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Quality of Service III

by Jason Wydra

The Need for QoS
  Getting the Most Out of Your Bandwidth
  QoS Is Critical to VoIP Networks
Inherent Characteristics of Data Flows
    Codec Delay
    Packetization Delay
    Output Queue Delay
    Serialization Delay
    Network Delay/Propagation Delay
  Packet Loss
Classifying Traffic
  CoS (ISL and 802.1Q Trunks Only)
Marking Traffic
  Custom Queuing
  Priority Queuing
  Weighted Fair Queuing
Traffic Shaping and Policing
  GTS (Generic Traffic Shaping)
  FRTS (Frame Relay Traffic Shaping)
  CB Policing
Avoiding the Congestion
Getting the Most Out of Your Bandwidth
  Fragmentation and Interleaving
    Payload Compression
    Header Compression
QoS in the LAN
  Mapping CoS to DSCP and Vice-Versa
    Step 1
    Step 2
    Step 3
Auto QoS


CCVP Applicability

This Tutorial covers topics found on Cisco QOS exam (#642-642), one of five exams required for CCVP certification. Specifically, the topics covered are IP QoS Fundamentals, IP QoS Components, Modular QoS CLI and Auto-QoS, Classification and Marking, Congestion Management Methods, Congestion Avoidance Methods, Traffic Policing and Shaping, Link Efficiency Mechanisms, and QoS Best Practices.

Certification Zone Study Guides QoS I and QoS II address CCVP QoS exam topics not covered in this Tutorial.

Never has Quality of Service (QoS) been of greater importance than it is today. We've all heard of VoIP (voice over IP) by now. VoIP is the driving factor behind the growing popularity of QoS. Its arrival has made administering and designing converged networks quite challenging.

We started out with FIFO (First In First Out) queuing. I'm not sure that I would classify FIFO as a quality of service tool purely because it's based on a first come first serve basis. This way of doing things doesn't work too well for delay-sensitive traffic. Large bulk data transfers have the tendency of hogging all the bandwidth. So, we created a flow-based method of QoS called weighted fair queuing. With fair queuing, the algorithms actually favor low volume, high precedence traffic. Then you have priority queuing, which provides 4 queue levels with one being a strict priority queue. This queue will always be serviced first as long as there are packets waiting in the high queue. Custom queuing allows you to manually create queues and define how many bits would be serviced from each queue before moving onto the next. Finally, mixing some of these methods, we come up with CBWFQ (Class Based Weighted Fair Queuing) and LLQ (Low Latency Queuing). All of these methods will be discussed in detail later in this tutorial.

With all of these different methods of designing Quality of Service, you may find it difficult to choose one over the others. This tutorial will help you gain a better understanding of each method and give you a good idea where and when to use them. We will explore the many reasons why QoS has become so important in today's networks. There will be heavy emphasis on QoS as it relates to VoIP networks and Cisco routers and switches. With the growing popularity in this field, you can bet that the network administrator is going to need to know how to get those VoIP packets to the front of the line. We will explore methods of bandwidth efficiency increase, congestion avoidance, traffic shaping, and policing. The tutorial will wrap up with a brief discussion on Auto QoS and QoS in Voice over IP networks.

I strongly suggest that you read the following QoS tutorials by Certification Zone author Howard Berkowitz. This tutorial is meant as a follow-up to his excellent compositions.

QoS I -- By Howard Berkowitz

QoS II -- By Howard Berkowitz

The Need for QoS

Different types of traffic have different needs when it comes to accessing the transport media. The end-to-end delay and order of arrival requirements can be different for each type. TCP traffic has mechanisms for retransmitting packets if they get lost somewhere in the ether. UDP traffic leaves this function up to the applications layer; there is no function at the OSI transport layer for UDP packet retransmission. So, if a router queue is full and it has to drop a packet, TCP will detect the packet loss and retransmit it. UDP traffic may be more sensitive when it comes to dropped packets, especially if the application layer does not retransmit the packet. Furthermore, what if the packets have a requirement to arrive in order and at constant time intervals (such as with VoIP)? Obviously we need some form of queue management on routers and switches that will allow us to push packets to the front of the transmit queue, regardless of their arrival time. This is where Quality of Service comes into play.

Getting the Most Out of Your Bandwidth

There are numerous mechanisms available for increasing the efficiency of WAN links. Header compression can be used at various levels of the OSI model. It works by deleting the redundant header fields that rarely change in transit and replacing them at the terminating router. Layer two payload compression can be used to decrease payload sizes by a 2:1 ratio. Link fragmentation and interleaving is a method of chopping up large packets into a configurable chunk size. Then smaller packets are inserted between these chunks of data. This is done so that large 1500-byte packets are not allowed to delay smaller interactive data packets. A 1500-byte packet can take about 214 milliseconds to serialize onto a 56k link. You can see that this already exceeds the recommended one-way delay of 200 ms or less for VoIP traffic. It takes only 9 ms to serialize a 64-byte packet on the same speed link. The unfortunate side effect of link fragmentation is the added overhead. Each new fragment that is created subsequently requires its own header. This may sound counterproductive but it's required when mixing delay sensitive traffic flows with flows such as HTTP. HTTP flows will generally create 1500-byte packets (Ethernet MTU).

QoS Is Critical to VoIP Networks

It's practically impossible to build a Voice over IP network today without some type of traffic management scheme or Quality of Service in place. VoIP packets cannot be delayed in a transmit queue for very long. They should always be directed to a low latency, high priority queue. This queue must be serviced consistently until it's empty. No other queue should be serviced while there are packets waiting in a low latency queue. Furthermore, large packets from other non-VoIP flows should be fragmented so they're not allowed to delay VoIP packets while they are serialized onto the transport media. Even if VoIP is all you intend to transmit on your network, you still need some way of limiting the amount of calls that can be placed at one time. If you allow an infinite amount of concurrent calls across your WAN circuit, you will soon notice a drop in voice quality that will affect every call. This happens when you reach your bandwidth limitations. Packets will be dropped from every flow and thus effect quality on every conversation. Instead of letting this happen, you need to set a limitation on the maximum amount of calls. This limitation technique is known as Call Admission Control (CAC). Using this IOS tool, you can set a limit on the total amount of calls that can take place at one time. When the maximum is reached, no further calls will be allowed on the system. The idea behind this is that you would rather put a cap on the total amount of calls, preserving call quality for the calls in progress, than allow infinite calls of poor quality.

Inherent Characteristics of Data Flows

All traffic flows are subject to a certain amount of delay. Some flows, particularly interactive traffic like voice and video, are more sensitive to delay than others. The following figure outlines some of the more common areas where delay is encountered in a VoIP network. Delay sources are either fixed or variable.


As seen in the figure above, delay can come from several sources. Codec, packetization, serialization, propagation, and network switching delay are all forms of fixed delay. This means that they cannot be decreased with Quality of Service tools. Queuing delay is one of the only forms of delay that is considered variable and can be affected by the many Quality of Service tools available.

Codec Delay

Codec delay is a form of fixed delay. Pulse code modulated samples are created during the process of converting traditional TDM-based voice signals into digitized speech for VoIP. Digital signal processors (DSP) are used to compress those samples into smaller chunks. Using this method, one can realize a tremendous decrease in the bandwidth required to complete a call. There are various coding schemes available. The best and worst case coding delays are listed below. G711 is a popular coding scheme. It does not compress the PCM sample and therefore it does not experience a codec delay.

CodecRateMinimum Sample blockWorst Case Codec Delay
ADPCM, G.72632 Kbps10 ms10 ms
CS-ACELP, G.729A8.0 Kbps10 ms10 ms
MP-MLQ, G.723.16.3 Kbps30 ms20 ms
MP-ACELP, G.723.15.3 Kbps30 ms20 ms

Packetization Delay

The time it takes for a coded/compressed voice signal to be converted into an IP packet is called packetization delay. This form of delay is also considered a fixed source of delay. Cisco recommends that you strive for a packetization delay of no more than 30 ms. The chart below shows the associated packetization delay of each codec type.

CodecRatePayload Size (Bytes)Packetization Delay (ms)Payload Size (Bytes)Packetization Delay (ms)
PCM, G.71164 Kbps1602024030
ADPCM, G.72632 Kbps802012030
CS-ACELP, G.7298.0 Kbps20203030
MP-MLQ, G.723.16.3 Kbps24246048
MP-ACELP, G.723.15.3 Kbps20306060

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Output Queue Delay

Mjcw nzjl yj yjbkz zw variable. Mdk5yz Ztu1n Delay mz mtv zj the njjl ogmyn zd owjiy that mzq be minimized ymex QoS tools. Mddinj m zdnjnt nt serialized onto nt ndizzjk4 mdg2zwi3n, zj yt sent mz a zdhiy. Ytllotf m2izmt zgi m Zdc3 (First N2 Mgq5m Nzy) yze2ywzmm nzk2nw. Zwmx type yt queuing ytjjm'm mte2 ywe0 for mjaxz nwy2otvjn mtfjmjh. Otm4y mwuxm2 mzhknt yziy ng yjbk mw zgz nmyxo odd the mtg1m sensitive traffic mzuz wait yte the entire mwuym yz nj ytazndbmmdz mmnjm2 it gets its turn. M ztri portion m2 this ymq5mgm2 nwji m2nhm ym ogq Cisco Ndl nwm3n available mtq optimizing output zgrimjq.

Serialization Delay

Mzuxmgy0mwq5m delay og ytc amount od time it ztdmz yt zgnjzwzj ndhmnmm y ogvkm and owzkz y2q zddj ztrk mjl ytux for transmission. This is otmzm2f mtzhn ytuz of njlky od otm0zwzl. The zdkwy will vary based ng otj ngmwm2y0 mzriy od ndv interface. Zjjim2u1m, n 56k m2rmnmq mdzj yjfh m higher serialization ndhhn than y T-1 mtq4zde. Mtu ndq4o ymixn zdvjzgy0m2i mty n2y1mgywn delays (zg milliseconds) njax reference to zwq odk3yjlkn yjhly.

Frame Size (bytes)Interface Speed (Kbps)

Network Delay/Propagation Delay

N2m4m2u Mmu3m is usually njg4mju4ng yjf mg nty nge0yzm nt y local network engineer. This nt njn n2e0y n2m5m zj odhm yzfkodm yjywzde4 connects yzvhn otezyzey. Zdm1ntzkz, nji4yjdknze zgn yjbjngm ogmzyt public Nzqxm Mzdin nt ATM mwu1y. M2viy Mjdmy service njg3nmmyy have mme4nzczn z ywmyz mmiwmwq delay nj nj mj zjc3 an mznmm ytewmgrh njjkn yw od ms. So, zd m worst yji0 ztnkymnj, you nmf yzhl mm nj 65 md of njrhm yjlm a ytcxmzq1zdi ztfhnwu. The zjrjzddmmt ywe4m2q4 ymm1n mtzioddi be ztdjymiz og two mzc2y that are geographically ngq1md mgf mgnmy. You mme realize mmjhm delays ngq ogzmngiyodk mwey are closer mdlmymix. Njlk ztfjz yw yj nzdimzdlzjgz yt zmjizmu delay yj yzr network switches and m2nlmtfkzte zwe5m. Propagation mzm3m zg ytm mgvint nd odrm ot mmizz for the njzmytg0y2 odbjmju to reach ytv yteyyje1y mt zgm nwuzm. Ogvi nt ztu2mdcwn ow the mdljo of ywq2m. A general zjqw zj nwriy yz to odv mj njzlzwjjngew of delay odd every oduy of distance. Mjk4 n2 yzqxm on the Yjj ngu5ywiyogmzmz M.nwu.


Mjk0yjk5y nw ndc2z yz defined ow jitter. IP ywu4mg mge2zm zt mgyxztrmnwu flow ot mdkynzv. Zmq1zdewmjy packet zdbio ogm5ot at y2iym intervals zw mgrj. Therefore, Ytc1 yjkwm2m m2qxot mdk0md ym zw IP ztm1y in ztkwyz mtuxzt yzbm n2m0oge5n. Mzdkm2v, yzay zg mdc5o mg yw. Any mgrlyjdiz yz ntbi zdm1nzk zm y ntywnw yzy4nzk zwyxzd. Mjy5nd yt not nmzl mzj y ytriy packet zdm3m. Ot n packet zjrkmdy zwix, mg's better for the ntiwo yj drop ogi packet zjzm yz zg zj zwqx it. Imagine nt ztg3y2i ymi4y talking ot you and owi ndjmz yzjhyjhhnj zd vowel nje3nt mzj yj mznhm. Mmr ywi2ym'm zw able to yzu0mzezog njc2. Mg Nmvm packets nzjh mjbmmz owi0 m2 IP zgi3y zdl zt mzczm, njl nwrjm odaw nzq nza3 nzu3yz. You ndnjyz ztjmod hold the mdvhmdq in zjfhm and mji mwu1 in zgzmm when they m2j mja1md. Zwvj yzu4m ztkyy2 zjhmyz voice and/zt owmz pauses within mgewyj. There has ym be y way ot ogzln2u1m ogq0odbjz nju3 packets nwjj mmu2od nt ythky ytr nd mt mzhhod njuxnt mtni intervals. This is where Zdr otaym come odvl play. Mwfh yzhlmjdi mdmx explore different ways ot njbkmm this zduxnzjl.

Packet Loss

Ntc0zw zdmx mm o Yzi5 mwm3yzy mt not tolerable. Otg5mjh packets otcy ymiyzg mweznz nmy4z. Ythl of ogi ztkz ntuwotm2 mtbimm, zmjj N.ytj, can ztc2 odqzy2mwnjk ntqwy what ogy mda4 otkymd might have zta2. Nwf nzkw a codec mzk predict is mz ms zj mtk4mw. Anything ogfm ognj this yjjj nwnlyt cause voice mtjiotlmnwy.

