Michael,

Traffic shaping at the perimeter level is great for instances like your
standard capped broadband line.  By lowering the priority of high bandwidth
uploading (BitTorrent, P2P, etc), you can increase the response time of your
other applications, like web surfing.  The magic shaper is configured to set
it up that way.

Shaping throughout the network is useful only if the traffic on the network
has already exceeded the capacity available.  Say, if you have a 1Gbit
internal trunk between two routers, and the trunk is totally saturated, then
shaping traffic before hitting the trunk would be healthy.  For most of us,
a few computers can rarely saturate the line.

That's why mostly, shaping is done on the perimeter, where the LAN traffic
exceeds the capabilities of the WAN line.  Any shaping done should feedback
to the internal nodes to slow down (I don't recall how traffic shaping's
implemented), and in essence, help control the flow through the pipe.


/sylikc


On 8/8/08, apiasecki at midatlanticbb dot com <apiasecki at midatlanticbb dot com> wrote:
>
> Most traffic shaping is between the WAN and the LAN Interface. Traffic
> shaping can also only be done with traffic leaving the interface.(WAN
> Interface=Upload Shaping, LAN Interface=Download Shaping)
>
> Most of the time, you set priorities for traffic, so for example. VoIP
> always has bandwidth available, while an FTP upload can be dropped at
> anytime.
>
> I don't know how m0n0wall does traffic shaping, but for pfSense this
> document explained it pretty well.
>
> http://www.openbsd.org/faq/pf/queueing.html
>
> Adam
>
> Michael Pope wrote:
>
>> I'm trying to understand how to implement traffic shaping. We haven't had
>> much need for it in the past.
>>
>> As I understand it, traffic shaping doesn't give much benefit if it isn't
>> implemented throughout the network. So, traffic shaping could provide
>> benefits within a network that has multiple subnets. (For example, a
>> multi-site network where the sites are connected using either site-to-site
>> VPN or a dedicated link).
>>
>> But, I'm not sure about the benefits of traffic shaping at the network
>> perimeter. How could it help your traffic if that traffic is immediately
>> off-loaded into a network that might/might not have shaping implemented?
>> It
>> almost seems like the high-priority traffic is getting into the HOV lane
>> right before the off-ramp.
>>
>> Can someone point me to an explanation or provide it themselves?
>>
>> Thanks,
>>
>> Michael
>>
>>
>>
>
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