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Author Topic: My DSL linesí latency 47ms  (Read 278 times)

Weaver

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My DSL linesí latency 47ms
« on: January 14, 2020, 09:09:26 AM »

What makes up my latency? I have interleave (hopefully, seriously) set to maximum on the controls at clueless.aa.net.uk but I canít be sure.
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CarlT

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Re: My DSL linesí latency 47ms
« Reply #1 on: January 14, 2020, 03:50:06 PM »

Modulation and demodulation of signal at modems and DSLAM(s) - including delay for convolutional interleaving / de-interleaving of symbols prior to modulation.

Travel across the BT Wholesale network to the relevant WBMC gateway where A&A connect to BTW via PPP sessions encapsulated in L2TP. Will be encapsulated and decapsulated multiple times potentially.

Decapsulation from L2TP at the A&A BRAS. I believe it uses LCP echos so nothing to encapsulate in PPP.

From the Highlands to A&A's network you're talking, give or take, 20-25ms across BT Wholesale. The rest will be interleaving, modem related excitement and any very slight delays either side.

psychopomp1 has BT Wholesale FTTP - his trip across the BTW network will be slightly shorter than yours as he's going straight to an NGA headend but you're talking a millisecond or two. The rest is xDSL versus FTTP.

HTH.
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Deploying better networks, not just faster ones.

Weaver

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  • Retd sw dev; A&A; 4 ◊ 7km ADSL2; IPv6; Firebrick
Re: My DSL linesí latency 47ms
« Reply #2 on: January 15, 2020, 06:59:35 PM »

So maybe 20ms for interleave / de-interleave ?
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neil

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Re: My DSL linesí latency 47ms
« Reply #3 on: January 16, 2020, 03:29:12 AM »

What makes up my latency? I have interleave (hopefully, seriously) set to maximum on the controls at clueless.aa.net.uk but I canít be sure.
you cant see in the stats?
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aesmith

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Re: My DSL linesí latency 47ms
« Reply #4 on: January 16, 2020, 03:05:29 PM »

So maybe 20ms for interleave / de-interleave ?

When I was on 20CN meaning interleave could only be "On" or "Off", it added roughly 20ms to the round trip time.  I don't know if that could be derived from the ADSL stats ..

====================================================================================
       ADSL Port Details       Upstream         Downstream
               Line Rate:      0.792 Mbps        4.811 Mbps
    Actual Net Data Rate:      0.780 Mbps        4.779 Mbps
          Trellis Coding:         ON                ON
              SNR Margin:        5.8 dB            5.6 dB
            Actual Delay:          5 ms              8 ms
          Transmit Power:       12.2 dBm          19.3 dBm
           Receive Power:        4.7 dBm           4.7 dBm
              Actual INP:        2.0 symbols       1.0 symbols
       Total Attenuation:       32.0 dB          52.5 dB
Attainable Net Data Rate:      1.244 Mbps        5.132 Mbps
====================================================================================
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