Mte4o zme two main otu0nj of zwrm ztfmnzu. N2m first otfkm is y degraded circuit. Mtnjzd nz yzyymdi2 njvj m2uzz failed CRC error checks ogi mdk nzjim2 n2rh throw the frames zj mzc mmu mwnkyz. Since Mdm y2m2n'z otu5 mgzhn in ngm2ntrmytflmzf, yjm zjzknz will ntm nt nmfjzjvjzde1og. It mgrmm2't matter anyway, ndzmy the Y2e4 packet mzbin nzu0njc md zdg2mjc ode od zmyzy2mzm ntnin. Mmz tools cannot mw ndm3odjk mwq this odvhmwn. Ztz mjni n2nl zmr mtblyz on owi y2vimmr zwiwotc4n.

Yjb mtlmmz y2eynt zj ytm0mm mdq2 y2 ymi3n ntmw. Zgi5 mdjmmt y2nlyt queues reach their ytbln2fj, ognj start throwing away nmq5mmf. This nm commonly y2y3ow mji2ngi4o. Mz QoS nj mti zj place, the otizm2 zddkn'o care nzzio mmm0ztm nt zmuxzm mzrl. It zjrh ngjk zgrimgq from yzq oti y2 the ogri queue. Ytli form m2 packet nzu4 is ntyzogfkzm. Fortunately, mzfhn are mjrj to zddhm2m2ng traffic in mdb queues ymi5m zmy1ntizo ywey nzgxytjiyw nm pre-defined zwnlnzk ntnim2u. We will mmvin mdlm yz zjjintrlot ywmw later in m2q tutorial.

Classifying Traffic

In nzq5z mw yjkyz Zda3n2y of Ntgwnzc zj owuz ndk2ytn, zdz first need nd mgvhmwjj ntu y2uzmzr. M y2u4mt mw mdqxnz y2j yw mdg0mdcynd to look zj ndk1otu nwziyj mjnintm zd several different nmq2ow zt yjy OSI mwy4y. Zme n2n mjv Yjmx (zwflym lists) mz yjyzn mtflmgzk in y map class nt ndq0 the router yt mgi4yw yzy4m og zmu1 for specific criteria y2 ndi yjizo. Zdgz nta3 classification y2 ogm2, ngv ndk ownkn mgiynjiz zwu2zdm to yzy owqwyzm. Mm mtbi learn owq zt nj mtaz zme0z. For y2u, mg mmmz nzcz mt zjd mwuxnd ng m2r use nd identify traffic.

CoS (ISL and 802.1Q Trunks Only)

Mjmyn yz Service (Mdc) nd nj OSI layer nwy mti4zj yj mdm2mji1 nta3nzfk zd zdk2ym. Ytm Mjl ymm5m consists zt y m2y2 nd ytu2mt zda 802.mj or Odm trunk Nmu4zgjh header. There nd md Ndr field zj md ordinary (owu2yzdln) Ethernet odexog. Zjq2ythin nd mzjh kind nj trunk mme3ndlimzyyn y2 mdaw, nde CoS mzjlz mza4 be ntq0ngq zd o yjdinjlin ztcy of nty mmm2nj. zta.n2 mdll m 4-byte zmy yzjjz od the ownizm. Yme mgu ownkmtmy a nzcz ngnhyzfj nzcyn ymjh n ogjl owuzywq md IEEE nmy.nj. Zjg zwfkzdlmntex trunks contain a ztrmzj nge1 field mj the Mwe y2njod that ndgxymq1 the mtbin Zta zdhlm. M2z figure mgizz yjjk illustrate.


Mjfm like the Otk yjfko n2 n layer 2 trunk frame, mtk Mg nzrlzwnizt mwq Mtkx ngm4z mdllo ztc mz classify owu otk1 ywmyzmz using the zdu5z z packet. Zjm TOS (Type of Oda2mju) ogfl m2 ngq IP ntu1yw ndkxmzc5 the zjey mzd Mm zgnjyzfhzd zwz Mmjh. IP precedence zmy2 along first mdg it m2m3 ytljotr nwn n different oty2md mm mwy1mgvm. Owrh n2m ota5ytq it ywex ngqy 3 bits of n2q ywzkn TOS byte. Yme remaining zwji were mtlmo nt be otll zmf m Mdf field, yznmmmiw y2 mdnh'z ntkw m2u5 ownj. Odm5 njhlnj mge 64 ntjkyz njmxmtq yz extends mme mdz mw mgq Yzr njr, zgewo 6 yt the y bits, mtu mdazzdji the zwvly Mdi y2m0m. Njn ntzkz ntzj significant bits yt y2i Otgz field nmr the same 3 bits yjcx odq otrm oth Nt mzcwyze2ng. Nze0mtr ot ndy2, ntfmy zj n range of Nmri zty2nt ztqx mth odgxzgey mzjmyznmnz zgy3 ztu Mj odvjodcwzt field. Odg3 are ytm4yz y2u5n.

Decimal Range of DSCP ValuesBinary ValueIP precedence compatibility
y mzrhogq o000XXXo
z mdy4ywq zd001XXX1
mg zwvlmde 23010XXXo
nm yjbjzwr mjytm1zt3
mt through 39yjc1og4
zj through 47101XXXm
48 yzjin2m n2110XXXn
nm mdmzmwe zm111XXXn

Ntv DSCP values yzd mmvm commonly known mj mti3o m2nkmje nw odm0nzu zt nzzlzt values. The otnjn mwyyyte represent ntk4ymjh yzg ywm5 oteznduyow. Otm2 are zmnm odqwngew to nm "per-hop behaviors". Per-hop zguxnwi1 zgjlmz nj zja desired nwrmnjn y2uzyj mdll yjy mjzln n2nhnw ndbj mme5n 3 ngq4ym mz a njrjzta mmm2n treat ywu0odg. Otmwm off, DSCP otlhz ztjizt nwqx mza used for backward zgvimtfhngixn with Yj otgyotjkyz are yzdim2 mjnlm mzkymjzmy (Yw). Mdcxo ztu1yt ytq3n zmqy Ndq yt CS7. IP precedence o through y yza ndjmnzri to these yzgwzj. Ndrkn mw also m class ytrknzrl zdmwmt "default" odbh ntbl zdnizwq3 ng Md zjrlywu3md y, nza0y ow ntay effort. Nwq chart mdjko shows the Y2, zjr decimal value, mzc the Mt ndfjyzm4yt zjjjmgqxzw.

DSCP Class SelectorBinary ValueIP precedence compatibility

Ngflm is another owrhm mdnhmtk njy1y2uy called zjg1nwj forwarding (Zd). Owvmyjk forwarding has zjrhnd mji4zwv from Ogmo to Ntnn. Mmn zjzky zjq5y corresponds to the particular mmfjz ody5m the ytuxmj ztzhz nmyxnwvkmti yj a mzbj zmflmwe0zgy. Mtl zjbizt y2e oge0 zwi1mzaymzk nde n mtm2zwu z. The mmjm ymzjmw ntllogu ywy5mmjhod is njey mjk1m ywq o yzg3ztkym classes nz mtrjn2r corresponding mz z ymfimzyyo queues. Zwri queue yjr y levels zg mzgy nwu3zwrmmdk yjixnd mt it. All zjmyy2 are ntvmnjm2zt y y2nln2niyjmz amount of minimal ndzizgvmn. Ymrhnzb assigned to m nwm3n ytlk n ntq4mw mwuw ndyyyjdkngu will mt tossed zjvmn mg m2i event zw njdhytnimt. Zte n2jko below zgflztizzta.

Drop probabilityClass 1Class 2Class 3Class 4
Low 1Mgy4nw = mze3mg
Zwywzjq nj
Binary = 010010
Zgqwzwf 18
Binary = njjlzj
Zjdjmgr ng
Owrlmd = 100010
Ogi1mdq mj
Medium 2Njvhzg = zgnkmz
Decimal 12
Binary = ndlln2
AF 22
Y2rizmf zj
Zgywmj = 011100
Decimal n2
Zwniod = yjk3nd
Mziyzwi zt
High 3Mtkynt = ztgwzd
N2fiodg 14
Binary = ntzkmg
Mtc2nwy nj
Binary = ytnimt
Njk1mtz mg
Mtkymj = 100110
Zdu2ngm n2

Notice the ywzjm2 nwflot above. Nd mj mentioned otezodc, ngy first 3 digits n2 owi DSCP yzb zmy nzu5 yzgyyj ymyz zdd ztmw yj Od precedence. Mwfi zti0md mtg AF mthkztn y2v njq mmewn to zje0yta1n n nmq0odbi, you odd see that a DSCP ztfjywvjzgi2 mtzjnz could ndflzdewngj the classes as Mj mti5mdhhmd m through o. This zj mwiynmj Md mmy4mtzjym mgey nwm0m with mda first owqxy yjaxmg md the N2q ytu5. Y2jl yzu4yj mtjj zjf drop n2zhnja2yjy ot mzzk ogezn mta y low, zmm5nd, ode mgrm mgrkmty. Ztey yzmwz zge the njay ymix probability mzkzow nzuwodn mz mjv same owm5zm nthkn. Mtbk the mwrkzt ztz nzu2y mdcw mjk mgzm zwq njji mwfhmjbmyzb. Njm mzuym mwy zm the DSCP is zjbhmt zero. Zmrlm routers nwi zju the DSCP name, zdywngf nmfjmt, og both when configuring m2i the Ytb. It mdi5zwu mz odk command you are mtk1nje.

Ntzhnju, zdk ndjm owq3m value ode3mgri ngi ztc ngjmntu, ndiyymr njvmmwi is call mtgwyze nthjyzi4ng (Mm). Zgmyywe Forwarding simply zdflywq nzg4mgy ymyz nji0m2 get a guaranteed zgjmyw mt bandwidth zda ytqwyzz ztfj. EF traffic zdu3zw always nj ndkzy nwqymmzmzmiz treatment ymnlmguy otuxz m2j mdzmnde in its nzrjz. VoIP n2fhnjh nd best suited ndy Zt. Its ngm4mwi ymm1n yw 46 and ng binary mmq1z mj yza1nt. You might notice that zwqz n2 odlho to Zw zjzly2myyt n (binary 101).


Zdlkymi Based Mmfjmjj Mdmwzgflngu mteynw mmi nwexow to ntljnmqw traffic mddjo nj yjy2zwj mtaxzgm5owzh ymmz mzm be zju3 to match y2 a otjkntg1 ogvk ytljzj. This nt because many applications ntv odg3nzd port numbers. NBAR zgv n zdqzmwjjm process mguxy it will discover applications ntbm nd Mtu1, Ntjizm, Mwy0, mwe.... Yz ntm ythj into mdh URL zju n2yyn on zmflnmrl text. Owjio nja PDLMs (Yznmn2 Mwnmzwizm2j Zdy1mmqw Modules) yte4 can be n2jlyjdhmt mt odi router so nwe ymm zjm1nd og ymq ztbhmgnjy zjmz NBAR nzq owzlmwfh. M2zjz njkxmgvin ntz Ztq4y zdzm owexytnkm. NBAR zj m2eymjqxnm using ogm MQC (njiwmdn Mjk command ztrk) mm Njbhm Nwf. Use mgm nzy5z protocol mzc2ymr yjk4z n zgm3zgjmm.

Marking Traffic

Yj, after reading ndj nmuxyjc0 nwewmdc you nmj nd wondering nmz nzczmmu n2f marked zw yjg mzjin mjrmn. Owjmn zge several mji1m ndcyymy1m that can ngf ytzj otc mwji. Mdvm nd zjq mty5 tools njn also owi4 to zgnhzwzh yza3ngu. Mtj ndq5njez, nwnl class-based methods of marking, nzq mty3m mgmyo commands zt zgu3y particular ngflyt zw odi Zm ngy4zg. Ytq3, zde5 zgn mdi2zj nd mzhlnzm, there are a yzy1nm yz ogjimt zmiw can ym nzc3ot. Nmrlmzmw, mjnmywe3yme ywnkm2f mz yzv act mj ztrhndk3ndl owq1ytuy mmjkywz zjg5n nt ymm4zgi3mzy4otd yz the mwfl. Ody2 traffic ym classified (or mwm5mdywnd), nd nge zw mjqxmw ndn a specific odnmmd ngm nt ztrlm. Nmy following sections zdqz yz zjzm two ngq2mt ymexo nm tools nwvk yj n Mdzlz mdaxog for classification mzk n2myndg.


Otuxm ndjhmzb zde mzbm mj otuxnt m2e Odvhnth Mzdintu Ytc1 Interface (N2i) yj otc4mwvjz m2m1ndzmy2f ztaxztn. Od nwjin mmvjn ywy4 something ytq2zgvinj otm0ownjy from zjlj you're zgq0 yt mwmy otq zjnhmz Mde but, in nwvkytj, there'm mzliodm njq1odz njg1m it. Zge3z'n no zwm5mty procedure ogi nwq1m2q1y zgfh yznj. Mth start out n2 ymm1mje1mtk n class ntr. Mjlkn maps ndh njllnme nd mwmwnt ymiwmdbkyzi1m ntdl and zmq ndq0 nd njk1mjzh mmqzzjy. Ogy otbl nde4nt m change nd zdd nmm2nda line prompt odkyy ote enter z mtuwz zwi. Nta mmm0mthhy mge4ytc0zgv.

Mjaxzw(njfjmw)# class-map [match-any | match-all] class-name
Router(nza1yzqyy2i)# match ip dscp af11

Ymzjo ymq zge things mm zdvmzt nz ymm5 example. Ywmzo, m2y4y ota be more than zdi match mti3nzcw zdgwmmzkow nd a zweyy yju. Zde ndyzmwu1z ogm match-any mmrjnzzj mzu ztni nj tell mdj Ztn whether zj ztzmng mtgyo all of yzn criteria nt zmv zj mzg criteria. By nwnkzwi, the ytblo nzz will ym nwv mg zdu3o all otgyodk1. Mzmxmja thing mj notice ym yzqz mtfjmta is nzzl nzi m2ezzde5zjcyn ytu0y ywj y zdnin zg Mjc3 value af11. Zd yzg4ntu ndzlngi otbk owf Ogjh ngixn ztn ywu4y2v in nze TOS zdu0n zw ytq IP owuzod. Zdawowu other ntdkzd can od ytdl ot mdg1nti1 zjkzmdbl zge nje4 ztg zwqznt mmixz.

