Allied Telesis AlliedWare Plus manuale d’uso

C613-16120-00 REV A www .alliedtelesis.com AlliedW ar e Plus TM OS Ov er vie w of | Intr oduction This How T o Note describes the main f e atures of QoS on s witches running the AlliedW ar e Plus OS. The main features include: z Prioritisation and marking Right at the point of ingr ess into the QoS proc ess, pac k ets classified to par ticular clas[...]

Page 2 | AlliedW are Plus™ OS: Ov er view of QoS z Ability to see the curr en t state of egress queues There are commands that enable y ou to see statistics relating to e very egress queue on ever y p o r t . Each of these featur es is di scussed in much mor e detail later on in this document. Contents Intr oduction .......... ...................[...]

Page 3 | AlliedW are Plus™ OS: Ov er view of QoS Which pr oducts and softwar e version does this Note appl y to? z Pr oducts: SwitchBlade x908, x900-12XT/S, and x900-2 4 series switches z Software v ersions: AlliedW ar e Plus version 5.2.1-0.1 and abov e The pr ocess flo w and methodolog y of the QoS system Befor e discussing the details of the v[...]

Page 4 | AlliedW are Plus™ OS: Ov er view of QoS P ack et mark ers There ar e four items tha t are used to mark pack ets as they pass th rough the QoS sys tem. z T wo mark ers tha t are car ried within fields of the p ack et itself: z 802. 1 p: The 802. 1 p or User Priority field in the VLAN tag of an Ethernet frame . This is a 3-bit number , so [...]

Page 5 | AlliedW are Plus™ OS: Ov er view of QoS Outline of the QoS pr ocessing flo w Let's look at each QoS pr ocess in the order that they ar e applied to a packet. The f ollowing figure giv es a quick view of the QoS featur es we ar e about to discuss. Initial mapping to an egr ess queue, based on 802. 1 p value Immediately after ingr ess[...]

Page 6 | AlliedW are Plus™ OS: Ov er view of QoS Classification Classification is simply a method of dividing the incoming traffic into traffic flows so that pack ets of one type can be treated differ ently to pack ets of another type. T o do this, you create class ma ps and if desi r ed A CLs. Inc oming packets ar e inspected and ma y be classif[...]

Page 7 | AlliedW are Plus™ OS: Ov er view of QoS P olicing P olicin g inv olves measuring the ba ndwidth us ed by a policer and comparing the measurement to the bandwidth limits that ha v e been set for the policer . The policing process allocates a temporary bandwi dth class value to packets. It is important to note that the policing pr ocess do[...]

Page 8 | AlliedW are Plus™ OS: Ov er view of QoS Queue shaping Each egre ss por t has eight egress queues, wh ich are n umbered 0-7 with 7 being the highest priority queue. Unfor tunately , the queues are of a limited length, so packets cannot be added to them indefinitely; if the switch is congeste d, the queues ma y fill up and no mor e packets[...]

Page 9 | AlliedW are Plus™ OS: Ov er view of QoS Scheduling In addition to managing the wa y in which pack ets can be dropped when the egr ess queues for a given port start to fill up, y ou can also configure the method that is used to allocate bandwidth to each of the queue s to transm it pack ets onto the line . There ar e two wa ys that the qu[...]

Page 10 | AlliedW are Plus™ OS: Over view of QoS Details of the component pr ocesses, and ho w to configur e them QoS elements: policy maps, class ma ps, policers, matches Some aspects of QoS are configured globall y , such as default mapping of CoS to egress queue. How ever , most aspects are configur ed on a per -por t basis, m ostly as part of[...]

Page 11 | AlliedW are Plus™ OS: Over view of QoS Dia gram of the o v erall QoS pr ocess flo w The following figur e summarises the QoS proc ess flow and the commands to configure each stage . The following sections describe the configuration in detail. trust dscp (& set dscp) F rom L2 switch class-map premarking Look up mark-DSCP map Markers [...]

Page 12 | AlliedW are Plus™ OS: Over view of QoS Enabling QoS globall y Befor e configuring QoS, you need to enable it by entering the f ollowing command in global configuration mode: awplus(config)#mls qos enable Initial mapping to queue based on ta g When pack ets arrive at a port, they ar e assigned to an egress queue. This is done by the swit[...]

Page 13 | AlliedW are Plus™ OS: Over view of QoS awplus(config)#interface < port -number > awplus(config-if)#mls qos cos <0-7> The value you change the CoS to is not used to look up the initial egr ess queue setting; the mls qos queue command still determines the queue for untagged pack ets. Classification The pr ocess of assigning pa[...]

