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Author Topic: Bearers  (Read 1111 times)


  • Addicted Kitizen
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  • Retd sw dev; A&A; 4 × 7km ADSL2; IPv6; Firebrick
« on: June 28, 2018, 06:21:28 AM »

Apologies for such an extremely basic question :

What exactly do ‘bearers’ get used for in DSL ?

I get the idea in general. You can have differing specs so as to get different points on the tradeoff axis between latency performance vs reliability according to application requirements.

What I do not understand though is

* How is one device or ‘end’ supposed to know what the various bearers are what they mean what they are for and so on? (Presumably the answer is that they just have to know because it is in a post-it note stuck in the wall somewhere or if you do not know then you phone someone up and ask them. For all I know, there may not even be any way for one end to query the other end to find out what is what? - I have not looked.)

* Is there any kind of standard as to how the bearers actually get used in general particular kinds of CPE? Meaning the semantics as well. Or Is it all just completely random - defined by individual ISPs, or vast wholesaler access providers such as BT?

I feel that I ought to know this. I admit I have little idea how I might try and look it up.


  • Addicted Kitizen
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  • Posts: 8976
  • Retd sw dev; A&A; 4 × 7km ADSL2; IPv6; Firebrick
Re: Bearers
« Reply #1 on: December 28, 2018, 01:58:50 AM »

If you have anything interesting in your Bearer x, x > 0, would you let me know?


  • Kitizen
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  • Posts: 1018
  • Uno comms 80/20
Re: Bearers
« Reply #2 on: December 28, 2018, 02:47:39 AM »

adsl info --stats
adsl: ADSL driver and PHY status
Status: Showtime
Last Retrain Reason:    0
Last initialization procedure status:   0
Max:    Upstream rate = 15620 Kbps, Downstream rate = 67851 Kbps
Bearer: 0, Upstream rate = 15538 Kbps, Downstream rate = 68776 Kbps
Bearer: 1, Upstream rate = 0 Kbps, Downstream rate = 0 Kbps

My stats if they are of interest. VDSL2 on Uno. VMG-1312-B10A
Tim & freenetname
Asus RT-AC68U and ZyXEL VMG1312-B10A Bridge on 80 Meg TTB Fibre


  • Kitizen
  • ****
  • Posts: 3052
Re: Bearers
« Reply #3 on: December 28, 2018, 03:39:23 AM »

This thread may interest you.

The Bearers in the xDSL link of an OpenReach FTTC/VDSL2 circuit are only used between CPE and DSLAM.
Nowhere else needs to know this.
It's negotiated between the 2 during the sync process.

Only when G.INP is active is another Bearer (Bearer 1) created.
It's not Retransmission data sent over Bearer 1 despite it only being created when Retransmission is in use.

ejs explains it well on the thread above.
BT FTTP 160/30 - BQM - speed test