Kitz Forum

Broadband Related => Broadband Technology => Topic started by: Alex Atkin UK on May 19, 2020, 01:17:08 PM

Title: A Query Regarding Retransmission
Post by: Alex Atkin UK on May 19, 2020, 01:17:08 PM
I've been reading https://kitz.co.uk/adsl/retransmission.htm and notice it makes no mention of why upstream G.INP is not available on ECI DSLAMs, only why its not available on certain modems.

Do we have an explanation?
Title: Re: A Query Regarding Retransmission
Post by: j0hn on May 19, 2020, 06:09:45 PM
It's not available on certain modems because the modem hardware (occasionally firmware) doesn't support it.

It's not available on the ECI M41 DSLAM because
... the hardware doesn't support it.
Just as it doesn't support system level Vectoring.
Title: Re: A Query Regarding Retransmission
Post by: Alex Atkin UK on May 19, 2020, 07:01:21 PM
Pretty much what I expected, but it just seemed odd with upstream depending more on your modem so you'd think it would be easier to implement at the DSLAM than downstream.
Title: Re: A Query Regarding Retransmission
Post by: burakkucat on May 19, 2020, 07:29:19 PM
The word is "retransmission" . . .

For the DS (relative to the end user) the transmitter is the DSLAM/MSAN, the xTU-C.
For the US (relative to the end user) the transmitter is the modem(/router), the xTU-R.

To be able to retransmit a data sequence, the device needs a suitably sized buffer to hold that data. It is far easier to implement at the DSLAM/MSAN than it is at a modem(/router).

Regard it as a hardware limitation.
Title: Re: A Query Regarding Retransmission
Post by: sevenlayermuddle on May 19, 2020, 09:10:05 PM
I've been reading https://kitz.co.uk/adsl/retransmission.htm and notice it makes no mention of why upstream G.INP is not available on ECI DSLAMs, only why its not available on certain modems.

Do we have an explanation?

I agree, thatís an interesting question.   It is the entity doing the retransmissions that needs increased resources.  So for upstream, the modem may need additional RAM in which to store data that has already been sent, on the off-chance it may need to be sent again. 

But if the modem is capable of buffering that data,  it is not obvious to me why a DSLAM would be unable to request that the modem retransmit it?


Title: Re: A Query Regarding Retransmission
Post by: Alex Atkin UK on May 20, 2020, 02:02:31 AM
But if the modem is capable of buffering that data,  it is not obvious to me why a DSLAM would be unable to request that the modem retransmit it?

^THIS was my point.  Seeing as I have the Zyxel VMG-3925-B10B on the G.INP trial as the Home Hub 5A was too unstable (same old problem as before I guess).

Its annoying as that line is starting to dip below the maximum upstream sync, which while its only 19555 (so not exactly noticeable in real-world usage), it could get worse as summer kicks in.