Enabling Optimized Network Operations

Transcription

1 A Poit of View Eablig Optimized Network Operatios The Evictio Mechaism Approach to Maagig Data Flows based o Importace Itroductio The explosive growth i the umber of users alog with differet types of etwork traffic such as YouTube, Skype, ad chat pose a real dager of brigig etwork traffic to a abrupt halt. This ca happe i a switch or router based etwork if the actual umber of data s exceeds the maximum umber of s the switch is equipped to hadle. This essetially meas that ew data s caot be added to the etwork beyod the specified limitatio. To prevet this abrupt halt of etwork traffic ad busiess disruptio, existig data s eed to be removed from the switch i order to accommodate the ew oes. Applicatio iterfaces such as OpeFlow help Software Defied Networks (SDNs) commuicate with the switches ad routers. As per OpeFlow Specificatio 1.0 to 1.3,¹ data ca be removed from the switch i oly oe of two ways: Defiig a expiry mechaism where the 'expires' upo reachig the hard or idle timeout. This timeout is defied by the user while cofigurig the. Whe the idle or hard timeout is ot defied, the s are ot removed uless the cotroller deletes them, ad therefore, they ed up occupyig space i the table. Data evictio ca also take place at the request of the cotroller. OpeFlow Switch Specificatio 1.4² itroduces a third optio called the 'Evictio Mechaism' that ca be used to remove excess data s based o ay oe of the three parameters. These parameters fall uder three categories of the data, lifetime of the data, ad other parameters. Importace is a ew evictio precedece field added uder specificatio 1.4. Whe a evictio mechaism is eabled o the basis of as per OpeFlow switch specificatio 1.4, the switch deletes s of lesser as defied at the time of cofigurig the. However, the specificatio does ot provide a preferred optio i cases where s of the same are ecoutered. This paper proposes a approach for data evictio whe data s with the same level of are ecoutered. There are may switches that are capable of supportig OpeFlow specificatio 1.4. However, we have cosidered oly Ope vswitch for the purpose of this paper. Uderstadig Data Flow Evictio I the SDN approach to etwork maagemet, etworks are decoupled ito two layers the Cotrol layer ad the Data Lik layer. As a result, the SDN eeds a mechaism to commuicate betwee the Cotrol ad Data Lik layers. OpeFlow protocol is oe of the several methods that ca be used for eablig such commuicatio. The coectio betwee the cotroller ad the switch is maaged by a secure chael. I the case of data s writte i a OpeFlow eabled switch of specificatios (1.0 to 1.3), wheever a table is full, the switch drops ew etries irrespective of their. Old s eed to be maually removed from the table. This affects the quality of etwork service. [1] Ope Networkig Foudatio, OpeFlow Switch Specificatio Versio 1.0.0, December 31, 2009, OpeFlow, OpeFlow Switch Specificatio Versio 1.1.0, February 28, 2011, Ope Networkig Foudatio, OpeFlow Switch Specificatio Versio 1.2.0, December 5, 2011, Ope Networkig Foudatio, OpeFlow Switch Specificatio Versio 1.3.0, Jue 25, 2012, [2] OpeFlow Switch Specificatio Versio 1.4.0, Ope Networkig Foudatio, October 14, 2013,

2 The ewly itroduced evictio mechaism for data s i OpeFlow eables the switch to automatically elimiate etries of lesser i order to make space for ewer etries. This eables smoother degradatio i performace whe the table is full. Here are some of the key cocepts used i the evictio of data s. Flow Table A table is a list of s where the is defied as a rule cosistig of match fields ad a set of istructios to be performed o the matchig packet. There are a maximum of 255 tables i a switch, ad if they are ot specified, all etries are etered i Table 0. The compoets of a table are give i Figure 1. I the Ope vswitch, the table cotais the etries writte by the cotroller. The icomig packets to the switch are matched with the cofigured etries, ad actios are performed whe packets are matched. If there is o matchig etry, the packet acts as per the preset table-miss etry coditios. This meas that it ca be set to the cotroller over a secure chael, dropped, or forwarded to the ext -table. Whe the packet reaches the cotroller, the cotroller ca add or update the etry both reactively ad proactively. Flow Removal I OpeFlow Switch Specificatio 1.4,⁴ a etry ca be removed from the table i oe of the followig three ways: Match Fields Priority Couters Istructuos Timeouts Cookies At the request of the cotroller directly by sedig a 'delete' By switchig the expiry mechaism By a optioal switch evictio mechaism Table 1 explais the removal by expiry mechaism. Figure 1: Mai compoets of table I the case of removal usig the evictio mechaism, evictio ca be doe based o three parameters lifetime,, ad other Timeout Cases Hard timeout OpeFlow (OF) Parameter Defiitio OF.Hard_timeout=20 OF.Idle_timeout=0 Results The expires after 20 secods. Idle timeout OF.Hard_timeout=0 OF.Idle_timeout=20 The expires whe oe of the packets are matched through the for the last 20 secods. Hard timeout Idle timeout OF.Hard_timeout=20 OF.Idle_timeout=10 The expires after 20 secods or if packets have ot bee matched through this for the last 10 secods. Hard timeout Idle timeout OF.Hard_timeout=10 OF.Idle_timeout=20 The expires after 10 secods, irrespective of ay packets passig through that. Table 1: Flow expiry mechaism [4] Ope Networkig Foudatio, OpeFlow Switch Specificatio Versio 1.4.0, October 14, 2013, 2

