Cisco PPP DS-3 limitations - 42.9Mbpbs?

Wed Feb 20 14:41:10 UTC 2002

we run HDLC on DS3 and we max at about 40.something too

not sure why, i just assume theres either overhead in the frames somewhere
or that the cards arent designed to run at line speed

we run HDLC, c-bit and CRC16 on PA-2T3+.. be interested if anyone knows
how to get the missing 10% :)

Steve

On Wed, 20 Feb 2002, Ehud Gavron wrote:

> 
> 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
> gavron at wetwork.net
> 

-- 
Stephen J. Wilcox
IP Services Manager, Opal Telecom
http://www.opaltelecom.co.uk/
Tel: 0161 222 2000
Fax: 0161 222 2008