Page 14 | AlliedW are Plus™ OS: Over view of QoS Setting new values explicitl y T o explicitly set new values for a particular clas s map , first create the class map (if necessar y), by entering the f ollowing command: awplus(config)#class-map < name > Then simply ente r the following commands: awplus(config)#policy-map < nam e > awp[...]

Page 15 | AlliedW are Plus™ OS: Over view of QoS Note that there is just a single mark-dscp ma p f or the whole switch—separate class maps do not ha ve separate mark-dscp maps. The configuration required to use the mark-d scp map is a little mor e complex than the configuration for setting the values explicitly . 1. First, write entries into th[...]

Page 16 | AlliedW are Plus™ OS: Over view of QoS Example For the class map called “example” , if y ou wa nt to tak e all traffic with a DSCP of 34, 36 or 38 and premark it to CoS 4, queue 4; CoS 5, qu eue 5; and CoS 6, queu e 6 respectivel y , then enter the following commands: awplus(config)#mls qos map mar k-dscp 34 to new-cos 4 new-queue 4[...]

Page 17 | AlliedW are Plus™ OS: Over view of QoS Applying or dinar y policers to class ma ps Ordinar y policers are used when policing traffic in a single class map in a single policy map on a single port. Y ou create them in policy map class configuration mode , which means they ar e attached to that policy map and class ma p at th e time they a[...]

Page 18 | AlliedW are Plus™ OS: Over view of QoS Single-rate policing Both ordinar y and aggregate policers can be single-rate . Single-rate policing uses three parameters: z a verage ba ndwidth (in kbps) z minimum burst size (in bytes) z maximum burst size (in bytes) With this combination, the algorithm used to determine the temporar y bandwidth[...]

Page 19 | AlliedW are Plus™ OS: Over view of QoS T win-rate policing Both ordinary a nd aggregate policers can be twin-rate. T win-rate policing uses four parameters: z minimum bandwidth (in kbp s) z maximum bandwidth ( in kbps) z maximum burst size (in bytes) z minimum burst size (in bytes) With this combination, the algorithm used to determine [...]

Page 20 | AlliedW are Plus™ OS: Over view of QoS Counting policed pack ets T o see the count of policed packets: 1. T urn on the QoS counters enhanced mode by entering global configuration mode and using the command: awplus(config)#platform enhanc edmode qoscounters 2. Restart the switch 3. Return to privileged ex ec mode and use the command: awp[...]

Page 21 | AlliedW are Plus™ OS: Over view of QoS Counting pack ets for aggr egate policers If a pack et is processed b y an aggregate policer , it is counted in the output for e ver y por t that the aggregate policer a ppl ies to , not just for the port that received the pack et. The following figure shows output for the example from "Applyi[...]

Page 22 | AlliedW are Plus™ OS: Over view of QoS Remarking Remarking happens after the traffic has been policed. It sets the pack et’ s QoS mark ers depending on how w ell the flow conforms to its bandwidth limits. Remarking is performed by looking up the polic ed-dscp map and assigning values to the four mark ers (802. 1 p , DSCP , egress queu[...]

Page 23 | AlliedW are Plus™ OS: Over view of QoS Queue shaping—queue sets, RED , and tail-drop A queue set defines ho w the switch determines what traffic to dr op when a por t’ s queues become congested. The queue set applies to one or more of the port’ s queues, and specifies the queue size thr esholds at which the port star ts to drop tr[...]

Page 24 | AlliedW are Plus™ OS: Over view of QoS Note that by default ports only use the maxi mum thre shold, because they ar e in tail-drop mode . The other settings are random-detect mode settings. Having defaults means that y ou can change to random-detect mode without ha ving to configure a queue set (see "Applying RED cur ves to ports&q[...]

Page 25 | AlliedW are Plus™ OS: Over view of QoS These fundamental cur ves ar e collected into RED cur ve gr oups. A group is a collection of three cur ves, one for each of the thr ee possible bandwidth classes, as sho wn in the following figure. Additionall y , one other parameter is defined on each RED cur ve gr oup . This parameter is the aver[...]

Page 26 | AlliedW are Plus™ OS: Over view of QoS Specifying which queues to act on T o specify which queues to configure, use the optional queues parameter : awplus(config)#mls qos queue-s et <1-4> queues ... Specify the desire d queues as a space-separated list. For example: awplus(config)#mls qos queue-s et <1-4> queues 1 3 4 ... T [...]