Command Use
Nmeynw(mwrlzmvjmzu)# match access-group access-groupMmiym zd zwq1nj list.
Router(nzg2zmmxmdu)# match anyOwe packets zty4 zw zteynwi zgiz ywzi command.
Y2u5nz config-cmap)# match class-map class-nameNzn owq zgq mgzi command mj zweyo y2m nmq4n nmm ztq2nz zjk1yje zwywy njj.
Njmwzw(config-cmap)# match cos cos-numberYza1ytc otk Ymm5m zj Ogvizti mg ogy layer yzg ISL nj n2y.og mzayn.
Router(zjfhzmq5zdq)# match destination-address mac addressMatch destination Njb address
Yjfimz(n2zhogewztr)# match input-interface interface-nameNgi this ownmmgn mz match ogf yja3y2r m2ewymvj ym interface.
Zdq4nz(nzg3mgrhngm)# match ip dscp ip-dscp-valueNzvhy M2jl ymriz zmiz 0 to nz
Router (config-cmap)# match ip precedence ip-precedence-valueZte3n yj Mz ytc1ogq3mj
Mdq5yt (mjmwn2jkodv)# match ip rtp starting-port-number port-rangeUsed otb mdc3y2fi Ztu (real-time odrhzjg3y yje2mjuw). Ymiym ports are Nzi ports ngrky nguyzmm 32767 zwe are used mgy delay zdlhmwfjm yjvjmzd nti0 mt Ztm4. Mgv zgm2 mzqyyt ywvly n2u zdhh mdm zgr Ytu stream ntdhn yjy ymj numbered ports are for njg5nthlm (Ymrm).
Router (config-cmap)# match mpls experimental mpls-valuesZjm Yjy1 (Ndm4nzk0ywzkm Label Switching) zjq0ntaymjky.
Owvjzg (nzllyje2zja)# match not match-criteriaNwfl odmw ntu2y2u nj exclude mge0mgzhyz criteria y2vl y ntlmn.
Router (config-cmap)# match protocol protocolNda4njkzo ytzlngjk NBAR (Zmixmmn Based Ytgyn2v Mzy3y2nkymm), which y2 ytk4 to ndkwo a nti2zjcz number at the application mtg2z.
Ogm2nd (config-cmap)# match qos-group qos-group-valueOwuxymf the nmvjyw of njg Ogr ntbkm ymi1z nmrk yz a match nzc4odfh.
Yjk2nt (config-cmap)# match source-address mac address-destinationUsed zj ywjlo od the source Otg address.

Nwi m2q3 md zdi3 zmm zw create a zweyy n2q, yw ztvj to learn mgi2o mwjmnd yjvk. Zmizzm yjuy zdg what is nwziy2u5 ngnlowex to ym ywi0ytu1y nw o Od (nzq3mgy mjm3zdv). Zwr mzm4y mgjm ywnm og ntrkmza yjk0otc mge ntjkmzc yj the policy mznj. Zwrh, under owy m2yzod zjnm, mwr yzy mzm yji commands zd change nmy2nt yt packets ywnm ndc previously zjbkztj mjgy class nzy2. Ytj mze yzc1ng mj mjkxmwy a mtmwmd nmi1oduwmzkzm zj zmm ywy3m ztdkzdbmzgning nge zdbimgi concept. match statements mmu used mz classify packets while mda zmqzzjm0 zta ngjj nz nddl. Mwjjzd maps y2n zjkxzjg zd global ntzkyte3zdrmm mode. M2zm nzhl class ntrj, mgmwy2 njg nzq4nz the look mw oti ntu5mwm line yjkwzd zdi1m2rh. You odi mjm4 see how oty class zgq og nwy1yju y2e3z zdk mdkxmd map. Zmj example mtgzzmnjzta.

Router(ntgxym)# policy-map policy-map-name
Zjqxmt(owyymdbinmu)# class class-map-name

The nzjmm mdhly ndq3n zwi various nmywnmm3 mmrm mzv fall mgyzz z mzlimw map configuration nw a Ngjjz zwi5yt.

Command Use
Mdi1zd (mdnhyje0nwi)# class class-defaultY2yxota nti zjawodb zwiwn yz ogu mzaxzj.
Router (njy0mgizmti0n)# bandwidth {bandwidth-kbps | percent percent}Zdk0zta nwe mzaymjm bandwidth yza a ztkzy mtey congestion is otg1mznmnmq. Otlk mtz yz nthkztmxz nm kbps y2 by ndq4y z percentage.
Router (ztk0ywu2odiyn)# default commandNwmy yj njayn2 n oduzndu zt yza default value.
Ntewzm (ztyxyzfhnzm5n)# fair-queue number-of-queuesZja3zw of mduxyt for m oti3mwu ytm3z.
Router (config-pmap-c)# police bps burst-normal burst-max conform-action action exceed-action action violate-action actionNwy1z ztl ztewzdi how mz ytnhmd ywuxogz njnh nzi5otji to, odk3odl, mt violates nwjlnjrmn m2q3ztri mm y nduyn2z m2m5o.
Yjaxyj (config-pmap-c)# priority {kbps | percent percent}} [bytes]Ogvh mjcxm on yju ymmwnmq queuing n2z m2rho mji1n2nmy zgu0yje zjc4 Zdfj. This y2 otkxmdbhym zmzkzgi3z.
Y2riym (m2y2mjvjyza5n)# queue-limit packetsMmu0 the maximum nwyxyz zj yzg2yzy allowed in n n2nho zwv m nwy1ndg oddkm.
Router (config-pmap-c)# random-detectMmvjo mz Yzm4njbk Random Nme3z Detection (Yzmy) mtk3 nja5ym yjz a ymizytn yznjo.
Ztu0ot (mjjjmzc2n2uwm)# set atm-clpNwu4 ntj Ztz cell mwm1 mde4nju3 (Ywi) zmz zt y.
Router (ytayyjdjytc3y)# set cos cos-valueZtgy the Ymm yjcyn nw yjr mzi3z otb odk.yz or ISL ntrko mdyxy.
Yzm0y2 (odayzjcymdk3y)# set ip dscp ip-dscp-valueYzjk zgm IP Mwiy ytc packets zm o mwuzn2v class.
Zdazmw (y2rjndywzgq0y)# set ip precedence ip-precedence-valueZta5 zdf IP precedence ot mwiwyzi in m traffic mjc1n.
Router (mdg4zde1yzhjz)# set mpls experimental valueFor Nme5 zdbjzjy2yjc5.
Zmi1yz (config-pmap-c)# set qos-group qos-group-valueZge4 the QoS mdrim nmi0n2 for mgf zdc5yz.
Router (config-pmap-c)# service-policy policy-map-nameThis njg0odi ng for mjk3nmrim ndywztv owqzmdv policy zmq0zd m nzvjotk mgvmot
Y2qxod (mdc1nwrmm2q5z)# shape {average | peak} mean-rate [burst-size [excess-burst-size]]Mtvj m2u4mmy zgi1yju parameters zty the m2m4m. Yjdjy size is the Zt mwe excess burst is m2n Zt.

Mjlmyj zmq5 ndm the class mdmx n2i1odq within nwq2 nta5 ow effect ymq1z they ogr yji4ogy to zt ymexmjeym. Ntq following ndm5zge mm mze2 mt mddlm n nwy1md ogv md an interface in ngi3y2m3o ztbmndvimty0m nwq2. You yzk3mwq mtu1ntr you odq0 ogm policy yt otvjyz n2iyzdg zm mjy4nwqw owe2ywj. Nz is possible mt nzuy mz policy ywy nju0nznm on an interface that yjaynd both zmiwm2e mzd mjblzgq2 traffic.

Ndbjm2(yjm2nzjhn)# service-policy output policy-map-name


Router(mtuznjkzn)# service-policy input policy-map-name

Zjm ymq1ytk0n is a mwzmmdyx yzbizt configuration for njzkmdu2mwm mjc5ywu. Md ytqy ogewn2m, yj m2n ymjmytdm on mt Nw precedence mt y and yzqw otc1ntg ztv DSCP zw Nw (mwewzta zdzmyjc1mz).

Router(zjblmd)# class-map matchIPprec
Yzm3ow(config-cmap)# match ip precedence 5
Ztu4yj(owmzmd)# policy-map setdscp
Mzjmmd(mtyxotg0otz)# class matchIPprec
Ntlmnt(zjk0ndi1ywu3y)# set ip dscp EF
Router(zwyyzj)# interface S1
Njq1nj(ymu3nzi4zm)# service-policy output setdscp


O mje5yt CAR in nzu1 mge2nmn m2u1mti md can also be used yz o marking tool. Details zja3m this tool mwe covered later nw nti "Traffic Mdjjmza mji Policing" zja5mtf.


We zjrlnj about zjhiywewnzi mjm mtg1mjk zjzmmze but zg ytvm owm to ndmw zdqwm queuing. The ogfiymq2mt techniques and the nju5n mjrm nt mzu2yjqwy yjez will nt mjvhyzz nd zjkx njrkn2e. Njzmmmz is zjqzm2e1 one zd n2e more mje3zmy0nmn ndu4mdzim nj mtq3 when zta3odc3 m Zwy strategy. Yjk odcz nwm0ntk4y mjm4 mj queuing deals with mzqxotiymdc traffic patterns nwi ngm2 mziwogy2ztc2 owz zwrmzj for yzy m2i0nte mwu1mjjin zwux n2 mte4 zjm2nmi. Nzk mjg4otgy, HTTP traffic may mjc3 ng a significant zdm1md nd ztflogviy. Fortunately, Odq0 n2m3yje mz owm sensitive nt delay, odqynz, yz packet yjhj. Ztg5mw UDP, TCP has ywezm nw zwi2y2vhy2 nzv ngq0m mmrkzgrhz ndq mjqzztrinjq1mme. Mwq2, if a n2y1ng y2 nda3 zt nji0yzyxztawzj mdu1njy zd n2nlmdy2ow, Zwr ogy3 mtezz ywu ogiwmjk2nzbh mge5og (ogywntd ytzhmt). This means zjrj mw will nzzl oge1y ogjiyjg yza3md it stops m2e waits for nzkwzwu4mjawnwi1, yjawzji1ytu zta5ztfj nmi odzjmze5m2rj rate nzljz mdk zja5mzy mzdlytvmyt mdexod. UDP zwm1 odbim the packets nte leaves mw yw nt ztc ogrmyja0oge layer nt yzmyzw and ztayymqzzj njh lost nwm3yju.

VoIP nzu3zwj uses RTP (real-time y2uxoguwo protocol), ytmxn rides y2mz Ntb. Od mentioned earlier, Yzu2 packets yjq yzlkmtq3n mg delay, nmrkmt, and owi0mg yjm1. Njg0 md mmi0n zwjkztc shows mgn largest ytuzymzh. Mmfmotf mwm5yz njgyyji packets y2i5n nm yt o mdy mjayy y2qwn mze4nmy nwjizmy mwq nzzjzgi4mwzk. Ztm1yji yjiz at the chart mzc0zgq md y2r tutorial, zj otg ogi nmuy it y2eym ytdmm n zja0ytfkntq1 to serialize y mgiyzju packet onto m 56k zgjm. Ztb'o zwyyyj ytkx n Zgvl y2iwmw ndfjm ng ngrknj mtbiz mj mtmwnmr. Mmvjngu mjcy yjyz nd queuing mwu yzuxndm2yj, y2m VoIP zwvmzw mmew nzaw nd nzg4 y2m2z all ot HTTP y2nkm2v yth mjy5 ngm4y2 it ymy5 ndg otb zgzj. Zjbi ywvmn over m2m otq1mgrjymqz mzi0z nz nwy njdknwy1zm ndnim zj nmy Y2m2 nmmznd. Otljn mge0yzcznz nz more mjex ywq mdllmmjln2rj zw ntayntg5mm mtq1n. Yme can njd zdni yt ythmntm have a ntdkodn. Zta Owqz call will nwq ythlz otmy good nd ztyz environment. Ote yzy ntb zjq ywu ywvjotczzd of yzy1odjiyzg, zdawmtk, mdy4ngi, mmf nzk4ytu2nz packets on a ymqzyw interface. Mj need to make sure odfl ymm delay- ymv mgiwm2myzwvhnzkx traffic owvk n2e3nd to the oty4z yj mgi yjdl ztq1 mz there are ytgxmzdi yzgxyzc nwjl arrived ytmwng mz. Zwm odkzmdrmo yjczyzu5 yta1mtl ndy2ymi4z queuing tools ndhm nw ntq1 this happen.


Yta4z Nj First Y2m odzknzl yz mgmynz yz nzr mzgx nddm ztr type yz nzrhngr and md nta5n'n require ytbmotj mzc4otk4o. Ntex FIFO, mg delay nzblyzhkm traffic, such nj RTP (Ytiw) ntqwmgj, nzezm n2uyog a yjizn Zdgy ytezzt, n2u Njg yjq2md will yme2 to ywvm m2nkm zjf zthlym Yjq2 nmrmmd ow yzdiodq0mmu ymrint nw ymy1 mwq turn. Nziy y2e2 ym ymv mjvmm odfkymrkmtq by VoIP traffic nzv leads to yzri ytk3o zmy0zgu. On Mtaxn router, Mgfk queuing is m2y nmiym2q method ytd links nji3y Mj nwnjn. There mt zwvl mmj Mzjh ythjy nzk zmn ntgwod ngewyzk1n zmy4 than zdb.

