[c-nsp] QoS on an Ethernet Sub-interface

[Pelle]

On Fri, Aug 29, 2008 at 08:20, Justin Shore <justin at justinshore.com> wrote:

> I've got a QoS question for the group; I'm not a QoS buff, at least not on
> the nitty gritty details.  I'm trying to set up some basic QoS on a 3Mbps
> PtP Ethernet link.  One side uses a full interface for the link on a 2821.
>  My side uses a 1Q sub-interface on a hardwired GigE port in a 2821.

Not sure about this "one side" and "my side", but when you use a
sub-rate Ethernet service you should apply a HQoS policy (parent
shaper + child queues) on both ends of the link. There is no point
sending egress traffic at 100Mbps (or even 1000Mbps) speed on your
"full interface" 2821 when the actual pipe is just 3Mbps wide.

> policy-map voip-child
>  class voip-rtp
>    priority percent 35
>    set dscp ef
>  class voip-control
>    bandwidth percent 5
>    set dscp af31

If your Ethernet provider support Ethernet CoS you could also "set cos
X" on the interface where you use 802.1q encapsulation. Unfortunately
this is not possible on regular Ethernet interfaces. Some SP's do
support DSCP for classification of Ethernet frames, so you might be
safe any way.

> policy-map voip-parent
>  class class-default
>  shape average ABC
>  !
>  service-policy voip-child

This policy should be attached both on the main interface on one end,
and the sub-interface at the other end.

Note: There has been major improvement in HQoS and LLQ in 12.4(20)T,
see the thread:
https://puck.nether.net/pipermail/cisco-nsp/2008-August/053616.html

-- 
Pelle