North American Network Operators Group

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Re: Cisco DS3 Questions..

  • From: Christopher A. Woodfield
  • Date: Thu Feb 21 14:13:16 2002

There's no reason to use frame-relay encapsulation unless you're actually going 
through a frame network.

For point-to-point circuits, from Cisco to Cisco, HDLC is the best choice, but 
it's proprietary (although Juniper has a Cisco HDLC mode). For 
anything else, I'd recommend PPP. 


On Thu, Feb 21, 2002 at 01:46:44PM -0500, Gyorfy, Shawn wrote:
> Since the topic exploded, what are your opinions on encapsulation of leased
> line DS3s.  We currently use Frame Relay for out Point to Point DS3
> connections.  Personally, I don't know why we use FR as our encapsulation,
> and so the question to all.  If you are running Cisco to Cisco, would it be
> wise to run HDLC or PPP?  Our DS3s' here are hardly maxed out, 15% or so, so
> I'm not complaining about the few extra bits I can squeeze out them but
> maybe that 15% can shrink to 10% with less overhead.  Opinions or examples
> of life appreciated.  
> Thanks
> shawn  
> -----Original Message-----
> From: Iljitsch van Beijnum [mailto:[email protected]] 
> Sent: Wednesday, February 20, 2002 4:28 PM
> To: Jon Mansey
> Cc: [email protected]
> Subject: Re: Cisco PPP DS-3 limitations - 42.9Mbpbs?
> On Wed, 20 Feb 2002, Jon Mansey wrote:
> > OMG! Arent we missing the point here? What about never running links above
> > 60% or so to allow for bursts against the 5 min average, and <shudder>
> > upgrading or adding capacity when we get too little headroom.
> > And here we are, nickel and diming over a few MBps near to 45M on a DS3...
> And why not? Obviously there is a reason why they're not upgrading,
> because there is plenty of traffic to fill up a second or faster circuit
> if packets are being dropped because of congestion. (Which has not been
> confirmed so far.)
> There shouldn't be any problems pushing a DS3 well beyond 99% utilization,
> by the way. With an average packet size of 500 bytes and 98 packets in the
> output queue on average, 99% only introduces a 9 ms delay. The extra RTT
> will also slow TCP down, but not in such a brutal way as significant
> numbers of lost packets will. Just use a queue size of 500 or so, and
> enable (W)RED to throttle back TCP when there are large bursts.

Christopher A. Woodfield		[email protected]

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