[AusNOG] ADSL2+ line sync data

[Mark ZZZ Smith]

----- Original Message -----
> From: Mark ZZZ Smith <markzzzsmith at yahoo.com.au>
> To: Tony <td_miles at yahoo.com>; "Beeson, Ayden" <ABeeson at csu.edu.au>; Guy Ellis <guy at traverse.com.au>
> Cc: "ausnog at lists.ausnog.net" <ausnog at lists.ausnog.net>
> Sent: Friday, 13 September 2013 9:41 PM
> Subject: Re: [AusNOG] ADSL2+ line sync data
> 
>  From: Tony <td_miles at yahoo.com>
>> To: "Beeson, Ayden" <ABeeson at csu.edu.au>; Guy Ellis 
> <guy at traverse.com.au> 
>> Cc: "ausnog at lists.ausnog.net" <ausnog at lists.ausnog.net> 
>> Sent: Friday, 13 September 2013 9:55 AM

<snip>

>> If at 2000m you get either 18/1Mbps ADSL2+ or 11/11Mbps VDSL2 then thats 
> fairly close to the same amount of total bandwidth (19 v's 22). This 
> probably doesn't please the user though as they 
> want faster downloads (to "obtain" the latest TV eps) and hence an 
> option to choose which "DSL" you want might be of benefit depending on 
> your intended usage of the link.
>> 
> 
> Sad thing about this is that doing that appears to be a good idea, but that 
> actual best thing for performance is symmetry, due to how TCP uses ACK feedback 
> to determine it's send rate. Congestion on the uplink, which is more likely 
> to occur when the uplink bandwidth is lower than downlink bandwidth, will slow 
> down downloads:
> 
> BCP69/RFC3449, "TCP Performance Implications of Network Path 
> Asymmetry"
> http://tools.ietf.org/html/rfc3449
> 
> 
> 


I should add that Google gets it, which is why their FTTP is symmetric.

http://googlefiberblog.blogspot.com.au/2012/04/construction-update.html


Q: I see a label on your diagram, “Gigabit Symmetric Fiber Connectivity.” What does that mean?