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[sheephouse]

Can anyone tell me what effect interleave depth 0 has?

Some time ago I asked my ISP (Plusnet) to switch me to fast path as my router reported interleave depth 0. They told me that interleave depth was fast path, so I assumed it was just the way my router displayed it.

Over the weekend I had my ISP reset my ADSLMax Premium connection because I had a very low profile. Following that reset my router reported the connection as fast path, and my latency reduced from around 40ms minimum to 18ms - nice!

However, this morning the line reset again (no errors reported by my router), and I'm now back with interleave depth 0 and 40ms+ latency.
The connection is still 8Mbps/0.8Mbps with SNR 8dB/13dB

[kitzuser87430]

May be a reporting error with the modem/router.

http://www.kitz.co.uk/adsl/interleaving.htm

Reading the above will provide more information, there will have been some errors which is why the DLM has applied interleaving again.

http://www.kitz.co.uk/adsl/DLM_system.htm

My ADSLMax connection also cannot handle fast-path when I recently tried it; the number of error seconds increased from, on average 200/day with interleaving, to over 700/day on fastpath; interleaving was re-applied after <24 hours on fast-path.

Ian

[sheephouse]

The lack of errors reported by the router is strange - I once saw 3 HEC errors during a thunderstorm, but otherwise I've never seen any errors reported at all which seems suspicious.

The kitz interleaving info is interesting, but it states that a depth of 0 means interleaving is off. I don't know what "off" means, as it is apparently different to fast path (the increase in latency shows that). And if it is "off", then I don't see how it would help the connection.

Also it suggests that the maximum sync rate with interleave is usually 7616kbps, but I have 8128kbps.

[c6em]

Only if you have an old modem/router unit that does not deal with or can handle "mode s=0.5" (It's complex!)
These old ones were indeed limited to 7176kbps sync when interleaving was on
A modern unit can do the full Adlsmax sync of 8128Kbps when interleaved.

Standard Adslmax ping will indeed be around 15Ms on fast path (ie Interleaving depth = 0) and around the 30 to 40ms when interleaved.

[sheephouse]

Ok, I have a Draytek Vigor 2860n+ so I assume it is new enough to support 8128kbps with interleave.

With interleave depth 0 I get latency of 40ms+, and with fast path 18ms. So there is definitely a difference between interleave depth 0 and fast path - but I don't understand what it is.

[ejs]

I think the interleave depth of 0 is not correctly reporting the actual interleave depth. Perhaps upgrade to the latest firmware, and since it's a Draytek, use the "modem code" with the highest version number.

[sheephouse]

I do have the latest firmware (applicable for the UK), and Plusnet have also told me it is interleave depth 0. When I asked to be switched to fast path they said interleave depth 0 was fast path, but it obviously isn't as when my router reported the connection as fast path it had much lower latency.
Still puzzled.

[roseway]

Interleave depth isn't the only determinant for latency. It's quite possible to be on fastpath and still have high latency.

[sheephouse]

Yes I accept that there are lots of causes of latency (the speed of light being one), but the point here is that latency has changed.  Here's a Thinkbroadband BQM graph that shows the change:


At 9.17am the connection changed from fast path to interleave depth 0.

[d2d4j]

Hi

Interleave depth 0 means off and interleave depth 1 means interleave on but no interleave is currently been applied to the line, so both of these indicate fast path as no actions are been applied.

I suspect your connected to a poor gateway

Have you tried dropping ppp connection and reconnect to see if it improves. It's called gateway hopping and you cannot set which gateway you use, it is assigned at the point of connection

Before gateway hopping, run a pathping, then gateway hop and run another pathping when you see your gateway has changed

Many thanks

John

[sheephouse]

The gateway hasn't changed - it was plusnet's ptw-ag01 gateway when the connection was fast path, and when interleave 0.  It has just dropped the connection again, and it is still ptw-ag01 so it doesn't seem to change often if at all.

The only time I have ever seen fast path on my connection was when support reset my connection on Sunday, which was changed back to interleave depth 0 this morning. I'm sure it is the difference between fast path and interleave depth 0 (whatever that difference is, it is more than nothing) that makes the difference in latency.

[kitz]

The kitz interleaving info is interesting, but it states that a depth of 0 means interleaving is off. I don't know what "off" means, as it is apparently different to fast path (the increase in latency shows that). And if it is "off", then I don't see how it would help the connection.

In very simplistic terms, there are two paths that DSL can use to transmit data over, think of them as channels.

The Interleaved path can apply interleaving.  Fast path cant.    However you can send data over the interleaved path, but if you set it to 0 or 1 then no interleaving is applied because there is no chopping up or re-arranging of data.

So back to channels.  When it came to paths, BT used to reserve fast path for TV (the old BT vision) whilst all 'normal' internet data was sent over the interleaved path.  Some of those with the old BTvision may recall how 500 kbps of their bandwidth was semi reserved for TV and they had 2 IPprofiles.   TV performs very badly with interleaving, so this is why they split how data could be sent.    Yet the beauty of the interleaved path is you can still use this channel and make it perform like fast path by setting interleave to 0/1. 

As eric says:-

Interleave depth isn't the only determinant for latency. It's quite possible to be on fastpath and still have high latency.

BTw can also apply RS encoding without Interleaving.  We have seen them do this before (mostly upstream vdsl),  however if you arent recording any FEC then it is unlikely.

I think if I were you I'd ask Plusnet to run a GEA Service Test / WOOSH test to get your DLM profile.   That way you'd have more information on what was going on.

[Weaver]

You can flounder around. Or you can just ask Kitz!

[sheephouse]

Kitz, thanks for your comments!
I don't think this is the WOOSH test result - but does it help at all?

xDSL Status Test Summary
Sync Status:   Circuit In Sync
General Information
NTE Status:   In Service   NTE Power Status:   NTE Power On   Bypass Status:   Bypass Not Activated
   Upstream DSL Link Information   Downstream DSL Link Information
Loop Loss:   15   27.5
SNR Margin:   14.8   9.5
Errored Seconds:   1   0
HEC Errors:   0   0
Cell Count:   67934   484130
Speed:   832   7968
Maximum Stable Rate (KBPS):   288   Fault Threshold Rate (KBPS):   288
Mean Time Between Retrains (Seconds):   86380   Mean Time Between Errors Upstream (Seconds):   86380
Indicative Line Quality:   A   Mean Time Between Errors Downstream (Seconds):   576

[ejs]

I suppose that because this is 20CN ADSL1, it doesn't say anything similar to "Medium delay (INP 1)" like 21CN ADSL2+ does. Unfortunately, I don't think the test results clarify anything.

I still think that another modem would display the interleaving depth as some integer greater than 1.