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Author Topic: PPPoEoA and RFC 2684 sec 6.2 _VC-MUX_ vs LLC (again) (again). groan  (Read 1035 times)

Weaver

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yes, I know, I know.

Looking back at this thread
    http://forum.kitz.co.uk/index.php/topic,19635.msg346076.html#msg346076

Can we say for certain that if you are doing all of the following
 i)   using ATM and ADSL
 ii)  using PPPoEoA ie PPPoE on the ADSL link, not just PPPoEoE on the LAN
 iii) not using a DrayTek modem that does PPPoEoE to PPPoA conversion internally
 iv) using RFC2684 sec 6.2 ("bridged pdus") VC-MUX not LLC

then VC-MUX works (don't have to use LLC) on
1) a BTW 21CN ADSL line
2) a BTW 20CN ADSL line
3) a TalkTalk ADSL line.

I can confirm (1) myself. As for 2, I forget whether or not I tested it properly when I was using 20CN. I had it in my head that VC-MUX / PPPoEoA / 20CN doesn't work back then, but don't know why I thought this. In the aforementioned thread j0hn says that VC-MUX / PPPoEoA / 20CN does work, but I can't find a reference.

Can anyone help me with 2 and 3?
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burakkucat

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Re: PPPoEoA and RFC 2684 sec 6.2 _VC-MUX_ vs LLC (again) (again). groan
« Reply #1 on: January 02, 2018, 11:33:17 PM »

I can confirm (3) for you . . . as it is a TT LLU G.992.3 based service that is used at "The Cattery".  :)

Edited to add: I have used some rather convoluted software/hardware set-ups in some of my earlier testing (about a year ago) and really need to "write it up" for posterity.
« Last Edit: January 02, 2018, 11:38:21 PM by burakkucat »
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Weaver

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Re: PPPoEoA and RFC 2684 sec 6.2 _VC-MUX_ vs LLC (again) (again). groan
« Reply #2 on: January 03, 2018, 12:33:10 AM »

Thanks Burakkucat, I somehow forgot that you were PPPoEoA.

That just leaves the case of (2). J0hn I think remembered a thread where (2) was discussed properly. [edit: I mistakenly wrote 1 originally]
« Last Edit: January 03, 2018, 12:45:22 AM by Weaver »
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burakkucat

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Re: PPPoEoA and RFC 2684 sec 6.2 _VC-MUX_ vs LLC (again) (again). groan
« Reply #3 on: January 03, 2018, 12:36:33 AM »

That just leaves the case of (1). J0hn I think remembered a thread where (1) was discussed properly.

Don't you mean (2) ?  ???

Quote
I have been working in expanding the section on the DLink DSL-320B-Z1 in the Andrews & Arnold support wiki. If any Kitizens would care to take a look, it's at http://support.aa.net.uk/Router_-_DLINK_320B&stable=0 (latest unapproved version).

I'll certainly take a look.

Edited to add: I had to use the following link http://support.aa.net.uk/index.php?title=Router_-_DLINK_320B&oldid=12284&diff=cur
« Last Edit: January 03, 2018, 12:48:49 AM by burakkucat »
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Weaver

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Re: PPPoEoA and RFC 2684 sec 6.2 _VC-MUX_ vs LLC (again) (again). groan
« Reply #4 on: January 03, 2018, 12:44:00 AM »

I did indeed mean (2), as you say, 20CN.

I discovered this from 2014

    http://forum.kitz.co.uk/index.php?topic=14509.0

So that's a "no" vote for 20CN. And something about a software change? Even worse then!

« Last Edit: January 03, 2018, 12:53:56 AM by Weaver »
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Weaver

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Re: PPPoEoA and RFC 2684 sec 6.2 _VC-MUX_ vs LLC (again) (again). groan
« Reply #5 on: January 03, 2018, 12:57:34 AM »

Rather confusing english: "It seems that PPPoE is only supported over LLC since last year." It looks as if it might be saying that llc was not supported earlier, but maybe it's saying that the situation now is 'llc-only'.
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burakkucat

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Re: PPPoEoA and RFC 2684 sec 6.2 _VC-MUX_ vs LLC (again) (again). groan
« Reply #6 on: January 03, 2018, 01:06:39 AM »

I discovered this from 2014

    http://forum.kitz.co.uk/index.php?topic=14509.0

So that's a "no" vote for 20CN. And something about a software change? Even worse then!

