[cisco-voip] Transcoding/Conferencing on the same ISDN Gateway

[Nick Matthews]

FWIW, if you're looking at 5+ CPS you're probably looking at an
AS5X000 box.  Many of the concurrent call numbers that are calculated
for gateways are not done at that high of a call rate (implying short
duration calls).

Regardless, you can run everything you want on the router (VPN, MTP,
Xcoding, full BGP table) as long as the parameters of the equation are
right.  If you scale your gateway the only problem is CPU usage, not
feature overload.  The only addendum to that is that most of these
numbers are calculated individually, so when you mix and match the
calculations aren't quite as accurate.  Which doesn't say much,
because depending on your call patterns you may get different results
from the posted numbers anyways.  Long calls = better for CPU, vad on
= better for CPU, codec selection = doesn't matter.  Most of the
problem you run into is the pure PPS of these streams rather than the
overhead, which is why MTPs and such can get you higher CPU pretty
quickly.  Xcoding and MTP roughly halve the amount of calls you can
make through the box.

hth,
nick

On Wed, Feb 10, 2010 at 5:21 PM, Rhodium <rhodium_uk at yahoo.co.uk> wrote:
> http://www.cisco.com/en/US/docs/voice_ip_comm/cucm/srnd/6x/gateways.html#wp1043594
>
> I am referring to CPS and not simultaneous call volumes. We have multiple gateways decked with 210 channels each (7 x E1) for redundancy and have higher call volumes but we are focused on CPS as that brings down the number of simultaneous calls on the gateways.
>
> Also our BHCA is in the region of 8000 so there is a slight difference in type of traffic flow we are seeing.
>
> Regards,
>
> J
>
> --- On Wed, 2/10/10, Matthew Saskin <msaskin at gmail.com> wrote:
>
>> From: Matthew Saskin <msaskin at gmail.com>
>> Subject: Re: [cisco-voip] Transcoding/Conferencing on the same ISDN Gateway
>> To: "Rhodium" <rhodium_uk at yahoo.co.uk>
>> Cc: "Peter Slow" <peter.slow at gmail.com>, cisco-voip at puck.nether.net
>> Date: Wednesday, February 10, 2010, 10:01 PM
>> Where in the SRND is the call limit
>> for various gateways listed?  I'd like to take a
>> look.
>>
>> The environment I was referring to was a UCCE build
>> performed by Cisco AS.  4 gateways w/ 10-12 PRI's each
>> handling upwards of 50K calls/day inbound and outbound - all
>> calls were transcoded on these gateways after the IVR and
>> before heading to agents.  During busy hour call volumes
>> weren't above 250 calls/gateway but I'd like to see
>> the reference.
>>
>>
>> Matthew Saskin
>> msaskin at gmail.com
>> 203-253-9571
>>
>> July 18, 2010 - 1500m swim (in the hudson), 40k bike, 10k
>> run
>> Please support the Leukemia & Lyphoma Society
>>
>> http://pages.teamintraining.org/nyc/nyctri10/msaskin
>>
>>
>>
>> On Wed, Feb 10, 2010 at 4:53 PM,
>> Rhodium <rhodium_uk at yahoo.co.uk>
>> wrote:
>>
>> Hi Matthew,
>>
>> Appreciate the feedback. I am just concerned that as this
>> is for a call centre, when the number of calls per second
>> (CPS) increases, the number of simultaneous calls
>> decreases... so I can see a deployment with 1 to 3 CPS
>> working with the setup you have described but with something
>> close to around 15 CPS, then according to the SRND, that is
>> a maximum of 255 calls (for a 3845). As we are decking out
>> the ISDN router with 210 channels, then that only leaves
>> headroom for 45 calls not including CPU overhead of SCCP,
>> which led to my mistaken recollection of transcoders and
>> ISDN GWs when it was transcoders and CUBEs.
>>
>>
>> I guess based on the setup I described, the more I think