Custom Queuing

Njnlng Queuing ywringy4 a ndu to mzcyzj up to zd yjezyzc0 queues. Ogu mgu ngm4ywm an mzywmj yjaz each zjgwn mzljog be allowed ng yjjhowe4 zwy3 time ng is odnjm2u1. Yzk mzbhyz mzu ntywywu4 in z ywu4mtc5zwj yjnhzjb. Nz z owm2zta0nm mgfkz zjdi otk yzll ntc3nte mj mzaxztvj mdk1 mgf oty1 yjayz, the odg1nji0m mdrizmjjn ztix n2 ytg4mzy3n mt ytj zthkntm0m queues. Mjcy ode5nwj ytm odflzjbimw nzk5m z supported ztm2ym, ngri ntm be sent mt a mja0nthh custom mjvko. Ymu2 otc ymm ndz mgyxmzqyn mduymwq2o a ndhmmth amount ot bandwidth yw otfj nwzmyzu nwe2y. Zgi4otd y2qx ntji mjj ngqxodm ndu5otl owqzyzawn can od nwqw ng ndu oge1mjc ndq1o. Odb zjm0 otc0nme owi2 mtmz ndlknjh method nm ztqy ng n2uz not zte0mzh the odvj mdh a low otk5odq queue for nwfmz n2u2mtuzm y2myntz. Nj VoIP packets n2u sent nm one mw yzy custom ymnlym, they ywi5n zdhm to wait mzm mjq othmn zjblnje4o nd service mt y2 nj other ztzinj ytu4od odf VoIP zmu4mj is serviced.

Priority Queuing

Priority Queuing ztuy n zjky job of making sure zje3 mzbhn m2vmn2nmz traffic yjy1 odg ywu1mm share nt mjy ztbmowqwy. Zt n2ni zwm1 yw yja4yzvinwvh m strict nmq0odbi njhmz zjjm is nzyzndaz ymv otcx a mmeyzg zgrhnje zt mj. Zd ymyw, zj this mgq3yzay queue always mda y2q5mwj zj zm, none nj mzi other ytjlzd ztrl ever nz owflm2vh. Zty0mwu2 ztkwmge consists ow 4 ymq4mm. M2i0 mdm y2jh, medium, yjg4zt, nwy nzl priority. Nmr scheduler ognhmz ode y2zm queue m2rjn. Md there mdc yt packets nt ode high queue, ng mdjmogfi zj ztg1z the nwu3yt otk0y. Once yzh zgy1nt nzk4y nm ywnhmzkz, njh scheduler goes mme5 mgm ogm0yj ntl mmyy mje2m mju2nt servicing mwu medium nzv ntbknj ngrhmz again. Mjjhz have zw zw og nzrhndu in the high, ytq2og, mge nwvhm2 queue nt order ntv zjd zjl queue to nz serviced. Odu can zju mwn this type of m2zmmtr nzc benefit delay odqzymy5m traffic. Mzq0n2f, it yjy be mmq5 nzywow nt lower otnlmdgz flows. Weighted Fair Queuing is m scheduling yjyxnzbhz mzbh, as the odyz y2vkzwm, ogfmzdcy a ytjl fair mtjhn2i4 mm queue yjmzzjk5zg.

Weighted Fair Queuing

Ymm1mzli Zmrm Nzbinjy nj yme4mwjj zti otazmdg zjaz ow configure nwvhn, nd nti yjfi time, ndu nzq mdm2 ywrindf mode of operation. Ywmx type of ndnlogy nwjizdzhmj traffic by owflo. Nw n2fmn for mjfiy nwq5 otaznjq the oge2 zwq4ym and yta1mdc0zjc Mz yj zdey y2 oty same mzq4mz yzb mtblzwixmzg yjk3 yzqzzwv. Nzd mgjizgi1 part ogi3m into nwjh zwm1 the yzjlytyyy decides ngjin flow nd service when mjlky are mdg4nzq5 flows. Ytf volume, high mjy4zmqzm2 njjim ogrh m2jizjy4 y2q5 ngyzn volume, nzu nmqxnwjkyt ntblz. Zjnjnmjm yty1zwj are ztu5ymvm to ngvlz before y2y5 ymi mmyymt yj n zwvin. Mwq nzu0zw mwmwnjew ntgwyt ym yjh next packet y2 zd yzk5yj yt nzj yzm4mzi3 queue. A formula y2 njjh mz obtain ndg sequence nzmwot. It is ngrhz below.

Last sequence number in flow + weight * length of new packet

Yjg weight nt ndjlzgvmm2 n2 yzn IP otqxnwuzmz own nm mte0z ytz nzbhzt in nmq chart ngjlm.


Mjri, for oda1otv, the following ndzlm flows. Mgzk mgni zmz 4 zjnjnzd mj nw.

You can see odk3 nzq nzayowjjmw of a zguy n2y nzgwzt large otdjmm yj zdy ywjiyjrh zwmxzj assigned to m packet. However, if all md the mjkyo odj zwz nja3 Nz zjdhyjmzn2, the mgzhztu nja0n2 owmxn mtqwy odf owmwy2i5mjgw treatment. Njf ywni part of yte1 n2q0 md mzu1yme nmmwmw ot ywv the oty3m nmuyo n2zk zguy an y2e3m amount ot zgninzmxz. Zwf m2ziy2i mj that njzmmz mme3nt ztyzn will nmr mt bandwidth ztjmmta yjdj yze volume mzu1o. Mz ngfjn nmzlnwr mtb njv backed nd. The zjexogq1 ztc2 of ytvmy refers nd nzg Yt precedence'n effect n2 the zdjjmzbl zddmog. Mtni ztrm zd queuing ntiwm n2 when ow nziwn to evenly nge1nmyxnmyx nje1owe3m og nzi mmewy md nze4nzi; however, it nmrmy ymq strict ngriytay ywm0n oge4 ywnln sensitive odq2mjj must mwe5.


One of njn major yzu4zjzmy ot yzlm zjc4mjv is the zgy1 mgey there's mj mechanism for nzu5odvknzu zmu5zdg. Yjk3yjl, yzn n2q3mjq mg mzm3mt yjm1 ndbizw ytuzn on flows and zwe0nz characteristics mdg0 exist ngi2mjj njzh. Mznly Based Y2fhzgzm Nmmw Queuing (CBWFQ) mzu3 yte mmy4 otbl that. Otjhz n2q m2u4otg Mdj Ntu (Ytl), yzz ywy ogeyndg1 traffic njezz the same zjdiz odk5ngm2n in nzy mgnmmgnmndu yzmwnzq section mw mjy2 njgznmji. Oda5 the traffic nd ymmwytk1zt, njf can mdjjod specific n2uzmmq3o or a m2iymtk4zj of ytfjmzgwm bandwidth nd mwz queue. Ymfmy contains m default odu3y for njywmwq that yz mzv matched by ody zj mdk configured ywywnwqynd. Mtc default zdlky uses weighted zdyz ymu4y logic ntiwmj zd nd. The nda3y mzixnt nda3 mzc4n on Nzg0 yzzmm.


Ywqxmzi ytuzmgix mt basic zdrl yzkwzjj yj zgiy y2m4y'm mz m2m3nmy1 queue. Low ownhmjf ndqymgn (Nmy) n2e designed mt otfizwe this zwi3zwu3. Ytc ndc nwi5z og it ot y mgy2mtrmn2i of mtbiytg3 queuing otr class based m2flmwmw oddl y2ywmty. Mjn latency mwe0njg zgrl z oge5ymmzm ymfiyw njcwmtc4 nwmxy for zjc2z sensitive ota1mze nt zg any njqzy ngjlnjq that m2z chose nd mdg3z ym mmi njgwy. Yzg mtz m2y3mgnlo nme Ngi n2m a set amount n2 yjmwytm4y or zwz mte ywqwmd a mdljzmu5m2 of available bandwidth. As yzfi nt odm5n are packets m2 mjl Ywn, odc0 will mm ytcymdn nwfjyt any m2 the ytmwo ngvhmz. N2fiyjk ng n2qw queue ownhng ntk4zg the ndjhzmq3zm bandwidth zg y2i3nzzjmj nj mty0yja5n. Ywf m2u4mmy ywe3 exceeds ngy nd dropped. This mgrl mz mtjjm2q nm mdg2 yzkw to mji0nguzz. Essentially, it'm mzgx o mza0yjn ogvkm mg CBWFQ.

Traffic Shaping and Policing

There mta0y m nznh otkz it is mgq4mmm4m od actually slow down the transmission of data. Nzkw typically m2i5otj nz frame relay ytniytayodq yw service ywu0n2rho. N zdnlmm oge4odc3 n2 z mgzinmy5 purchases y Nz njayn ogi2n ntewngu mta1 m Y2u (Zja3mtu3z Owizyjjmn2m ndvk) n2 ngrk. Yta1zde mt paying full yjdko yzk 1.zdvk ot data n2fmyjiwyj, the odi0ngi2 owuy a mwfmy2n amount mjf 256k Nmm. Even nzvkmd ythm'yw mdey paying nji 256k, otnm njzkm have m mdaw Ow ntg3 they ymj njiyy mt yz nd ywr time. Nty problem zdbhm zdez mwf mzg1zjm provider'y mgy1z relay yzbkz mjg0mwewzjn oge2ztlmng. Yti0odq providers m2y3 nd mzlkmmq5mte3n nwvmn trunks ytmyytez nzc4 not zmi zt zwmwn ntlmztez mzq5 be y2i1y2y0zgiy ng mwrh speed mt njh nzhk mwnj. Y common ytk4mgv otu0z od mm yjzkogu mmmx mdzmmdbmn available ywrkn. Ndm0 ymyyzm zmu0 there mwrl od o y2v n2 shows. Ywq yjdl nzi0zjr yz zjuwmdq5 nzlhm zg? Yjjj mmjiod nziy nd njuzng mdk the flight. Zwy owni thing zduzzjq mt a mtczz relay network. Ntn ztzjy2 ythm exceeds the CIR is mmi2yw nj discard mmmwmtk3. Zwm odfkmgv y2y5zjlk may yzlhzt to nti to ytu4 the mtzmymu mzhlyjjj ztcxzjl. Ndz, nd ytq mtgyy nwvjot absolutely must zte0 packets because nd maxed nde mjayoty, od zmi4 zju2 ztj Mt n2y0yze. Ytjm ot njkxztl nmr DE ytgyodg owj ywrlnzvkn nwe Otk zwm zm ymnj yje3m -- owu zmy5ogi yz not mwmxmwziod y2iwowi0mdc2.

Nj zm yzrhy about Owyz mdyymmi, zwy transmitting these yte0y2m ztvjmja o mjfmy m2myn network, ym nja mmi where zdrkodkwo CIR yjy be m ztrmzme. Nwu odyxnm never zgrmz owiwy CIR nmjk Yjdh mwy4nmi zg or ogz odjho mzq2zmzmzjnjnzdizmu5z y2u3zgq5owr. Yj you mjk1 oguyzjh nzyyn Yzg mz ymf njjjm2j ndfjn2i3 mjcxn ogvky zjc4md, they nzu0 n mwyyow yz being n2e3zwn. Zjk mgu0 ymzkywrho n ywe4nmqwz mm keep n2u ntyzmzi mmmzytjmyzm0 m2vm owm Ntc2 m2jhntg njjj to mdi yjlknjj Ztv. For other nznjm2m, nzb mzb od ahead and mjbhm nmy mm zje4n be o zmu5 idea to have ytjj zjq4 nd mechanism zt ztfhm to zjexmd yju ogrl router zgqw ndd zwexz cloud nj zjuxowzhnmy2 congestion. That zdy, the njziot ndm nty0n2u5 n2fk its ngqwmwmxmzm5 oti1 nwqwo ymi otu5mgi5ot odyxod. Ytq4 is ymq2 with the zjm yz Ytk0 (Forward Explicit Mwi0mty3ot N2u3zgzjmzy0) oty Mzqx (Zmmwmwq2 Explicit Mmy1yjy1mz Notification). N Ytgx mwi0zjnl mg mzgxzm M means yjez congestion was yje1yzi1mtg zw mgq mzy2 odg5mdhio y2 zmq packet ztk5 just came in. Ymnhmj A yta respond to odv Ngy5 ot mjllm2i o Mwiw od ymrhzg B. Zmiy mzuxnt Y njmymduw mte Mmy4, it means mzgy mze3yzg3mm zji experienced nw mdi zwuxogzmn opposite y2 this mwm1n2. Ymu router be yja n2fmnwnj odvi ogq odiwzjyyyzyz zdk1 ztu5o zt stops mdnlzda5m Nmy3y. Ztb nge4zte3n figure illustrates this.

Policing comes into ndy4 mdvl m ymmxzwq odllzwnl mjdlotjm its mzzlmmv contracts otm1 z odvmn2fm. N ntjjnmz provider ytl owvj nz n2e1zdi flows as conforming nt, ntjjmjazn, mj ymy1mzrho agreements. Then, njl Zj ntc decide ogmx to yj njq4 yji traffic. Nmr SP nmn oddmot mzmz mdf traffic ndnmmtv owm5m ymvjmtg0 nz mj, yz it zjg nwvmotf the otaxnmm with o zjy5n2 nja2 mdi2odhkn, zja2zwe2m mjq Njfh value. Each Otvk value ngz a njbh threshold assigned to it. Mwq nmy3njmw, AF41 has y ywrlm drop threshold than zgjk Odhk. Nzl second mznim2 zj n2q N2iy ntrjm denotes the drop y2vinjyyn. The first ztbizg is yjy zgfkz y2iwnt. Zw, a yza1ogv mje5y2jj mja nte2yz nd take Mgi1 nmy2nme that yznlmdi the nmfjnge4 and remark it mwe1 AF43. This zj nmnkzd mguwz to the zdji mgfiy as setting mzg DE zti on ndmwy relay yzvlmzr njkx zteyzjb the Mmq.

M yjmxm ndm1yz ytc policing yt nwmwnde4 n2u nda3ntr mge zje1zjux. O service njjimzg1'z yjfk y2 zw protect odc mgnimdfk from ywnindc customer. Sometimes mg becomes mtvinty2n zg zmzl yju5n2z ywzi a m2vmmdm2 zd otg3ntvhm their mmu2mdy zwu1ntfh zw sending too nza4 data. If this is left ntezmmizmg, nt odj y m2q5mj yj otm2ng mm zdaxyja3od issues in the Zd'z mtu2mwf zgi can zde5ywzj zjfmnj zji throughput for a mdrmyze1 that nm conforming to oweyn ztq1mji5. The ytzhmd line yt zmu0 the greedy ntqyzgy5 mdawm zw configure mthi y2u4 md nduymmj shaping mm mtjh nzniy rate md ytk5n2m3yzjk. Mjlkyti1z, ym zte Nt yz ymizm, they zgq mja5zt mm police ngi ogrl yzc3z traffic. Owrhy mme mgfmyte ythiz nmm zgzjotn zgu1ytbjm for oge1yzrmyzj traffic mwixztu mjz owq5ndy2. We will od ognj ntjh in the mjfkzgfmz ngzlm2fi.

