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[Mo]

Hi,
Long story short I got two routers in hand from two different ISPs.
Old router is a ZTE H168N the other one is a Zyxel VMG 3625-T50B.
The ZTE one is showing fastpath on the down stream when I plug it, but Zyxel one is on interleaved since I have switched to it 2 months ago.

This is from the Zyxel router:
=============================================================================
    xDSLFwVersion:      FwVer:5.12.23.0_B_A60901 HwVer:T14.F7_0.0
       Line State:      Up
       Modulation:      ITU G.993.2(VDSL2), G.998.4(G.I
       Annex Mode:      ANNEX_B
=============================================================================
TPSTC type: 64/65B PTM TC

near-end interleaved channel bit rate: 36861 kbps
near-end fast channel bit rate: 0 kbps
far-end interleaved channel bit rate: 0 kbps
far-end fast channel bit rate: 4094 kbps

near-end FEC error fast: 0
near-end FEC error interleaved: 5464
near-end CRC error fast: 0
near-end CRC error interleaved: 0
near-end HEC error fast: 0
near-end HEC error interleaved: 0
far-end FEC error fast: 0
far-end FEC error interleaved: 0
far-end CRC error fast: 0
far-end CRC error interleaved: 0
far-end HEC error fast: 0
far-end HEC error interleaved: 0
DSL uptime : 1:55, 4 secs
DSL activetime :0 min, 16 secs

Downstream:
relative capacity occupation: 100%
noise margin downstream: 6.3 dB
output power upstream: 8.0 dbm
attenuation downstream: 11.9 dB

Upstream:
relative capacity occupation: 100%
noise margin upstream: 15.3 dB
output power downstream: 13.0 dbm
attenuation upstream: 0.5 dB

Bit table:
carrier load: number of bits per tone
tone   0- 31: 00 00 00 04 44 44 44 44 44 4a aa a9 99 88 86 54
tone  32- 63: 4a bb bc cc cc cc dd cd cd cd cc dd cd dd dc cd
tone  64- 95: cc cc cc cc cc cc cc cc cc cc cc cc cc bc cc cb
tone  96-127: cb bc bb cc cb cb bb bb bb bb bb bb bb bb bb bb
tone 128-159: bb bb bb ab ba ab ab bb ba ab bb ba aa bb ba bb
tone 160-191: aa ba aa aa aa aa aa aa aa aa aa aa 99 aa aa aa
tone 192-223: 9a aa 99 99 78 9a a9 99 99 9a 99 99 99 9a 99 99
tone 224-255: 99 99 99 99 99 99 99 99 99 99 99 99 99 99 99 98

And image from the ZTE router is attached
So, is there something wrong with the Zyxel router or is just a matter of time to settle it self?
Thank you.
I reside out side the UK btw.

[mofa2020]

Welcome to the forum, Mo.

So I think it is the chipset difference between the two routers, as the ZTE only supports 17a profile while the Zyxel supports 35b. I would test the PING to the your ISP's closest server on speetest  (and use a wired connection for the test to eliminate any wifi differences) I think the delay will be 0ms on both routers although the zyxel is reporting interleaved but it is not showing the interleave delay like the zte.

[Mo]

Hi mofa,
I attached the speed test for the Zyxel router, as for the ZTE router i can't make the test as I'm not currently subscriber with the provider.

Zyxel router indeed have the option to run on profile 35b but currently the line is running on profile 17a.(should I unmark the 35b profile option from the setting?)

Also the electricity was down couple days ago and when it came back I noticed that noise margin for the down stream was around 13db and then gradually decreased to stay at 6-7 db! Any thoughts about that matter?

[mofa2020]

Now I think there might be a interleave delay but actually it is so little 10ms is not that much. Although the router doesn't show the line profile but I do not think your line on a 35b port given the speed test result but try disabling it and see if it makes any difference.

For the power cut and SNRm, sometimes this happens but do not worry about it DLM will sort the line as you said. The only workaround is using a UPS so the router will have power when electricity is cut.

