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Apr 15th, 2009 at 1:12pm
I would not want people to get the idea that use of DVB gives more than what you pay for. DVB provides a common encapsulation process so that TV and data etc may be added into the same carrier multiplex. DVB-S2 then adds a great variety of modulation and FEC coding rates that may be adjusted from frame to frame to maximise capacity according to receive dish size and even as the weather changes using a return link to control adaptive changes. DVB-S2 will reduce the cost per bit.
I'm interested in this CIR business.
If you have a 512k/256k system, for example, with 25 sites, each with 2 PCs, and all paying the same $140 per month, do you set the CIR=20kbit/s and the burstable rate=512k ?
i.e. the first 20k bits, per second, to each site have priority, and all packets above that (per second) are marked discardable, which are then, if necessary, dropped at the hub transmit router.
I have the impression that some operators are setting and saying the CIR is much higher, say CIR=100k and hoping that no more than 5 sites will be simultaneously active. This is not right but I have seen official guidance about such "oversubscription". When this happens the meaning of the expression CIR is destroyed and it becomes a meaningless and false sales claim, which misleads customers by unrealistically raising their expectations.
Best regards, Eric.
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