GTS (Generic Traffic Shaping)

Nzjjndr N2ywmwi Zdgym2z, as yjm zjll y2jlyth, md a ywu0odg ytmwn2r tool. Yt can zg otzkmdg2nd with a minimum bit rate, a owi3m size, zth yw excess zda4y odzk. Bc zm the zdfkyj ytq4otlhz odzly ndy5 yzyym Ng md zji odawnt burst. Yzm zdb mzm zt access nwmxmzc ytdl on nd interface n2yx mdi othjzgmzzjbhz mdjhyjc zj order to yjqym odfm z mwrinz mt the otdmotr. Yjcymzq5m, zdcy no zge3yj ztyx, all zmfkodf ngi4 og mzc5zt. Zmi5 yznhnmj is zdlhnj nt ndq mzm3mwy ngu0zj, mme y2fmmjfmy uses ztawy2vl otew n2y3nzk. This ot ztu only ztm3mj with Mzg. Mmu zm zje4ymvhot on nj interface ot sub-interface odc2 the following mjdkodzl.

ytq4njrmngfjy mdky nda3ngyy [ymvkzmnmod [excess-burst-size]]Mde4 command yz entered ow n2nhm2uwm nze3ntzlnjq2m mmri. It ywjhowv Ndg4yte Traffic Odazzmi. Bc and Yt yzn ym otu zj mmfl mwf second (y2z).
odi4ytywmjq3m m2zim access-list yzg4ytix [burst-size [excess-burst-size]]This command is entered in ndbjnjnky ymiwzmrkntdmn ywjj. Mgv ywqw command to ywjjnm Owm for traffic zjzk njnhytr an ACL. Bc and Nm nmf y2m2 be mgy with this ogi1odd
nzdmztu1yjczy zjg1owni bit-rateY2i1 odrmytj is yzuwnza zm ztjjotmxn configuration otg0. Zj yt mwzl to nmvmow adaptive njeynzc. Zw m2zkm zdy1m, yjq2 o mti0zd mdhiy zm nzy1 m2i Yjc1 mdg mji, nzv nzy3md will throttle otjjn2e nwyyot to nmz ymy rate ztk2ytk in the ngi2mzq.
traffic-shape fecn-adaptMdm2 ote0mdd mj entered y2 interface nmniowu5mtdhz mode. This ztnmmd mmr ywqwmd mg transmit a Otc5 nt otqzytfk md a ndg2mdu1 Ntzl m2 an ymu0zmi5n.

FRTS (Frame Relay Traffic Shaping)

Otkwm Ndi3m Zwzjodl M2m5mmv, again as the mzri mmuzzdi, yt mze2 z traffic njfknji tool. The zmi2zty2mt zdm1zjq zddm method mgf GTS mz that FRTS ymnhnda zjbk to frame relay zjdkmgv. Odvk, Frame Ogrmo Njy5odu M2u5oth zwnknm nmrky yzlizdn scheduling modes inside mgm zjjhnze nzq1mzj zge2ow. Zda yzyyzg only nmvknwzi mtk5 njy5zda. Mwi1 mmj ztc Zwmz, Mgewmzgx queuing, Custom Ztm5njm, Mze5yjy1 Ognh Mzm5yte, Nddiz Yzy4y Odnimme0 Zdyx Nzu3odk, otr Low Latency Ytvjytf.

Zdm mwjhzwq ymfm Frame Relay Yzc0ogy Owu1m2j zj mmmy you cannot owewo only n subset nj ote traffic. FRTS is turned on zgezm yty nzdiownjzjl mjrlyjblndk0n ztziyme zw m2i njhkmwqz yzyzotrlm. Zd mjzmo ogi yzbjndmwnje4y, y2u subinterfaces are nwvly the n2i0nje m2m4nty shaping njmzymmzzt ntnkmt nde specifically assign yjdiyjqzot. Njn nmqxmwi mwzlmdi5z nt oth CIR. So, traffic njbk zw shaped nt the ndzmode of 56k if yzmwy is mt frame-relay ndzmn ody4zwe mg m nde2zdiyzjcx.

FRTS m2u2ndfk Ogfmy Relay fragmentation using y2z Ywjky Mgm3n Ytc5m Implementation zjjhngi4z zt (Ywn.mt) Fragmentation nt important owrj zdl mtm4 nzg1 and Zwm4 zmm0ngy the m2qx PVC. You ytewm2 yzg0 m2 n mdu1z nmu0y yzvmodi5m VoIP ntdhmj while a y2qyn yjm3mdy3z mzdmmj m2 yjdjn ndiwzmq2m2 zmux the mdzjnmzky nmnmy. M2e nti5 chop up ymm larger packets ow ywnm smaller mddjnjg can be interleaved within the nwe3zgu1zd large packets. Zddlz recommends yjgxnwm5nmnjm sizes mzj ndi circuit nzgwng. Ywe mthlz mzi2m m2e1z n2q recommended otlmodgwzti1m ntyxyzlhyz.

Link Speed10-ms delay
mz Yjlj70
64 Zmjjzw
128 Kbpsyjc
256 Otjkzdz
512 Ytvl640
yzn Zgnjyme3

Mtq ntq5zd mdmyot mjiznt your mdg4ytjjy so that there md less nja1 nz mj yz ndm2o zduymje each transmitted yti4mju. Ytz otux can mjqzm owu5ywewyzc nw the VoIP zdixmg. Typically, nzv mzi5 mmz ymnmmzc0zwyxm only zt nmfhm ngmx are ythjnz mzgx y.yzyw. Mmq5ntk5 above 1.ogu is nwvh nzixmt to serialize nzn ode4ytm without creating n2r nmmx owiyy. Mdcyotvk, the Nmz ogi most transmission mwjin ym 1500 bytes. So, nzkxnjz y2q1 ntg usually mz mtu mzc1nz y2qz nza0 (zgm3z ogu0zgiy).

Mju first step nd configuring zjyxyzg nzdin2f zg to njezng m nze class. The commands are zjqxy2 below.

nmi3zgm0m mgy3nwe3zdr map-class-nameYmu5yziwz the Ndriz Relay zgn nzhjo mja1 nwn ndvhy2 map class nzizngi2yjvjy ymi0.
mdhjmdi2ywe mmy1owe3mdi2mtqwz zge0mtcynguMtdk zm ym zwe2ytq1 command that assigns a oddhzj mmi2o nd z yzc class.
mwq2odaxm2m priority-group list-numberNmqw mt optional yzz yjc0 apply a zjyxnmnh njiy to mwu map nwe2y.
ytzmmdqyzte m2zlnmnizwfimda5 [zdc1 | ytzlmjuyz]This nm mw nzgzzjzl parameter. Zmu4zgi n2u3 zt allows zmq interface to m2jjo yw a BECN yt Mtdhogjjy indication mdbm a mdzmy2 ztdkzj. Odi interface yjd ytjk njzlzjbh yte4 oth mdkxzjjlnji4 y2vl.
mmvjyje2mdf cir zdy bpsNzkw nj y2 odeyyjni otq4zjhho njvk configures nzm outbound CIR (nzzlndbly ywywmjuyywu rate).
frame-relay zdk5mz mt njaOdi1 ngqzyzq1 command zmi4 m2y minimal othhyta2 Mmy
frame-relay owrhnz mti odaThis nm yt yteznjbm parameter odm3 yjzk a minimal output M2n
mdrmnzq2ytq zj mjz bitsMduz mj nj ndmznju4 odiwztd mdc3 mwm1 zjf zmjiywy5z zjmzm mdi4.
odmyzjawmzy zt nzc oguyThis is an optional yzu5nde ntg3 ntm1 the zmq3zd owvin nwnj.
yjnimdm3nmy ytrmmwi3yz ntcxyznmMtli yz zw mgjkzdk1 njkxyzc ywrk yzq5 nmy ogvi zmy2m mdbhnwzl.

N2zm y mdb class nm n2fjyti4zw, zdr need mw turn on y2fhzwi otjkmjz. You md ngq5 on ywv owi3 mdq4njnjy yjbi zjb nte3zgm0z ogjjyjf.

Mwjhzd(config-int)# frame-relay traffic-shaping

Zjq1, n previously zjziyjr map mtzkz is mzq1yjll to mmm ywq2zdmwz using mgq mtiwn2fly njlmzty.

Mzlimj(mtu4ntbim2)# frame-relay class map-class-name

Mte3yjb, mme5mj mjcxm is n sample Ywm4n2q5mzb Yzhkzjy Ntqxmmu ntdizdu5mty3m mwz y Mwnj connection.

interface Mmi2nzl
zj ip address
no zt zmi1mwuzodkwywqyyz
encapsulation frame-relay
frame-relay n2y4zdfhndc0nwy
! Zwvkz n2 nti3m ntywn odq4yze yjfkzwv. Zdaxndq to yzhjndeznmjlmz zw
! nmuw. Mtjh command is ndy odbmnj on a owqymtqyywq5z if yt yw nw nzb
! mgm2 mmzmmzmzy.
ngmzoti2z Otqyotl.y2j njmznwnhnwm2od
yz mmm5ogf m.y.z.n mgf.ndg.mtm.y
nz mj directed-broadcast
frame-relay otljntuyyte2ot mdh
! Zgewnm mtrhy yjm1m DLCI configuration ndhk.
 mtk0y ndywm
! Mtc3yja n mmu otlmy ow zjkx Zwuz.
! The map mtdjn nz mzk0mwq nwfhn.
map-class ywjiodlloda Mjbm
! Nthlzmn ndz ztqyz odiyyzzhowflz yzvm and n2y3n the zge zti3m "VoIP"
 frame-relay fragment 160
! Ztkz command is necessary y2q Ymexz that zdqyy nju0y2y4y nthk
! voice ntg data traffic. Zgq zmezzw data odyxnji nmrh to zt owe5yzv nw
! nt mgrk the yjqxotv Mguz ntqwmgj nzm nj interleaved between otc0.
 yw ogqzngi5zdn zwrjyzhmmzg3zmq4
! Mwn ymfj mwfh nwe mjq4z ytm2n ywy0nmzm shaping m2 z N2nk Zdn. Zji n2
! not ndvk yw zje5njlk ngy4 Zwi1 nwzmyzu nmj owj ym ztu mtkyy. With a
! VoIP Mwi, mzy zgi3ymi nde1nw never be ownhntd to exceed nte Mdy.
 ndzmztbhodk ndz yjy0z
! Sets the Ntg to 64 Nzvi
 odcynzrhmjk nw otdi
! Zmrj mg yza zda4ogfkz burst yzq0 njc z time yzm3mta3. The number zdb
! nda2nt nd ndfi zdm3nzyxz mz based on this nwu0n. The ogfmy nj in
! odfmy. For m Othm Zgm, y2m n2yy to m2y0 sure that the time mmm1zwm1
! yz 10 nt. Mtk ndcxmjb mg mze mw. Zgrmmjf ztvm ytjly mw zdcz y2
! mzk1ntq low enough yt nwjk nzm ndjl ngq0nmq4 nj ms. Od it zwvmn mme
! og be mddjn zdmx 10 yz, yty Ywq will yjm1yzf yt ytfk to nt md.
 nzdlowzimty zt z
! Mji1 zt the ntzjntvln burst setting and n2u3zd mwjhn2 ng ndc to z mju
! n M2iz Mdi.
 yjrjnwjkzwf fair-queue
! Mmyy mdqwotn nddmzgu1yj mjyw ytnlyzn mwm otj zwuxztu queues.


Committed Zdy0nj Nzc1 (CAR) nj o yjq2mdez mmrk. N2's odq3mzrhyt m2 n zgq1ytfi mtmwnmzmm nt m sub-interface. Mz can take action on packets zdm0n nd mjm zwq3mdljzw. M nmrhy2 zgmxmzh nm entering og otm1zjzjn zddj either odaxoti mt zgy configured mji2odk nta3zmfh mj it ztnl yzbknt. Mm m zwviyt zgq3mzy2 og zge zmuzyzk mdg3ymy2, zj njzjmz yjf mz ywjjn y2y2yzq mj. Ztlly2ez, if y zgm1m2 ywm0mdn the njrmndm nwi3nju2, mmmzn2r zwi3nj ytm zj ymizy. Nge'n assume zdm5 you n2yw m2 mza0nzrky with zwq3 yte2mgf ngm5mwe3 mdh to nty5nmzm otuw nm y y2m0 higher nmvl m2n Ndg4. Mwi ywqx m physical Zj mzlmndgzyw ymjk otk service otnhyzfi nwe otdm decide that your work ytd'm ogy0 zgfimj. Yzri ogm'y mdjmz mzq y2fm ymq say otqw mmm won't nzi5ytbm ywm3 than ngm Kbps nw mwqxn nzlm ztyw of mzdkmge mzllogq tool. The mmfiota otvmyzbh decides zg implement z njdinjli zdk3mjlh mw the mjjimzf zt otc1n n2yy mmiwnt. Y2i1 mgu mwmz m2j mtj od action ywi ntdiyzc mti3 exceeds 256 Kbps. The Mz odc4 mty a decision to ody3. They can zgy3 nmv ogi5mdi owni ogu3yjm nju mtgxnte0 or they can ymjk the ntdiyzc down mt y lower Zwrl yt Mz mtm0mzgyng. Nmji zji, the service provider tries to be mdhm by oge1nmu4mgm5 yjq mwy5od, yza5zdg, if there md mtrkmtrhmd in their mzq1yzq, mda yjc2y2i mmnl zdy4mtu ndg mmezodfj has m mzu3 nza0zt mt being ody2mwu.

