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Author Topic: Broadcom-type CLI stats question - ‘max’ rate vs ‘bearer 0’  (Read 1051 times)

Weaver

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My ZyXEL VMG1312-B10A modem reports the following in response to one of the basic stats queries in the CLI:

Code: [Select]
xdslctl: ADSL driver and PHY status
Status: Showtime
Last Retrain Reason: 8000
Last initialization procedure status: 0
Max: Upstream rate = 296 Kbps, Downstream rate = 3332 Kbps
Bearer: 0, Upstream rate = 445 Kbps, Downstream rate = 3082 Kbps

Apologies for having asked this kind of question before.

My question: what is ‘Max’, given that it is lower than my Bearer 0?

I only have one bearer, which is not surprising.

Another question: Do any of our ADSL 1/2/2+ users have multiple bearers? I have seen multiple bearers with VDSL2, I think. Is that correct?
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burakkucat

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Re: Broadcom-type CLI stats question - ‘max’ rate vs ‘bearer 0’
« Reply #1 on: December 28, 2018, 12:54:00 AM »

For my circuit, restricted to ADSL2 (ITU-T G.992.3), I see --

~ # xdslctl info --state
xdslctl: ADSL driver and PHY status
Status: Showtime
Last Retrain Reason:   8000
Last initialization procedure status:   0
Max:   Upstream rate = 1024 Kbps, Downstream rate = 6212 Kbps
Bearer:   0, Upstream rate = 1019 Kbps, Downstream rate = 5119 Kbps

~ #

The "Max" line is reporting what the device "believes" the circuit is capable of achieving, if all is well. The "Bearer" line is reporting the current synchronisation speed.

For VDSL2 (ITU-T G.993.2) circuits, there are two "Bearer" lines shown. The first, "Bearer:   0", is as above. The second, "Bearer:   1", shows the channel used for management processes. And ejs will correct me if I've got it wrong!  ;)  Ah here is the post, for which I was searching --

"Bearer 0" is the normal pathway for normal traffic. "Bearer 1" is only used when the retransmission of one or more packets is required.

This seems to be a common misconception, due to the fact that "Bearer 1" only appears with G.INP. With G.INP, "Bearer 0" is used for user data traffic, including retransmitted data, and "Bearer 1" is used for overhead/management traffic - things like organising bitswaps and exchanging stat values with the other end.
« Last Edit: December 28, 2018, 01:14:48 AM by burakkucat »
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Weaver

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Re: Broadcom-type CLI stats question - ‘max’ rate vs ‘bearer 0’
« Reply #2 on: December 28, 2018, 01:43:05 AM »

So I’m afraid I’m still mystified then. The modem finds the current sync rate to be beyond that which is ‘believable’? Do we know where this comes from / how it’s calculated? I should ask whether it’s something that is sent to the modem by BT, rather than something calculated by the modem as a function of internally sourced values only?

As for the bearer 1 thing :

I wasn’t looking down the whole command output, so I was talking nonsense. I was just seeing the first part only, as I was using the quick stats summary feature of the ‘johnson’ custom firmware.

@Burrakucat: So bearer 1 is for the retransmission requests, and other control PDUs in G.998.4 ? I need to read the documents properly then. That’s a very logical idea, keeps the traffic types apart easily.

I don’t know anything about Broadcom PhyR, but having looked at the whole output of xdslctl info --show, I see that I have no bearer 1 listed at all. I can see ReXmt counters listed, so I am assuming that PhyR really is turned on?

@Burrakucat - I forget - is your TT line LLU? I don’t remember what kit there is at your exchange end?

