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Anonymous
(Unregistered)Thu 30-Aug-12 11:58:35
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Fastpath on Sky FTTC


[link to this post]
 
My line is still on interleaved after 10 days (I know the DLM on FTTC is different, but still it's been 10 days), I have a feeling it was supposed to start on fastpath but it did not. The openreach engineer unplugged the modem to test the line after it was already connected up and working fine (D & E sides were originally mixed up at the cab), is that the cause? And I'm wondering if/when it's going to go to fastpath?

My line is stable at 9.65MB/s (using internet download manager and a 1GB tbb test file).

Useful Info:
Sync:-
Downstream: 79996
Upstream: 20000
That's according to the sky router, I'm now using a Buffalo WZR-HP-G300NH router instead as it out performs the sky router (the sky router can't handle those speeds, it tops out at around 9.3MB/s I think).

Ping from PC to the bbc is 15ms,

I'm pretty sure the openreach engineer said the downstream SNR was 16 and up was 12.

I haven't touched the modem.
Standard User Zadeks
(experienced) Thu 30-Aug-12 12:57:50
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Re: Fastpath on Sky FTTC


[re: Anonymous] [link to this post]
 
How do you know 15ms is interleaved?

Where are you located?
Standard User StephenTodd
(member) Thu 30-Aug-12 13:17:44
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Re: Fastpath on Sky FTTC


[re: Zadeks] [link to this post]
 
I'm on BT Infinity. I am not interleaved, and have a ping to bbc of 20ms.

Best indication is to unlock the modem. Failing that, try 'tracert bbc.co.uk'. The first hop will give a better indication. Mine is 7ms even without interleaving. Some luckier BT users get 5ms or 6ms pings all the way to bbc.

--
Moved (with trepidation) to BT Infinity 2 for upload speed. Happy BE user for several years.


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Anonymous
(Unregistered)Thu 30-Aug-12 14:04:12
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Re: Fastpath on Sky FTTC


[re: StephenTodd] [link to this post]
 
Here's a traceroute that I've just taken. I'm in lancashire.
Tracing route to bbc.co.uk [212.58.241.131]
over a maximum of 30 hops:

1 <1 ms <1 ms <1 ms DD-WRT [192.168.11.1]
2 * * * Request timed out.
3 19 ms 17 ms 16 ms ip-84-38-37-12.easynet.co.uk [84.38.37.12]
4 18 ms 19 ms 19 ms te0-1-0-0.er11.thlon.ov.easynet.net [89.200.135
97]
5 17 ms 15 ms 19 ms ntl-ge2-9.prt0.rbsov.bbc.co.uk [212.58.238.189]

6 * * * Request timed out.
7 15 ms 15 ms 15 ms ae1.er01.rbsov.bbc.co.uk [132.185.254.46]
8 16 ms 17 ms 15 ms 132.185.255.60
9 15 ms 15 ms 15 ms 212.58.241.131

Trace complete.
Anonymous
(Unregistered)Thu 30-Aug-12 14:43:33
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Re: Fastpath on Sky FTTC


[re: Anonymous] [link to this post]
 
So I went ahead and "hacked" the modem, they are below. From memory I think it's the D line that refers to interleaving. Am I on fastpath or interleaved?

xdslcmd: ADSL driver and PHY status
Status: Showtime
Retrain Reason: 0
Max: Upstream rate = 32417 Kbps, Downstream rate = 134704 Kbps
Path: 0, Upstream rate = 20000 Kbps, Downstream rate = 79999 Kbps

Link Power State: L0
Mode: VDSL2 Annex B
VDSL2 Profile: Profile 17a
TPS-TC: PTM Mode
Trellis: U:ON /D:ON
Line Status: No Defect
Training Status: Showtime
Down Up
SNR (dB): 20.9 13.1
Attn(dB): 0.0 0.0
Pwr(dBm): 13.1 -1.9
VDSL2 framing
Path 0
B: 239 236
M: 1 1
T: 23 5
R: 0 16
S: 0.0955 0.3771
L: 20107 5410
D: 1 1
I: 240 255
N: 240 255
Counters
Path 0
OHF: 94337 25644
OHFErr: 0 0
RS: 0 1666041
RSCorr: 0 0
RSUnCorr: 0 0

Path 0
HEC: 0 0
OCD: 0 0
LCD: 0 0
Total Cells: 23988724 0
Data Cells: 1226 0
Drop Cells: 0
Bit Errors: 0 0

