turn is too heavy for most applications (low computing power, high throughput, etc.).
TESLA is one of the promising new efficient algorithms for SOURCE authentication.
This article is not mentioning key managment algorithms whose most promising one is LKH (Logical Key Hierarchy).
Regards,
Michael Noisternig
The Web conferencing link is somewhat problematic. The term itself is inaccurate, and many mentioned technologies on that page do NOT multicast. Should we pick the technologies that actually multicast, and link them from here? -lynX
Sincerely I don't see any technology on that page using multicast in any way, so I removed it. -- SymlynX 06:24, 4 May 2006 (UTC)
Instant messaging is to a large amount a one-to-many medium. Even if people aren't engaging in chatrooms all the time, every change in presence status is sent to all "buddies". Yet none of the technologies used to that purpose implement any multicasting as they should, no surprise they either have to operate in a centralized way, which defeats privacy, or cannot scale properly when operating in a decentralized way. Don't you think this problematic fact needs mentioning in both documents? -lynX
The article mentions that IRC uses Multicast, but does it? I dont think it does, atleast not apparant to the end-user? More specifically mIRC uses only TCP, as far as I've seen.
The following discussion is closed. Please do not modify it. Subsequent comments should be made on the appropriate discussion page. No further edits should be made to this discussion.
There seems to be no objections to merging the IP multicast content from this page onto the separate IP Multicast entry. Given that there are two entries (and I think it makes sense for there to be two), it doesn't make sense for the majority of the content on IP multicast to be here. So I'm moving it. Stephen.frede 06:51, 11 July 2006 (UTC)
OK, move is done. I actually ended up rewriting most of the content. See IP Multicast. Stephen.frede 10:29, 11 July 2006 (UTC)
Someone who claims "IP Multicast, which do not count as multicasting, because they are actually local broadcasts" I would suggest has a bit of a problem understanding IP multicast and that is our problem, but I give up, go on calling it IRC multicast and other made up silliness if you insist, hopefully cluefull folks will drop over to the discussion page and will see that there is someone who arguably knows a thing or two about multicast takes issue with what you're writing. jtk Wed Nov 22 06:50:11 UTC 2006
What is the status of this merge initiative? At present, this article is almost exclusively about IP multicast. It even says so in the introduction - The word "multicast" is typically used to refer to IP multicast. -- Kvng ( talk) 16:56, 21 August 2008 (UTC)
This page is an archive of past discussions. Do not edit the contents of this page. If you wish to start a new discussion or revive an old one, please do so on the current talk page. |
And what's the difference to broadcast, as in "broadcast adress x.x.x.255"? -- Abdull 08:38, 30 May 2005 (UTC)
Others can correct if I am wrong. I suppose you can think of multicast as a controlled or selective way of broadcasting over a wide area network (not just within the loca area network).
The broadcast address in a IP subnet (which x.x.x.255 is one example) can only be used to talk to all hosts the local broadcast domain (eg on a Ethernet LAN). This address maps directly to broadcast address like Ethernet's ff:ff:ff:ff:ff:ff address. Any packets to this address does not go outside the IP subnet.
This is in contrast to multicast, which allows sending packets to all nodes which subscribe to a particular multicast ip address/
--sdf
I'm currently writing on a chapter about how broadcasting (tv/radio stations) evolved to multicasting on the internet, also describing things like broadcast domains in a rather simple matter. I'd rewrite it to fit in this article if that's appreciated... -def
Routers are layer 3 devices that do not use spanning tree protocol.
1. Broadcast is a special multicast group. That is an all hosts group. In IPv4 there are actually two distinct forms of a broadcast address. The first is the limited local broadcast address of the form 255.255.255.255. When an IP datagram is sent to this destination, it is sent to all hosts on the local network. Datagrams to this destination will not be forwarded by a router. The second form is the directed broadcast address and the actual destination IP address depends on the network being referred to. Generally speaking we say that the network bits are set to the network address of the destination network and the host bits are set to all binary 1's. For for example, if you want to send a broadcast to all hosts on the 192.0.2.0/24 network, you set use the network bits to the network address, which in this case is just the first three octets (192.0.2) and the host bits, the last octet to 255, resulting in final destination address of 192.0.2.255. What would be the directed broadcast address for 192.0.2.0/25? 192.0.2.127.
2. I'm not sure what is meant by "pose as the sender" comment. I think they are essentially saying that if you let everyone in the group share the same key, then how do you know who the actual sender is. This is actually a separate problem and the original author I think is a little confused. That part needs to be ripped out and changed completely.
3. Web conferencing, instant messaging and IRC are hardly multicast technologies as the term multicast is commonly used. Again, I think someone is confused. Those need to be ripped out.
I will plan on doing a major update of this article shortly.
Multicast and the protocols surrounding multicast snooping and routing have been widely implemented in almost every network vendors equipment (accept for the more entry level devices). Multicast scales very well across the LAN/WAN (if the network supports it). A 5mbps MPEG stream could be sent to ever user on a network while only using 1 x 5mbps worth of bandwidth on any one link.
The reason that the internet doesn't support multicast (don't forget the MBONE) is not because of the protocols as much as it would require a massive configuration change and upgrades globally to implement the protocols. Which mean that every phone company, ISP, cable company, DSL and Cable modem manufacturer would have to be on board and agree to make the changes at the same time. Never going to happen.
That is why, in part, the Internet 2 came to be. The I2 (like the original internet) connects universities, k-12 and government agencies together on high bandwidth connections. The entire I2 is multicast enabled. This means that if a video is being multicast from NYU, someone can watch at Berkley, Bowling Green.
