DOCSIS 3.0 improvement over 2.0?

dparm

Limp Gawd
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Jun 26, 2007
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I am reading personal anecdotes that running a DOCSIS 3.0 modem, even if you are not pushing the ultra-high cable Internet speeds, will result in improved performance. Something to do with better decryption or QAM interpretation. I can't recall the specifics but people have said they saw a 20Mbps connection perform at 24+ just by swapping to the newer modem.

Any truth to this? My SB5120 is still humming along just fine but the upgrade bug has bit me...
 
A lot of people are saying they see this...by simply replacing their D2 modem with a D3 modem.

Quite a few that I'd trust also (colleagues).
I'm sure it depends on a LOT of stuff...who your ISP is, what region you are in, your ISPs equipment down to your local node, etc etc.
 
Yes, if you can use a Docsis 3 modem do so.

It does result in higher speeds on most cable providers
 
Comcast. Downtown Chicago (in a large residential high-rise).

Right now we're paying for 20/2 though I do see faster periodically. Typically it is UNDER 20 though -- I'd say 12-14 on average. Goes through periods of very poor performance at times.
 
I was paying for 25 but only getting about 20 and random disconnects until I upgraded to a new DOCSIS3 modem and that got me up to the full 25 and no disconnects.
 
Same here but I believe that the D3 modems are more resilient when it comes to signal degradation. My SB5101 was getting touchy when I would see a quick dip in the signal strength from the node. My 6120 has been rock solid since I got it.
 
I actually just did this last night. We have 35mbps down 6 up. With a the old motorola (SB5101) we got 35mpbs down 6 up. With the new sb6121 we get 35mbs down 6 up.

So no improvement but we get the exact speed we are paying for. This is on comcast. The old modem would lose connection maybe once every 3-4 months but I'm pretty sure that was comcast's fault since it would lose it for hours and resetting it wouldn't help.

The main reason I got it was because comcast increases the speed every so often and the old modem I had was capped at 38 mpbs I believe. Might as well be future proof.
 
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comcast recently upgraded my d2 model to a d3 modem. i pay for 30/5 and that is what i was getting with the d2 modem, with the d3 modem i get about 35/6.
 
The main benefit of switching to a D3 modem is channel bonding. With a Docsis 2.0 modem, al la 5101, you get one downstream and one upstream channel to transmit data on. If either of those channels are saturated due to high usage or there's data errors due to noise, then your connection with suffer certain stability issues. On a modem cable plant a D3 modem will bond to four or more downstream channels and two or more upstreams, thus spreading the bandwidth utilization over several potential transmitters (back at the head end). This provides you a better chance of getting the QOS you've been advertised even during peak hours. Furthermore, when node noise issues effect the upstream channels one upstream may continue to perform with less errors while the other is bombing out. A D3 modem may continue to talk clearly during these periods of noise or at worse, suffer less.

All in all, a D3 modem is more resilient on a cable plant that supports their features.
 
The main benefit of switching to a D3 modem is channel bonding. With a Docsis 2.0 modem, al la 5101, you get one downstream and one upstream channel to transmit data on. If either of those channels are saturated due to high usage or there's data errors due to noise, then your connection with suffer certain stability issues. On a modem cable plant a D3 modem will bond to four or more downstream channels and two or more upstreams, thus spreading the bandwidth utilization over several potential transmitters (back at the head end). This provides you a better chance of getting the QOS you've been advertised even during peak hours. Furthermore, when node noise issues effect the upstream channels one upstream may continue to perform with less errors while the other is bombing out. A D3 modem may continue to talk clearly during these periods of noise or at worse, suffer less.

All in all, a D3 modem is more resilient on a cable plant that supports their features.
This is the only reason to upgrade. If your cable operator does not support 3.0 in your area, you will not see any benefit.
 
Hello Dear HardForum Experts.
I will appreciate your valuable support and recomendations with the following issue:
I have an Internet Provider Service with the following caracteristics:

Information
Standard Specification Compliant DOCSIS 2.0
Hardware Version 1
Software Version SBG901-2.1.2.0-GA-02-188-NOSH
Cable Modem MAC Address 74:f6:12:67:95:b5
Cable Modem Serial Number 318158122102562101014008


Downstream Channel
Lock Status Locked Modulation QAM256
Channel ID 4 Symbol rate 5360537
Downstream Frequency 561000000 Hz Downstream Power -4.4 dBmV
SNR 35.9 dBmV
...................................................................
Upstream Channel
Lock Status Locked Modulation QAM64
Channel ID 1 Symbol rate 5120 Ksym/sec
Upstream Frequency 38800000 Hz Upstream Power 52.3 dBmV

And since two weeks there has been constants drops and rebooting issues, I attached the log file for further reference:

