Suggestions for resolving packet loss on bonded Fusion

Internet access discussion, including Fusion, IP Broadband, and Gigabit Fiber!
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by stephencsu » Wed Sep 21, 2011 8:15 pm
I've gone back and forth with support trying to resolve my problems with packet loss on bonded Fusion and wanted to post my experience to see if any users might have suggestions on what else to try.

I'm over 14k feet from the CO and had a stable 1536/384 ADSL1 interleaved line with AT&T for the last 2 years. Last week I ported my line and added a 2nd bonded line. The Sonic.net performance on my ported line using ADSL1 interleaved is around 1200/384 while the new line is around 1300/288. The ADSL2+ interleaved performance is 100-200 better on downstream and the same on upstream. I'm using a ZyXEL P-663HN-51 and plugged directly into the NID (i.e. no internal wiring).

If I only have one line or the other plugged in but not both, my connection is stable (i.e. no packet loss on ping to http://www.sonic.net) as long as I have the upstream speed capped at the value mentioned above. Once I plug both DSL lines in, though, I have packet loss of ~10% if the second line is the primary connection and packet loss of 25+% if the first line is the primary connection.

Multiple line tests were performed by Sonic.net confirming that the DSL line itself was well within spec. An AT&T technician checked the line on Saturday at the NID and also confirmed that the line was clean.

Sonic.net support:
- suggested sending a new modem. I received a loaner ZyXEL P-663HN-51 modem today but the behavior is identical to my original modem.
- suggested that the problem was the ZyXEL RJ-11 Y-cable. I rewired to combine the two lines from the NID into a 2-line RJ-11 plug, but the behavior was identical to the ZyXEL Y-cable.
- suggested trying to switch from Interleaved to Fast. Other than a lower sync rate and a higher error count, the behavior was identical to Interleaved.
- suggested that the lines have matched speeds. This seemed to work when both lines were capped at 512/288, but why would I pay for two lines configured to be slower than a single line? Setting both lines at 1188/288, which held sync, showed the same level of packet loss as when the lines did not have the same speeds.
- intended to send a Comtrend modem but inadvertently sent the ZyXEL. A loaner Comtrend is supposed to arrive on Friday.
- said that a port change at the CO was considered a drastic last resort.

Any other suggestions?
by dane » Thu Sep 22, 2011 10:49 am
If each circuit performs well individually, but suffers when both are up, this is generally a near-end-crosstalk (NEXT) problem. We see it most often when people use flat satin cable or other non-twisted or cat-3 cable for the jack to modem connection. With bonded service, you really do not want ANY non-twisted wire in the path, particularly at the "near" side (near to you), as the crosstalk between the two can be a problem.

That's the only tip that comes to mind at the moment. Speeds need not match with g.bond ATM bonding, but I don't know if having one interleave and the other fast path is a problem or not. Setting both at interleave is probably a safe bet.

-Dane
Dane Jasper
Sonic
by stephencsu » Thu Sep 22, 2011 11:30 am
Thanks for the suggestion. I'll make a custom cable using Cat5e cable.
by dane » Thu Sep 22, 2011 11:53 am
Even Cat-3 is fine, as that's what the outside plant cabling is. They key is NO untwisted "flat satin" style cable.

-Dane
Dane Jasper
Sonic
by stephencsu » Thu Sep 22, 2011 7:15 pm
Switching to a twisted pair cable didn't help. If NEXT is the problem, it's happening at the two-line RJ-11 port on the modem itself. I tried physically separate twisted pairs which were only joined at the final RJ-11 at the modem and that didn't help either.
by dane » Thu Sep 22, 2011 8:10 pm
Must be something else then. :)

Ring up support, they can come on site with a modem and test at the MPOE, make adjustments, and if there's any indication of copper trouble, dispatch AT&T. Just dial 611 from your Fusion line, they are there until 11pm.

-Dane
Dane Jasper
Sonic
by stephencsu » Fri Sep 30, 2011 6:36 pm
Switching to a Comtrend 5631 appears to have cleared up the packet loss issue. Fortunately I was inadvertently sent two Comtrends, because the first one I tried lost sync every 1-2 minutes. The second one, knock on wood, is holding a stable bonded signal with no packet loss.
by pnfisher » Sat Jan 07, 2012 7:23 pm
stephencsu wrote:If I only have one line or the other plugged in but not both, my connection is stable (i.e. no packet loss on ping to http://www.sonic.net) as long as I have the upstream speed capped at the value mentioned above. Once I plug both DSL lines in, though, I have packet loss of ~10% if the second line is the primary connection and packet loss of 25+% if the first line is the primary connection.
I recently upgraded to bonded Fusion and ran into this exact same problem with the ZyXEL P-663HN-51 -- at least 10% packet loss when both lines were up. 0% packet loss with just one line up (didn't matter which line).

This is a known bug with the ZyXEL P-663HN-51. Unfortunately, the problem is not widely known within the support staff at Sonic.

The workaround is to enable Annex M support on the ZyXEL. It doesn't matter if Annex M is off or on at the DSLAM, but Annex M support must be enabled on the ZyXEL CPE to work around the packet loss problem.

The ZyXEL defaults to disabling support for Annex M (at least when the reset button is used). This is a problem.

Since Annex M is off at the DSLAM for my lines, it makes no sense why Annex M support needs to be enabled on the CPE to prevent the packet loss problem.

It seems like the correct fix would be an updated firmware. I'm actually somewhat concerned about all the ZyXEL installs out there in the wild -- less technically inclined users aren't necessarily going to notice 10% packet loss.
by dane » Sat Jan 07, 2012 7:40 pm
We've got lots of customers using the ZyXel in it's default configuration who are not seeing any packet loss, FYI.

-Dane
Dane Jasper
Sonic
by pnfisher » Sat Jan 07, 2012 7:53 pm
dane wrote:We've got lots of customers using the ZyXel in it's default configuration who are not seeing any packet loss, FYI.
That's good to hear. I'm using the ZyXEL in bridge mode with wireless off, which is not the default config. So perhaps there are additional settings (or line conditions) needed in order to trigger this bug. I can easily reproduce the packet loss problem tho -- disable Annex M support, 10%+ packet loss -- enable Annex M support, 0% packet loss. Very bizarre.
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