>> about it, the more I am inclined to make it "off
>> box". Am I over riding financial judgement with caution
>> too much?
>>
>> Regards,
>>
>> J
>>
>>
>>
>> --- On Wed, 2/10/10, Matthew Saskin <msaskin at gmail.com>
>> wrote:
>>
>> > From: Matthew Saskin <msaskin at gmail.com>
>>
>> > Subject: Re: [cisco-voip]
>> Transcoding/Conferencing on the same ISDN Gateway
>> > To: "Rhodium" <rhodium_uk at yahoo.co.uk>
>> > Cc: "Peter Slow" <peter.slow at gmail.com>,
>> cisco-voip at puck.nether.net
>>
>> > Date: Wednesday, February 10, 2010, 9:37 PM
>>
>>
>>
>> > I regularly see single gateways
>> handle
>> > all functions (PSTN termination, conferencing,
>> transcoding)
>> > for sites of all sizes.  I know of nothing
>> [design-wise]
>> > preventing you from doing this.  In fact, I can think
>> of
>>
>> > some very large installations I've seen that were
>> done
>> > by advanced services where 3845's were being used
>> to
>> > terminate 10-12 PRI's plus handle a few hundred
>> > transcoding sessions.
>>
>> >
>> >
>> > Matthew Saskin
>> > msaskin at gmail.com
>> > 203-253-9571
>> >
>> > July 18, 2010 - 1500m swim (in the hudson), 40k bike,
>> 10k
>> > run
>> > Please support the Leukemia & Lyphoma Society
>>
>> >
>> > http://pages.teamintraining.org/nyc/nyctri10/msaskin
>> >
>> >
>> >
>> > On Wed, Feb 10, 2010 at 4:24 PM,
>> > Rhodium <rhodium_uk at yahoo.co.uk>
>>
>> > wrote:
>> >
>> > Hi Peter,
>> >
>> > Thank you for your reply.
>> >
>> > I dug out a report from Cisco Advanced Services that
>> stated
>> > that CUBEs should only be used for SIP trunks and not
>> for
>>
>> > transcoding/mtp. Knew I read something somewhere. Just
>> not
>> > the details... :)
>> >
>> >
>> > So we are all definite that for an ISDN GW, we can
>> use
>> > re-use the DSPs for transcoding in line with
>> Cisco's
>>
>> > recommendations? I want to recommend getting a
>> dedicated
>> > router for these functions but need to justify the
>> cost so
>> > if there are no design recommendations, then I guess I
>> can
>> > just put it all on one box.
>>
>> >
>> >
>> > Regards,
>> >
>> > J
>> >
>> >
>> > --- On Wed, 2/10/10, Peter Slow <peter.slow at gmail.com>
>> > wrote:
>> >
>> > > From: Peter Slow <peter.slow at gmail.com>
>>
>> >
>> > > Subject: Re: [cisco-voip]
>> Transcoding/Conferencing on
>> > the same ISDN Gateway
>> > > To: "Rhodium" <rhodium_uk at yahoo.co.uk>
>> > > Cc: cisco-voip at puck.nether.net
>>
>> >
>> > > Date: Wednesday, February 10, 2010, 5:02 PM
>> >
>> >
>> >
>> > > That is not necessarily correct. It
>> > > depends heavily on the type of
>> > > gateway you're talking about, and the number
>> of
>>
>> > transcoding
>> > > or
>> > > conferencing sessions you might be needing.
>> >
>> > >
>> > > -peter
>> > >
>> > > On Wed, Feb 10, 2010 at 7:24 AM, Rhodium <rhodium_uk at yahoo.co.uk>
>>
>> > > wrote:
>> > > > Hi Experts, :)
>> > > >
>> > > > I am sure I read somewhere in a design doc
>> or the
>> > SRND
>> >
>> > > that it is not advocated to put transcoding or
>> > conferencing
>>
>> > > resources on a voice gateway handling about 150
>> > calls.
>> > > >
>> > > > Am I recalling right or are the old brain
>> cells
>> > > getting weaker with age.
>> >
>> > > >
>>
>> > > > If that is correct, a link would be
>> appreciated
>> > as I
>> > > can't find it.
>> > > >
>> > > > Regards,
>> > > >
>> > > > Jason
>> > > >
>> > > >
>>
>> > > >
>> > > >
>> >
>> > > >
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>>
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>> >
>> > > >
>> > >
>> >
>> >
>> >
>> >
>>
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