Sat Jul 07 19:16:36 2012 Notice (6) Modem Is Shutting Down and Rebooting...
Sat Jul 07 19:16:36 2012 Critical (3) Received Response to Broadcast Maintenance Request, But no Un...
Time Not Established Critical (3) DHCP FAILED - Requested Info not supported.
Time Not Established Notice (6) Ethernet link dormant - not currently active
Time Not Established Critical (3) Init RANGING Critical Ranging Request (17) Retries exhausted
Time Not Established Critical (3) No Ranging Response received - T3 time-out (US 4)
Time Not Established Critical (3) Init RANGING Critical Ranging Request (17) Retries exhausted
Time Not Established Critical (3) No Ranging Response received - T3 time-out (US 2)
Time Not Established Critical (3) Received Response to Broadcast Maintenance Request, But no Un...
Time Not Established Notice (6) Ethernet link dormant - not currently active
Sat Jul 07 18:43:04 2012 Notice (6) Modem Is Shutting Down and Rebooting...
Sat Jul 07 18:43:04 2012 Critical (3) Received Response to Broadcast Maintenance Request, But no Un...
Time Not Established Critical (3) DHCP FAILED - Requested Info not supported.
Time Not Established Critical (3) No Ranging Response received - T3 time-out (US 1)
Time Not Established Notice (6) Ethernet link dormant - not currently active
Sat Jul 07 18:27:46 2012 Notice (6) Modem Is Shutting Down and Rebooting...

What Do you think is causing the problem ?

Best Regards,
Victor S.
[email protected]
 
"Upstream Power 52.3 dBmV"

That is a bit high. It's best if it is lower than 50dBmV. 53 is around the limit for stable connectivity. Probably explains the connection issues. Not much room to move around if there is intermittent signal issues.

How is your cable modem connected to the coax line? Are there any splitters? Is the coax cable screwed in snuggly? Have you called your ISP to see if they can help or send a tech out?
 
"Upstream Power 52.3 dBmV"

That is a bit high. It's best if it is lower than 50dBmV. 53 is around the limit for stable connectivity. Probably explains the connection issues. Not much room to move around if there is intermittent signal issues.

How is your cable modem connected to the coax line? Are there any splitters? Is the coax cable screwed in snuggly? Have you called your ISP to see if they can help or send a tech out?

As mentioned it looks like weak signal. -4.4dBmv is a bit low on the downstreams also. Can you eliminate any splitters or put the cable modem higher in the chain?
 
Hello , thank You for the prompt response,I have noticed one splitter from the outlet wall to the modem, and there are constant fluctuations all the time, the provider indicates the need to change the modem but I'm not sure the root problem is the IP poor service or the outdoor installation is damaged. Since Saturday there have not been drops of the modem, but still the upstream signal remains unstable:
------------------------------------------------------------------------------------
Downstream Channel
Lock Status Locked Modulation QAM256
Channel ID 4 Symbol rate 5360537
Downstream Frequency 561000000 Hz Downstream Power -3.7 dBmV
SNR 35.1 dBmV
--------------------------------------------------------------------------
Upstream Channel
Lock Status Locked Modulation QAM64
Channel ID 1 Symbol rate 5120 Ksym/sec
Upstream Frequency 38800000 Hz Upstream Power 53.0 dBmV
---------------------------------------------------------------------------
Best Regards,
 
So the cable line comes into your home, then into what? How many splitters are involved here? A diagram would help us.

Generally speaking, the line should come into the building then into one 2-way splitter, one leg to your cable modem, the other leg to another splitter for your digital cable boxes, DVRs, etc. If you don't have TV service at all, then there shouldn't be any splitters hooked up. Simply plug the cable line direct into the wall jack.

For that matter, as a test if you have TV service, try disconnecting the TVs and plug your cable modem directly into the line coming into the building. Then check the signals and test your internet connection. If the signals are better and you don't have any dropouts, good internet speeds, then the problem is either weak signals, too many splitters, wrong type of splitters, bad connectors, bad splitters, etc. You should have the ISP techs come out and investigate that further.
 
I am reading personal anecdotes that running a DOCSIS 3.0 modem, even if you are not pushing the ultra-high cable Internet speeds, will result in improved performance. Something to do with better decryption or QAM interpretation. I can't recall the specifics but people have said they saw a 20Mbps connection perform at 24+ just by swapping to the newer modem.

Any truth to this? My SB5120 is still humming along just fine but the upgrade bug has bit me...

My cable company explained to me that D3 is capable of using more streams, and may provide better performance during times of heavy network load or partial network trouble.

D3 is also needed if your service is above 35 or so Mb/Sec. I forget the exact number, but that's about where D2 runs out of thru-put.

It can also help if your cable company has Speed Boost. If your allocated speeds are 20-25Mb/Sec, speedboost an, for a time, push you way over that and hit the ~35Mbit/Sec limit of D2 hardware.

I used to see about 34Mbit/Sec speeds when speedboost would kick in. After changing to a D3 modem, I see it exceed 50Mbit/Sec during Speedboost periods.
 
My cable company explained to me that D3 is capable of using more streams, and may provide better performance during times of heavy network load or partial network trouble.

D3 is also needed if your service is above 35 or so Mb/Sec. I forget the exact number, but that's about where D2 runs out of thru-put.

It can also help if your cable company has Speed Boost. If your allocated speeds are 20-25Mb/Sec, speedboost an, for a time, push you way over that and hit the ~35Mbit/Sec limit of D2 hardware.

I used to see about 34Mbit/Sec speeds when speedboost would kick in. After changing to a D3 modem, I see it exceed 50Mbit/Sec during Speedboost periods.

Yeah when they first deployed D3 around here I used to be able to hit over 100Mbit on speed boost!
 
DOCSIS 1.1 adds QoS support
DOCSIS 2.0 adds improved upload speed
DOCSIS 3.0 adds channel bonding and IPv6 support
 
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