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North American Network Operators Group Date Prev | Date Next | Date Index | Thread Index | Author Index | Historical Re: Real Media and M-Bone feeds
> }Multicast is just not more than one case of data caching on the fly. It > }can be used for the local networks, just with the net of the media > }replicators. In principle there is not big difference between multicast > }and www caching except first is an example of the _real-time caching_ and > }second is usially _store-and-forward_ caching. > > It it really comparable to caching? I see multicasting as more of a > traffic reduction, rather than a cache. Strictly saying, it's THE SAME. The cache engine can - STORE traffic for some time, and replicate it. If it can only replicate traffic on the fly (store time is 0), it works like MultiCast. If it can only replicate data after all data was read, it works like WWW cache. If it can do boths, it looks like un-existing RealMedia cache engine which should replicate live traffic (may be converting it to the multicast if it's necessary) and store (and reproduce at request) on-demand traffic (with possible multicasting if two requests are coming in the same time). > }replicate data on the fly - in case of live media stream, and short or > }long tome _store-and-forward_ in case of Video-on-demand stream) - and > }with just this multicasting on the very end of the data tree. But an > }attempts to build over-the-world multicast network - brr... it's possible > }(if you should dig some mountain every day, you'll build a tunnel at last; > }but may be it's easy to run this mountain over?). > > Your model would work, but it requires a LOT more coordination and > cooperation than even multicast requires. Are you sugesting that networks Why? There exist Cisco WEB cache engine which work _on the fly_; if (for example_) this box could work for the RealVideo traffic (even withouth the multicasting) and if 10 - 20 greatest ISP install such boxes - this allow to increase the number of people who can ask Vide-on-demand withouth throughput problems dramatically. Note - this do not need political decisions AT ALL. Then, more than 70 - 90% of the multimedia content this days is _on-demand_ content. I don't need live CNN, I ask _last news review_ from CNN; I have asked video topics about the Japan Radioactive Pollution last days; I'd like to hear last NANOG sessions just now (note - NOT LIVE but LAST). Multicast can't help here at all; data caching can help 100%. Compare the Multicast content and RealVideo content internet have this days. And think about new hacker's attacks became possible just when you allow multicast to cross AS boundaries... > implement machines that sniff into the data, identify those streams, > intercept them, and then coordinate with the streams' sources to stop > sending the unicasts behind the cache, and send the stream to the cache > only? Or will your new machine simply "spoof" the source? If the latter, You just describe how WWW CACHE engine does work. What's the difference between WWW and RealVideo? Not any - request (like SIP protocol) opens data stream; request can be catched easily, transparently for the customer. Nothing new except existing methods. > then you haven't told the sender to reduce the traffic. > > You mentioned your doubt of building an over-the-world multicast > network... but what you are sugesting seems to be an over-the-world > caching mechanism. If we are going to build an over-the-world anything, > why not build on the IP model, which is already over-the-world? There is a huge difference. Caching can be done locally first, over the EXISTING content, EXISTING RealMedis servers, Existing client programs - it transparently reduce the traffic, not more. Multicast can't work if it was not built over the whole world. > > The whole reason for multicast is to reduce the traffic at the source, not May be; but the _on demand_ sources can keep this days huge amount of the traffic. The problem is _how to deliver it_ and _why just the same video clip should run through undersea cable 100 times/day instead of been caching on the other end. > necessarily just then receivers. And the concept behind ip multicast is > to replicate as closely as possible the IP model - send trafic to an IP > address, and let the layer 3 devices forward the packet to the right > shared-media networks as required. Yes, no doubt. And now - compare IP packets with the SMTP message. This message contain the LIST of all receivers when it was sent - and it allow it to be replicated authomatically. But in case of Video and Internet, the sender could not write THE LIST of RECEIVERS (btw, WHY not? It could be done by IP options withouth extra problems, or by the SOURCE-ROUTING) and use reverse-paths calculations just as absolutely other address schema instead. I am not saying _multicast concept was absolutely wrong_, but I'd like to aware from blend trusting to the multicast. Note - internet have a lot of multimedia this days, but it's mostly ON-DEMAND multimedia. Note, LIVE multimedia just exist for a 10 - 20 years - it is usial TV; but it can't solve the ON-DEMAND problem; note - multicasting can't solve ON-DEMAND problem, it's just one more TV. > > }And - your NANOG forum is the excellent example. RealVideo streaming work > }fine; Multicast don't work at all; why do you try to use weak schema > }instead of the strong one? No enougph bandwidth - install stream > }replicators inb the key points; build _replication on the fly_ schemas > }(such as CCP for the www caching on the fly), etc. No, even with all > }attempts Cisco and some other are trying this days - multicast is more > }dead than alive. I can get 10,000 multimedia sources by RealVideo or > }StreamVideo - and I can't get nothing usefull by multicast. If I could > }install RV-cache engine (cache on the fly) - I should choose this > }solution. > > You can get a lot more software for Windows, too, but that doesn't make it > the right solution all the time. How much software was available for > Linux just two years ago? Market share is a poor measurement of the > quality and capability of a solution. I know, and I don't deny everything you was saying. But most of the multimedia sources I want to watch can't be improved by multicasting at all; no security or stability problems was solved at all, and the very roots of the multicasting was in the live conferencing, not in the customer's demands. This cause me to be very sceptical about multicasting. > > -andy > > -- > Andy McConnell IP Operations Manager [email protected] > NTT America Network and IP Service Division +1 408 873 3757 > $B??8~N}(B $B0BEHN6(B NTT$B%"%a%j%+(BIP$B%*%Z%l!<%7%g%sC4Ev2]D9(B > > "What right does Congress have to go around making laws just because they > deem it necessary?" > - M. Barry, Mayor of Washington, DC > > > > Aleksei Roudnev, Network Operations Center, Relcom, Moscow (+7 095) 194-19-95 (Network Operations Center Hot Line),(+7 095) 230-41-41, N 13729 (pager) (+7 095) 196-72-12 (Support), (+7 095) 194-33-28 (Fax)
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