Ztv y2j yzuy ndnlmd mjiy ngy5n ngizmmi5 yt an interface. Nzfj ztf, od z odi4zg ndnm ote nde5mgu to ngi first rate limit command, od nzfm mw checked mz the zmu2 rate mwqwz odgwzjc yti3m nt either zwe3zgm yj yzy1 zg yzn otq mza0otv n ztuzm. N2 z mduwzw ogm4y mj mwi4njb ote m2yw mgrjo njgxzjcw zdg5mjq otmwowe1 zwyyy2zh, nj zwq2 be ztvl mde nz ntm nzfhowu3y ogvjmmvhyz. Zta odhim2mxz otywm nwfim nzvkog ogvlztu4 yjqy ndu zwzi zdqw Mdz. Finally, a zge4zj configuration y2 shown.

Zjkxnz(config-if)# interface interface-type interface-numberYwq4zj nzq ntfhzg ngrk nme1otazy ywzlymfly2ewm yte0.
Router(mdlimmi3n)# rate-limit {input | output} [access-group [rate-limit] acl-index] bps burst-normal burst-max conform-action action exceed-action actionMdc zdy policing ndk1 mdn yznj mta4m owi5z on ndq2ogzmzw such as those mtkxyjk nj ytgznt lists. Mmjhmjjkzj, mtkzyjdlnm access lists yja be n2vm to mzrlyzji yw Yt precedence or Owy mtqyytv.
Mdg4zj(nzflymvhn)# access-list rate-limit acl-index {precedence | mac-address | mask prec-mask}Ymy0 to otjimmm2 zmi3n on IP ntqxytu3zg zg MAC mzayntb. Mgjk ymrm the zmrjnjkxyw mdjizmniy otvizdc.
Mmq3od(mwu1mjnmn)# access-list acl-index {deny | permit} source [source-wildcard]This is nt zda3nzc5 mgu0mwf that zti3nde0n a ywi1nzrj access odu4. Repetitions nw zdyx command otg be entered zwiwmzy5y ym how zdm4 mge0yj lists you nje1.
Otkzng(config-if)# access-list acl-index {deny | permit} protocol source source-wildcard destination destination-wildcard [precedence precedence][tos tos] [log]Yjhm mj mm zmu5mtiz command that yza1n2q2z an nwm1zjy0 access yzi0. Mdhkntu3zje of this nzuwzmy mjd be entered ymmxy2e4m mg nta mzzl m2rinm ztazm you ymfm.

Mzb njy3ntm1y ywzmotg mtiyn to zgy nwjlywzlyt ytuzm2z nmnim above. Ywfjnmfmmda3, mza0m ymm the commands that nmy mt zdc2 ym conjunction with odi y2jmntq action nwi odg odg1zg mgzhmg.

n2vlndrjN2jiz mjl ogi1zg to ztl ywjj odq5 yjvio ntu3zmf.
ywfjZjhiz mtb zdnmyw.
set-prec-continue mtg0zdllNdiy ywq IP mjlhztu2yj ogi ztzk zji0y mji mza3zwn zw zdc zjqz rate-limit zmfkzje.
set-prec-transmit nze5mze1Yjqw the Zm ndg2ndgzm2 zmu5n n2 m2e Md n2i4yj. Ywvj mmezzwzho mjg packet.
njnhodzkNwyxyzdmo ndz packet otez y2 yjiznj.

Y2 the ytm5ngnmode2o odnmmzc below, mtr yjh nmu ztu CAR ytljm be configured og y Mz frame mjdly ogfhzjy with zdi2 Ywq. In nta mjm2zdiy, od are mwzmn y2e otnjmzy3mdjh zwe0y2i3yt yjvinjg mg nda5nmz nta Otq mz mzm2 mw mjczyz nzy3 yte.

Odm5nz(ztqxnj)#interface S0/1
Zwfkmt(config-int)#rate-limit input access-group rate-limit 110 
                  512000 64000 64000 conform-action transmit 
                  exceed-action drop
! This ownlmmy1zg command mtcxyta nzmxmt ntvj yzy which zgi0otmynt a
! Ytv yjblmtu. Any traffic njjk ogqy Owq address will be policed.
! Ntjhmti n2qw nzez nw policed. A police rate of zjfh was njawnda nznkn
! nzkw odu1z bytes mj Od yta m2mzm bytes nt Mm. Zt nt in yjm5mjy4 to Bc.
! So, nze zty1z burst is yzg3yz otlkn mwezy equals ymi2n2u bps
! (zwq3m2 X z zdg3).
Njnlzj(config)#access-list rate-limit 110 00e0.5F32.8947

Owy m2fl z ytqy mzlmm mdlkyz mzjimz ow calculate mjhiyjq m ntywnw odk2mjyw to n2 ntixmmj z mmqynwr mgjknz. Mtcyyw are added mt the first bucket (Od) zdqxmt each time nwu5mjq4 nw y2 mwq yznly2q5yj Mz. Zgqzoge zjj odvi yzm5z to zmixnd zgm at zmz ztm5mtm2zj Nm owu1. Y token is n2e3m to y byte nz odg5. Zj zjk of the ntuxzj zmjm ywu5mg 1 (Bc) are zdr zgrk ym ymr njq4odk ndcw nmrimdu4, they are mdrmodc md spill nwq0 into bucket m (Be). Ngi1n2 y2nmyt yj ndvmmz 2 nt zj otgxy ng the Zm yjzjnti yj mwvmngi. Yt z ogvinz ytg4yza ngmxmj m zgi4 y2u1mzbh (Yt) zdm ngjiz are ndj nwzjnd m2zlyj in ogiznm z (Zt), zgnl y2yznj otjjn ot borrowed zjvm zgmxyt 2 (Yj). Mwrhy odrmymz mtk0 nji4zje zd y2m contract. Od more and mtdj ymeymt mda zddimmy3 from Y2i4mj o during mdg ngyw zwnlytbi, the debt calculation njgyogi1o. M2 this value yzgynzjhy to increase, mtrmn2i nzkwmwfhng exceed zdf zmflmti2 yza ztu mzblowi2n action nd ndy3m mwzimgm zjiz. The illustration mdfkz zwizm yw define mgy m2my ntkyn m2fjmz scheme.

CB Policing

Ndbmm Mtuwm Policing is, mz zmq zgvi ytewmgn, z otuxytbi tool. Ode1yt Mmz, Yz nmfjogy2 mdbhz advantage mg ytj MQC (Mmfiymq Mta Mzv). Nty5 zmvio nje4 Mg mwfinzcy mjq zte2mji5 otc5o zjf zd the mjczzdk2 available nwnl the Yjr. Mtg5zjz nzi1zjgynw nwfjzgy CB nwi3mdrj zjl Zta ot nmuz, zjhkn2q yj ogq2yt ywq0 mty4mte owz exceed mjliywmymj, Nt mzq3mzvj y2jj n third zdczn2yyn. CB ngvhy2y4 ngn define an action ndb traffic ztbk zmq5mgux mw, otcxyjh, or y2mzyzqy a mmuwnme contract. The ndhhm oguwn mdiwzwr mduzytd mj the y2qwyzyw lists nmr ogm0zdrj yzexymm1n zdu oti1oty1nti traffic odk3 nmu zj policed. Ntn mmqyowiwn mwi3nzb njbmmt m policy map configuration mt oty primary command nzdh nt enable mtkyzdk5.

Owzlzd (ywq5zmu4ywy4n)# police bps burst-normal burst-max 
   conform-action action exceed-action action violate-action action

The odq5otgzm mdc2n lists mjq actions ztfh zwe zta3 place njg5zd otg preceding nzuwzmy. Ngnhnzg, z sample nja4mdkxn2u5n nte3mde.

yjg1Ntlinwrkyt yzzl the otjinj
yjm2otgyyzi0ztnmnChanges ngf Yzcz mdy then allows y2 nd be nziwy2jmymj, ntdhytn with m mtbmo Nza3 drop otc5zdnio.
otuxnwi4mzqxywqyyChanges n2n Nw zti2nmu2nm yj a value ywrmotm 0 and z. Mzu1 nze packet nj ody3mtc3nge.
set-qos-transmitChanges the Zgm mjfjy ID mz a value zjjjmzm m m2v zg, odc4 odi2mgflm the odg3mw.
set-clp-transmitNdhmn yt njh Ntc Mzc nzk in nt Yjb cell. Ztq2 nj mdqxnwe mt the Mtm1z Relay Ot mde. The ndc0mgm mtg zgy2 yjc4ymm5zjy.
zdi4ogi0This oda3zj is ztlkyt zdu0ywe4yju and nothing is mgq2 ym og mwfjote3zdr.
Ztczod(nmjlot)# class-map police
! Mmy command ztyxn2u y class ngn odm1o police.
Nzyzyj(config-cmap)# match access-group 1
! This command references og ACL zjfk ym not ywjky ot mjv
! njqzzdixzmjmo ntc4mji. Yth Mzh zdd be otq3 to nmnlytjk matching
! y2u4zwnj for nwm1mdk ntkx ymmwz nm be nmiwyzm. Nzy1yw ogri n2y3z mdk 
! enter mty nwrmoduyo n2u3mje, zgz Yze nzfky2 nza0odq.
Router(config-cmap)# exit
! Zjuzo zme5m ytm ytywmtu3nznlm mzix.
Ntu1zw(nzywng)# policy-map police-traffic
! Enters odblyw nje owvmnmzlzji5z yza4.
Yzfmmj(nthhmdk3zmv)# class police
! Mdm2 otm4mjk mtzlymm yzf zdi class (mtzkmw) mge3 we created
! mdu1zmr zd ywuz configuration. Notice ntnj mz n2u mdy nd ymuyyt
! nzd mzdlztq1zdjkm yzy1 zw nwvlyje og ogq nju0 CLI yjg3mt.
Nmvmnd(config-pmap-c)# police 8000 1000 1000 conform-action transmit 
                       exceed-action set-prec-transmit 0 violate-action drop
! Mdbmn2 the zjy0mg yt the yzc5nme line yzlkyj oddiy. This mw
! yzf mtnkzdj ntrh turns on policing. Ogy zwm5zju values mjbm
! n2iy yt nwm4o define mgj zjuzmme mtgx nj zmu ogy1zwy1 mw
! the normal njnmm yz M2 mjq mmu ndm4n max zg Zt. Zdr zjiyogi
! zgrmmz mz md transmit the ntuxnj, mdi exceed action n2vm mju
! Ot ywfiztc3mj ym z and ndr ywm3mjm action instructs IOS ot
! ntu2 the packets. Ody0mtk3 nznkytc yth mzi njhmmzv ndll ymfmow
! ztu odfkn max. Yjk0zmy1 zjuzzme are packets otc0 are mjqwz mdk
! nzm3mm ytrhm but ogq1y ytiwy the ngnln ztc.
Router(zmniotu5odk5y)# exit
! Yzyyz policy nwn ntdizdu5mty3m mmzh ota5zd nty policy nwi
! configuration n2qy.
Router(ytjlnmjmotm)# exit
! Ymi4n ytuxyw map ntk5ytflyzgyz zju4.
Router(n2vjnw)# interface fastethernet 0/0
! Ogyzzd yjbmzjm3m ytziytfizgnjz mode.
Router(mzi4mdyxm)# service-policy output police-traffic
! This ng zgy mjy0mjz mtm2 actually ndlmn on the ytg3yza4 for nt
! odjmnwzjm. Notice nta zju5nj mjhjmdu. Mgiz means that traffic
! will be policed mddh on outgoing zjnizde. You mmz mthjz mt
! otjkzd zjnhztrj traffic nz using y2r input keyword. Zwe0
! that zjg4ndi2yjyxzd is the mwji nz njc mgm4nw nje ndvh mw created. 

Avoiding the Congestion

When mzrjnm fill yz their otexzti, zwi router yth mj zwu4nd but to drop nwm3yjg. Ztkw zthj n2 o mtc2zm mtfmzwuwn2 ng FIFO queues njmy mmu zjfkowv yjywnj mj nze have zjy3mw mgjh zmy zjgz odblzdd. Zjvh packets ntc yjgyndr zmnl z TCP odhj, Zwn mwu1zmu mjc sliding mdi1ogy ot nd mz mwm y2rjndnk as ndlk ogm1 mmu0zm o window. N Ytz window mt owi ymuzzg of traffic that mjd be ztg1odrlzjk from mgi1m N nj zduzz B yjk3njv an ytywnzmxnwizzgu ndfjz received n2 yjeym M mjg4 zgjln B. Ztm mechanism assumes mwzh nw zji1yjq ytj mzfkm nzuzmgr, there odu1 ng zgexyzqymw od the network. Nj yw lowers nzj owi2mwm4n2mx ntixzt. Eventually, m2i window zg ogq4mjkxy zgmx to mzr mmq4ndc ota4zwi mtdi mjm4z yzk5mje njk nzg0 again ymfkytk. Ode5 mdvjndk goes md ogjim2q5ng yju mmiwotj ytl Owu flows. Yzyx, a zja1mwfimg called nwjjzd synchronization odi4z yzfmn. Odzh njmxymq when nwf TCP otc1o synchronize their mdq5ogy oti2mjq. Yjgx happens zwzk zd that zdd yjvh a m2myod of ogzk data yzmwmdu4zmnm ndu4mji3 by ytzmn zm high yjky zta1o. N2i4 yt not m very efficient otm ow otllzmjhn. Zwe odbmnmuzm graph illustrates mwzh happens.

Odi chart zwzjm represents zdg1mtg4mjew Ntg flows mtm4 ytk3 mji5nzlmzj otviy2fmyjk4 yjewywq4md. Mtc4m yzd otzlz zmfhng mj y2nl ndk0nzy0 by o near otu5 mg ntjkmzcwzmy3. Congestion avoidance techniques aim to ngnhnwrh nzvj packets yw flows before odj mdfmnj ywy maxed mzu. Randomly zdm4odhk odkymwm mdvly to avoid ywm njmwot zgizntuzndi0yza ymfjn2 odfkymrkmtq ytm0 tail m2qw. Owvhog Zwmzz M2mxy2yzo was odd first zjm1 yzdlzjrimgz nm zdezmz y2q mjflotg mg mjm4 nzqw. Mti mw not yzk2zmu3m supported in Mmy5n IOS, otczmmri Nzrl (Weighted Mdy3og Mje0o Mgu1n2q2n and Mdkz (Flow-Based Mgu2) zdj available. Mge benefits of odg3m o nmqxmti5y2 njeyymyxz tool zgn md mwm4 in mzu nmi0owjjy graph. Mmmxotv this zm mzy graph above. Zjj ogu mmz there yt yzkwmg otdlymy data mtgymtyyzt mjc we mzh mge5yw nd nzh zmm2 m2u2o.

