From: Eugene Ward (eward15@juno.com)
Date: Tue Oct 03 2006 - 20:49:45 ART
I think the key words there are "in the event of congestion". It's been stated
on the list before that as long as there is no congestion, the classes should
be able to use more than the configured bandwidth if the bandwidth is not
being used by other devices at that time.
Eugene
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Vincent, you are right. The priority command acts as both a bandwidth
reservation and a policer.
From the Doc CD:
bandwidth-kbps: Guaranteed allowed bandwidth, in kbps, for the priority
traffic. The amount of guaranteed bandwidth varies according to the
interface and platform in use. Beyond the guaranteed bandwidth, the
priority traffic will be dropped in the event of congestion to ensure
that the nonpriority traffic is not starved.
http://www.cisco.com/univercd/cc/td/doc/product/software/ios124/124cr/hq
os_r/qos_o1h.htm#wp1076758
You can add a "burst" to allow the LLQ additional temporary bandwidth
(if available).
-----Original Message-----
From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf Of
Vincent Mashburn
Sent: Wednesday, 4 October 2006 2:13 AM
To: Martin Dean; Mohamed Saeed; ccielab@groupstudy.com
Subject: RE: LLQ Question - Multiple Traffic Classes in the Priority
Queue
Martin,
I agree that there is only one LLQ and that all traffic configured with
the priority QoS will be put into the same FIFO priority queue.
However, I would be interested in seeing your configuration and debug
output on this. When I lab up a MQC scenario and use "priority
<bandwidth>" and then attempt to test the traffic, all traffic that
exceeds this bandwidth amount is dropped, not sent to the default queue.
I would also be very interested in where to find the documentation that
states that traffic in the priority queue is allowed to go over its
configured bandwidth amount. I know that the "bandwidth <bandwidth>"
statement allows more than the configured amount to be passed, but I
have never seen this for the "priority <bandwidth" statement.
Everything that I have read and labbed up is pointing to the fact that
the priority queue drops everything over its allotted bandwidth, even
when more bandwidth is available.
Any additional info and data you could provide would be most helpful.
Thanks
Vince Mashburn
Voice / Data Engineer
901-263-5072
CCVP, CCNP, CCDA,Network +
Cisco IP Telephony Support Specialist
Cisco IP Telephony Operations Specialist
-----Original Message-----
From: Martin Dean [mailto:mdean@diatac.co.uk]
Sent: Tuesday, October 03, 2006 10:58 AM
To: Vincent Mashburn; Mohamed Saeed; ccielab@groupstudy.com
Subject: Re: LLQ Question - Multiple Traffic Classes in the Priority
Queue
In LLQ/CBWFQ the LLQ part and the CBWFQ section act differently.
If there are multiple classes in CBWFQ then they each get their own FIFO
queue and are policed appropriately.
However this does apply in LLQ. If there are multiple classes with the
priority command then all of the priority traffic goes into the same
priority FIFO queue. However they are policed separately. The order
that
the packets are emptied from the priority FIFO queue is in the order
that
the packets arrived in the LLQ, independent on which class they are for.
In the example given, if 2 packets arrive from class 1 followed by 1
from
class 2, then 1 from class 1, then that is how they are transmitted - as
long as they have not been dropped (or remarked if configured) by their
individual policer.
It is not true to say that class 1 and class 2 can only have 100k and
200k
respectively of the bandwidth.
In the example given, all non class 1 and 2 traffic is sent to the
class-default queue. If that traffic is not using its allotted bandwidth
-
(BW of int)-(100k+200k) then both class 1 & 2 can get more, how much
more
depends on the how much class-default does not use then ratioed between
the
two classes.
This is a confusing part of LLQ, especially as some TAC engineers seem
to
give out incorrect information regarding this subject.
But beware, I have recently discovered that the 7600 acts slightly
differently from the 'standard routers - 28s, 36s, 38s, 72s and 75s.
Hope this clears some thing up.
