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Date: Thu, 13 Feb 2003 11:54:34 -0500 From: "Bender, Andrew" <abender@taqua.com> To: "Mathew Lodge" <Mathew@CPlane.com>, "Charles Youse" <cyouse@register.com>, "Bill Woodcock" <woody@pch.net> Cc: <nanog@nanog.org> Errors-To: owner-nanog-outgoing@merit.edu Don't forget that the signaling agents that drive the DSPs also = contribute to load on the host / control CPU.=20 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=20 taqua.com > -----Original Message----- > From: Mathew Lodge [mailto:Mathew@CPlane.com] > Sent: Wednesday, February 12, 2003 6:46 PM > To: Charles Youse; Bill Woodcock > Cc: nanog@nanog.org > Subject: RE: Voice over IP - performance >=20 >=20 >=20 > 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=20 > interface can=20 > >actually encode/decode 48 simultaneous g729a voice streams without=20 > >issues? Any idea what the CPU utilisation is - or is this=20 > handled in=20 > >separate DSPs in the voice network module itself? >=20 > On these particular Cisco boxes, the DSP does the all audio=20 > filtering,=20 > CODEC functions, echo cancellation, jitter buffering &=20 > adjustment, silence=20 > suppression (AKA voice activity detection, if you turned it=20 > on), and also=20 > prepends the RTP and IP headers. The router CPU just has to=20 > forward the=20 > packet that's generated by the DSP. >=20 > Router CPU utilization is therefore a function of the number=20 > of packets per=20 > second that the voice card generates and the size of each=20 > packet, plus=20 > signaling overhead. The packet size and rate depend on the=20 > CODEC itself=20 > (higher compression CODECs generate smaller packets), the=20 > sample size (20ms=20 > is the Cisco default, reducing or increasing it makes the=20 > packets smaller=20 > or larger and the packet rate higher or lower, respectively),=20 > and whether=20 > voice activity detection is on (roughly halves the packet rate). >=20 > If you leave the default settings in place (no VAD, 20ms=20 > sample size),=20 > you'll be OK with any of the CODECs. >=20 > Mathew. >=20 >=20 > >C. > > > >-----Original Message----- > >From: Bill Woodcock [mailto:woody@pch.net] > >Sent: Wednesday, February 12, 2003 2:43 PM > >To: Charles Youse > >Cc: nanog@nanog.org > >Subject: Re: Voice over IP - performance > > > > > > > Does anyone have any real-world figures for VoIP=20 > performance on > > > various platforms? In other words, how many calls=20 > can an otherwise > > > unused e.g., Cisco 2600 be expected to handle if it's=20 > the conversion > > > point from trunked voice calls to IP. Some rough numbers for > > > different codecs on different hardware would be very=20 > useful. Most > > > specifically I'm interested in Cisco router platforms=20 > 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. =20 > Basically, if you run > >g711, you're limited by the number of PRI channels on the=20 > box. If you run > >g729a, you're limited by the number of DSPs you can fit in=20 > 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 >=20 >=20
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