[AusNOG] ADSL2+ line sync data

[Mark ZZZ Smith]

----- Original Message -----
> From: Mark ZZZ Smith <markzzzsmith at yahoo.com.au>
> To: Joshua D'Alton <joshua at railgun.com.au>
> Cc: "ausnog at lists.ausnog.net" <ausnog at lists.ausnog.net>
> Sent: Saturday, 14 September 2013 10:15 AM
> Subject: Re: [AusNOG] ADSL2+ line sync data
> 
> 
> 
>> ________________________________
>>  From: Joshua D'Alton <joshua at railgun.com.au>
>> To: 
>> Cc: "ausnog at lists.ausnog.net" <ausnog at lists.ausnog.net> 
>> Sent: Friday, 13 September 2013 10:25 PM
>> Subject: Re: [AusNOG] ADSL2+ line sync data
>> 
>> 
>> 
<snip>
> 
> Symmetry doesn't eliminate congestion (nothing does), 

And to clarify what I mean by this, TCP attempts to push the network into congestion to measure and then maximise the use of the available capacity between the end points. When packets are lost, TCP considers that to be a sign of congestion and backs off its send rate.


> but it can provide 
> equal performance and quality in both directions for TCP and other protocols and 
> applications. Video can be the same quality in both directions, not better in 
> one direction than the other (asymmetry of bandwidth is going to put a real 
> cramp on telemedicine, as the patient will see the doctor really well, but the 
> doctor won't see the patient really well - and doctors won't accept that 
> because their malpractice premiums would then go up). Uploads will have as much 
> congestion effect as downloads. 
> 
>> 
>> I don't know exactly what ratio is 'ideal',
> 
> True, but the IETF do, and they're the experts on Internet protocols. They 
> designed TCP, and they've published an RFC that has become a Best Common 
> Practice on how asymmetry impacts its performance.
> 
> If you read nothing else, read the following from the summary,
> 
> "Asymmetry, and particular high asymmetry, raises a set of TCP performance 
> issues."
>