You raise a valid point. I believe after having this discussion with
Wendell, we agreed that the traffic that could not be sent into a time
interval was sent in the next time interval.
I believe I had this discussion with Narbik some time ago as well.
I agree.:-)
QOS provides only more questions that is not backed up by documentation.
It has been a subject that has occupied my time since I worked on StrataCom
gear, some years back.
Enjoy the scenery man!!!!
Paul
-- Paul Negron CCIE# 14856 CCSI# 22752 Senior Technical Instructor > From: Marko Milivojevic <markom_at_ipexpert.com> > Date: Sun, 7 Aug 2011 12:30:04 -0700 > To: Paul Negron <negron.paul_at_gmail.com> > Cc: gp <gs4me2me_at_gmail.com>, Carlos G Mendioroz <tron_at_huapi.ba.ar>, > <ccielab_at_groupstudy.com> > Subject: Re: shape on 3560 > > Addition of PQ on Cats completely messes things up for other queues > and understanding what happens in them. > > Even without PQ in the mix, Carlos raises a valid question. Alas, one > which is impossible to answer. > > He's right in saying that shaped queues get a priority in comparison > to shared. However, this priority is only reflected in the bandwidth > allocation part. They carve up the total available bandwidth. Whatever > is left for allocation after shaped queues is carved up by shared > queues. > > Now, when it comes to dequeueing part, this is when things are truly > interesting. Carlos mentioned a case when the whole port is > oversubscribed and suggested how the queues will be used. I agree and > very much disagree with what he wrote. The problem is - it all depends > on several things a) time interval; b) number of packets in each > queue; c) size of each individual packet. > > Remember the old CIR = Bc / Tc formula. Well, it still applies. We can > only send so many bytes in each time interval to satisfy to total > transmission rate. > > Now, what happens when we oversubscribe the port *and* the queues. > Will packet be transmitted if there are available tokens in the > bucket, but not enough to send the packet? In, for example CQ, the > answer is yes. in CBWFQ and HQF, the answer is no. How about SRR? > Cisco doesn't document this (at least I couldn't find it), but this is > important. Now, what happens if, for example, we run out of bytes in > an interval to send due to dequeueing method used... Where does the > next interval start? Q1, or the next queue where the previous interval > stopped? Again, something Cisco doesn't document, but is rather > important. > > Analyzing QoS is immensely fun topic to me. I think it's an essence of > networking, but I'll stop now :-). I have some wonderful sequoia trees > to see! > > -- > Marko Milivojevic - CCIE #18427 > Senior Technical Instructor - IPexpert > > FREE CCIE training: http://bit.ly/vLecture > > Mailto: markom_at_ipexpert.com > Telephone: +1.810.326.1444 > Web: http://www.ipexpert.com/ > > On Sun, Aug 7, 2011 at 12:04, Paul Negron <negron.paul_at_gmail.com> wrote: >> I agree with Marko on this one. >> >> The Delay cannot be verified to be 40/30/30 since you cannot measure how >> many packets from the Priority Q are actually being serviced in relation to >> the WFQ scheduler that only spits out one packet at a time. >> >> Also, what delay are you referencing for a 40/30/30 share. Queuing delay >> only? >> >> What about CPU, Serialization which change pending the packet size. Sure, >> Serialization delay is almost non-existent with Ethernet designs but it is >> still there. Thus, you cannot guarantee effective throughput. >> >> Paul >> >> -- >> Paul Negron >> CCIE# 14856 CCSI# 22752 >> Senior Technical Instructor >> >> >> >>> From: gp <gs4me2me_at_gmail.com> >>> Reply-To: gp <gs4me2me_at_gmail.com> >>> Date: Sun, 7 Aug 2011 20:16:40 +0200 >>> To: 'Carlos G Mendioroz' <tron_at_huapi.ba.ar>, 'Marko Milivojevic' >>> <markom_at_ipexpert.com> >>> Cc: <ccielab_at_groupstudy.com> >>> Subject: RE: shape on 3560 >>> >>> So queue which is shaped has guaranteed bandwidth in relation to shared >>> queues? >>> >>> Gp >>> >>> >>> -----Original Message----- >>> From: Carlos G Mendioroz [mailto:tron_at_huapi.ba.ar] >>> Sent: Sunday, August 07, 