Kitz Forum
Broadband Related => Broadband Technology => Topic started by: GigabitEthernet on August 10, 2012, 10:08:25 AM
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Hello,
I have recently been migrated to 21CN and I have a few questions to further educate me on 21CN (since I haven't used it before or experienced it):
1. Why has the speed increased to 8000Kbps from 7000Kbps despite being on the same ADSL Max service, just on 21CN rather than 20CN. Is it to do with the IFTN (Infineon chipset)?
2. I am syncing at 8000Kbps with interleaving switched on. I thought with interleaving the max was 7616Kbps? Does 21CN have different limits?
3. Should I do anything over the first 10 days if there is a 10 day training period?
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Re item 2
On ADSL1/20CN it depends on the router:
Some only do 7616 as you said and as BT originally also said was the max on interleaved lines
Some manage more-
The BT Voyager 2110 will, but only up to 8096 as a max
Others which implemented mode s=0.5 which was an addition to the original international DMT spec' I think will do the full 8128 and I've seen two lines in the past indeed doing the full 8128/interleaved
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As c6em says its to do with S=1/2 mode. Which basically is a more efficient algorithm for encoding of RS code words meaning less overhead needed for error correction.
Although it was implemented with adsl2 (increasing speed from 8>12Mb) and then adsl2+ (12>24Mb), Some of the MSANs which BT installed for maxdsl - such as the Fujitsu Geostreams - were able to utilise S=1/2 mode as long as your router was also compatible.... this is why some maxdsl lines can sync at >8128 even if interleaved.
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hmm ive seen plenty of 8128k / 448k sync'd ADSL lines including my own at old address back in 2006..? (DG834Gv3)
....am I missing something here?
- ive never heard of this 7616k max sync before OR that BT stated that 7616k was max you could get on ADSL1 - its always been 8128k max on 20CN ADSL1 (IPstream) - I know the profiling system means you cant get more than 7150k
learn summit new every time i come on here - thats why i love it :)
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12.2 What does the maximum line rate fall to if interleaving is applied?
The line will be reduced to 7616 kbps.
From BTw
https://www.btwholesale.com/shared/document/Products/Broadband/IPStream/dsl_max_myths_legends_issue1.pdf
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wierd.... never knew that, s'funny how a lot of people were getting 8128k - I mean it was very common to get that if line was capable, at least seemed that way
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It seemed to be fairly common when maxdsl first came in, but gradually over the next few years the higher sync rate appeared more often.
This could be due to updating of the exchange MSANs (or MSAN firmware?)... also more people would be updating to newer routers.
When maxdsl first came in, many users were still using the same routers that they had for say 512/1Mb/2Mb fixed rate. Whilst many of these would work fine with maxdsl, not all of them (eg the old Solwise/Voyagers some of the older STs - even the old frog modems were still in use) supplied by some ISPs back then were not adsl 2/2+ compatible nor able to use s=1/2 mode algorithm.
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i was on AOL 2Mb when they put us on 8Mb free when BT upgraded, we were using the BT Voyager USB Modem thing lol.. memory is vague but I did end up getting a Netgear DG834Gv3 off them - dunno if it was for the 8Mb or if I mangled one from them later, probably the latter- I remember we only got 4Mb but the line was easily capable of 8Mb as we got that later with Entanet
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My memory is hazy now, but Im pretty sure that AOL fobbed off many of their users for quite a while imposing speed caps of around 2 or 4Mb even when lines were capable of the full 8Mb. I do remember seeing some very interesting transcripts of conversations between their users and CS, that shall I say made quite a fairy tale with their excuses :D
The DG834v3 s were one of the routers that should be able to support s=1/2 mode, so that could be why you perhaps didnt notice it.