From: Carlos G Mendioroz (tron@huapi.ba.ar)
Date: Fri Jul 13 2007 - 15:42:05 ART
Djerk,
Djerk Geurts @ 13/07/2007 08:23 -0300 dixit:
> Carlos,
>
>> Djerk,
>> this is exactly what I was saying, so we agree.
>> (Nobody remembers custom queueing ???)
>
> Correct. Nobody _wants_ to remember custom queueing... ;)
>
>> I don't understand the PQ(LLQ) thing you are bringing up though.
>> PQs have priority, which is a police statement. They get ALL the
>> bandwidth, even first thing (PQ, right?) but up to this much.
>> AFAIK, a queue becomes a PQ when you use the priority keyword,
>> and this implies the policing of it, so there is no way you can
>> have a PQ w/o policing.
>
> Apparently this is not true, CCO doesn't help here as there are too many
> conflicting docs on QoS there.
>
> One has to distingush here between software (up to 7200) and hardware (7300
> GSR CRS-1) based platforms. The priority key-word, like you say, enables the
> priority queue. However the word strict has come to mean (to me at least) a
> policed PQ. The confusion is that a priority statement with bandwidth %
> isn't a policed PQ, resulting in 'unpredictable' behaviour when shaping VoIP
> traffic. So does this mean it is a strict PQ? I recall something from
> Networkers this year that best practice is to use the priority keyword with
> a police statement and not use the bandwidth option on the priority
> statement.
>
> So please correct me if I'm wrong Cannes was back in January after all and
> I've not had the time since to look it up in my notes or hand-outs. Btw, I
> don't trust CCO anymore on the subject of QoS...
>
> I understand that things may be different from what they said at Networkers
> to what we study for the lab. Networkers referred to the CRS-1 mostly (due
> to marketing?) while the lab uses only SW based routers.
Well, this is possibly above my level of knowledge, and I usually agree
with things being far more messier than it shows.
But:
1) MQC is a syntax. If the implementation in a platform of a given
config is different from another, I would call this a bug (or a feature:)
2) PQ is PQ is PQ. I don't really know what "strict" PQ is.
If there is a strict, there should be a loose version of it ? :)
3) As far as I know, there is no way to make a queue a PQ without using
the priority keyword. Percent only changes the meaning of the numbers,
by scaling them.
4) priority implies policing. Allmost. The implied policer only works
when queue management is engaged (i.e. interface congested).
Configuring an explicit policer engages it (the policer) all the time.
>
>> The whole thing I was trying to say is that the default queue
>> works like a "low priority" queue, but without the grace of
>> the policing of the rest, and thus the starving possibility.
>> (when no bandwidth is assigned)
>
> I agree totally
>
>> BTW, queues don't need to know their bit rates, just their "share"
>> of available BW. In your examples, 3/4/3 or 1/5/4.
>
> And again 100% correct
>
>> -Carlos
>
> Djerk
>
BTW, do you have any pointer to NW presos ?
Take care,
-Carlos
-- Carlos G Mendioroz <tron@huapi.ba.ar> LW7 EQI Argentina
This archive was generated by hypermail 2.1.4 : Sat Aug 18 2007 - 08:17:40 ART