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So what would be the throughout one should expect to see from a speedtest or downloading if their VDSL line synced at 40000/10000kbps ?
and would the math also be the same for speeds from 2000/2000-> 80000/20000kbps?
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probably around 37mbit/sec if all is working ok.
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Is their a specific math behind it all... a percentage maybe... do you know any sites where I can get this information?
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Register (or login) on our website and you will not see this ad.
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I calculate around 7.5% loss mark then for throughput over the sync rate
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Maximum TCP/IP throughput is 96.8% of the sync rate.
The other differences are down to the various overheads on your home network etc
Even 100 Mbps Ethernet does not deliver 100 Mbps but a couple of Mbps below this.
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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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OK...
So I'm syncing at 66000kbps ... I can only achieve a max throughput of 60700kbps...
I feel this is around 2000kbps shy of its capability...
Nothing shocking I know but curiosity 
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Yes. The overhead is essentially down to overheads on the framing, IP and TCP overheads.
The usual maximum packet size is 1500 bytes (there are so-called "jumbo-packets", but they are only used for specialist purposes, like local storage over IP and require special support). However, within that 1500 byte packet there is a 20 byte IP packet header and a 32 byte TCP header. That gives you a payload of 1448 bytes. However, there is also an Ethernet framing overhead comprising another 38 bytes. So, for every 1448 bytes of data there are 1538 bytes sent over the link. That's 94.1% payload efficiency, which means for a 40mbps sync there is a maximum of 37.6mbps data throughput available.
The proportion is the same no matter what the sync speed. So an 80mbps will have a maximum TCP payload throughput of 75.2mbps.
*** edited as there was a slight mistake where I'd used 1440 as the payload size ***
Note that this is for IPV4. IPV6 has larger overheads.
Also, there is an overhead for "ack" packets in the opposite direction (About 4%, so downloading at 40mbps requires a minimum upload bandwidth of 1.6mbps).
UDP protocols have different overheads, but that's not normally used for speed tests.
Edited by deleted (Wed 01-Apr-15 14:07:37)
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Have you checked the current IP Profile rather than the sync?
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Have you checked the current IP Profile rather than the sync?
64mbps (BTw IP Profile)
Edited by mlmclaren (Wed 01-Apr-15 13:34:29)
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That calculation is surely only covering the TCP & IP headers. Surely it's necessary to include the Ethernet frame overheads too (unless the stats reported by the modem include an allowance for that).
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Maximum TCP/IP throughput is 96.8% of the sync rate.
I do believe these are now no longer in use under G.INP enabled. 96.8% are probably less now.
Before G.INP
BT IP 77.44Mb
After G.INP
BT IP 77.35Mb
Edited by adslmax (Wed 01-Apr-15 15:15:00)
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I haven't checked your numbers, but you're right about the scale of overhead for IP and TCP headers over Ethernet LAN.
However, the bulk of the overhead between router and ISP is encapsulated in the "IP profile".
The difference between a sync speed of 40,000 and the corresponding IP profile of 38,717 is an indication of the volume of IP data that can be transferred over the DSL link; essentially, 3.3% is the overhead of getting your IP packets from the router to the ISP (including those extra 8 bytes in PPPoE).
With an IP profile of 38717, the throughput of "a download" (ie just the payload data) is around 37.5Mbps at absolute best. This reduction is accounted for by the headers in IP and TCP.
On an 80/20 connection, the IP profile is 77.4Mbps, and the top end throughput during a download around 75Mbps.
Note: G.INP reduces the IP profile slightly (0.1Mbps).
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Here are some stats from my Zen connection. First column is BRAS speed, second is SYNC (line) speed and then BRAS/SYNC. Average at the end as a %age.
| Text | 1
23
45
67
89
10 | 64387 66519 0.967949
58873 60823 0.9679457900 59818 0.967936
59714 61692 0.96793760056 62045 0.967943
59745 61724 0.96793861729 63773 0.967949
60293 62289 0.96795660643 62651 0.967949
Average: 96.7944 % |
Edited by deleted (Wed 01-Apr-15 15:48:18)
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I halved it from the throughput on the 80/20 service.
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Note: G.INP reduces the IP profile slightly (0.1Mbps). Are you sure about that?
