From: SIMON HART (simon.hart@btinternet.com)
Date: Mon Apr 11 2005 - 08:01:05 GMT-3
Steve,
It was for this reason that I thought that you could only have one priority queue!! It does appear that Cisco documentation contradicts that fact. I have worked for several Service Providers that deliver MPLS services, and for this reason they all have only ever offered one Premium service i.e. priority queue
Simon
stephen skinner <stephenski@gmail.com> wrote:
ok guys ,
if that`s the case , which is the highest prioirty ,prioirty queue. ??
E.G
all of the below class are important ,and must have prioirty over non
selected traffic.
if i create 3 prioirty queue`s which one is the important one ?
class 1
permit voice
class 2
permit telnet
class 3
permit http
policy-map me
class class 1
prioity 100
class class 2
prioirty 100
class class 3
priority 100
which prioirty queue gets serviced first ? .
TIA
steve
On Apr 9, 2005 9:20 AM, simon hart wrote:
> Jelle,
>
> Thanks for the link and the test. After Tim's mail I tried it too and to my
> surprise it accepted more than one priority. Well, one does live and
> learn!!
>
> S.
>
> -----Original Message-----
> From: nobody@groupstudy.com [mailto:nobody@groupstudy.com]On Behalf Of
> Jelle Borsje
> Sent: 08 April 2005 15:35
> To: ccielab@groupstudy.com
> Subject: RE: priority command in MDQ
>
> Hej,
>
> Interesting. I also throught there could only be one
> priority queue, but I was wrong. I just tried it on a
> router, and it accepted 4 priority queues in the
> policy-map (didnt try more). In the following link
> Cisco is actually stating that it can be configured on
> multiple links, but should only be used for
> voice-like, constant bit rate traffic.
>
> http://www.cisco.com/univercd/cc/td/doc/product/software/ios121/121newft/121
> t/121t3/dtcfgbst.htm
>
> The link here explains what the difference is between
> queues defined with the priority and bandwidth
> commands:
>
> http://www.cisco.com/warp/public/105/priorityvsbw.html
>
> The 2 types of queues are intended for 2 very
> different types of traffic, and have therefore
> completely different characteristics. A strict
> priority queue cannot exceed the configured bandwidth
> during congestion, while a queue configured with the
> bandwidth statement can. A policy-map is not
> restricted to only 1 priority queue it seems.
>
> Greetz
> Jelle
>
> --- ccie2be skrev:
> > Hi Simon,
> >
> > Actually, according to Wendell Odom, you can have 2
> > priority queues. I
> > don't remember all the details or how scheduling is
> > done between the 2
> > priority queues but it should work.
> >
> > I've never tried it, but I wonder what happens when
> > 2 priority queues are
> > configured and then 3 priority queues are
> > configured.
> >
> > Would IOS take the 3rd priority queue command or
> > would it give you an error
> > message?
> >
> > It's interesting to think about but probably not
> > that relevant in terms of
> > the lab.
> >
> > Tim
> >
> > -----Original Message-----
> > From: nobody@groupstudy.com
> > [mailto:nobody@groupstudy.com] On Behalf Of
> > simon hart
> > Sent: Friday, April 08, 2005 7:48 AM
> > To: steve.skinner@uk.pwc.com; ccielab@groupstudy.com
> > Subject: RE: priority command in MDQ
> >
> > Steve,
> >
> > With CBWFQ/LLQ, the order by which you enter the
> > classes/queues does not
> > dictate the manner by which the traffic is
> > scheduled, with the exception of
> > the priorirty queue,
> >
> > With CBWFQ without a priority queue and under
> > congestion conditions each
> > queue is 'dequeued' to the configured bandwidth
> > command. The exact manner
> > by which the scheduler takes this packets and puts
> > them onto the TX-ring of
> > the interface is proprietary and has not been
> > published by Cisco, therefore
> > we can only guess at this particular scheduling for
> > each queue ( I expect
> > the manner by which each queue is serviced is
> > similar to WRR).
