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RE: Cisco PPP DS-3 limitations - 42.9Mbpbs?

  • From: Goodwin, Dustin T [IT]
  • Date: Wed Feb 20 11:28:56 2002

Assuming this utilization figure is correct the other way to milk a higher
utilization out of the link is by using Random Early Detect (RED) or
Weighted RED. This will eliminate jagged utilization pattern you see in
fully consumed link which is caused by TCP window synchronization. RED will
give you a smoother utilization line that is closer to maximum theoretical
throughput of the link.

- Dustin -

-----Original Message-----
From: Ehud Gavron [mailto:[email protected]]
Sent: Wednesday, February 20, 2002 9:24 AM
To: [email protected]
Cc: [email protected]
Subject: Cisco PPP DS-3 limitations - 42.9Mbpbs?

At a recent consulting opportunity, a client was
only getting 40.9Mbps on their DS-3 (clearchannel
DS3 over OC12 to the IP provider).
(PA-2T3 to PA-2T3, unloaded CPU, drops occur when
peak octets out per sec/8=40.9M)

The client asked us why 40.9 was less than 44.210.

The IP provider indicated that "Cisco told us the
maximum theoretical rate of an interface doing
DS-3 with PPP encapsulation is 42.9."

I can't find documentation to the 42.9.
I can't find documentation that indicates that the
PPP overhead is somehow magically excluded from
the IfOctetsIn and Out...
I can't find documentation as to why 40.9 is
the observed rate.

Frankly, all my DS-3s (HDLC encap) go up to 44.210,
so I was hoping I could share in the collective
wisdom of NANOG readers who have DS-3s to IP
providers, and can provide real observed feedback.

Please reply privately.  Please let me know privately
if you want a summary.  Thanks!

Ehud Gavron
[email protected]