General Discussion
  >> Fibre Broadband


Register (or login) on our website and you will not see this ad.


Pages in this thread: 1 | 2 | 3 | 4 | 5 | 6 | 7 | [8] | (show all)   Print Thread
Standard User BatBoy
(legend) Mon 12-Dec-11 18:49:58
Print Post

Re: SNRM & Error levels


[re: john2007] [link to this post]
 
In reply to a post by john2007:
I guess RS means Reed-Solomon, the algorithm used in Forward Error Correction.

Most routers seem to use RSCorr for the FEC count (the count of packets with errors which were successfully corrected with the Reed-Solomon algorithm) and RSUnCorr for the CRC count (the packet was too severely damaged to correct and so fails the CRC).
No, RS means Regenerator Section as used by SDH. http://en.wikipedia.org/wiki/Synchronous_optical_net...



______________________________________________________________________________. __________________
Standard User asbokid
(regular) Mon 12-Dec-11 20:23:22
Print Post

Re: SNRM & Error levels


[re: BatBoy] [link to this post]
 
That's interesting. Though in this context, RS means Reed-Solomon:

The following excerpt is taken from the source code of the xDSL device driver for Broadcom's 63xx SoCs [1] [2]

Text
1
23
45
67
89
1011
1213
1415
1617
1819
20
/* showtime monitor counters */
 #define kG992ShowtimeRSCodewordsRcved              0 /* number of Reed-Solomon codewords received */
#define kG992ShowtimeRSCodewordsRcvedOK            1 /* number of Reed-Solomon codewords received with all syndromes zero */#define kG992ShowtimeRSCodewordsRcvedCorrectable   2 /* number of Reed-Solomon codewords received with correctable errors */
#define kG992ShowtimeRSCodewordsRcvedUncorrectable 3 /* number of Reed-Solomon codewords received with un-correctable errors */#define kG992ShowtimeSuperFramesRcvd               4 /* number of super frames received */
#define kG992ShowtimeSuperFramesRcvdWrong          5 /* number of super frames received with CRC error */#define kG992ShowtimeLastUncorrectableRSCount      6 /* last recorded value for kG992ShowtimeRSCodewordsRcvedUncorrectable */
#define kG992ShowtimeLastWrongSuperFrameCount      7 /* last recorded value for kG992ShowtimeSuperFramesRcvdWrong */#define kG992ShowtimeNumOfShortResync              8 /* number of short interrupt recoveries by FEQ */
 #define kG992ShowtimeNumOfFEBE                     9 /* number of other side superframe errors */
#define kG992ShowtimeNumOfFECC                    10 /* number of other side superframe FEC errors */#define kG992ShowtimeNumOfFHEC                    11 /* number of far-end ATM header CRC errors */
#define kG992ShowtimeNumOfFOCD                    12 /* number of far-end OCD events */#define kG992ShowtimeNumOfFLCD                    13 /* number of far-end LCD events */
#define kG992ShowtimeNumOfHEC                     14 /* number of ATM header CRC errors */#define kG992ShowtimeNumOfOCD                     15 /* number of OCD events */
#define kG992ShowtimeNumOfLCD                     16 /* number of LCD events */


cheers, a

[1] http://huaweihg612hacking.wordpress.com/2011/07/26/b...

[2] ftp://downloads.netgear.com/files/GPL/DG834GBv4_V5.0...
(see, for example, the file ~/DG834GBv4_V5.01.01_src/bcmdrivers/broadcom/char/adsl/bcm96348/softdsl/SoftDsl.h)

Edited by asbokid (Mon 12-Dec-11 20:39:44)

Standard User BatBoy
(legend) Mon 12-Dec-11 20:46:35
Print Post

Re: SNRM & Error levels


[re: asbokid] [link to this post]
 
Oh dear, they're wrong too wink



______________________________________________________________________________. __________________


Register (or login) on our website and you will not see this ad.