Since attaining exactly 60,000kbps I've had a 58.01Mbps IP Profile. Rather than the 58.07Mbs I would expect from the 0.9679 factor. Download speedachieved during the test was - 51.52 Mbps
For your connection, the acceptable range of speeds is 40 Mbps-58.01 Mbps .
Additional Information:
IP Profile for your line is - 58.01 Mbps # xdslcmd info --pbParams
xdslcmd: ADSL driver and PHY status
Status: Showtime
Retrain Reason: 0
Last initialization procedure status: 0
Max: Upstream rate = 16964 Kbps, Downstream rate = 58800 Kbps
Bearer: 0, Upstream rate = 16961 Kbps, Downstream rate = 60000 Kbps
Bearer: 1, Upstream rate = 0 Kbps, Downstream rate = 0 Kbps
Discovery Phase (Initial) Band Plan
US: (7,32) (871,1205) (1972,2782)
DS: (33,859) (1216,1961) (2793,3970)
Medley Phase (Final) Band Plan
US: (7,32) (871,1205) (1972,2782)
DS: (33,859) (1216,1961) (2793,3970)
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77.44 -> 77.35 here.
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Yes. The overhead is essentially down to overheads on the framing, IP and TCP overheads.
The usual maximum packet size is 1500 bytes (there are so-called "jumbo-packets", but they are only used for specialist purposes, like local storage over IP and require special support). However, within that 1500 byte packet there is a 20 byte IP packet header and a 32 byte TCP header. That gives you a payload of 1448 bytes. However, there is also an Ethernet framing overhead comprising another 38 bytes. So, for every 1448 bytes of data there are 1538 bytes sent over the link. That's 94.1% payload efficiency, which means for a 40mbps sync there is a maximum of 37.6mbps data throughput available.
The proportion is the same no matter what the sync speed. So an 80mbps will have a maximum TCP payload throughput of 75.2mbps.
*** edited as there was a slight mistake where I'd used 1440 as the payload size ***
Note that this is for IPV4. IPV6 has larger overheads.
Also, there is an overhead for "ack" packets in the opposite direction (About 4%, so downloading at 40mbps requires a minimum upload bandwidth of 1.6mbps).
UDP protocols have different overheads, but that's not normally used for speed tests.
Ethernet frame headers are 14 bytes + 4 more if using 802.1Q + 2 byte checksum, TCP headers are 20. The overheads are 18 bytes for Ethernet, 8 for PPP, and 40 for TCP/IP = 68 bytes per frame.
If the modem and PPPoE router support baby jumbo frames you get 1460 bytes of payload per 1528 bytes on the wire or 1452 bytes per 1520 on the wire if not.
EDIT: Forgot the VLAN tags - extra 4 bytes, and checksum, another 2.
Also the acknowledgement overhead is very unlikely to be 4% as virtually nothing acknowledges every frame and if it did download speeds would be tedious over any kind of latency, selective and cumulative acknowledgements are used to reduce round trip and effect of loss.
Edited by deleted (Wed 01-Apr-15 17:06:32)
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Unchanged sync?
79,987 -> 79,999, it says.
How about these settings?
before:
Bearer 0
INP: 0.00 0.00
INPRein: 0.00 0.00
delay: 0 0
PER: 1.65 3.98
OR: 116.09 64.22
AgR: 80103.09 20063.54
After G.INP:
Bearer 0
INP: 46.00 47.00
INPRein: 0.00 0.00
delay: 0 0
PER: 0.00 0.00
OR: 0.01 0.01
AgR: 80614.82 20102.08
Bearer 1
INP: 4.00 4.00
INPRein: 4.00 4.00
delay: 3 0
PER: 16.06 16.06
OR: 95.62 31.87
AgR: 95.62 31.87
I *think* "AgR" means aggregate rate, and includes some of the overhead bits, as well as the main "throughput" we want from the link.
What we see as "sync speed" should be a combination of the throughput on both bearer 0 and bearer 1. Bearer 1 is close to using 0.1Mbps. But bearer 0 has gone up from the original... so it depends what the other overheads are.
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Wow so a 0.1 or 0.2% difference. I'll go throw a party
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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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Unchanged sync?