> >
> > Now by configuring a Priority queue, you are
> > changing the scheduling of the
> > CBWFQ somewhat. The Priority queue will get
> > serviced first, if their are
> > packets in its queue, up to it's configured
> > bandwidth. Once the Priority
> > queue has been dealt with the scheduler will now
> > service the other queues in
> > the manner described previously.
> > This type of queueing is important for latency
> > sensitive applications such
> > as Voice or Video.
> >
> > A couple of points on the priority queue,
> >
> > 1. You can only have one priority queue (you
> > configuration is incorrect in
> > this regard.)
> > 2. The priority queue should only represent 30% of
> > the Max Reserved
> > Bandwidth of the Interface. You can go higher,
> > however you can run into
> > problems, it is not unknown for the CPU to sky
> > rocket under such conditions.
> > 3. You should only put one type of traffic in the
> > Priority queue. If you
> > are trying to deliver a Voice service (under an
> > SLA), then you want to make
> > sure that the voice is behaving as expected, if you
> > mix it up with other
> > traffic (such as Video), you cannot guarentee
> > latency and jitter of the
> > voice traffic.
> > 4. The priority command does not define a strict
> > priority for scheduling
> > each class.
> >
> >
> > Your Policy below will be doing this
> >
> > VOIP will be policed at 1Mbps and conforming traffic
> > marked as IPprec 4
> > (Flash Override)
> >
> > Backup Servers will be policed at 250Kbps
> >
> > All other traffic will be marked with IPprec 5
> > (Critical)
> >
> > Under congestion conditions your VOIP will be
> > guaranteed 1Mbps and this
> > 1Mbps will be dequeued before any other traffic.
> >
> > Your other two queues do not have any bandwidth
> > configured, therefore under
> > congestion conditions the BackupServer and Class
> > Default queue will compete
> > for bandwidth. However under these conditions the
> > BackupServer will only
> > 'compete' up to its policed rate. I would suggest
> > entering a bandwidth
> > command on the BackupServer class in order to
> > guarentee its policed rate.
> >
> > Your show command shows that you have one strict
> > priority queue, that will
> > be (i think but needs confirmation) treated as
> > Conversation 264 on the
> > ouptut scheduler and that this particular queue is
> > policed at 1Mbps and will
> > bc at 25K bytes, therefore the Tc for the priority
> > queue is 200ms.
> >
> > HTH
> >
> > Simon
> >
> > -----Original Message-----
> > From: nobody@groupstudy.com
> > [mailto:nobody@groupstudy.com]On Behalf Of
> > steve.skinner@uk.pwc.com
> > Sent: 08 April 2005 11:36
> > To: ccielab@groupstudy.com
> > Subject: priority command in MDQ
> >
> >
> > guys .
> >
> > i have this config
> >
> > i am trying to understand the prioirty command
> > within the class .
> >
> > according to my understading ,the prioity command
> > sets a Strict Priority
> > per class in the policy .
> >
> > but as i thought you would usually only have 1 type
> > of traffic per class
> > ,as in this case ,why do i need to prioritise the
> > only traffic type in this
> > class .
> >
> > i have put my most important class at the top of the
> > policy ,so this will
> > get queued first . but other than that i didn`t
> > think i would need to do
> > anything else.
> >
> > TIA
> >
> > steve
> >
> > class-map match-any Steve_VOIP
> > match access-group 90
> > class-map match-any Backup_Servers
> > match access-group 111
> >
> > !
> > policy-map Siemens_Trunk
> > description 1000Kbs Class 1 voice policy
> > class Steve_VOIP
> > police cir 1000000
> > conform-action set-prec-transmit 4
> > exceed-action drop
> > priority 1000
> > class Backup_Servers
> > police cir 250000
> > exceed-action drop
> > class class-default
> > prioity 100
> > set ip precedence 5
> > !
> >
> > output from policy
> >
> > Strict Priority
> > Output Queue: Conversation 264
> > Bandwidth 1000 (kbps) Burst 25000 (Bytes)
> >
> >
> >
> >
> _________________________________________________________________
> > --------------------- End of message text
> > --------------------
> >
> > UK M&A deal confidence survey 2005
> > http://www.pwc.com/uk/dealconfidencesurvey
> >
> >
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>
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