Multicast is also a term used on a Warcraft 3 map known as Defense of the Ancients. It is a passive spell used by the Ogre Magi that gives him a chance to, as the term suggests, multicast his spells onto targets.
If this is really information someone is looking for, it definitly belongs into a seperate entry.
I don't know what the intention of this edit is, but I think the original version made more sense. Revert? -- lynX 11:23, 24 January 2007 (UTC)
In the "Routing Schemes" figure, it's unclear whether the labels ("anycast", "broadcast", etc.) correspond to the illustration above or to the one below (below is what's intended, I believe). This is especially confusing if the figure is read from top to bottom. DRE 19:01, 30 May 2007 (UTC)
What is Windows Media Player multicast?-- Hhielscher 19:57, 17 November 2006 (UTC)
A friend proposed to me a simple multicast scheme in which the sender lists the unicast addresses of all destinations, and then intermediate routers split the packets. This eliminates the need to maintain receiver groups, at the expense of scalability - but it would be nice for small applications, on the order of a few dozen receivers. Can anyone refer me to research on this topic? Is there any reason this scheme is unworkable? Thanks. Dcoetzee 23:08, 13 October 2009 (UTC)
I was somewhat proud of recent edits to the first paragraph. I think it is a bit confusing to use the term Multicast addressing bolded or partially bolded in the lead as there is a separate article called Multicast address. Kbrose ( talk · contribs) has reverted this edit with the following comment: No, in networking it does not refer to the message but the addressing and routing process, perhaps in television it's the message. This is news to me. Anyone else have input or a reference on this? -- Kvng ( talk) 06:15, 26 August 2010 (UTC)
Here is a link for use of term in TV.
Kbrose ( talk) 16:19, 26 August 2010 (UTC)
The article suggests that IP multicast is used in internet television. This is doubtful, because Internet routers do not have enough state to remember the multicast information for all television channels (as explained later in the article). Perhaps it's just wishful thinking? — Preceding unsigned comment added by 173.66.54.78 ( talk) 17:23, 15 May 2012 (UTC)
They don’t have to remember all the channels; only the ones in actual use. Like for Usenet, there would be a directory function that maps user requests to multicast addresses. 71.38.204.2 ( talk) 18:26, 15 November 2017 (UTC)
"IP Multicast is widely deployed..." -- I think this is misleading, Fabiovh ( talk) 14:27, 23 February 2009 (UTC)
Would anybody care to add an overview of reliable multicast?
The article says: "... applying that to IP Multicast traffic would enable any of the receivers to pose as the sender. This is clearly unacceptable".
How is it possilbe to pose as the sender? Can anyone please explain why is it unacceptable in a language that will be understood by someone who's not a cryptography expert?-- Amir E. Aharoni 07:47, August 29, 2005 (UTC)
This article is lacking substantially in several parts. Just to point out something on multicast (group) security, what makes this all so challenging is finding efficient algorithms for (1) key management (for assuring confidentiality within dynamic groups) and (2) source authentication. What the paragraph about security issues is talking about is the problem of using symmetric keys for authentication which only allows GROUP authentication (vs. source authentication). The cited sentence should rather say something like "Use of symmetric keys for authentication would enable any of the receivers to IMPERSONATE the sender.". Asymmetric cryptography on the other hand in turn is too heavy for most applications (low computing power, high throughput, etc.).
TESLA is one of the promising new efficient algorithms for SOURCE authentication.
This article is not mentioning key managment algorithms whose most promising one is LKH (Logical Key Hierarchy).
Regards,
Michael Noisternig
The Web conferencing link is somewhat problematic. The term itself is inaccurate, and many mentioned technologies on that page do NOT multicast. Should we pick the technologies that actually multicast, and link them from here? -lynX
Sincerely I don't see any technology on that page using multicast in any way, so I removed it. -- SymlynX 06:24, 4 May 2006 (UTC)
Instant messaging is to a large amount a one-to-many medium. Even if people aren't engaging in chatrooms all the time, every change in presence status is sent to all "buddies". Yet none of the technologies used to that purpose implement any multicasting as they should, no surprise they either have to operate in a centralized way, which defeats privacy, or cannot scale properly when operating in a decentralized way. Don't you think this problematic fact needs mentioning in both documents? -lynX
The article mentions that IRC uses Multicast, but does it? I dont think it does, atleast not apparant to the end-user? More specifically mIRC uses only TCP, as far as I've seen.
The following discussion is closed. Please do not modify it. Subsequent comments should be made on the appropriate discussion page. No further edits should be made to this discussion.
There seems to be no objections to merging the IP multicast content from this page onto the separate IP Multicast entry. Given that there are two entries (and I think it makes sense for there to be two), it doesn't make sense for the majority of the content on IP multicast to be here. So I'm moving it. Stephen.frede 06:51, 11 July 2006 (UTC)
OK, move is done. I actually ended up rewriting most of the content. See IP Multicast. Stephen.frede 10:29, 11 July 2006 (UTC)
Someone who claims "IP Multicast, which do not count as multicasting, because they are actually local broadcasts" I would suggest has a bit of a problem understanding IP multicast and that is our problem, but I give up, go on calling it IRC multicast and other made up silliness if you insist, hopefully cluefull folks will drop over to the discussion page and will see that there is someone who arguably knows a thing or two about multicast takes issue with what you're writing. jtk Wed Nov 22 06:50:11 UTC 2006
What is the status of this merge initiative? At present, this article is almost exclusively about IP multicast. It even says so in the introduction - The word "multicast" is typically used to refer to IP multicast. -- Kvng ( talk) 16:56, 21 August 2008 (UTC)