That's was when g.inp was put on
Edited by adslmax (Wed 01-Apr-15 18:56:49)
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79,987 -> 79,999, it says.
How about these settings?
before:
Bearer 0
INP: 0.00 0.00
INPRein: 0.00 0.00
delay: 0 0
PER: 1.65 3.98
OR: 116.09 64.22
AgR: 80103.09 20063.54
After G.INP:
Bearer 0
INP: 46.00 47.00
INPRein: 0.00 0.00
delay: 0 0
PER: 0.00 0.00
OR: 0.01 0.01
AgR: 80614.82 20102.08
Bearer 1
INP: 4.00 4.00
INPRein: 4.00 4.00
delay: 3 0
PER: 16.06 16.06
OR: 95.62 31.87
AgR: 95.62 31.87
I have the same setting as your too. From 79987K to 79999K with g.inp enabled
adsl info --stats
adsl: ADSL driver and PHY status
Status: Showtime
Last Retrain Reason: 0
Last initialization procedure status: 0
Max: Upstream rate = 35828 Kbps, Downstream rate = 105285 Kbps
Bearer: 0, Upstream rate = 20000 Kbps, Downstream rate = 79999 Kbps
Bearer: 1, Upstream rate = 0 Kbps, Downstream rate = 0 Kbps
Link Power State: L0
Mode: VDSL2 Annex B
VDSL2 Profile: Profile 17a
TPS-TC: PTM Mode(0x0)
Trellis: U:ON /D:ON
Line Status: No Defect
Training Status: Showtime
Down Up
SNR (dB): 12.3 16.3
Attn(dB): 11.3 0.0
Pwr(dBm): 12.5 -1.3
VDSL2 framing
Bearer 0
MSGc: -6 -6
B: 130 97
M: 1 1
T: 0 0
R: 8 8
S: 0.0518 0.1554
L: 21468 5457
D: 16 8
I: 139 106
N: 139 106
Q: 16 8
V: 14 2
RxQueue: 57 39
TxQueue: 19 13
G.INP Framing: 18 18
G.INP lookback: 19 13
RRC bits: 24 24
Bearer 1
MSGc: 186 58
B: 0 0
M: 2 2
T: 2 2
R: 16 16
S: 5.3333 16.0000
L: 48 16
D: 3 1
I: 32 32
N: 32 32
Q: 0 0
V: 0 0
RxQueue: 0 0
TxQueue: 0 0
G.INP Framing: 0 0
G.INP lookback: 0 0
RRC bits: 0 0
Counters
Bearer 0
OHF: 0 0
OHFErr: 0 0
RS: 3149995456 2180637
RSCorr: 98965 35962
RSUnCorr: 0 0
Bearer 1
OHF: 23406070 432546
OHFErr: 0 0
RS: 280872840 3810562
RSCorr: 57 142
RSUnCorr: 0 0
Retransmit Counters
rtx_tx: 1720 835
rtx_c: 1713 802
rtx_uc: 0 0
G.INP Counters
LEFTRS: 42 10
minEFTR: 79982 19997
errFreeBits: 458725840 116574474
Bearer 0
HEC: 0 0
OCD: 0 0
LCD: 0 0
Total Cells: 2004966366 0
Data Cells: 604942676 0
Drop Cells: 0
Bit Errors: 0 0
Bearer 1
HEC: 0 0
OCD: 0 0
LCD: 0 0
Total Cells: 0 0
Data Cells: 0 0
Drop Cells: 0
Bit Errors: 0 0
ES: 0 0
SES: 0 0
UAS: 0 0
AS: 376021
Bearer 0
INP: 46.00 47.00
INPRein: 0.00 0.00
delay: 0 0
PER: 0.00 0.00
OR: 0.01 0.01
AgR: 80614.82 20102.08
Bearer 1
INP: 4.00 4.00
INPRein: 4.00 4.00
delay: 3 0
PER: 16.06 16.06
OR: 95.62 31.87
AgR: 95.62 31.87
Bitswap: 748/748 1161/1161
Total time = 4 days 8 hours 27 min 1 sec
FEC: 98965 35962
CRC: 0 0
ES: 0 0
SES: 0 0
UAS: 0 0
LOS: 0 0
LOF: 0 0
LOM: 0 0
Latest 15 minutes time = 12 min 1 sec
FEC: 178 64
CRC: 0 0
ES: 0 0
SES: 0 0
UAS: 0 0
LOS: 0 0
LOF: 0 0
LOM: 0 0
Previous 15 minutes time = 15 min 0 sec
FEC: 1072 223
CRC: 0 0
ES: 0 0
SES: 0 0
UAS: 0 0
LOS: 0 0
LOF: 0 0
LOM: 0 0
Latest 1 day time = 8 hours 27 min 1 sec
FEC: 10030 2673
CRC: 0 0
ES: 0 0
SES: 0 0
UAS: 0 0
LOS: 0 0
LOF: 0 0
LOM: 0 0
Previous 1 day time = 24 hours 0 sec
