Re: [tcpm] I-D Action: draft-ietf-tcpm-cubic-00.txt

Hi,

A detail:

the beta factor (for multiplication when there is congestion) is 0.7, not 0.8, since Linux kernel 2.6.25 from 2008.
The draft talks about beta as a (1-beta) multiplication factor - so, accordingly, to capture the current implementation state, in section 3.5:

***
When a packet loss occurs, CUBIC reduces its window size by a factor
   of beta.  Parameter beta SHOULD be set to 0.2.
***

should be:

***
When a packet loss occurs, CUBIC reduces its window size by a factor
   of beta.  Parameter beta SHOULD be set to 0.3.
***

Side note: personally I find this use of beta confusing - "reduce by ..." indicates subtraction to me, and I'm not sure if "reduce by a factor of" is easily parsed by everyone as "multiplied by (1- ...)". Just like the code, I would therefore rather write:

***
When a packet loss occurs, CUBIC reduces its window size by multiplying it with a factor
   of beta.  The parameter beta SHOULD be set to 0.7.
***

... and change (1-beta) to beta below. But that's just a matter of style/taste I guess.

Cheers,
Michael

> On 19. jun. 2015, at 09.12, Zimmermann, Alexander <Alexander.Zimmermann@netapp.com> wrote:
> 
> This is just a resubmission of draft-zimmermann-tcpm-cubic-01 as WG item.
> Received feedback will be addressed in upcoming versions
> 
> Alex
> 
>> Am 18.06.2015 um 21:24 schrieb internet-drafts@ietf.org:
>> 
>> 
>> A New Internet-Draft is available from the on-line Internet-Drafts directories.
>> This draft is a work item of the TCP Maintenance and Minor Extensions Working Group of the IETF.
>> 
>>       Title           : CUBIC for Fast Long-Distance Networks
>>       Authors         : Injong Rhee
>>                         Lisong Xu
>>                         Sangtae Ha
>>                         Alexander Zimmermann
>>                         Lars Eggert
>>                         Richard Scheffenegger
>> 	Filename        : draft-ietf-tcpm-cubic-00.txt
>> 	Pages           : 14
>> 	Date            : 2015-06-18
>> 
>> Abstract:
>>  CUBIC is an extension to the current TCP standards.  The protocol
>>  differs from the current TCP standards only in the congestion window
>>  adjustment function in the sender side.  In particular, it uses a
>>  cubic function instead of a linear window increase of the current TCP
>>  standards to improve scalability and stability under fast and long
>>  distance networks.  BIC-TCP, a predecessor of CUBIC, has been a
>>  default TCP adopted by Linux since year 2005 and has already been
>>  deployed globally and in use for several years by the Internet
>>  community at large.  CUBIC is using a similar window growth function
>>  as BIC-TCP and is designed to be less aggressive and fairer to TCP in
>>  bandwidth usage than BIC-TCP while maintaining the strengths of BIC-
>>  TCP such as stability, window scalability and RTT fairness.  Through
>>  extensive testing in various Internet scenarios, we believe that
>>  CUBIC is safe for deployment and testing in the global Internet.  The
>>  intent of this document is to provide the protocol specification of
>>  CUBIC for a third party implementation and solicit the community
>>  feedback through experimentation on the performance of CUBIC.
>> 
>> 
>> The IETF datatracker status page for this draft is:
>> https://datatracker.ietf.org/doc/draft-ietf-tcpm-cubic/
>> 
>> There's also a htmlized version available at:
>> https://tools.ietf.org/html/draft-ietf-tcpm-cubic-00
>> 
>> 
>> Please note that it may take a couple of minutes from the time of submission
>> until the htmlized version and diff are available at tools.ietf.org.
>> 
>> Internet-Drafts are also available by anonymous FTP at:
>> ftp://ftp.ietf.org/internet-drafts/
>> 
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