Don't forget that the signaling agents that drive the DSPs also contribute to load on
the host / control CPU.
We have found that this can be a very willing consumer of utilization on the platforms
under discussion... folks with super low hold calls would be the ones likely to be
challenged by this; particuarly with those boxes that still have the 4500-class
processor in them.
Regards,
Andrew
taqua.com
-Original Message-
From: Mathew Lodge [mailto:[EMAIL PROTECTED]]
Sent: Wednesday, February 12, 2003 6:46 PM
To: Charles Youse; Bill Woodcock
Cc: [EMAIL PROTECTED]
Subject: RE: Voice over IP - performance
At 03:23 PM 2/12/2003 -0500, Charles Youse wrote:
I'm assuming in the case of, e.g., a 2650 + dual T-1 PRI
interface can
actually encode/decode 48 simultaneous g729a voice streams without
issues? Any idea what the CPU utilisation is - or is this
handled in
separate DSPs in the voice network module itself?
On these particular Cisco boxes, the DSP does the all audio
filtering,
CODEC functions, echo cancellation, jitter buffering
adjustment, silence
suppression (AKA voice activity detection, if you turned it
on), and also
prepends the RTP and IP headers. The router CPU just has to
forward the
packet that's generated by the DSP.
Router CPU utilization is therefore a function of the number
of packets per
second that the voice card generates and the size of each
packet, plus
signaling overhead. The packet size and rate depend on the
CODEC itself
(higher compression CODECs generate smaller packets), the
sample size (20ms
is the Cisco default, reducing or increasing it makes the
packets smaller
or larger and the packet rate higher or lower, respectively),
and whether
voice activity detection is on (roughly halves the packet rate).
If you leave the default settings in place (no VAD, 20ms
sample size),
you'll be OK with any of the CODECs.
Mathew.
C.
-Original Message-
From: Bill Woodcock [mailto:[EMAIL PROTECTED]]
Sent: Wednesday, February 12, 2003 2:43 PM
To: Charles Youse
Cc: [EMAIL PROTECTED]
Subject: Re: Voice over IP - performance
Does anyone have any real-world figures for VoIP
performance on
various platforms? In other words, how many calls
can an otherwise
unused e.g., Cisco 2600 be expected to handle if it's
the conversion
point from trunked voice calls to IP. Some rough numbers for
different codecs on different hardware would be very
useful. Most
specifically I'm interested in Cisco router platforms
but other
vendor stats would be appreciated as well.
Actually I just ran the dollars-per-simultaneous-call numbers for
different models for some friends. I'll append it.
Basically, if you run
g711, you're limited by the number of PRI channels on the
box. If you run
g729a, you're limited by the number of DSPs you can fit in
the box. The
numbers I ran were assuming g729a.
-Bill
Cost
per
Package which can handle 23 simultaneous calls:call
CISCO1760 10/100 Modular Router $1,595
VWIC-1MFT-T1 1-Port RJ-48 Multiflex T1 $1,300
PVDM-256K-12 3-DSP Module (9 calls) $1,200
PVDM-256K-20HD 5-DSP Module (15 calls)$4,000
Total $8,095 $352
Different package which can handle 23 simultaneous calls:
CISCO2650 10/100 Modular Router $3,295
NM-HDV-1T1-24E Single-Port T1 Voice NM$9,100
Total$12,395 $539
Package which can handle 45 simultaneous calls:
CISCO2650 10/100 Modular Router $3,295
NM-HDV-2T1-48 Dual-Port T1 Voice NM $9,800
Total$13,095 $291
Package which can handle 46 simultaneous calls:
CISCO2650 10/100 Modular Router $3,295
NM-HDV-2T1-48 Dual-Port T1 Voice NM $9,800
PVDM-256K-20HD 5-DSP Module (15 calls)$4,000
Total$17,095 $372
Upgradeable package which can handle 46 simultaneous calls:
AS535-2T1-48-AC-V AS5350-V/2T1 $18,900 $411
Package which can handle 92 simultaneous calls:
AS535-4T1-96-AC-V AS5350-V/4T1 $33,600 $366
Package which can handle 184 simultaneous calls:
AS535-8T1-192-AC-V AS5350-V/8T1 $58,700 $319
Upgradeable package which can handle 184 simultaneous calls:
AS54HPX-8T1-192AC AS5400HPX/8T1 $65,500 $356
Package which can handle 644 simultaneous calls:
AS54HPX-CT3-648AC AS5400HPX/CT3$170,300 $265