Ah, yes. Now that you have reminded me, I remember reading Mick's thread and was puzzled why such a change would have been made to the bRAS software.

I read the statement -- "It seems that PPPoE is only supported over LLC since last year." -- and presume the intention is to convey your latter interpretation. I.e. "As of last year, PPPoE support can only be provided using LLC on 20CN hardware."
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Weaver

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Re: PPPoEoA and RFC 2684 sec 6.2 _VC-MUX_ vs LLC (again) (again). groan
« Reply #7 on: January 03, 2018, 01:28:06 AM »

I see that BT SINs 482 and 485 both make no mention of PPPoEoA + VC-MUX. SIN 485 is describing 20CN only I'm pretty sure [?]. Is SIN 482 also 20CN-only?

I'm wondering if SIN472 is roughly the equivalent to 482 but for 21CN ?
« Last Edit: January 03, 2018, 01:31:10 AM by Weaver »
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burakkucat

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Re: PPPoEoA and RFC 2684 sec 6.2 _VC-MUX_ vs LLC (again) (again). groan
« Reply #8 on: January 04, 2018, 12:29:19 AM »

Perhaps looking at the publication dates may help decide which came first . . .

STIN472 Issue 1.0 19/07/2007
SIN472  Issue 1.0 02/04/2008
SIN482  Issue 1.0 12/03/2008
SIN485  Issue 1.0 19/06/2008
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richi

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Re: PPPoEoA and RFC 2684 sec 6.2 _VC-MUX_ vs LLC (again) (again). groan
« Reply #9 on: February 18, 2018, 01:56:56 PM »

I recently switched to what my Billion calls "PPPoE" on my 21CN line, to debug a weird authentication timeout issue. It seems to work fine. I'm using VC-MUX.

With PPPoA, I would often see two or more timeouts when PPP/LCP tried to authenticate. But no such problem with PPPoE(oA).
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Alex Atkin UK

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Re: PPPoEoA and RFC 2684 sec 6.2 _VC-MUX_ vs LLC (again) (again). groan
« Reply #10 on: April 19, 2018, 07:19:59 PM »

Out of curiosity, is there any particular reason NOT to use LLU anyway?

I remember reading a long long time ago that its perhaps not as efficient or something, but I certainly never had any problems with it.  Being able to use a better router always gave me a superior result to using VC MUX and being forced to use PPP on the modem/router itself.
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Weaver

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Re: PPPoEoA and RFC 2684 sec 6.2 _VC-MUX_ vs LLC (again) (again). groan
« Reply #11 on: April 19, 2018, 09:11:14 PM »

LLC is more overhead, so depending on the packet size you are transmitting / receiving this could mean one more ATM cell so for a ~ 1500 byte packet that would mean 3% speed loss. But if the MTU or packet size you happen to have means that the overhead will fit into one ATM cell with or without the extra overhead of LLU compared with VC-MUX then there is no speed difference in that one particular case, but there will always be _some_ cases where LLC is worse, depending in the length.

If you use PPPoEoA IP MTU 1500 (1500 + 8 = 1508 baby jumbo frames on PPPoEoE, on a router-to-modem link) the LLC will cost you that extra 3% as it pushes you into another almost completely wasteful ATM cell. If you use the common IP MTU 1492, then using LLC won't make any difference on full length packets.
« Last Edit: April 19, 2018, 09:20:26 PM by Weaver »
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Alex Atkin UK

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Re: PPPoEoA and RFC 2684 sec 6.2 _VC-MUX_ vs LLC (again) (again). groan
« Reply #12 on: April 22, 2018, 01:11:39 AM »

Could explain it as I'm not sure if I was using an 1500 MTU back then.  Though to be honest, I have not seen any obvious benefit to using it now either, I just do it on the principle of it being optimal and less prone to issues.
« Last Edit: April 22, 2018, 01:15:04 AM by Alex Atkin UK »
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