Moderator billford
(moderator) Mon 12-Dec-11 21:02:00
Print Post

Re: SNRM & Error levels


[re: BatBoy] [link to this post]
 
You've had several warnings about your aggressive posting style and refusal to admit possible error, take some time to think about it a little.

~~~~~~~~~~~~
Bill

[email protected] __________________Planes and Boats and ... __________________BQM
The author of the above post is a thinkbroadband moderator but it does not constitute an official statement on behalf of thinkbroadband.
Standard User WWWombat
(committed) Mon 12-Dec-11 21:18:48
Print Post

Re: SNRM & Error levels


[re: BatBoy] [link to this post]
 
In reply to a post by BatBoy:
No, RS means Regenerator Section as used by SDH.

BT have SDH coming into my house? Where's the rest of my 40Gbps gone then?

And someone had better tell Fujitsu they don't need to bother installing fibre anywhere... BT have been cunningly doing it already.
Standard User XRaySpeX
(eat-sleep-adslguide) Tue 13-Dec-11 01:02:59
Print Post

Re: SNRM & Error levels


[re: asbokid] [link to this post]
 
Don't worry! Batty is just stirring you up, as is his wont, with false info.

1999: Freeserve 48K Dial-Up => 2005: Wanadoo 1 Meg BB => 2007: Orange 2 Meg BB => 2008: Orange 8 Meg LLU => 2010: Orange 16 Meg LLU => 2011: Orange 19 Meg WBC
Standard User Bald_Eagle1
(regular) Tue 13-Dec-11 08:00:17
Print Post

Re: SNRM & Error levels


[re: asbokid] [link to this post]
 
Hi asbokid,

In reply to a post by asbokid:
Here is the parameter list for the function call webGetCfgEntry() found in the .asp resource at http://192.168.1.1/html/status/xdslStatus.asp :

Text
1
23
45
67
89
1011
1213
1415
16
var DSLStats =
<%webGetCfgEntry(InternetGatewayDevice.WANDevice.1.WANDSLInterfaceConfig.Stats.Showtime,    HECErrors|
    ATUCHECErrors|    CRCErrors|
    ATUCCRCErrors|    FECErrors|
    ATUCFECErrors|    X_ATP_HECErrors_2|
    X_ATP_ATUCHECErrors_2|    X_ATP_CRCErrors_2|
    X_ATP_ATUCCRCErrors_2|    X_ATP_FECErrors_2|
    X_ATP_ATUCFECErrors_2,stStats);
%>;


Before serving up that .asp resource, the Huawei's scripting engine dynamically populates the parameters to the function:

Text
1
23
45
67
89
1011
1213
14
var DSLStats = new Array(new stStats("InternetGatewayDevice.WANDevice.1.WANDSLInterfaceConfig.Stats.Showtime",
    "292008",    "0",
    "1074551",    "0",
    "42205",    "105",
    "0",    "0",
    "0",    "0",
    "0",    "0"),
null);


In the above example from Paul's line, we can determine the following:

Text
1
23
45
67
89
1011
1213
..
  HECErrors              = 292008  ATUCHECErrors          = 0
  CRCErrors              = 1074551  ATUCCRCErrors          = 0
  FECErrors              = 42205  ATUCFECErrors          = 105
  X_ATP_HECErrors_2      = 0  X_ATP_ATUCHECErrors_2  = 0
  X_ATP_CRCErrors_2      = 0  X_ATP_ATUCCRCErrors_2  = 0
  X_ATP_FECErrors_2|     = 0  X_ATP_ATUCFECErrors_2  = 0



The acronym "ATUC" is jargon for ADSL Transceiver Unit in Central Office [3]. In plainspeak, ATUC means the DSLAM.

Similarly, the xDSL modem in the consumer premises is known by the official acronym ATU-R, where 'R' means Remote.

Just to confuse things further, ATU-C and ATU-R are identified in the Broadcom driver source code as the "Far End" (FE) and the "Near End" (NE) !

So ATUCHECErrors is a count of the HEC Errors measured at the DSLAM.



I eventually realised that the example you used from my connection has not been posted in this forum thread, but obtained elsewhere smile


I can confirm that the values shown are indeed the values displayed in the modem's GUI.

e.g.
Text
1
23
..
  FECErrors              = 42205 is displayed as Downstream FEC errors in the GUI  ATUCFECErrors          = 105   is displayed as Upstream   FEC errors in the GUI



Just to be 100% clear what is being said here, are you confirming that the modem's GUI is CORRECTLY reporting CRC, FEC, & HEC errors, or just confirming just how INCORRECTLY it reports them, citing a real-life example?

Unfortunately I don't have the actual xdslcmd info --stats log to go with the example used above, But previous log examples have highlighted the "discrepancies" between the data it contains & the data as displayed in the GUI.


Paul
Standard User asbokid
(regular) Tue 13-Dec-11 21:52:30
Print Post

Re: SNRM & Error levels


[re: XRaySpeX] [link to this post]
 
In reply to a post by XRaySpeX:
Don't worry! Batty is just stirring you up, as is his wont, with false info.


More of a Les Dawson than a Liberace, when it comes to hitting the right notes?!

cheers, a
Standard User asbokid
(regular) Wed 14-Dec-11 00:14:58
Print Post

Re: SNRM & Error levels