ES: 0 0
SES: 0 0
UAS: 40 40
AS: 158

Path 0
INP: 0.00 0.00
PER: 1.64 6.12
delay: 0.00 0.00
OR: 116.56 203.67

Bitswap: 0 0

Total time = 3 min 21 sec
FEC: 0 0
CRC: 0 0
ES: 0 0
SES: 0 0
UAS: 40 40
LOS: 0 0
LOF: 0 0
Latest 15 minutes time = 3 min 21 sec
FEC: 0 0
CRC: 0 0
ES: 0 0
SES: 0 0
UAS: 40 40
LOS: 0 0
LOF: 0 0
Previous 15 minutes time = 0 sec
FEC: 0 0
CRC: 0 0
ES: 0 0
SES: 0 0
UAS: 0 0
LOS: 0 0
LOF: 0 0
Latest 1 day time = 3 min 21 sec
FEC: 0 0
CRC: 0 0
ES: 0 0
SES: 0 0
UAS: 40 40
LOS: 0 0
LOF: 0 0
Previous 1 day time = 0 sec
FEC: 0 0
CRC: 0 0
ES: 0 0
SES: 0 0
UAS: 0 0
LOS: 0 0
LOF: 0 0
Since Link time = 2 min 37 sec
FEC: 0 0
CRC: 0 0
ES: 0 0
SES: 0 0
UAS: 0 0
LOS: 0 0
LOF: 0 0
Administrator MrSaffron
(staff) Thu 30-Aug-12 14:48:06
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Re: Fastpath on Sky FTTC


[re: Anonymous] [link to this post]
 
Interleave with a depth of just 1, i.e. hardly on at all.

Andrew Ferguson, andrew@thinkbroadband.com
www.thinkbroadband.com - formerly known as ADSLguide.org.uk
The author of the above post is a thinkbroadband staff member. It may not constitute an official statement on behalf of thinkbroadband.
Anonymous
(Unregistered)Thu 30-Aug-12 14:54:04
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Re: Fastpath on Sky FTTC


[re: MrSaffron] [link to this post]
 
Isn't that adding around 7ms?
Standard User BatBoy
(legend) Thu 30-Aug-12 15:01:18
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Re: Fastpath on Sky FTTC


[re: Anonymous] [link to this post]
 
ISPs (rarely, users) have the option to use interleaving of packets to counter the effects of burst noise on the telephone line. An interleaved line has a depth, usually 8 to 64, which describes how many Reed–Solomon codewords are accumulated before they are sent. As they can all be sent together, their forward error correction codes can be made more resilient. Interleaving adds latency as all the packets have to first be gathered (or replaced by empty packets) and they, of course, all take time to transmit. 8 frame interleaving adds 5 ms round-trip-time, while 64 deep interleaving adds 25 ms. Other possible depths are 16 and 32.

"Fastpath" connections have an interleaving depth of 1, that is one packet is sent at a time. This has a low latency, usually around 10 ms (interleaving adds to it, this is not greater than interleaved) but it is extremely prone to errors, as any burst of noise can take out the entire packet and so require it all to be retransmitted. Such a burst on a large interleaved packet only blanks part of the packet, it can be recovered from error correction information in the rest of the packet. A "fastpath" connection will result in extremely high latency on a poor line, as each packet will take many retries.



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Administrator MrSaffron
(staff) Thu 30-Aug-12 15:02:42
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Re: Fastpath on Sky FTTC


[re: Anonymous] [link to this post]
 
I think that depth of 1 is the best that Openreach run at, some sources claim modem with D=1 is actually fastpath.

What is the problem you are trying to solve?

Andrew Ferguson, andrew@thinkbroadband.com
www.thinkbroadband.com - formerly known as ADSLguide.org.uk
The author of the above post is a thinkbroadband staff member. It may not constitute an official statement on behalf of thinkbroadband.
Administrator MrSaffron
(staff) Thu 30-Aug-12 15:04:48
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Re: Fastpath on Sky FTTC


[re: BatBoy] [link to this post]
 
As that source is ADSL specific I am wary of quoting it for use with VDSL2

Fastpath is rare for any VDSL2 deployment, seems if you want lower latency then you need to wait for Fibre on Demand

Andrew Ferguson, andrew@thinkbroadband.com
www.thinkbroadband.com - formerly known as ADSLguide.org.uk
The author of the above post is a thinkbroadband staff member. It may not constitute an official statement on behalf of thinkbroadband.
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