PA23
join:2001-12-12
East Hanover, NJ
| reply to nltech
Re: Cisco 851 Throughput Question
Take a closerer look at how cisco comes up with the value of 5Mb/s its using an absolute worst case scenario for throughput.
cisco rates their products in PP/s (Packets Per second) so it stands to reason that a smaller packet can not pass as much data.
If you calculate the throughput with a 1500 byte packet using cisco's formula at the top of the document you get:
10000 (PP/s) * 8 (bits per byte) * 1500 = 120,000,000 or 120Mb/s or faster than the interfaces on the unit
I think I read some place that an average packet size on the internet is roughly 300 bytes. If this is true then you can expect the following performance:
10000 (PP/s) * 8 * 300 = 24,000,000 or 24Mb/s
What you will find however is it is not your router becoming the bottleneck, instead you'll find that your bottleneck will be the host or hosts you are talking to.
In addition, I think you will be very hard pressed to find a consumer router that has the performance of the 851 since all of them have the same limitation in terms for forwarding rate in PP/s. Any router that shows its throughput numbers you can be sure was tested with 1500 byte packets. You can prove it to yourself, use ttcp between two machines and vary the packet size as you get smaller the throughput will go down.
Hope that clears up cisco's throughput ratings.
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It's the end of the world as we know it, and I feel fine |
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nltech
join:2007-06-13
West Haverstraw, NY
| Still considering the 851 but after seeing this throughput comparision still a bit confused. These tests use iperf with a TCP window size of 16.0 kBytes
»www.smallnetbuilder.com/componen···art,119/ |
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kamikatze
join:2007-11-02 | If it helps, i have a Cisco 871 at home, doing PPPoE, nothing else. Bittorrent-wise it goes up to 26Mbps (~3.3MB/s). Nothing higher. Considering the 851 has the same CPU only half the memory, i'd say it will pretty much do the same. |
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PA23
join:2001-12-12
East Hanover, NJ | so my estimated numbers were pretty close huh, I said about 26 Mb/s and you get 24Mb/s.
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It's the end of the world as we know it, and I feel fine |
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Phraxos
Premium
join:2004-06-12
UK
| reply to kamikatze
said by kamikatze  :Considering the 851 has the same CPU only half the memory, i'd say it will pretty much do the same. Not sure where you got the processor info from?! I'll bet that an 851 with extra memory comes nowhere close to an 871 performance wise.
I would go for at least an 871 for a 30Mb service especially considering the price difference.
Cisco stuff is much better made and much more sophisticated/versatile but if you just want a simple cheap router that will do the job 98% of the time don't buy a Cisco router, you will be wasting your money. |
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PA23
join:2001-12-12
East Hanover, NJ
| 871 is 2 1/2 times faster than the 851
25,000 PP/s vs 10,000 PP/s
see: »www.cisco.com/web/partners/downl···ance.pdf (which has already been posted)
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It's the end of the world as we know it, and I feel fine |
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kamikatze
join:2007-11-02
2 edits | reply to Phraxos
CPU specs: »www.freescale.com/webapp/sps/sit···bTdG2977
quote:
Delivering an ideal combination of price, performance and low-power operation, the MPC8272 Family supports CPU frequencies ranging from 266 MHz to 400 MHz while offering the benefits of low power consumption (0.8 W at 266 MHz).
If you open up a 870 you'll see 266MHz printed on the CPU.
I don't have a 850 here but that CPU doesn't go any slower.
Maybe the ALTERA chip is different.
The 870 has an EPM3128ATC144-7N.
»www.altera.com/cgi-bin/devsearch···=EPM3128
Can anyone look inside the 850? |
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rhard49
join:2001-04-12
Merrick, NY
| I just opened the 851 cablevision gives you Same MC8272 processor marked 266/200/66Mhz same altera chipset.
I use an 871w with a fios 20/20 connection. I have switched my plans several times started with 20/5 went to 35/10 finally settled out 20/20 as the best for my needs the 871 has worked perfectly at all speeds. |
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