ddruker
join:2000-08-13
Palo Alto, CA | Why big gap between attainable rate and realized rate? I've got bonded fusion.
After upgrading my external DSL splitters to new ADSL2+ splitters, I'm seeing improved performance, but my modem is also reporting a relatively large gap between my downstream actual vs. attainable rate.
Anyone know why I might be achieving what the modem says is 92% of the attainable rate upstream but only 79% of the attainable rate downstream?
I did call sonic tech support and the person I talked to was nice and tried to help but wasn't able to explain the discrepancy or narrow the gap. Also, I'm getting zero downstream errors.
Mode: ADSL2+
Line Coding: Trellis On
Status: No Defect
Link Power State: L0
PhyR Status: OFF
Downstream Upstream
SNR Margin (dB): 6.1 10.9
Attenuation (dB): 40.0 23.6
Output Power (dBm): 0.0 12.5
Attainable Rate (Kbps): 18356 2484
Rate (Kbps): 14614 2294
Slave Info
Version: 1.0.37-1.1-A2pB025c1.d20l-4.5.5_C37
Status: Showtime
Channel: Fast
Mode: Unknown
PHYR: OFF
Upstream Downstream
Rate (Kbps): 1211 7227
SNR Margin (dB): 6.4 6.1
Attenuation (dB): 20.9 36.5 |
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 DaneJasperSonic.NetPremium,VIP
join:2001-08-20
Santa Rosa, CA
kudos:7 | Just a guess, but maybe we've capped at the 14614Kbps rate for stability?
-Dane |
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eugenek
join:2002-06-14
Palo Alto, CA Reviews:
 ·SONIC.NET
| reply to ddruker
consider voting for the 'ability to switch between Annex A and M' .. expanded to include viewing and changing your line settings 
»sonicnet.uservoice.com/forums/13···ters/top |
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ddruker
join:2000-08-13
Palo Alto, CA | reply to DaneJasper
The tech I spoke with said that I was uncapped. He played with a number of settings but was unable to get the modem to connect at a higher percentage of the attainable rate. Should I just give up, or should I call back in? |
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DaneJasperSonic.NetPremium,VIP
join:2001-08-20
Santa Rosa, CA
kudos:7 | I don't think we're likely to know what your modem is projecting here. I'd suggest contacting the modem maker and asking them what this max attainable field is supposed to mean.
-Dane |
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ddruker
join:2000-08-13
Palo Alto, CA | Thanks Dane - I have bonded fusion; the Comtrend bonded DSL router I have was provided by your team. So I would expect your guys might be somewhat familiar with what that particular field is supposed to mean. I think I'll just call in again and see if I get someone who has a bit more depth than the first guy - he was nice and responsive, he just didn't seem to know why what he expected to happen as he twiddled the various bits on your side didn't actually happen.
I'm happy with the service - it's been solid and reliable and the value is fantastic. |
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DaneJasperSonic.NetPremium,VIP
join:2001-08-20
Santa Rosa, CA
kudos:7 | This really wouldn't be something support can or should be able to answer, I'm sorry. Please don't repeatedly call in hopes someone might know, they're astoundingly busy.
I will hazard a guess, and perhaps Liebold here can weigh in, as he seems to know more about this stuff than even I do!
I am guessing that max attainable is the calculated maximum sync based upon measured attenuation, in the absence of impulse noise, margin, and disturbers. In other words, if only loss was considered, and not interference, how fast could the link possibly go.
-Dane |
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 leiboldPremium,MVM
join:2002-07-09
Sunnyvale, CA
kudos:2
·SONIC.NET
·Pacific Bell - SBC
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Comtrend NexusLink 5631 Slaveinfo |
If the maximum attainable rate on the modem was accurately predicting the maximum speed at which the line can operate in the absence of artificial restrictions imposed by the DSLAM (minimum SNR, maximum rate) then the value should always be higher or equal then the actual rate currently in use.
Take a look at the attainable rate and actual rate for the 2nd line on my Comtrend NexusLink 5631. In the downstream column the maximum attainable rate is indeed higher (significantly) then the actual rate. However in the upstream direction the modem firmware calculates a maximum speed that is lower then the actual speed currently used by the line!
On the first line attainable speed is higher then actual rate in both directions as one would expect them to be.
Clearly the predictions of attainable speed cannot be fully trusted. Attainable speed is helpful when the ISP is selling speed tiers to judge whether or not upgrading to the next tier makes sense. With an ISP like Sonic.net where there are no speed limits imposed the only rate that is important is the actual speed negotiated between modem and DSLAM.
--
Got some spare cpu cycles ? Join Team Helix or Team Starfire! |
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DaneJasperSonic.NetPremium,VIP
join:2001-08-20
Santa Rosa, CA
kudos:7 | Yup, yup, and thanks Liebold for jumping in! (Still would love it if you'd drop in on »forums.sonic.net sometimes!)
On the older AT&T ADSL1 network, there is a "relcap" percentage which is similar - current sync as a percentage of projected max capacity. This is useful because if someone has a relcap of 80%, you know they can't upgrade - if it's 75% for example, you'd know that an upgrade would gain them little. If it was 40%, you could presume an upgrade to the next tier would mean a doubling in speed while still staying at a stable 80% relcap.
In an uncapped de-tiered environment, as Liebold points out, it's less useful - your connection goes as fast as the modem can negotiate and sustain a connection.
-Dane |
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