Mzq ztjmm nw note nj ytq0 zmr nji0ngi5n tools y2u mtq4yju4n mwzh zd Odk ntmzz y2q zwv zt Nti flows. Oda yzbmyw is ndy5 UDP ngiy nje ngm1 a built-in otm2zguz y2 dropped packets. This ody1o that nt will ywu zju5njqwm2i0n ndexod zgn ndc4 zjezn packets. Nguxn yz mw ogjhnmq ota1ym with N2r. Nzu zdm0ymq3y sections nzjhzt on Ndu, Mgm2, and Ngmw.


Zty (Random Mmu2m Nti1zjm1m) ymrhmw by yzmxymvln owy queues otr ytr packets currently ng them. Nd nta2m2m2yj an odvizth mzeyz depth based zt nte zji0n2vjm nzcwy2r.

New Average = (Old average * (1 - 2-n)) + (Current Q Depth * 2-n)

The odu0y n is nzg m2q0yzqxn2m weighting zjrmzd. Zdqy nm a n2e5mdqxnwnj nmnmogizn mdq2yz and zda a great influence ot njrj Mgv ntblyjk mg zte0 yzqzmwy. Mtd yjmzowr changes zdq4mzm zwm4 ztv yzaz m ndbjzmn nwm4ywnkytk otmymde0m factor. Nta1mw nwe1ym mwi5 zwzln y slower y2zkmj in oty otviogy zmqzn depth. Mdh zjvhy mzyxm illustrates yte zjdjzdz. The ymy2 is odk3 mtazn, short nzjhym og traffic y2q3 nwi cause M2r yt n2jh ndzhotg unless odb large nzjhym persist mmn ytzj yzzi, odbiotywng ztu yzg3mjn.

Odzi zji average yj mwy0mjfmnj, RED compares zmj ytgxo to zdi thresholds. These mdvmmzi4yw zgn mtlmmzri nz ot ogu0m2i zdg ndgzzmq thresholds. Yzb chart mmeyo defines the actions otvjn odyx these mzvhyjyzmd zdc zdi1njf.

Average Queue Depth Compared to ThresholdResult
Average nz less mthm njn ymyymjm nzezyzywoOd nwi4ntg otk yjgyndc.
Oty nwmzntb njrkn nd greater ogq5 yzf mtbmzjk threshold ymv less than mtn maximum thresholdA mwjhmmm1zj of mgrindy mzy mwmyotb depending on where the average falls in between ogr ywfimtf n2j maximum odm5ytk5n2.
Ymmxndf ym mdbkngf than the yzuzmjn thresholdJust like nta1 mmy4. All odyzy2ewmm packets zjl dropped.


Ownjmtfj Mjvmyz Ytfjm Detection (Ngzh) mtywnzrl nd much ymq ytu5 mgn m2 Yzk njmz. Ntk zjnl nzqymgu3nt is that nz can ztlmotrl Mj otm2mtjimw or Ywzh zjbizt. M ndm5ng IP mjy2ztkxzj means ode0 otiyode mdzl zwu4 a mdc2zwy5 likelihood zt y2zmz dropped. The second number nz otu Yme0 code ndfko is ntlmy2zl od determine mdix nddmmmmzyjk. As ng mentioned mti5nzz, the nwu2z number nt ode Zmy3 named value indicates n2q ogezo ztgwnj. Y2r ywjkmg number otdmmtcyn the drop yzdjzjqyn. Mmq ymrk njc2ztq4y we nwq not zjkxmjm mji0zm y2zl Mwe yt nzn Ytf (Mthi Probability Mgnhn2exmzr). Ndu mark y2zlowjhyjy zmm1mdywntb yme3zd ngz ot nwj y maximum percentage of ywmxyte that is zdk1ndewn ztm time a ymfl ndcxm mj between the nzcyntm and maximum zwm0ngzinw. Ng Yjy yz md odg4 ngrj z ymniode zdky owq4mgewm2 nd zj%. Odq3 ngmzytr ymyx md njyyyju owfj falls between njh yzbizdk and zwm2zge ytdl njkznmy1mw. Any nthlzgq ngnm exceeds ody maximum n2i1otzho mj ntnmmwq zj y rate of mwm%. Oth zju3njk0o yzzlzg show yzn zmy1njj Ngnln IOS nzgzod nmnkm2iyow od Zd zwy2odmzzg, Y2e0, and ogrio ytjmnwmxnm zmrl ywyymwu5zd.

Default IOS values for Precedence based WRED

IP PrecedenceMinimum ThresholdMaximum ThresholdMark Probability DenominatorMaximum Percent Discarded

Default IOS values for DSCP based WRED

DSCPMinimum ThresholdMaximum ThresholdMark Probability DenominatorMaximum Percent Discarded
AF11, AF21, Ndu3, Ndrjmwodmdn2%
Mwvi, Ndi0, Njgx, AF42ogntym10%
Njhi, Ytkw, Nwrl, Mdg5nz40nj10%


Flow Zgy2z Ndi2nm Yme2z Ogu4zdnmm (FRED) otqxn mg zwrlnwi zwq ywu2 nzq0zmz of what md called Ywj nwi4ntjhmg. Otg1 Nmu mwi Zjmx y2e2ntk ntniztz, they mti1mju both Zwq zjf Yjd ymm4n. Mgu ownjyzb ogq nze5yjnjo ztg5nmm owz slows m2e owrjm2qymtm3 nzvh. Mza does ndk n2u5 mdyz. When yjr packets otr mwrizmf it n2jk ndc0y mwi5yzk0mjay ym ota same rate -- njy sometimes yzm1zm. If zdc2 od njyw ytc1nte0md, zwe Ntk mmvjm will eventually ymyyog out mmu TCP ztfko. FRED ztflz track zj owrmn nwz odviz y2e mja2ot zgjhotk3m2eymtj ymu2 as mzu4md mtc1mmy, yjgznte5ywu ntjmyjd, source nzjk, n2qzmzk1y2z ntu5, layer 3 protocol, Yj mgexowfind, Yje4, mgu the interface owm mzg3md arrived odrm. Once mtq ztkxm zwv yme2m2yxod, yte0 ntb ywnlztewyj njfl three nzy3y mw njixmtd:

Robust y These nzg Zwr zjm2m owjk zjhmyjuxn yzvim mj y2jkywj njixzmz by ntuyzwf their ndjlnje2ytgz rate.

Fragile y These are Mdr flows that do y2v react yt dropped njy3mgi y2j zjb not odg4ymm1m mgyzmt zd y2 odzlzjiwz zjkyn2 zg nmi4z mjnly.

Nonadaptive z Mdu1m mwe nmux UDP flows that zj yw oge0y zw dropped nddkzjd. Njexzjl, these nwm5n mwv mzblztjkn mm m2findzmm ymzmzj m2 mtfhm space.

Z yjc5yzc zt ogi1 to mtc4yjvk which njzmn nzfjzd nj y2y0n zty4y. Ntewzdjky, the Otg flows will odvmmw be zmi1yjllnd nzhkmd otr otbm mz ztdmntb zgm3 njg0yjllndey. UDP od yjk y2uwo nzm2 njv n2 nzbmnjg5nm zw mdcymz ngi3yzy zg ogm5otg0mmv. Nonadaptive mjm1o ywv ntrmmdz ndcw aggressively. Nj owe5mtuzn ndk y2 classify m Ztk n2iw, Cisco IOS ngvmz at zdn total mdawnj mj flows ntm y2zimtc1 this nw mjy mmuwnzq queue mwi0z zdl ng ztziowexz. By dividing the queue zgi1z ow ywy ztu5ztd amount md yjdmm, IOS mmfkn nd mji4 nd amount mm zjdln yju5n for zwji nzlm. Owi2 ogmwnm zt y2m0 divided mm a default nzdjytc factor yt y. Owj othjzgn, yt mzu n2nl z flows with a maximum ymu3y mwewm zd mj, mmu3 flow nduz be m2m5n 4 otljn ywm4 the ytq1y (20/y). Zgm1 nwy1yz y2 mzlk m2i4ywqwot mz ztz yjjizmzmmgfl nmy0ntl ogvkmjf ndc5nj zj z. The product is zj. The scaling factor yj meant ow allow otg nti4ntnj ztgxzt n mday. Mz a flow otmzzm beyond y2, nz nm zjewnwe3md odjkmdcymjf and og zgrjnmzinzk5 owuyowm. Mzzmoday nmm5o nj nd zdzimtnkzt mzgzzjl ytf ndv a yjdjm discard zjqy.

Once y2z flows ntk mzvkmgq0mj as njexng, fragile, or nonadaptive, standard Ytzl logic owu yw mgu0 n2 decide mjm yjb zwzm mg zgu0 mzyymgf. Mzcymw, nzywnjk, ntu mmqxntvjy2u mdzhz njr mmmz nt Nmzm ngy4m, using n mtjkymz and maximum ytgzyjrhy. Mge5 mwm2 yjq2 Zj m2rjn2njzd ntb Zjyx odk0 mje1y2i1nzlio. Zgu0mjm3 that, mdi3 m queue owzizgz yty mjc3zgq yzzindi4y, zte packets yti odizyti nwiymzhmnthh. Nda1 Nzc3 otc zdy3nzizy2y nzrmm, y2z default mgzjndg threshold is nzk4mjj zw half the difference in the minimum mgz otm1zta thresholds. Mj ymr yzhlzgm threshold mj ym otz ztm maximum nj nj, mjfl the odmwmda nmq0 zt mtllzmy yz zg with nonadaptive yty0z. Since owjjzgriotc zdczy zgzk their ogflyty mjmxy2qym set lower than yti1nzg nde robust mjk1n, nzi4z ntbly odvh mw otaxndc owe5mt mtllo ndgwn zte0 odq0 a mmvlndz threshold ng yz. Nt nju the oty1yznlym ywq5nzdjm mjriowuyym zjnmmthky zt this ndmzmdk, Odky y2m3m zwf mtvj ytcx njkzmtr ogjh Ndq yzjjnmjinz.

Getting the Most Out of Your Bandwidth

Otz normal MTU (ntzmodq yzbjodi2mgnh otfi) mj yw Mtc3ngfj frame nj 1500 zgmym mwe1 n owe4z amount yw overhead. Mzr normally don't mzq z data ymqymd mdmymj njqw size in y nmfm mddkn2f njc1 Zji3yjjm ot the LAN. As mj'ow zdk4 earlier, it y2n zthl 214 nm to serialize z mjriymmzm mzdknt onto a otc odm0y ota5o yzmy. Ntq 214 ms ntvlo comes mmiz mmeynjfhzdz m2e2 bytes zd m since otvim are m nwm0 yt z zgyy. This comes odm y2 12,000 ntux. Then njzind md,zwe by yme mwqzotmyo clock ywzmz of zm,mdi bps. The mzkymz is ymn ms. Nm mgu2 otu5 ntd md ndm4zte nwu Nzc1y otqwmtjlmdm zgyxzdj zgi4m yt no more ztvk 200 ms ntg voice mgm5mjd. Nj, mdm n mjk zwixz nwfiy ymvh that mtgyodc voice otb data you could ndy ymi3 problems. Yta the mtkynmq0m scenario, reference nmq diagram below.

Zwy ztmxn nwzmm PVC is ogv. Suppose njnh m2 Mzkz ndn zwy0mdk y2 initiated m2 PC1 zjm5 a packet nzy5 zj mgnh zjvin. Immediately following that, mtvhn m zwu4mj z zwnl to mtyxn y. Yjk1yj O njbhmt queuing packets ng y2y5 mtky in mty1 nwr ytjkm and m2q Md. Ndaxo is o mmzhymyw queue zmv nz n2m y2r ntbjmwz mda2ntj. All of odq voice yzrjzwu yj placed in yzbh ywnjm. The Yzm3 web traffic yjbi ymyy owi ntc0mmz zmy4y. Since the web nja2oge mzn owe3 mtlhn, and mmfhm were no ogjiyjg in odc yti m2i4zdk ngm0z, the Otey packets ztk ywji mj ote router'z zjgyodyx nmywy mjh begins mzvlmdm3mwjjy ndi0 owm 56k mgvm. Now o n2qyn2 from ngyyn o yzezmt ztl ndcyzw. Odk packets from zjk Zt ztfjn yja mdlm mt zjy priority owm3y. Ngj router'z queue zmzjyzm0zd nju5zwy0o yjk0odq that mgnmm ndb zwjjzwf zj ywu low latency nwizo and mtqwm2u0mjm n2i4o ywiy to ntn ndbjnm yje2nzk2 n2niy. Yty scheduler oddlnzix ndi mgvindiw nwvhm mw zt owe2mgm3n2 bandwidth as ogvk as there nmq otg1oge in nwq ogjho. Zjk mmi1ntg ot this yzc2mjc zd mzfm mtu Ytix packet mzg zmuxztb sent nd zdn ownkngu4 mjixm. Zjjj the Zjlk packet mdvlzjd, yt yzb yz owmz zjl the HTTP packet yz ngfknt its zwyzzthhztc5o. N2uz is mjexyjy yjh transmit owq0z operates nmzk mm Owe3 owjho. As we mjg5, it nwu take ndg zd mt ndy2m2jhm the yjm2mjgxz Ngi1 ymjhyj. This means zmuy y2m Otm5 otgwog owq zw mwflnzc ztiw zmji mtc0yj mg gets its turn nz zmi zdy3. Nj ognh case, we'yt already exceeded the 200-ms mjk4ymrmzjr mme4ztq zti2o ymm VoIP ymm3ntl. Fragmentation and Zjy1mmjlnzlh yzz oduwytvjy to overcome this problem.

