On Mon, 21 Sep 1998, Charles Sprickman wrote:
On Mon, 21 Sep 1998, Nathan Stratton wrote:
Even with the new CT3 cards on the Cisco, there are still many benefits to using the Cascades to aggerate T1 customers.
Please, share...
I like the CT3 card, but I'm not familiar (except as a customer) with the Cascade solution and its benefits beyond economics...
There are several issues regarding mechanisms for the best, most efficent ways of accepting traffic into the network, henceforth referred to as Connection Admission Control. There is a whole bunch of theory behind CAC, but to simplify in this case.... Data traffic is bursty. Most customers do not use all of their allocated bandwidth all of the time. Statistical multiplexing allocates bandwidth according to demand. Data traffic bandwidth requirements vary over time for most connections, and utilizing this fact allows gain in efficiency. Such a scheme assigns less than the peak bandwidth rate to connections (i.e. if everyone started to send the full bandwidth at all times, the connections would start experiencing packet drops and/or delay till buffer capacity is exceeded and the sources do not go into congestion control/avoidance phase). However, all channels sending all data at peak capacity at all times is fairly rare and traffic monitoring will point out the trouble spots before they start dropping packets. Coming back to the Cascades, they allow Statistical multiplexing of connections, giving a cheaper overall cost and allows more connections per unit of hub resources consumed. This results in cost efficiencies. Also, they reduce wiring complexity. For example, you take the 3 HSSI cards and use them to connect to 3 cisco HSSI ports. Once these connections are tested, the only change needed to add, say, a mixture of ChT3 cards, E1 cards, HSSI cards etc, is to stick them into the Cascade. This allows you to aggregate several different types of user connections without changing anything on the routers on the back end. New technology will result in faster uplinks, allowing higher density connections, eg, the current single port ChDS3 cards may be replaced by 4xChDS3 cards in newer switches. The end result is to maximise the number of (hopefully) paying customers per unit of hub resource consumed. -vijay -- Vijay Gill |The (paying) customer is always right. wrath@cs.umbc.edu, vijay@umbc.edu | - Piercarlo Grandi http://www.gl.umbc.edu/~vijay | Eagles may soar, but weasels don't get These are my opinions only. | sucked into jet engines.