FEC: 50973 12702
CRC: 0 0
ES: 0 0
SES: 0 0
UAS: 0 0
LOS: 0 0
LOF: 0 0
LOM: 0 0
Since Link time = 4 days 8 hours 26 min 59 sec
FEC: 98965 35962
CRC: 0 0
ES: 0 0
SES: 0 0
UAS: 0 0
LOS: 0 0
LOF: 0 0
LOM: 0 0
Edited by adslmax (Wed 01-Apr-15 19:01:45)
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Since attaining exactly 60,000kbps I've had a 58.01Mbps IP Profile. Rather than the 58.07Mbs I would expect from the 0.9679 factor.
From what I have seen from a number of G.INP active connections, it appears that IP Profile is now around 96.69% of Sync speeds rather than the 96.79% for non-G.INP active connections.
e.g. Your connection:-
60,000 * 96.69% = 58,014
My connection:-
22,399 * 96.69% = 21,657 (21.66 Mbps according to BT's Wholesale tester)
adslmax:-
80,000 * 96.69% = 77,352 (reported as 77.35 Mbps according to BT's Wholesale tester)
Edited by deleted (Wed 01-Apr-15 22:37:19)
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Brilliant - thanks .
For some reason it never occurred to me to do the reverse calculation.
So on these we now need to multiply the IP Profile by 1.034 to get an approximation of the sync. (Though I always found it easier to multiply or divide by 0.9679 depending on which way I was going).
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(Though I always found it easier to multiply or divide by 0.9679 depending on which way I was going).
Me too.
I haven't seen all that many G.INP Sync/IP Profile stats to date, so I can't be 100% sure.
However, of those that I have seen, the 96.69% does seem to be a 'near enough' calculation factor.
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Here is mine with the ECI modem replaced with my HG612 (SP08) unlocked...
# xdslcmd info --stats
xdslcmd: ADSL driver and PHY status
Status: Showtime
Retrain Reason: 0
Last initialization procedure status: 0
Max: Upstream rate = 33585 Kbps, Downstream rate = 90476 Kbps
Bearer: 0, Upstream rate = 20000 Kbps, Downstream rate = 79999 Kbps
Bearer: 1, Upstream rate = 0 Kbps, Downstream rate = 0 Kbps
Link Power State: L0
Mode: VDSL2 Annex B
VDSL2 Profile: Profile 17a
TPS-TC: PTM Mode(0x0)
Trellis: U:ON /D:ON
Line Status: No Defect
Training Status: Showtime
Down Up
SNR (dB): 8.6 14.7
Attn(dB): 8.5 0.0
Pwr(dBm): 13.1 -7.9
VDSL2 framing
Bearer 0
MSGc: -6 -6
B: 130 97
M: 1 1
T: 0 0
R: 8 8
S: 0.0518 0.1554
L: 21468 5457
D: 16 8
I: 139 106
N: 139 106
Q: 16 8
V: 14 2
RxQueue: 57 39
TxQueue: 19 13
G.INP Framing: 18 18
G.INP lookback: 19 13
RRC bits: 24 24
Bearer 1
MSGc: 186 58
B: 0 0
M: 2 2
T: 2 2
R: 16 16
S: 5.3333 16.0000
L: 48 16
D: 3 1
I: 32 32
N: 32 32
Q: 0 0
V: 0 0
RxQueue: 0 0
TxQueue: 0 0
G.INP Framing: 0 0
G.INP lookback: 0 0
RRC bits: 0 0
Counters
Bearer 0
OHF: 0 0
OHFErr: 0 0
RS: 536380896 3398568
RSCorr: 933 321
RSUnCorr: 0 0
Bearer 1
OHF: 434178 435830
OHFErr: 0 0
RS: 5209401 1743320
RSCorr: 0 7
RSUnCorr: 0 0
Retransmit Counters
rtx_tx: 1660 47
rtx_c: 14 47
