[c-nsp] shaping outbound

Arie Vayner (avayner) avayner at cisco.com
Sun Dec 25 12:57:16 EST 2011


You are correct in general, but in many (most) cases Internet
applications are TCP based, and policing them would make the TCP adjust
the actual rate.


-----Original Message-----
From: cisco-nsp-bounces at puck.nether.net
[mailto:cisco-nsp-bounces at puck.nether.net] On Behalf Of Pete Templin
Sent: Sunday, December 25, 2011 15:24
To: Dan Letkeman
Cc: cisco-nsp
Subject: Re: [c-nsp] shaping outbound

On 12/24/11 2:49 PM, Dan Letkeman wrote:

> I'm confused as to when and where it is possible to shape traffic.  I 
> have a 50Mbps internet connection from our ISP and I would like to 
> shape some of the download traffic using our 2821.
> Any idea on how to go about this?  Or Am I stuck with buying a 
> ridiculously expensive packet shaper or something of the sorts?

You might be stuck.

In the grand scheme of things, it's too late: you should shape as the
traffic enters the bottleneck, and/or police certain classes as desired.

  Once the traffic arrives on your router, the congestion has occurred,
and there's not much to be done about it.

UDP/ICMP won't learn from shaping, so they can still overtake the
internet link if you were to shape outbound to the LAN.  That's where
the packet shaper appliance would potentially do better: it can throttle
the upload traffic to influence the download traffic responses.


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