[Mo]

Okay so I did unchecked the option of using profile 35b and it did impacted the latency by some degree I can feel it in gaming. But still downstream is in interleaving🤷‍♂️

[kitz]

interleave delay but actually it is so little 10ms is not that much.

The image is large for my screen, but it looks like the test may have been done over wifi which would account for a small amount of latency.

FECs are no longer positive proof that the line is interleaved as Openreach (& other Service Providers*) can use a small amount of error protection without using interleaving.  The line has G.INP (G.998.4) enabled, so FECs without interleaving is perfectly normal behaviour.

As already mentioned by @mofa, the router reporting interleaved does not necessarily mean that the line is using interleaving.
FTTC & G.INP use the interleaved path to transmit data over, but when it is set as 1/1, then it is the same as FAST path. ie not interleaved.  Whilst not impossible, it is more unusual for a line to be interleaved if it has G.INP... but it will be using the interleaved path for data transmission.. usually set at 1/1.
Both modems appear to sync at the same rate, if your line had interleaving applied, then it would cause overheads and a slower sync rate.  So based on the evidence Ive seen I'd say its more likely that you are Interleaved 1/1 on the Zyxel, which is the same as FAST mode.

 


*Noted you are not in the UK and not on an Openreach connection

[Mo]

The image is large for my screen, but it looks like the test may have been done over wifi which would account for a small amount of latency.

That's correct but I get the same results using an Ethernet cable.

As already mentioned by @mofa, the router reporting interleaved does not necessarily mean that the line is using interleaving.
FTTC & G.INP use the interleaved path to transmit data over, but when it is set as 1/1, then it is the same as FAST path. ie not interleaved.  Whilst not impossible, it is more unusual for a line to be interleaved if it has G.INP... but it will be using the interleaved path for data transmission.. usually set at 1/1.

If that's the case aren't the rate of the downstream should be stated in the (near-end fast channel bit rate) line?
Maybe there is a greater amount of interleave delay on the Zyxel?
I just want to eliminate any factors could be related to the the router it self in handling the connection.

[Alex Atkin UK]

FECs are no longer positive proof that the line is interleaved as Openreach (& other Service Providers*) can use a small amount of error protection without using interleaving.  The line has G.INP (G.998.4) enabled, so FECs without interleaving is perfectly normal behaviour.

As already mentioned by @mofa, the router reporting interleaved does not necessarily mean that the line is using interleaving.
FTTC & G.INP use the interleaved path to transmit data over, but when it is set as 1/1, then it is the same as FAST path. ie not interleaved.  Whilst not impossible, it is more unusual for a line to be interleaved if it has G.INP... but it will be using the interleaved path for data transmission.. usually set at 1/1.

Isn't G.INP technically a form of interleaving?  This seems to account for the confusion that some modems report it as interleaved and others fastpath.  But if G.INP is on then I don't think traditional interleaving can be enabled at the same time, so its always going to be G.INP in use with low delay.

[kitz]

>> Isn't G.INP technically a form of interleaving?

Noooh. People get confused with Error Protection and Error Correction.
The theory of G.INP is to do away with overheads (such as Interleaving) that reduce the line rate, hence the infamous "They steal your bandwidth" PhyR quotation by Broadcom when marketing their proprietory name for it.

Interleaving can be switched on independently, (but seldom is). 

G.INP is explained in more detail here, but the cut down version is G.INP encapsulates the data, stores it in a buffer and is only re-sent if an error occurs and the data has to be re-requested.   If anything G.INP is more like the traditional form of error correction ARQ or TCP retransmission...  only G.INP operates at a lower level between modem <-> DSLAM rather than high up in the {TCP/IP stack} between PC <-> Server.  It occurs at the physical layer opposed to the software layer.
G.INP only kicks in if there is an error.  Redundant data isnt unnecessarily transmitted.

