Cell Relay Archive[Date Prev][Date Next][Thread Prev][Thread Next] [Date Index][Thread Index][Author Index][Subject Index] Re: CBR? Required to reserve BW even if no CBR traffic?
The issue is quite simple. A switch must reserve enough bandwidth so that when the CBR traffic comes, it goes through. However, an ATM access device will not always transmit cells, even when using a CBR virtual circuit. This enables the switch to use this unused bandwidth on a temporary basis. Thus, you cannot add another CBR VC on top of the unused one, as it may come "alive" in any moment. But, if you are also providing UBR services on the same switch, than those services may enjoy the momentary "happy hour". The same is more or less true for ABR and VBR services. To clarify things, always separate between reserving the bandwidth and the actual transmission - they are not the same and different rules apply. Regards, Oren Minzer ECI Telecom I've been trying to research if a vendor is ATM Forum compliant (or has a good design). They say that any unused CBR traffic is available for anybody else's use. Looking at TM4.0, I only see that if a switch accepts a CBR connection then it must provide what was contracted for. I've also heard how inefficient CBR is because the bandwidth goes to waste. If a vendor has CBR in the highest queue, then couldn't CBR traffic that was ramping up just start using that queue and still get his QoS satisfied? Thanks. -- Richard L. Brandt - Richard@Brandt.net "The faster the network, the quicker it goes down." |
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