the engineer gave it to you straight. They use cascades reduce the per
port costs on the cisco. Cisco recently added channellized T3s, but this
is years after UUNET made their design decisions. I know htis because I
heard it from the person who did hte design at UUNET.
jerry
I have never heard complaints about the Cascades for T-1 termination
except where they are terminating too many sessions in the Cascades and
the router couldn't handle that many sessions. This was a bigger problem
before the 7500 series routers came out and more importantly the RSP4s.
Fortunately UUNet doesn't terminate T3s into Cascades or ATM switches
(yet...)
-Deepak.
the engineer gave it to you straight. They use cascades reduce the per
port costs on the cisco. Cisco recently added channellized T3s, but this
is years after UUNET made their design decisions. I know htis because I
heard it from the person who did hte design at UUNET.
Even with the new CT3 cards on the Cisco, there are still many benefits to
using the Cascades to aggerate T1 customers.
<>
Nathan Stratton Telecom & ISP Consulting
www.robotics.net nathan@robotics.net
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...
Thanks,
Charles
><>
Nathan Stratton Telecom & ISP Consulting
www.robotics.net nathan@robotics.net
--
"No king is saved by the size of his army; no warrior escapes by
his great strength." - Psalm 33:16>
> jerry
>
=-----------------= =
Charles Sprickman Internet Channel |
INCH System Administration Team (212)243-5200 |
spork@inch.com access@inch.com |
= =----------------=
Charles Sprickman wrote:
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...
Well, they cost an arm and a leg for one. You get some really nice port
density, but your per-port costs can be pretty high. With a CT3IP, the best
you can do is 28 T1s per cisco slot. With the frame relay solution,
theoretically you can do several times that many T1s per HSSI port. You
will only notice this if many of your customers only use a small fraction of
their T1. This is the same as the standard packet-switched versus
circuit-switched argument.
I personally like the CT3IPs as well, but they only address half of what the
Cascade solution addresses.
Alec
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
Fortunately UUNet doesn't terminate T3s into Cascades or ATM switches
(yet...)
Yes they do. But they will only do this if you are a fractional
customer of less than 20Mbit or so. Anything higher gets a dedicated port.
bye,
ken emery