[re: Bald_Eagle1] [link to this post]
 
In reply to a post by Bald_Eagle1:
I eventually realised that the example you used from my connection has not been posted in this forum thread, but obtained elsewhere smile

I can confirm that the values shown are indeed the values displayed in the modem's GUI.

e.g.
Text
1
23
..
  FECErrors              = 42205 is displayed as Downstream FEC errors in the GUI  ATUCFECErrors          = 105   is displayed as Upstream   FEC errors in the GUI



Just to be 100% clear what is being said here, are you confirming that the modem's GUI is CORRECTLY reporting CRC, FEC, & HEC errors, or just confirming just how INCORRECTLY it reports them, citing a real-life example?


If only the firmware was open source and then we would know for sure. We could trace the source of the data right back to the kernel driver.

There are several places where Broadcom and/or Huawei could get it wrong. The driver itself presumably records the correct data. That data is directly retrieved from the kernel by xdslcmd using Unix system calls known as ioctls. So xdslcmd is most likely to report the correct data, but even that tool incorrectly reports the attenuation levels in certain places.

Huawei uses a middleware server in between the embedded web server and the xdsl device driver. And then there's that scripting engine in the webserver itself, and then there's some Javascript which actually renders the data on a web page. So there are many places where programming bugs could be introduced. Some of the source code has comments in Chinese, so that was presumably written by or for Huawei rather than by Broadcom. So the problems of language misunderstandings introduce another avenue for bugs.

I kind of think that Broadcom may as well release the driver source code under an open source licence, so that others can work on it. Since the source code has been leaked all over the internet anyway, there is no commercial advantage in keeping that code proprietary.

The DSP code which runs on the second MIPS core in the 6368 CPU is a different kettle of fish, and Broadcom unsurprisingly guards that code with great care. All we have of that code is a 500kByte binary blob.

But the character device driver (accessed through the device node /dev/*dsl) may as well be open source now, so that these bugs can be worked on.

Unfortunately I don't have the actual xdslcmd info --stats log to go with the example used above, But previous log examples have highlighted the "discrepancies" between the data it contains & the data as displayed in the GUI.

Paul


I still don't understood what those discrepancies involve.

EDIT:

Okay, I just looked at JustAnother's post at [1]. The uptime may relate to total DSL uptime accumulated since the last reboot of the Huawei.. Which means if there were multiple DSL sessions, between which the Huawei was _not_ rebooted, then that uptime figure would be a summation of those session durations. Only a suggestion, mind!

As for the (large) figure reported by the web interface for FEC errors... wasn't that solved by john and WWWombat? Since the same figure is reported under the heading "RSCorr" in 'xdslcmd info --stats', isn't it the number of 'correctable' errors that were caught, before the data blocks were passed to the RS code for correction? Those blocks don't need re-sending since Reed-Solomon coding reserves redundant bytes for the purposes of correction. At that stage, the errors were counted as RSCorrectable, rather than as RSCorrected.

It is a very poor web interface in the Huawei. For someone with the enthusiasm, it wouldn't be difficult to patch it though. Between these four walls, there's a security flaw in the Huawei's web server that can be used beneficially to execute arbitrary code on the device. It can be used to retrieve whatever statistics you want from the xDSL kernel driver.


cheers, a

[1] http://forum.kitz.co.uk/index.php/topic,10289.msg205...

Edited by asbokid (Wed 14-Dec-11 00:38:55)

Standard User BatBoy
(legend) Fri 16-Dec-11 22:07:06
Print Post

Re: SNRM & Error levels


[re: asbokid] [link to this post]
 
In reply to a post by asbokid:
In reply to a post by XRaySpeX:
Don't worry! Batty is just stirring you up, as is his wont, with false info.


More of a Les Dawson than a Liberace, when it comes to hitting the right notes?!

cheers, a
Looks like you were suffering a sense of humour breakdown. Don't worry, you weren't alone. Possibly mass hysteria?



______________________________________________________________________________. __________________
Pages in this thread: 1 | 2 | 3 | 4 | 5 | 6 | 7 | [8] | (show all)   Print Thread

Jump to