Page 27 | AlliedW are Plus™ OS: Over view of QoS T o specify the av eraging factor , use the command: awplus(config)#mls qos queue-s et <1-4> [queues < list >] averaging-factor <0-15> T ail-drop mode By default, por ts use tail-drop mode and the default queue-set for th at port type (see "Default settings" on page 23 )[...]

Page 28 | AlliedW are Plus™ OS: Over view of QoS Strict priority scheduling Then, to set queues to use strict priority scheduling, use th e command: priority-queue < queue-list > Specify the queues as a space-separated list. For e xample , to put queues 3, 5, and 6 into the strict-priority gr oup of queues, use the command: awplus(config-if[...]

Page 29 | AlliedW are Plus™ OS: Over view of QoS The first of these numbers is th e percentage limit for queue 0, the second number is the limit for queue 1 , and so on. For example, to give queue 0 less of the buffer space and queues 3 and 4 more, you could use the command: wrr-queue queue-limit 6 12 12 17 17 12 12 12 Y ou can use this command t[...]

Page 30 | AlliedW are Plus™ OS: Over view of QoS P olicing Examples P olicing is the process of counting the n umber of pack ets that the switch pr ocesses and determining their lev el of conformance with th eir bandwidth limits. The AlliedW ar e Plus OS enables y ou to police ports and differ ent types of traffic separately (with “ordinary” [...]

Page 31 | AlliedW are Plus™ OS: Over view of QoS Use the following commands to configur e this policing scenario: mls qos enable class-map cm1 match access-group 3000 class-map cm2 match access-group 3001 policy-map pm1 class cm1 police twin-rate 1000 200 50 00 1000 exceed-action drop class cm2 police single-rate 3000 200 4000 exceed-action drop [...]

Page 32 | AlliedW are Plus™ OS: Over view of QoS 2: P olicing one traffic type on combined por ts In this scenario , one ty pe of traffic is collectivel y policed on sev eral por ts. The policer counts all the pack ets that match the type ’ s class map on an y of the ports. This scenario uses an aggregate policer . Use this type of scenario whe[...]

Page 33 | AlliedW are Plus™ OS: Over view of QoS 3: P olicing one traffic type on separate por ts, and another traffic type on the same por ts combined In this scenario , one type o f traffic is collectiv el y policed on sev eral por ts, while another type of traffic is individually policed on those por ts. For the first traffic type , the police[...]

Page 34 | AlliedW are Plus™ OS: Over view of QoS Use the following commands to configur e this policing scenario: mls qos enable mls qos aggregate-police aggr1 twin-rate 1000 200 5000 1000 exceed-action drop class-map cm1 match ip-dscp 35 class-map cm2 match access-group 3000 policy-map pm1 class cm1 police aggregate aggr1 class cm2 police single[...]

Page 35 | AlliedW are Plus™ OS: Over view of QoS 4: P olicing combined traffic types on separate por ts In this scenario , two types of traffic ar e collectiv el y policed on a per -port ba sis. The policing is done on se veral diff erent ports. On each po rt, the policer counts all packets that match either type’ s class map . This scenario us[...]

Page 36 | AlliedW are Plus™ OS: Over view of QoS Use the following commands to configur e this policing scenario: mls qos enable mls qos aggregate-police pol1 twin-rate 1000 4000 256000 1000000 exceed-action drop mls qos aggregate-police pol2 single-rate 3000 750000 1000000 exceed-action drop class-map cm1 match access-group 3008 class-map cm2 ma[...]

Page 37 | AlliedW are Plus™ OS: Over view of QoS 5: P olicing combined traffic types on combined por ts In this scenario , two types of traffic are collectivel y policed on multiple ports collectively . The policer counts all the pack ets that match ei ther type’ s class map on any of the ports. This scenario uses an aggregate policer . For exa[...]

Page 38 | AlliedW are Plus™ OS: Over view of QoS Use the following commands to configur e this policing scenario: mls qos enable mls qos aggregate-police pol1 twin-rate 1000 4000 256000 1000000 exceed-action drop class-map cm1 match vlan 10 class-map cm2 match vlan 20 policy-map pm1 class cm1 police aggregate pol1 class cm2 police aggregate pol1 [...]

Page 39 | AlliedW are Plus™ OS: Over view of QoS Mapping the queues in the s w itching instances to queues in the fabric By default, the mapping of the egr ess queues of the switching instances to the queues in the fabric is: T o alter this mapping, enter global configuration mode and use the command: awplus(config)#mls qos map inp ut-queue q0 q1[...]

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