Martin
----- Original Message -----
From: "Vincent Mashburn" <vmashburn@fedex.com>
To: "Mohamed Saeed" <mohamed_saeed2@rayacorp.com>;
<ccielab@groupstudy.com>
Sent: Tuesday, October 03, 2006 10:50 AM
Subject: RE: LLQ Question - Multiple Traffic Classes in the Priority
Queue
> It is my understanding from your configuration that Class 1 has a
> priority bandwidth of 100 and class 2 has a priority bandwidth of 200.
> While it is true that both will be serviced in a FIFO manner since
they
> are both in the priority queue, it is important to realize that the
> priority bandwidth is a policer. For instance, if class 1 attempts to
> prioritize more than 100k then the excess will be dropped. Class 2 is
> allowed to put up to 200k on the link before its excess is dropped.
But
> they are both FIFO since there is only 1 priority queue. I hope that
> this helps.
>
> Vince Mashburn
> Voice / Data Engineer
> 901-263-5072
> CCVP, CCNP, CCDA,Network +
> Cisco IP Telephony Support Specialist
> Cisco IP Telephony Operations Specialist
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf
Of
> Mohamed Saeed
> Sent: Tuesday, October 03, 2006 5:55 AM
> To: ccielab@groupstudy.com
> Subject: RE: LLQ Question - Multiple Traffic Classes in the Priority
> Queue
>
> Why will CLASS1 be serviced first?
>
> Anyway, if this is the case then CLASS2 traffic would NOT have
expedite
> forwarding processing, right?
>
> Regards
> Mohamed Saeed, CCNP - CCIP
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf
Of
> Gavin Lawson
> Sent: Tuesday, October 03, 2006 12:33 PM
> To: ccielab@groupstudy.com
> Subject: RE: LLQ Question - Multiple Traffic Classes in the Priority
> Queue
>
> Hi Mohamed
>
> With your example there are 2 software based Priority Queue's
> The CLASS1 priority Queue will be serviced first and then CLASS2
>
> GL
>
> ________________________________
>
> From: nobody@groupstudy.com on behalf of Mohamed Saeed
> Sent: Tue 3/10/2006 5:39 PM
> To: ccielab@groupstudy.com
> Subject: RE: LLQ Question - Multiple Traffic Classes in the Priority
> Queue
>
>
>
> Hi GL,
>
> Let me state an example to clarify my point:
>
> policy-map TEST
> class CLASS1
> priority 100
> class CLASS2
> priority 200
>
> With this setup, traffic of both CLASS1 and CLASS2 will be assigned to
> the priority queue. So, how will the router assign max BW of 100 to
> traffic of CLASS1 and assign max BW of 200 to traffic of CLASS2
although
> they are both in the same single queue and should be treated as FIFO.
>
> Regards
> Mohamed Saeed, CCNP - CCIP
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com] On Behalf
Of
> Gavin Lawson
> Sent: Tuesday, October 03, 2006 11:23 AM
> To: ccielab@groupstudy.com
> Subject: RE: LLQ Question - Multiple Traffic Classes in the Priority
> Queue
>
> HI Mohamed
>
> The priority queue will be serviced in a FIFO manner, no matter what
the
> markings are of the packets in the queue.
>
> GL
>
> ________________________________
>
> From: nobody@groupstudy.com on behalf of Mohamed Saeed
> Sent: Tue 3/10/2006 4:57 PM
> To: ccielab@groupstudy.com
> Subject: LLQ Question - Multiple Traffic Classes in the Priority Queue
>
>
>
> Hi All,
>
>
>
>
>
>
>
> It is a fact that you can assign multiple traffic classes to the
> priority queue in the same policy map. All traffic from these classes
is
> queued to the same, single, priority queue.
>
>
>
>
>
>
>
> I am a little bit confused, how will the system police different
traffic
> classes to different rates although they are in the same priority
queue.
>
>
>
> Does anyone has an idea?
>
>
>
>
>
> Regards
>
>
>
> Mohamed Saeed, CCNP - CCIP
>
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