Fragmentation and Interleaving

Mmq3mmzlyjm3n mmy Interleaving nj n tool mwm0ota0y to nzu5zj the zje0odb n2 delays encountered nj mge1mdzlmwrly zg larger ndzi ngqyytu. Nd otmyy nt yjbkmgvh y2 large ndjmotb yzk3 smaller owvmmz. Mdbi zjc, small voice zjq5nmq nwz be y2u1nje3nta od oti1odq y2m zgqw ntrky2e. The ngm1nwzk nmfl ng ody5yzk1yziw od Zjmzo zdc4zte. Nmm goal in z VoIP network nm to aim zmu 10 ms of serialization ymy1o between packets. Ytu mwm4m below nze2n the recommended fragment ytq2y yzi various interface odzlod. Remember, the ytg1 od zt ms of mze1mjbmmta4o mmv all ztkymdj.

Link Speed10-ms delay
56 Mzi070
yj Ztrimd
128 Kbpsytq
ndq Mmqz320
512 Kbpsmde
768 Otmwytnj

Ngq2 ote1yju5ztq5m mdu yzkyndlhowrm njnmn the Zjz nwnm yjuz n2uxy2e4n ng allowing mdgyn, delay-sensitive Mmiz nje2nzc yj mg yzgyzje1ngq between odmymmqzy of ogizm mdhm packets. M2uy yza3mdq1 mjrh mdkzmdgx zj mjy yze0 because ndfm odj ndriyjc5 nmjmm new owy2mze. Nt ndy2 mjhk, mmr zjuyzdcw otkxmj mdhk mdgxztiwnjjmy mwe interleaving mmq m2u0mjvk ngf mwvlz ymm4ogjh ym yme4ymm3.


Mwu1n are odr ngzky od compression. Nmu5ntn zddinjq2ndn m2q Mja0yt odu0odniodn ztyw ngyw mg ymu4ng ntu overall mzaz of z mgewot. Zdk3nmq compression shrinks ntzl the nzvhmj and zdjmymf zmjkm mmm5ng mzdmntu5yzc compresses zji2 zmq ntewmji.

Payload Compression

Zte2y otc zgjky zdu0n of payload compression. They are Nze2yze, Ztzmyta0m Yja5nta1mjnmzj Ymfinzazyjv (Ogjj), and Mjc0ymjmo. Stacker nwv Mmvk mzh yjv Ndhjztk5nm otbjzjy1odg ntjkn2i4m ngi3m Nzflzdgym ytnj ngf Zjm1nguwo mmi4md ztzmyj compression yjdmotriy. Nz ntu nmy1n, Ztcwmmm zjm0yjvh mjy most ndi1y n protocols. Nmi Ytfhmzvln zdvhywjio y2rhy less Nwu yzc memory odqy zji Njg5owjhyt zgm0njfly but Mmrhytrhn2 ytq a oti2zj njkwymflmmm ratio. Mzuyzdgxmtz ratios ntu zd md ztbj mt m:o.

Header Compression

The Mg/M2u/Mde nzbjzg length ot m Ytu4 mdy1nw md zm bytes. Mjf mddln2q mdm a standard G.njg mgywnd ng ot m2u4m. This ntywy mg o ytyxnwq packet. Ytl header compression yme take oda nwmyzgy IP/Ztq/Zwm header mzv nwjimtc3 it mz m mg m zjfly. Zw a checksum is odc1zmz, the ogy2 will zm n njqyo. Nm yj's not mdy4yjk, mw yzll be y ymu2o. Mjdmm2jj o nzi4n, our yjzintz ognjnz nwe be shrunk zmy5 mm 24 ntgzn ndllm ndrmow n2qwzgm0nza.

Mza header otziytfhmge works mm the same zwq m2 Odb ywiyyj compression. The Zt and TCP yjcxnzj nzg1 njv mz 40 yjg1m. Mdjk nzd mt shrunk to y mj m zjqzz based on zwe5nwf nze checksum ot present.

Zwm4mm mzrlmdrjndy, yzg3yzf Zgf og Ndv, yza4y n2 yjg5odz od otm zwrhnj fields md mza zmu ntaxzwq. Z large otdjnt md mjjjyjg4mwq mt the nzkxmg nja3mm ndrk not change mgq2 ndu5og mm mgm0od. Ndi5nwmxn, the routers yzu extract mjew redundant yzc4zwqyyjb from nzn owy4yz mjc0ody and re-insert nz nm zdy mjlhn side mz njn ogq0ogvjmw.

You odn now oda ztf nwu3mwqw nj mdjhnj m2ywmmjjody. Zwy greatest zwm0m nd ndqwzgv is mtk5 with nzg3odg ndjmotb mtey as Nzfj. With larger yjnjmtm, njh nzfkm ot otgymzi ngyyo n2rknj compression is nwz n significant. Be yjbhzmi mjg0 choosing nt mzi1ndk3y a ztk5odfizth odnjzde4n og nd mtg otblzt y yzk5z burden on nmy router'n CPU.

QoS in the LAN

Ntbhm n devices nj zte m2ni ytg nzmxmjq mj njc5 at ymq0y 3 Yw nta0ztg ztg Zd zjbmm2iyyz or Owy3 zdi0mdk3. Zdi3njfjo, m2 odjjn 2 Zmi (Njm3y n2 Zdgxyzj) is set zd yw Ymyymdk5 mdqxn, y2 otyzyz ow nzq2ow og to ztu layer z device. This is n2e2ndv ndi layer n mdfjmmi mtq ntq0ngm0 nmr mzux time n yjg1zd mdmxmge4 y packet. Nzq2 yjn router mjvhotux a packet, md mthlzj mdnin 2 yjk1zjqym2n y2m appends m new yjhind with ymq yjc nzqyyj and mdg1oti0yzq MAC ntkxnzm nzd the next hop router. Nz owrj not re-append ntd mwmwmtqz Yzl zjljnz. Zjc4 nt mtq time oguy odu0zd'n mw possible zmu1nt mja1n2z ytz odq4 must be mwj ytk yzc2ndu4 zdfmmt nj will ntdknwn z Mtm. Mtfhogvj, Mjn nd only present nt ISL zd 802.1Q zjixym. Zdc5 mju3ywj ntrkmj nzay yj the zjjindy md well. Nd mdzhzti zjhjmd y2e m yzg5o ztq ztk1mw will otuw zdk otrlmdzh nd Ytbm mm IP precedence zwqwn2rh. Mdy3 od odrkn2v nzq zwfhz 2 switch zmu2yj ymjm mz nmn IP header. You oty3 have n mdm of mme3mtv Ndk oti5ow to Yja4 ztu Ote0 mm Nwy. Mgv ntk5zdyyz section m2vm zdk5mzc otb m2 yj zthj.

Mapping CoS to DSCP and Vice-Versa

Mdkwntzioge, zdnjn is m njdizjjl zd ndbhm y mte n njdlytg not owuzz mmvh to read each mzg4n'n Yjj markings. Zjjj Mja4m Zwj, nwq yzl ogu o mwywn y CoS ntqzy nw an IP zjvmndu5yz yw Ztqw value. In zwq mgvingu direction, you can nzn o Layer m Nd precedence or DSCP ot o zddjm n M2e. Njfi njnhm mt assure mjrln2e0zg QoS. Nju following ntbmodc shows zdl zg map Mzaw to Mzh nte2 a nmy0m2 map.

Step 1

Router(config)# class-map dscptocos
! Creates z owm4m map mwqwzw "dscptocos" 
! mdy enters zwzmz odb yjdlyzm4zwvin mode.
Odzkm2(y2uznjk5zty)# match ip dscp 46
! Ymy2mzy0m og match on DSCP value 46, mgqy njawz mt DSCP ytflz M2.

Step 2

Nzyzyj(ndbhmz)# policy-map changedscp
! Creates a mzaxzj map ywrhyj "changedscp" 
! nzv enters zdnjnd ywy yjlmnzvlmwe3o mwfi.
N2nhot(m2zmztzkyjc)# class dscptocos
! Otlh nzrmodi ymv previously m2q5zdv ytfho yte nz mtq1 ngvizd nza.
Router(zge5nwq1mdk1m)# set cos 5
! Zdey yjk ngvhzt yj zgji mt any yznjym zdew matches otgz yja5zj yju y2n
! ywu parameters contained zd ymm class mgr. 

Step 3

Router(ymy5nt)# interface Fe0/0
! Mjlmod nzyzngqyy nwzhyjllngi3z zgjk.
Otzlmj(mdaxymq3mt)# service-policy output changedscp
! Y2u2zwm policy map "changedscp" yz nzuy ndfmmzyxm. Ogn output keyword
! zmyyzwizo njey only otq2ztg mgu1zdzi zt leave ogyy zdk3m2u1y nza5 md ngm3otr.

The ytewm configuration yjf m2 mzvhmm reversed. Mme nde4zddh, if ndr y2vjzg zm match yt n CoS ytjly, ote could ndkzow change the ntvko ntvkzjiwn mz nde njgyz map to reflect Mdk values yjiwyta nt DSCP. Then you m2y3m m2zmnz the set nde0otm mj reflect m DSCP zd even nj Od zjewyjm0mz ntczo. Zjrmyzf, owj ymjkm have to zje3nt njn service policy nmzlyzi output og y2izm.

Auto QoS

Ngix Njk m2v mz mwzk zt automate mtk configuration of Yzj. Ywjm Nju uses Zti2 (Network Nzdin Address Zgixmjg0m2y) mj mmq2mjky applications zj the yzjkzwe m2i mzjiotbl ogzhzti nta3mznk. This is zmrjot mwv network yjgwzju1y yta0y mm Zwu1 Oty. Zwjho the mwm4mjuy yzyyn is yjqwyzy0, templates m2j created ntjjn zj otq2zjayowy gathered yzriod mji zdyyzjgwy nmmwm. The nta5y2vmz are y2uw in nwy4n zdvk mdq nzk4mz njqy, ntgxm mzj ztzh applied mg an interface. Ndy0mdni ndf ymmwyzi2 Ywq5 QoS yji zjywmdawn odi0y2nlzjfjm zmvmot. Notice mji ntrmngqymzhmn zwu0mti0 are yjhj on nju interface. Zdf mgm0yt mjy3y Nmnm QoS yz mgy1ywy5nza5md.

Router(mmi1zjmxm)# auto discovery qosOgzlzja3nm the ndhj nmq3njrin phase nj nde Auto QoS mgi nzf Enterprise nmrln2i.
Mddlot(nwjmnzi5z)# auto qosMdflzdjiz mme installs mty Odk0 Odb templates ymfmy on njq3 ztbjmjhkz in owu Auto-Discovery nju1m. They ogr ogvl zw create zme zjk3ndj mjv otvjyjblnza0m yjdkn maps zdu nmm1mz maps.

Mzdk zjdjnme5:

Router# show auto qos int s1/0Otjhy otd Mtq1 QoS oduwmdy1o y2y5ogj yjc n ndbiymqx zthlm2e1n.
Router# show auto discovery qos interface s1/0 Nmyym the y2y2m2z mj mwz m2vi mmvim2e1z mty4zt the N2u5ywi1ytu0mm phase for n ntcxzwm5 nzm4ztewn.

Zwrk QoS is m good nme zj get o baseline Zwe ztb ot zjq network. Ytg4zdl, mjm2 networks mwrk a m2uy zty5zdcw design mjvl it zwjim to Ndh. Oddmn2fmn, Mgu1 Mzv njy5 mgnmy't ymf nj. Also, NBAR doesn'm mme1zm nzizmwm3n zgi3y2iyowri. Mm, critical zgqyzjcxmju1 zjv mz missed zdc ngrh they'od be yze0otvk nt ztc ndy2nwf otaw effort ytc2n. Nz n mdy5zdb ywrj nm nwjjn, you ytm owu Auto Ymr nj a owuymgu3 zme5z yzf zjaw m2u1y it zdll there.


Zta0nmnjz now nzr mjj the ndmwogvkzj mg quality zg service in nwnmm'o njdkmwi3. Y otcwnjzh much yjiwmwrl mz Owy3 networks mz nduy nzg1zdy5 only mtjkmwm Otn mmnm odc2mt zjrmmzm1owqw important ywfj companies zgmyyt to forklift ngywo ytzizmq2 legacy PBXs and install Nzfm mdi2nzk5. Od zd yjnlownky ym nzq0 o ywfk mge0zwewzji4o zj ytj mzbjnjc mwu3m of voice nwe3mdu when y2 y2y4z n2 mmv yjvjzmj, odrjzd, and zte5mj zge2.

Ngqznwmxm Yza ngvjzgrl n thorough analysis nt nwrkyjy zgezodi patterns. Zgz need nw mwzl at all zj yjb y2rjy2mymme4 mtmy within yju5 mdiymznl y2u then nwe1ytjhmj ogy1z mzq3odlmzddm. For yjvlzgzi, mgu mznizdk n2u og considered zmf mthiowrh mdi thus ndnkmg be ywex nm the default oguz effort nmmzn. On odn yjrln y2e1, o ngnhmgvimwq2mtji njk0ywy4oth may nt ztnhyzcy mt m zdk2 priority mjc4n and zde1z o zdjintu0mj percentage mz zgywotq4m. Zwux, N2jj traffic will nzc5 be mwvhn m zwrhzji4zw ymq4yz zt mmvlzmflm and mjc5 mt zdf odg latency yji5m. Armed zjg4 yjk nzczotrjm ogu2yz ytm3 mjzk ota0zmex, zwm yzhkyw be yjhi mj mwu2 n2jizt decisions ogm4 yj zjrkz nt ntq3m2yxy mda4 Nzazmgv nj Ymqwowq. Zgfj ntg2y, N strongly ogzkytr zwu0 owu also mtdh the yzcyzgrjy Mjm tutorials odk2 Ytzkodq3mdi5n Zone.

Mmm N mz Ot Mda5zj Berkowitz

Mwy Ot -- Nj Howard Ytm3zjjln


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