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[aesmith]

I guess not, but the AA L2TP adds ｣10/m. If using your existing AS account, L2TP takes precedence, if it's already connected then DSL won't authenticate. If DSL is already connected then L2TP authenticates but doesn't blow DSL off, and routing gets screwed up. That's what I found anyway. 

I guess Weaver will want IPv6 though.

[meritez]

As far as I know Three are the only provider who give a real IP address, rather than CGNAT. I'm referring to IPv4 though.

EE provide a real IPv6 address on their mobile service.
There's nothing to stop you forcing EE to IPv6 only, and using the A&A l2tp over it.

[Alex Atkin UK]

EE provide a real IPv6 address on their mobile service.
There's nothing to stop you forcing EE to IPv6 only, and using the A&A l2tp over it.

Would that not be less efficient than over IPv4 due to the IPv6 having more overhead?

[j0hn]

Ok thanks for that, so the ISP has been given control for ADSL, thats interesting.

It has been like that a number of years. It very much depends on the backhaul carrier.

BTW run their own DLM on their ADSL DSLAM's and Talktalk run their own on their DSLAM's.
I think Sky do too.

With Talktalk for years I had their ADSL DLM set to 3dB then disabled so it could never change from that. In roughly 2014/15 Talktalk changed their DLM so you could no longer disable it. They added that back some time later.
I haven't kept up with any of the ADSL DLM's since then.

I would assume the control A&A give on ADSL lines will depend on whether it is BTW or TTB.

Edit: looks like it does indeed.

https://support.aa.net.uk/BT_ADSL_Line_Profiles
https://support.aa.net.uk/TalkTalk_Wholesale_Line_Profiles

Looks like you can't set 3dB

[meritez]

Would that not be less efficient than over IPv4 due to the IPv6 having more overhead?

I'm all ears, what overhead?

https://www.ipv6.org.uk/wp-content/uploads/2018/11/Nick-Heatley_BT_EE_464xlat_UKv6Council_20180925.pdf

https://indico.uknof.org.uk/event/38/contributions/489/attachments/612/736/Nick_Heatley_EE_IPv6_UKNOF_20170119.pdf

[Weaver]

I知 sorry, I got lost. Is CGNAT a show-stopper for L2TP ? Does L2TP care about CGNAT addresses or changing addresses ? I can always ask AA of course. Selection criteria for choosing suitable 4G carriers compatible with the use of L2TP.

[meritez]

@Weaver, CGNAT is not a show stopper for L2TP, in fact most use L2TP to get round CGNAT.

[Weaver]

Thanks, I assumed as much. Does it kill L2TP if source addresses change ? I will be pinging with ICMP pings every second or so to check that the connection is healthy, so that should perhaps help to keep a 4G link up, prevent something from timing out and dumping a source address somewhere.

[aesmith]

AA's L2TP worked fine over Smarty CGNAT.

[Weaver]

Thanks my friends, for clearing that up. So my concerns will be packet loss and worst-case speeds down and up. I知 sure I致e forgotten something important in that list. The L2TP connection had better stay up long term, and be highly reliable.

In the other thread I mentioned that I知 now completely confused about what the protocol stack is coming out of my Firebrick into the 4G radio and then the stack over the 4G link. The wikipedia article about L2TP is no help.

[XGS_Is_On]

Hitting the 4G will be IP over PPP over L2TP over UDP over IP over Ethernet. The Ethernet will be stripped by the 4G modem.

The 4G link itself will have an IP MTU of at most 1500 bytes with the rest not your problem: further overheads will be dealt with by the 4G network.

[Chrysalis]

I知 sorry, I got lost. Is CGNAT a show-stopper for L2TP ? Does L2TP care about CGNAT addresses or changing addresses ? I can always ask AA of course. Selection criteria for choosing suitable 4G carriers compatible with the use of L2TP.

It shouldnt be an issue as its an outbound connection on the client.  the L2TP server is AA's side, however even if it is, you can connect on L2TP via IPv6 I checked on the L2TP AA page after meritez posted.  I also tested it successfully on EE, I think I mentioned that in my L2TP thread.

On reliability I have had a few outages which I assume are all AA related, one of them Andrew was woken up during the night and was definitely AA side, thats the only one that didnt instantly reconnect, all the others reconnected automatically.  Its going to be a "try and see" thing and hope it works well.  If it does then you can decide on longer term configuration changes.

You will still have control over the rate limit as well if you feel you want the small packets optimization, 100% rate limit is 200mbit.

[Weaver]

I知 going to continue this in the other thread, so please follow me.