rtx_uc: 0 0
G.INP Counters
LEFTRS: 0 0
minEFTR: 79999 19997
errFreeBits: 8509374 2126447
Bearer 0
HEC: 0 0
OCD: 0 0
LCD: 0 0
Total Cells: 1072874717 0
Data Cells: 283695004 0
Drop Cells: 0
Bit Errors: 0 0
Bearer 1
HEC: 0 0
OCD: 0 0
LCD: 0 0
Total Cells: 0 0
Data Cells: 0 0
Drop Cells: 0
Bit Errors: 0 0
ES: 0 0
SES: 0 0
UAS: 138 138
AS: 6974
Bearer 0
INP: 46.00 47.00
INPRein: 0.00 0.00
delay: 0 0
PER: 0.00 0.00
OR: 0.01 0.01
AgR: 80614.82 20102.08
Bearer 1
INP: 4.00 4.00
INPRein: 4.00 4.00
delay: 3 0
PER: 16.06 16.06
OR: 95.62 31.87
AgR: 95.62 31.87
Bitswap: 2918/2918 12/12
Total time = 1 hours 58 min 32 sec
FEC: 933 321
CRC: 0 0
ES: 0 0
SES: 0 0
UAS: 138 138
LOS: 0 0
LOF: 0 0
LOM: 0 0
Latest 15 minutes time = 13 min 32 sec
FEC: 64 113
CRC: 0 0
ES: 0 0
SES: 0 0
UAS: 0 0
LOS: 0 0
LOF: 0 0
LOM: 0 0
Previous 15 minutes time = 15 min 0 sec
FEC: 64 3
CRC: 0 0
ES: 0 0
SES: 0 0
UAS: 0 0
LOS: 0 0
LOF: 0 0
LOM: 0 0
Latest 1 day time = 1 hours 58 min 32 sec
FEC: 933 321
CRC: 0 0
ES: 0 0
SES: 0 0
UAS: 138 138
LOS: 0 0
LOF: 0 0
LOM: 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
LOM: 0 0
Since Link time = 1 hours 56 min 13 sec
FEC: 933 321
CRC: 0 0
ES: 0 0
SES: 0 0
UAS: 0 0
LOS: 0 0
LOF: 0 0
LOM: 0 0
#
Edited by D_an_W (Wed 01-Apr-15 22:57:14)
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Your 77.35 ties in with Bald_Eagle_1's 0.9669. Your earlier 79987 giving 77.44 doesn't fit with anything, particularly the previous 0.9679.
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bear in mind profile != throughput.
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Sorry my mistake:
My past 79987K was BT IP Profile 77.42Mb throughput 74Mb
Now 79999K were BT IP Profile 77.35Mb throughput 74Mb
Edited by adslmax (Thu 02-Apr-15 01:09:21)
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Here is mine with the ECI modem replaced with my HG612 (SP08) unlocked...
For interest do you know what your stats were before G.INP?
Plusnet unlimited FTTC
BT Infinity 2
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So my IP profile for a line sync of 66mb should be 63.81 with G.INP
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Yes. So? .
Or was it a remark to the OP/everyone? We moved on to IP Profile long ago. The first few replies, including yours, did that.
With nearly all ISPs throughput is considerably less, as you suggest.
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Not really from the HG612 as the ECI gave slightly better speeds but I was at 79987 / 19999 when it was first installed.
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So my IP profile for a line sync of 66mb should be 63.81 with G.INP Or a bit more. We tend to work on exact syncs to calculate the IP Profile. For people unable to see their sync we work backwards from the BT Wholesale Diagnostic Test. That gives the IP Profile.
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