2011 8:05 PM >>> To: Marko Milivojevic >>> Cc: gp; <ccielab_at_groupstudy.com> >>> Subject: Re: shape on 3560 >>> >>> Marko, >>> you say that all queues have guaranteed BW but not delay. >>> I don't fully understand that. >>> >>> Are you saying that the delay for a packet of some class is not bounded? >>> If not, delay is also guaranteed. >>> >>> If you have 3 queues, one with 50Mb shape and the other two 1/3 the BW >>> on a 100 Mb link, anything below congestion (and below 50Mb) will be >>> just served, but if the 3 queues try to get 40Mb, what will be the >>> effective throughput of each ? >>> I would say 40/30/30. >>> >>> -Carlos >>> >>> Marko Milivojevic @ 07/08/2011 14:22 -0300 dixit: >>>> All queues are guaranteed bandwidth, but not the delay. SRR is round-robin >>>> alghoritm. Shaped queues are assigned bandwidth first and whatever remains >>>> is >>>> used by shared queues, but servicing the data in queues is always equal >>>> between all the queues. >>>> >>>> When you enable PQ, Q1 is serviced until empty and only then Q2-4 are >>>> processed according to the SRR configuration and remaining bandwidth in the >>>> time interval. >>>> >>>> -- >>>> Marko Milivojevic - CCIE #18427 >>>> Senior Technical Instructor - IPexpert >>>> >>>> Free CCIE Training: http://bit.ly/vLecture >>>> >>>> Mailto: markom_at_ipexpert.com >>>> Telephone: +1.810.326.1444 >>>> Community: http://www.ipexpert.com/communities >>>> >>>> :: Sent from my phone. Apologies for errors and brevity. :: >>>> >>>> >>>> On Aug 7, 2011, at 2:42, "gp" <gs4me2me_at_gmail.com> wrote: >>>> >>>>> I read somewhere that shaped queue is processed before shared. >>>>> Unfortunately >>>>> cannot find it:) >>>>> >>>>> Is it possible to guaranteed some traffic bandwidth to be processed before >>>>> other with limit in task that it cannot be mapped in priority queue >>>>> because >>>>> some other traffic more important is mapped to priority queue? >>>>> >>>>> For example: >>>>> Q1 - traffic X - priority >>>>> Q2 - traffic XY - less important than traffic X, more important than >>>>> traffic >>>>> XYZ >>>>> Q3&Q4 - traffic XYZ >>>>> >>>>> >>>>> Regards, >>>>> Gp >>>>> >>>>> >>>>> >>>>> -----Original Message----- >>>>> From: Marko Milivojevic [mailto:markom_at_ipexpert.com] >>>>> Sent: Saturday, August 06, 2011 10:46 PM >>>>> To: gp >>>>> Cc: ccielab_at_groupstudy.com >>>>> Subject: Re: shape on 3560 >>>>> >>>>> Sharing and shaping has nothing to do with priority queueing. I.e. >>>>> shaped traffic is not processed before shared - it's only limited to >>>>> certain percentage of the traffic, while shared queues are simply >>>>> guaranteed a minimum. >>>>> >>>>> You can configure shaping as a percentage of negotiated speed, of >>>>> course. By default 100% of interface bandwidth (negotiated speed) is >>>>> available for all queues. If you want to limit Q2 to say, 33% you can >>>>> configure it as "srr-queue bandwidth shape 0 3 0 0". However, if you >>>>> want to limit it to say 5 Mb/s REGARDLESS of the negotiated speed, >>>>> this cannot be done on 3560, as this is a policing and policing is not >>>>> available in the outbound direction on 3560. >>>>> >>>>> -- >>>>> Marko Milivojevic - CCIE #18427 >>>>> Senior Technical Instructor - IPexpert >>>>> >>>>> FREE CCIE training: http://bit.ly/vLecture >>>>> >>>>> Mailto: markom_at_ipexpert.com >>>>> Telephone: +1.810.326.1444 >>>>> Web: http://www.ipexpert.com/ >>>>> >>>>> On Sat, Aug 6, 2011 at 13:19, gp <gs4me2me_at_gmail.com> wrote: >>>>>> Thank you Marko for explanation, it helps. >>>>>> >>>>>> What confusing me if I have a task to guaranteed some traffic for example >>>>>> 10Mbps on giga interface on switch, and I cannot use priority queue, so I >>>>>> want to send that traffic before packet in shared queue in way to put it >>>>>> in >>>>>> shaped queue which will be served before shared queues. >>>>>> >>>>>> The problem is that I donb t know what type of interface will be >>>>>> connected >>>>>> to my switch (1Gbps or 100M) and that is value from which will be >>>>>> calculated value for shaping on particular queue. >>>>>> >>>>>> For example: >>>>>> Negotiated speed = 1Gbps >>>>>> Srr-queue