>> some modems report it {G.INP} as interleaved and others fastpath <<

Nothing to do with G.INP I'm afraid.   
Using the interleaved path opposed to FAST for "normal data" has been around since ADSL (MaxDSL)..  Prior to VDSL and Pre G.INP. I briefly touched on the subject way back in 2006 when explaining Interleaving.  Modems have been confusing people about interleaving being switched on since the early days of ADSL2+. 

Note: ADSL2+ and VDSL has the capability of switching on Interleaving and Error Correction as separate parameters.  Data by default is usually sent using the interleaved channel with a depth of 1 which is the equivalent of FAST path.

BT/Openreach tends to reserve the FAST channel for time critical applications such as VoIP and IPTV. Normal internet data for activities like browsing, emaill, file transfers is transmitted over the Interleaved channel.  The amount of interleaving depends on your line conditions and is controlled by the DLM.

>>  But if G.INP is on then <<

G.INP uses Bearer 1.  "Normal" data goes over Bearer 0
Each of these Bearer Channels have 2 pathways (FAST & Interleaved) that can independantly set.

Snip from my linestats

Code: [Select]

                        VDSL2 framing
                        Bearer 0 <------------------- Bearer Channel for normal data
MSGc:           -6              150
B:              178             236
M:              1               1
T:              0               5
R:              6               16
S:              0.0712          0.3771
L:              20780           5410
D:              1               1 <------------------- Interleave depth 1 (off)
I:              185             255
N:              185             255
Q:              16              0
V:              2               0
RxQueue:                42              0
TxQueue:                14              0
G.INP Framing:          18              0
G.INP lookback:         14              0
RRC bits:               0               24
                        Bearer 1 <------------------- Bearer Channel for G.INP
MSGc:           186             -6
B:              0               0
M:              2               0
T:              2               0
R:              16              0
S:              5.3333          0.0000
L:              48              0
D:              3               0
I:              32              0 <------------------- Interleave depth for G.INP data
N:              32              0
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


[kitz]

>>  I don't think traditional interleaving can be enabled at the same time,<<<

Interleaving can be switched on independently, (but seldom is)

I was actually looking for something else,  but just stumbled upon this which shows a G.INP line with Interleaving depth 4.  I think my own line has also had  Interleaving with G.INP a few times.  The line also has high INP = 56.
.

Code: [Select]

Line attenuation (dB):  21.3 0.0
Signal attenuation (dB): Not monitored
Connection speed (kbps): 49116        8812
SNR margin (dB):        3.3 5.6
Power (dBm):            12.9 6.3
Interleave depth:        4 4
INP:                    56.00 46.00
G.INP:                  Enabled Enabled
Vectoring status:        5 (VECT_UNCONFIGURED)

RSCorr/RS (%):          11.0648 0.0768
RSUnCorr/RS (%):        0.0000 0.0000
ES/hour:                0 0




Compare to mine - non interleaved.

Code: [Select]

DSLAM type / SW version: IFTN:0xb206 (178.6) / v0xb206
Modem/router firmware:  AnnexA version - A2pv6F039i.d24e
DSL mode:                VDSL2 Profile 17a
Status:                  Showtime
Uptime:                  45 days 2 hours 21 min 19 sec
Resyncs:                0 (since 23 Jan 2024 11:33:12)

Downstream Upstream
Line attenuation (dB):  0.0 0.0
Signal attenuation (dB): Not monitored
Connection speed (kbps): 79999 20000
SNR margin (dB):        10.8 13.5
Power (dBm):            4.3 4.3
Interleave depth:        1 1
INP:                    46.00 0
G.INP:                  Enabled Not enabled
Vectoring status:        5 (VECT_UNCONFIGURED)

[Alex Atkin UK]

Thanks for the refresher, I didn't realise interleaving could be different between bearers.

[mofa2020]

Yes, I saw many lines with G.INP enabled and has interleave depth especially on download yet the delay is reported 0ms. For my line it is G.INP enabled both down/up and the line on fastpath I did an experiment and disabled G.INP and the line synced. with interleaved both down/up, once enabled G.INP again it synced fastpath.