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Two ADSL2+ lines-- One significantly slower than the other

zschallz
Hooked
Posts: 6
Registered: 24-03-2017

Two ADSL2+ lines-- One significantly slower than the other

I have two ADSL2+ lines installed running on Plusnet Business. One line is new, the other line is older (installed in 2013). The new line is roughly 20% faster than the old one, even with the same modem, plugging into the faceplate, etc. The new connection achieves 16.5 down / 1.3 up and the old one achieves 13.0 down / 0.85 up.

Modem Stats - New Connection

 

Mode: ADSL_2plus    
Traffic Type: ATM    
Status: Up    
Link Power State: L0    
 
  Downstream Upstream    
Line Coding(Trellis): On On    
SNR Margin (1 dB): 6.1 7.4    
Attenuation (1 dB): 29.0 17.3    
Output Power (1 dBm): 0.0 12.6    
Attainable Rate (Kbps): 19860 1328    
 
  Path 0   Path 1  
  Downstream Upstream Downstream Upstream
Rate (Kbps): 19815 1279 0 0

 

Modem - Old connection

Mode: ADSL_2plus    
Traffic Type: ATM    
Status: Up    
Link Power State: L0    
 
  Downstream Upstream    
Line Coding(Trellis): On On    
SNR Margin (1 dB): 6.1 5.5    
Attenuation (1 dB): 28.5 15.1    
Output Power (1 dBm): 21.0 12.0    
Attainable Rate (Kbps): 17532 1208    
 
  Path 0   Path 1  
  Downstream Upstream Downstream Upstream
Rate (Kbps): 16427 976 0 0

 

I've asked Plusnet why one is significantly slower than the other, but nobody seems to know. The master sockets are literally right next to each other and share the same entry point into the building (I watched the BT Engineer install the new one).

 

The only notable differences in router stats I can see is that the Output Power differs between the two routers (I read this may be a reporting error), and the new connection is able to achieve nearly 100% of its "attainable rate."

Does anyone have any ideas why my new connection is so much faster than the old one? How is it able to achieve nearly 100% of its attainable rate when the other can't?

Moderator's note by Mike (Mav): Post released from Spam Filter

9 REPLIES
ian007jen
Rising Star
Posts: 392
Thanks: 4
Fixes: 2
Registered: 06-09-2007

Re: Two ADSL2+ lines-- One significantly slower than the other

Have you tried swapping the routers over?   I bet your speeds also "swap over".

 

Probable within manufacturing errors of components etc

 

Ian

zschallz
Hooked
Posts: 6
Registered: 24-03-2017

Re: Two ADSL2+ lines-- One significantly slower than the other

Sadly I get the same speeds on the slow line even with a newly supplied modem from Plusnet.
Community Veteran
Posts: 4,918
Thanks: 341
Fixes: 16
Registered: 10-06-2010

Re: Two ADSL2+ lines-- One significantly slower than the other

Can you get any further stats details from the modems?

I think there are two possibilities:

1. The slower line has interleaving on and the faster line doesn't, but surely someone at Plusnet should have spotted this.

2. The slower line is connected to older and slightly worse equipment at the exchange. You could probably see this if you had stats which include the vendor code of the equipment.

zschallz
Hooked
Posts: 6
Registered: 24-03-2017

Re: Two ADSL2+ lines-- One significantly slower than the other

Thanks!

The old line DID have interleaving on. I spotted this and requested a line reset a month ago. Interleaving coming off helped the ping by 7ms or so, but no real effect on speed.

I have command line access to the modem in question so I think I can get the vendor code with some googling. Will report back on that.
zschallz
Hooked
Posts: 6
Registered: 24-03-2017

Re: Two ADSL2+ lines-- One significantly slower than the other

Hello,

 

The vendor codes between the lines appear to be different.

I suspect nothing can be done about this? Would having a different modem matching the DSLAM better help? The old line's modem does sync the new line a bit slower.

 

 

...Or is my only option to switch the line to an LLU provider to ensure I get unplugged from that card (or would I remain there)? 

New Line
 > adsl info --vendor
adsl: ADSL driver and PHY status
Status: Showtime
Last Retrain Reason:    8000
Last initialization procedure status:   0
Max:    Upstream rate = 1328 Kbps, Downstream rate = 19712 Kbps
Bearer: 0, Upstream rate = 1279 Kbps, Downstream rate = 18279 Kbps

ChipSet Vendor Id:      IFTN:0x827a
ChipSet VersionNumber:  0x827a
ChipSet SerialNumber: 
 
 
Old Line
> adsl info --vendor
adsl: ADSL driver and PHY status
Status: Showtime
Last Retrain Reason:    0
Last initialization procedure status:   0
Max:    Upstream rate = 1172 Kbps, Downstream rate = 17480 Kbps
Bearer: 0, Upstream rate = 936 Kbps, Downstream rate = 16427 Kbps

ChipSet Vendor Id:      TSTC:0x0510
ChipSet VersionNumber:  0x0510
ChipSet SerialNumber:   00000000000000000000000000000000?
zschallz
Hooked
Posts: 6
Registered: 24-03-2017

Re: Two ADSL2+ lines-- One significantly slower than the other

Looks like TSTC = Texas Instruments and IFTN = Infineon.

 

Looks like Infineon bought Texas Instruments DSL business in 2007, so the old line's equipment must be at least that old:

http://www.infineon.com/cms/en/about-infineon/press/press-releases/2007/INFXXX200706-065.html

Community Veteran
Posts: 4,918
Thanks: 341
Fixes: 16
Registered: 10-06-2010

Re: Two ADSL2+ lines-- One significantly slower than the other

I think TSTC is the older one (they may not have immediately changed the vendor codes when corporate ownership changed, the business was later split off to become Lantiq, who continued to use the IFTN code).

Unfortunately, the difference in performance wouldn't be considered a fault, so it would be difficult to get anything done about it.

I doubt using a different modem at your end could solve the issue, it's more a limitation of the equipment at the exchange. If you have any different modem/routers readily available you've got little to lose by trying them, the BT Home Hub 5A and Plusnet Hub One are probably the most common devices using a modern Lantiq chipset.

Switching to a LLU provider would definitely get your line disconnected from the BTWholesale TSTC equipment and connected to the LLU kit.

Browni
Seasoned Champion
Posts: 1,521
Thanks: 430
Fixes: 35
Registered: 02-03-2016

Re: Two ADSL2+ lines-- One significantly slower than the other

One thing worth bearing in mind is that both lines are performing very well for the reported attenuation, pop the figures into a calculator such as http://www.kitz.co.uk/adsl/max_speed_calc.php and you'll see what I mean.
I must have been really bad in a previous life. This is my 3rd ISP in a row that uses lithium.
zschallz
Hooked
Posts: 6
Registered: 24-03-2017

Re: Two ADSL2+ lines-- One significantly slower than the other

Thanks for the helpful replies! 

I guess I should count my blessings. There'd be no guarantee that the LLU kit is any better, I suspect. Sky is the only available, which I guess would use BE's old kit.

As far as reported attenuation, I'm surprised it's as high as it is because we're probably a 10 minute walk to the exchange, but I guess the copper took the long way. Wink

Hopefully fibre comes to my cabinet eventually and I can stop sweating a few megabits.

Thanks, all!