3 parameters. Flows with lower lifetime are evicted whe the evictio is based o the lifetime parameter. Similarly, s of lower are evicted whe evictio is based o the of data s. Fially, i the case of evictio based o other parameters, the specificatio remais silet. The Challege: Eablig Optimized Network Operatios As metioed earlier, multiple users ad differet types of traffic requests ca cause a data overload that ca brig a etwork to a gridig halt. It therefore becomes ecessary to maage data s optimally for superior etwork performace. The problem arises whe a add- request is geerated ad the followig evets occur simultaeously: The -table is full Evictio is eabled o the basis of The same value of is assiged for the least importat s I this case, the behavior of OpeFlow switch is ot defied uder OpeFlow specificatio 1.4 o how to delete the etry. The ext sectio discusses a approach that ca be leveraged to resolve this problem. Usig the Evictio Mechaism i OpeFlow: A Suggested Approach for Leveragig the New Feature This approach applies whe the evictio mechaism is set for evictio based o the of data s ad it ecouters s of the same. I this case, the switch checks the of ecoutered s ad evicts the with the least. If the data s have the same, the the switch calculates a value ad the with the lower value is evicted. The followig formula is used for calculatig the value: The four use cases give below further elaborate the approach to evictio based o. = Number of packets passed matchig the duratio of Use Case #1 Let's assume that the switch ca hadle oly four s with the ad set as follows: Flow 1 96, = 10 Flow 2 97, = 11 Flow 3 98, = 12 Flow 4 99, = 12 A ew with a value of 95 eters the switch, but there is o space available i the switch to accommodate it. As the value of for the icomig is lower tha the least value of for existig s, the icomig is discarded. 3

4 The path followed for this sceario is depicted by a dotted lie i Figure 2. Icomig of lower tha existig s Switch If space i table No Yes As the is of lower Evictio mechaism Delete of lowest Delete of lower Delete of lower Figure 2: Flow chart depictig s ecoutered with lower Use Case #2 Agai, we assume that the switch ca hadle oly four s with ad set as follows: Flow 1 96, = 10 Flow 2 96, = 10 Flow 3 98, = 12 Flow 4 99, = 11 Let's say a ew with 97 eters the switch ad there is o space curretly available i the switch. As per the table etries, two s (Flow 1 ad Flow 2) have the same level of ad value. I this case, the value of (determied as per the formula show above) decides which of the s with equal (of 96) is replaced by the ew icomig. 4

5 The path followed for this sceario is depicted by the dotted lie i Figure 3. Icomig of higher tha existig s Switch If space i table No higher Yes As the is of lower Evictio mechaism same differet same differet Delete of lowest Delete of lower Delete of lower Figure 3: Flow chart depictig s ecoutered with the same ad same Use Case #3 I this sceario, let's agai assume that the switch ca hadle oly four s with ad set as follows: Flow 1 96, = 10 Flow 2 96, = 13 Flow 3 98, = 12 Flow 4 99, = 11 5

6 A ew with 98 eters the switch ad there is o space available i the switch to accommodate it. I this case, the with less ad lower (Flow 1) is evicted. This sceario is depicted by the dotted path i Figure 4. Icomig of same tha existig s Switch If space i table No higher Yes As the is of lower Evictio mechaism same differet same differet Delete of lowest Delete of lower Delete of lower Figure 4: Flow chart depictig s ecoutered with same ad differet Use Case #4 For our fial use case, we are yet agai assumig that the switch ca hadle oly four s with ad set as follows: Flow 1 96, = 10 Flow 2 97, = 13 Flow 3 98, = 12 Flow 4 99, = 11 A ew with 96 eters the switch ad there is o space i the switch. I this case, as the value of the ew ad the lowest value of the s i the -table are the same, the switch checks the of the. If the ew has greater tha 10, a existig (Flow 1) is evicted from the table ad the ew is added. I case the ew has a value of less tha or equal to 10, the ew is discarded. 6

