[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

[LDM #ZJU-572512]: Darn that LDM! ;-)



Gilbert,

> Check this out...from NWS Central Region Headquarters...
> 
> 497
> NOUS73 KBCQ 032050
> ADMCRH
> 
> TO: ALL
> FROM: CRH
> SUBJECT: OC3 cutover follow up
> 
> ********** PLEASE SHARE WITH ENTIRE STAFF **********
> 
> 
> ***PLEASE SHARE WITH STAFF***
> 
> ALL,
> 
> THE OC3 CUTOVER PROBLEMS EXPERIENCED TODAY WERE A RESULT OF
> MTU ISSUES ON WFO/RFC ROUTERS AND LDM APPLICATION SOFTWARE.
> THE MTU AFFECTED PACKET TRANSFER RATES THAT DIRECTLY
> IMPACTED THE WAY CERTAIN WEB PAGES LOAD. THE LDM SOFTWARE
> WAS OVER RUNNING THE LOCAL WFO/RFC BANDWIDTH AS IT IS A
> SMART APPLICATION THAT AUTOMATICALLY DOES TCP CONGESTION
> CONTROL, WHICH SAW THE NEW OC3 AS A LARGE PIPE AND KEPT
> SENDING MORE DATA, WHICH IN TURN CHOKED THE LOCAL WFO/RFC
> BANDWIDTH, RESULTING IN RSYNC FAILURES AND SLOW DOWNLOAD
> SPEEDS. WE HAVE RATE LIMITED LDM HERE AT CRH ON THE OPSNET
> FIREWALL AND HAVE BEEN RUNNING SUCCESSFULLY. WE WILL
> CONTINUE TO MONITOR AND ADJUST AS NECESSARY TOMORROW.
> 
> IF YOUR SITE HAS ANY ISSUES OVERNIGHT WITH RSYNC, PLEASE
> CONSULT YOUR LOCAL IT STAFF AND IF NEEDED, OPEN A TICKET
> WITH OPSNET. PLEASE DO NOT OPEN A TICKET WITH NIDS UNLESS
> DIRECTED.
> 
> THANKS FOR YOUR PATIENCE AND ASSISTANCE DURING THIS MAJOR
> TRANSITION.
> 
> STEVE

Well, that explains the email we just received from them.

> ?
> ---
> 
> Hey, they admit it's a smart application. I fully agree! :-)

So do I. :-)

Actually the problem isn't the LDM. The problem is caused by the interaction of 
a TCP connection and its congestion algorithm with the lack of implementation 
of the Early Packet Discard algorithm in routers.

> *******************************************************************************
> Gilbert Sebenste                                                     ********
> (My opinions only!)                                                  ******
> Staff Meteorologist, Northern Illinois University                      ****
> E-mail: address@hidden                                  ***
> web: http://weather.admin.niu.edu                                      **
> Twitter: http://www.twitter.com/NIU_Weather                            **
> Facebook: http://www.facebook.com/niu.weather                           *
> *******************************************************************************

Regards,
Steve Emmerson

Ticket Details
===================
Ticket ID: ZJU-572512
Department: Support LDM
Priority: Normal
Status: Closed


NOTE: All email exchanges with Unidata User Support are recorded in the Unidata inquiry tracking system and then made publicly available through the web. If you do not want to have your interactions made available in this way, you must let us know in each email you send to us.