Here’s the full output from line #3:

Code: [Select]
> xdslctl info --show
xdslctl: ADSL driver and PHY status
Status: Showtime
Last Retrain Reason:    8000
Last initialization procedure status:   0
Max:    Upstream rate = 410 Kbps, Downstream rate = 3352 Kbps
Bearer: 0, Upstream rate = 445 Kbps, Downstream rate = 3082 Kbps

Link Power State:       L0
Mode:                   ADSL2 Annex A
TPS-TC:                 ATM Mode(0x0)
Trellis:                U:ON /D:ON
Line Status:            No Defect
Training Status:        Showtime
                Down            Up
SNR (dB):        2.7             5.6
Attn(dB):        64.0            40.3
Pwr(dBm):        18.2            12.4

                        ADSL2 framing
                        Bearer 0
MSGc:           52              14
B:              35              46
M:              4               1
T:              3               1
R:              12              12
S:              1.4717          3.3007
L:              848             143
D:              2               8

                        Counters
                        Bearer 0
SF:             31748009                494474
SFErr:          1481            21
RS:             1381038430              921303
RSCorr:         30669           3974912
RSUnCorr:       3138            0

ReXmt:          38974           0
ReXmtCorr:      37191           0
ReXmtUnCorr:    3251            0

                        Bearer 0
HEC:            3679            19
OCD:            1               0
LCD:            1               0
Total Cells:    3717511973              537880286
Data Cells:     115116152               16694223
Drop Cells:     0
Bit Errors:     180413          1698

ES:             184             22
SES:            9               0
UAS:            180             180
AS:             511477

                        Bearer 0
INP:            26.00           2.50
INPRein:        0.00            0.00
delay:          8               7
PER:            16.00           16.50
OR:             28.99           9.69
AgR:            3097.23 453.88

Bitswap:        110424/112050           17590/17590

>

[off-topic] @Burrakucat : has your line improved in recent years ? Your downstream seems to be rather better, as I seem to vaguely remember some downstream sync rate figure just over ~4 Mbps from some stats you posted a good while back.
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j0hn

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Re: Broadcom-type CLI stats question - ‘max’ rate vs ‘bearer 0’
« Reply #3 on: December 28, 2018, 03:55:06 AM »

Quote
xdslctl: ADSL driver and PHY status
Status: Showtime
Last Retrain Reason:   8000
Last initialization procedure status:   0
Max:   Upstream rate = 296 Kbps, Downstream rate = 3332 Kbps
Bearer:   0, Upstream rate = 445 Kbps, Downstream rate = 3082 Kbps

Do you happen to know what the Up SNR was at the time?

As B*cat says, Max (or max attainable) is what the modem thinks the current lines attainable is.
If the Up SNR had dropped quite a bit that would explain the modem reporting a lower attainable rate.

Resyncing at that moment in time would result in a lower upstream sync.
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burakkucat

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Re: Broadcom-type CLI stats question - ‘max’ rate vs ‘bearer 0’
« Reply #4 on: December 28, 2018, 04:01:33 PM »

I don’t know anything about Broadcom PhyR, but having looked at the whole output of xdslctl info --show, I see that I have no bearer 1 listed at all. I can see ReXmt counters listed, so I am assuming that PhyR really is turned on?

Remember that Broadcom's proprietary PhyR is not G.Inp (ITU-T G.998.4). However they are similar in purpose and effect.

Quote
@Burrakucat - I forget - is your TT line LLU? I don’t remember what kit there is at your exchange end?

Yes, the line is LLU'd. I am told that the exchange-based MSAN is a Huawei product. However when I interrogate the circuit for the manufacturer of the MSAN's line-card chip-set I see --

~ # xdslctl info --vendor
xdslctl: ADSL driver and PHY status
Status: Showtime
Last Retrain Reason:   8000
Last initialization procedure status:   0
Max:   Upstream rate = 1024 Kbps, Downstream rate = 6312 Kbps
Bearer:   0, Upstream rate = 995 Kbps, Downstream rate = 5119 Kbps

ChipSet Vendor Id:   IFTN:0x71c8
ChipSet VersionNumber:   0x71c8
ChipSet SerialNumber:   
~ #

IFTN -- Infineon

Quote
[off-topic] @Burrakucat : has your line improved in recent years ? Your downstream seems to be rather better, as I seem to vaguely remember some downstream sync rate figure just over ~4 Mbps from some stats you posted a good while back.

I'm not aware of any significant improvement but then I do not meticulously keep statistics -- I just use the circuit.
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Weaver

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Re: Broadcom-type CLI stats question - ‘max’ rate vs ‘bearer 0’
« Reply #5 on: December 29, 2018, 01:44:21 AM »

J0hn has solved it then. Given the huge jumps up and down in upstream SNR that has to be the answer.
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