[c-nsp] traffic shaping inbound wan?

[Andre Beck]

Hi Oli,

On Fri, Jan 13, 2006 at 08:39:17AM +0100, Oliver Boehmer (oboehmer) wrote:
> 
> As Linn has already said: Once the packet has been received on an
> interface, we cannot queue it as there are no suitable queues on input.

One could emulate them. You are already doing this, it's called
hierarchical MQC and can be used to get i.e. a tunnel interface
(which has no traditional queues) to do full-featured QoS. The
point is that a shaper *is* a queue, or at least behaves like
one. So attaching a shaper to incoming traffic is not impossible
per se, it's just very likely a software thing and not backed by
hardware, so performance might be prohibitive.

> It just doesn't make sense.

I'd like to solidarize with the others who posted in this thread that
this can be seen to the contrary. Shaping is generally way friendlier
to overall traffic behavior than is policing, as shaping, at least with
cooperative hosts, will induce very little overall packet loss, by
instead introducing some more delay. The core point about ingress
shaping is that you can use it to "move the queue to your equipment",
by shaping to a rate somewhere 10% below the real line rate the other
side will use when sending. This way, you can get more control over
the queue, even with a non-cooperative transmitter on the other side
that just uses a large FIFO queue. Yes, this is more of a CPE issue.
But Cisco builds CPEs as well (let's say 876s) and I'd really like
to see them beeing able to ingress shape (or to shape correctly at
all[1]).

[1] When I tested this, shaping towards a VLAN SVI was configurable,
    but didn't work. Shaping towards a BVI wasn't even configurable.
    As you *must* use a BVI if you want a 876W to do regular AP operation
    (which is essentially a modified bridging), and you cannot do ingress
    shaping either, you essentially have no shaping on the 876W at all.
    Bad for a DSL CPE IMO. Last tested on some 12.4T.

Andre.
-- 
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-> Andre Beck    +++ ABP-RIPE +++    IBH Prof. Dr. Horn GmbH, Dresden <-