bandwidth shape 0 100 0 0 >>>>>> Queue 2 will be shaped to 100Mbps >>>>>> >>>>>> Negotiated speed = 100Mbps >>>>>> Srr-queue bandwidth shape 0 100 0 0 >>>>>> Queue 2 will be shaped to 10Mbps >>>>>> >>>>>> In other way as I understand there is no way to hard code shape value >>>>>> regarding to negotiated speed? >>>>>> >>>>>> Regards, >>>>>> Gp >>>>>> >>>>>> >>>>>> >>>>>> >>>>>> -----Original Message----- >>>>>> From: Marko Milivojevic [mailto:markom_at_ipexpert.com] >>>>>> Sent: Saturday, August 06, 2011 7:42 PM >>>>>> To: gp >>>>>> Cc: ccielab_at_groupstudy.com >>>>>> Subject: Re: shape on 3560 >>>>>> >>>>>> It will be using the bandwidth available to the SRR. >>>>>> >>>>>> Cat2#sh mls qos interface fa0/18 queueing >>>>>> FastEthernet0/18 >>>>>> Egress Priority Queue : disabled >>>>>> Shaped queue weights (absolute) : 25 0 0 0 >>>>>> Shared queue weights : 25 25 25 25 >>>>>> The port bandwidth limit : 100 (Operational Bandwidth:100.0) <<<<<<< >>>>>> The port is mapped to qset : 1 >>>>>> >>>>>> See the "port bandwidth limit" line - that's the BW available to the >>>>>> SRR. It is derived from the negotiated speed by default, but can be >>>>>> limited using "srr-queue bandwidth limit" command on the interface. >>>>>> >>>>>> Now, let's see if configured bandwidth influences this in any way: >>>>>> >>>>>> interface FastEthernet0/18 >>>>>> bandwidth 50000 >>>>>> ! >>>>>> >>>>>> Cat2(config-if)#do sh mls qos int fa0/18 qu >>>>>> FastEthernet0/18 >>>>>> Egress Priority Queue : disabled >>>>>> Shaped queue weights (absolute) : 25 0 0 0 >>>>>> Shared queue weights : 25 25 25 25 >>>>>> The port bandwidth limit : 100 (Operational Bandwidth:100.0) >>>>>> The port is mapped to qset : 1 >>>>>> >>>>>> Doesn't look like it does. If I change the bandwidth limit. >>>>>> >>>>>> interface FastEthernet0/18 >>>>>> bandwidth 50000 >>>>>> srr-queue bandwidth limit 25 >>>>>> ! >>>>>> >>>>>> Cat2(config-if)#do sh mls qos int fa0/18 qu >>>>>> FastEthernet0/18 >>>>>> Egress Priority Queue : disabled >>>>>> Shaped queue weights (absolute) : 25 0 0 0 >>>>>> Shared queue weights : 25 25 25 25 >>>>>> The port bandwidth limit : 25 (Operational Bandwidth:27.28) >>>>>> The port is mapped to qset : 1 >>>>>> >>>>>> Whenever in doubt - ask IOS :-) >>>>>> >>>>>> -- >>>>>> Marko Milivojevic - CCIE #18427 >>>>>> Senior Technical Instructor - IPexpert >>>>>> >>>>>> FREE CCIE training: http://bit.ly/vLecture >>>>>> >>>>>> Mailto: markom_at_ipexpert.com >>>>>> Telephone: +1.810.326.1444 >>>>>> Web: http://www.ipexpert.com/ >>>>>> >>>>>> On Sat, Aug 6, 2011 at 01:18, gp <gs4me2me_at_gmail.com> wrote: >>>>>>> Hello experts, >>>>>>> >>>>>>> >>>>>>> >>>>>>> When doing shaping on 3560 interface does reference bandwidth is >>>>>>> configured >>>>>>> bandwidth with bandwidth command or negotiated speed? >>>>>>> >>>>>>> >>>>>>> >>>>>>> For example the switch port is connected on Fast Ethernet router >>>>>>> interface >>>>>>> and I configured bandwidth 1000000 on switch port. >>>>>>> >>>>>>> With srr-queue bandwidth shape 0 100 0 0, will queue 2 be shaped on 10 >>>>>>> or >>>>>>> 1 >>>>>>> Mbps? >>>>>>> >>>>>>> >>>>>>> >>>>>>> Thank you! >>>>>>> >>>>>>> >>>>>>> Blogs and organic groups at http://www.ccie.net >>>>>>> >>>>>>> _______________________________________________________________________ >>>>>>> Subscription information may be found at: >>>>>>> http://www.groupstudy.com/list/CCIELab.html >>>> >>>> >>>> Blogs and organic groups at http://www.ccie.net >>>> >>>> _______________________________________________________________________ >>>> Subscription information may be found at: >>>> http://www.groupstudy.com/list/CCIELab.html >>>> >>>> >>>> >>>> >>>> >>>> >>>> >>> >>> -- >>> Carlos G Mendioroz <tron_at_huapi.ba.ar> LW7 EQI Argentina >>> >>> >>> Blogs and organic groups at http://www.ccie.net >>> >>> _______________________________________________________________________ >>> Subscription information may be found at: >>> http://www.groupstudy.com/list/CCIELab.html Blogs and organic groups at http://www.ccie.netReceived on Sun Aug 07 2011 - 13:43:06 ART
This archive was generated by hypermail 2.2.0 : Thu Sep 01 2011 - 06:05:56 ART