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Conference irocz::common_brouters

Title:Digital Brouters Conference
Notice:New common-code brouter family: RouteAbout, DECswitch 900
Moderator:MARVIN::HARTLL
Created:Mon Jul 17 1995
Last Modified:Fri Jun 06 1997
Last Successful Update:Fri Jun 06 1997
Number of topics:929
Total number of notes:3736

909.0. "PPP configuration for Satellites links" by BARNA::DSMAIL () Tue May 20 1997 10:57

    
I have to install two RouteAbout 90 EW using synchronous lines with 	
PPP data link .The conection between routers is make througth satellite.

The line will work at 64 Kbps and I need some hints to solve the following	

The satellite introduce a 250 ms delay .

				
				[Satellite]

                                  delay 250 ms

			       /	   !
!-------!		      /		   !                   !-------!
!  RA90	!>PPP/0-----[modem]__/	   64Kbp   !____[modem]--PPP/0<! RA90  !
!	!						       !       ! 
!  EW	!	                                               !  EW   !
!	!>	                                              <!       ! 
!	!                                                      !       !
!-------!                                                      !_______!



Any recomendations to configure routeabout PPP timers ?????

Thanks in advanced

Luis Miguel Sanchez

NAC CSC Barcelona
T.RTitleUserPersonal
Name		DateLines
909.1MARVIN::TURNERNeil Turner IPEG REO, 830-4140Wed May 21 1997 04:579
What problems are you seeing, you do not make it clear whether
you are seeing problems or just anticipate them?

The default retry timer on PPP is 3000mS which should be fine
with your 250mS delay. This timer is only used whilst the
link is initialising, once up PPP is an unacknowledged datalink
so I don't envisage and problems over your connection.

Neil
909.2satellite link up and running.Performance ?BARNA::DSMAILFri May 23 1997 11:5539
	Thanks for your quick response.
	

	Really I wanted to advance to the problems because I have no 
	experience about satellite links and I was afraid about link
	establishment and its performance.

	Well , now I know a little more and I tested the configuration
	in the customer site , but I had some performance problems.

	Following explains you the  parameter configuration and its results

	With PPP configuration parameters:

        Maximum frame size=2048 Bytes (default) making ftp with a file size 3MB
	the transfer speed arrives to 20Kbps aprox.

	Maximum frame size=512  Bytes (default) doing a ftp with the same file size
	the speed becomes to 14 Kbps.
	
	Maximum frame size=4088 Bytes (maximun ) the tranfer speed arrives to
	28 Kbps .

	With max frame size 4088 Bytes and CCP compression enabled we reached the 
	max speed 42 Kbps.

	Note that the channel speed is 64 kbps .

	Doing a ping  the response time was 

	Packet size 64 bytes ------- 550 ms
	Packet size 4000 bytes ----- 1600 ms aprox.

	What do you think about ? 

Thanks in advance

Luis Miguel Sanchez
909.3TCP window size?MARVIN::TURNERNeil Turner IPEG REO, 830-4140Thu May 29 1997 03:529
I don't think your problem lies with PPP since as I said before it
is an unaknowledged datalink protocol. However I am not sure what TCP 
will do when it is used on a link which has such a long round trip delay
(550mS in your case). It is going to need a large window size in order 
'fill up' this delay and therefore saturate the line. I don't know enough 
about the behaviour of TCP, but I suspect that its default window size 
will not be large enough to make best use of the line.

Neil