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[Weaver]

[Moderator edit: This thread has been created by splitting it off from the Draytek Vigor 130 sync speed thread.]

When I was writing about the DLink I should have said G.INP not just INP.

Since the OP is on ADSL2+ (correct?) the DSLAM presumably won't speak G.INP ? Or is this different because it's Sky iirc not BTx. I haven't heard of G.INP being in use with ADSL2 even though I know retransmissions are in the G.992.3 standard - if we're talking about the same thing.

I didn't know that the DLink doesn't do G.INP, and I haven't look because if I'm right, then I can't use it because BTW 21CN doesn't have it I believe, as I suggested.

When you see INP do you think this refers to the combination of R and M parameters in G.992.3? (Amount of FEC bits.) Higher R (and greater interleave depth) equals better reliability. Higher R means more overhead so less true throughput.

I hadn't noticed that there's no upstream G.INP with ADSL2+, I've learned something so thanks for that.

Does Sky speak SRA for ADSLx?

As for G.INP with the DLink, provided a modem wins in real-world speed tests as opposed to just getting the best sync rates, which you need to do to take account of the differing levels of overheads (PPPoEoA vs PPPoA and possibly differing R and M [or S] plus any other overheads), then it just wins and the fastest is the fastest, provided it is reliable. I myself wouldn't let the G.INP feature be the sole deciding factor, unless the line has really bad noise problems and things just won't work properly otherwise. It's an important thing to have nonetheless. It also depends on how you feel about ultimate speed vs reliability/predictability tradeoffs.

[ejs]

The formula to calculate the INP value is in Table 7-7 of G.992.3.

I've heard people say that Sky LLU ADSL2+ does indeed use G.INP. And the stats I quoted indicate it is in use.

G.INP (G.998.4) defines the retransmission scheme for VDSL2 (G.993.2), ADSL2+ (G.992.5) and ADSL2 (G.992.3). Retransmissions are not in G.992.3 itself.

And yet Weaver, you say you choose the maximum possible amount of interleaving for your lines... so if you could have G.INP, I would have thought you'd want it.

[Weaver]

I'm being a bit thick, apol.

You bet, I would love G.INP, but was under the impression that I can't get it from a BT 21CN ADSL2+ DSLAM. Am I wrong?

So that's an advantage of Sky then? If I'm understanding.

Am always extremely interested in alternative G.993.2 or G.993.5 modem candidates.

[Weaver]

I see it in table 7-7. Missed that, thanks for clearing that misunderstanding up.

[Weaver]

There's no consistency, some modems seem to quote more of the derived parameters in that table 7-7, and not all of the basic ones in Table 7-6. A variable mixture.

Apologies for me getting off topic, I should have asked in the relevant ‘zopiclone’ thread elsewhere.

[Weaver]

When I saw ReTxEnable, I just assumed that it was something to gate the feature on / off in the UI, if you see what I mean. I didn't take it to mean that it was actually in use, as you said. Good for Skye though if it's so.

[Weaver]

I can't remember where I got the idea from that BT 21CN ADSL2+ doesn't offer retransmissions - I think there may have been an earlier thread about this?

[ejs]

We encountered one instance where Broadcom's proprietary PhyR was being used, not G.INP, with no particular insight into why it had been switched on, apart from the fact that only the most modern 21CN ADSL2+ exchange equipment is Broadcom and therefore capable of PhyR.

[burakkucat]

Continuing the OT theme (for which, of course, I shall blame Weaver if a moderator happens to notice) here follows some data from my ZyXEL VMG1312-B10D --

$ xdslctl profile --show

Modulations:
        G.Dmt   Disabled
        G.lite  Disabled
        T1.413  Disabled
        ADSL2   Enabled
        AnnexL  Disabled
        ADSL2+  Disabled
        AnnexM  Disabled
        VDSL2   Disabled
Phone line pair:
        Inner pair
Capability:
        bitswap         On
        sra             On
        trellis         On
        sesdrop         Off
        CoMinMgn        Off
        24k             On
        phyReXmt(Us/Ds) On/On
        Ginp(Us/Ds)     On/On
        TpsTc           AvPvAa
        monitorTone:    On
        dynamicD:       On
        dynamicF:       Off
        SOS:            On
        Training Margin(Q4 in dB):      -1(DEFAULT)
$

I haven't a clue what the string "TpsTc" means but in its returned output the "A" signifies ATM, the "P" signifies PTM, the "a" signifies G.992.X (ADSL modes) and the "v" signifies G.993.X (VDSL modes).

[Weaver]

So in Burakkucat’s case, the SRA On could either mean that the CPE is potentially willing to speak SRA, or that it is actually doing it because TalkTalk’s DSLAM can do so to and they have agreed on it. It just strikes me as ambiguous, but who knows. This might be the ZyXel config / UI talking to us, or a reflection of current state. A good test would be stats from another similar G.992.3/5 model of CPE but on 21CN say to see if we get a different result, which might have a chance of proving something one way.

Admins: Feel free to split the last few posts off if so desired and if there's an appropriate point.

[PhilipD]

Hi

So in Burakkucat’s case, the SRA On could either mean that the CPE is potentially willing to speak SRA, or that it is actually doing it because TalkTalk’s DSLAM can do so to and they have agreed on it. It just strikes me as ambiguous, but who knows. This might be the ZyXel config / UI talking to us, or a reflection of current state. A good test would be stats from another similar G.992.3/5 model of CPE but on 21CN say to see if we get a different result, which might have a chance of proving something one way.

Admins: Feel free to split the last few posts off if so desired and if there's an appropriate point.

That display just shows the current configuration, and most of those options are "ON" but only do something if allowed/supported at the other end.  When I had a Billion router (Broadcom) on Tiscali LLU ADSL2+ which did support SRA, the only way I could see that was on was the sync rate would change but no retrains counted.

Regards

Phil

[Weaver]

That's really good to know, that some service providers’ DSLAMs speak SRA. It's a real shame BTW doesn't do it with ADSL 2/2+.

[Weaver]

@burakkucat - TpsTc perhaps is TPS-TC = G.993.2 Transport Protocol Specific – Transmission Convergence

[burakkucat]

Yes, that would be it. Thank you. 

[Weaver]

Did we ever establish whether or not Burakkucat’s TalkTalk LLU DSLAM supports G.998.4 and so the facility is active, it was that config display just showing that the modem was willing to support it if it was available?

And so I would have a better ADSL2 service if I were on Sky LLU then because I would get low-level G.998.4 retx then provided that I got myself a better modem. And the same might be true for a TTB LLU line or x other LLU.