7 This is depicted by the dotted lie i Figure 5. Icomig of same tha existig s Switch If space i table No same or higher higher Yes As the is of lower same same/ lower higher Evictio mechaism Delete of lowest Delete of lower Delete of lower Figure 5: Flow chart depictig s ecoutered with differet or same ad differet or same Drivig Busiess Agility As virtualizatio ad cloud computig become pervasive, there is a growig eed for automatio ad rapid deploymet of services. Techologies such as SDN cotrollers help busiesses gai icreased busiess agility by separatig etwork services ad traffic maagemet from the uderlyig hardware. They eable the desig of flexible ad scalable etworks that ca readily adapt to evolvig busiess requiremets. Whe adoptig a switch-based approach to etwork desig, it is imperative that data s are optimized. Busiesses that adopt a combiatio of the evictio mechaism optio provided by Ope vswitch ad our suggested approach will be able to prioritize data s based o their. This will eable them to gai ehaced efficiecies ad optimized etwork operatios for better busiess outcomes. 7

8 About the Authors Shashwat Srivastava Shashwat Srivastava is a developer i the Telecom busiess uit at Tata Cosultacy Services (TCS), focusig o techologies such as IPetworkig, routig ad switchig, WLAN, ad SDN products. Srivastava cotributes to ext geeratio techologies ad is also a active member i ope source forums such as the Ope vswitch. Chhavi Kat Chhavi Kat is a developer i the Telecom busiess uit at TCS, focusig o techologies such as SDN, Chef, routig ad switchig, IPetworkig, ad WLAN. Over the last two years, Kat has bee a key cotributor to ext geeratio techologies. Sheea Goyal Sheea Goyal is a developer i the Telecom busiess uit at TCS, focusig o SDN products such as OpeDaylight, Floodlight, ad other vedor specific SDN cotrollers. Goyal has bee cotributig to ext geeratio techologies ad is also a active member of ope source forums such as OpeDaylightCotroller. 7

9 About TCS' Telecom Busiess Uit For over three decades, TCS has worked with compaies i the Commuicatios idustry, helpig them develop world class solutios ad systems, simplify operatios, augmet etwork services, diversify ito ew markets, ad stay ahead of the competitio. Our solutios address the etire ladscape of telecom busiesses, ragig from greefield start-ups to large cable ad satellite compaies ad equipmet vedors. Our partership model leverages ready-to-deploy platform solutios, proprietary frameworks, ad solutio accelerators to eable our cliets to lauch ew products ad services quickly. TCS' ivestmets i ext geeratio platforms, mobility solutios, capabilities, ad lab ifrastructure are aliged to address our cliets' key busiess imperatives of operatioal excellece, customer experiece, ad reveue ehacemet. We have helped eterprises ulock busiess value i the areas of Digital Chael ad Commerce, Customer Isights, Mobility Solutios, Hosted OSS/BSS (HOBS), IOT & M2M Platforms, Coected Device Maagemet, B2B Platform Ecosystem ad Services ad Network Abstractio layers. Cotact For more iformatio about TCS Telecom Busiess Uit, visit: global.telecom@tcs.com About Tata Cosultacy Services Ltd (TCS) Tata Cosultacy Services is a IT services, cosultig ad busiess solutios orgaizatio that delivers real results to global busiess, esurig a level of certaity o other firm ca match. TCS offers a cosultig-led, itegrated portfolio of IT ad IT-eabled ifrastructure, egieerig TM ad assurace services. This is delivered through its uique Global Network Delivery Model, recogized as the bechmark of excellece i software developmet. A part of the Tata Group, Idia s largest idustrial coglomerate, TCS has a global footprit ad is listed o the Natioal Stock Exchage ad Bombay Stock Exchage i Idia. For more iformatio, visit us at IT Services Busiess Solutios Cosultig All cotet / iformatio preset here is the exclusive property of Tata Cosultacy Services Limited (TCS). The cotet / iformatio cotaied here is correct at the time of publishig. No material from here may be copied, modified, reproduced, republished, uploaded, trasmitted, posted or distributed i ay form without prior writte permissio from TCS. Uauthorized use of the cotet / iformatio appearig here may violate copyright, trademark ad other applicable laws, ad could result i crimial or civil pealties. Copyright 2015 Tata Cosultacy Services Limited TCS Desig Services I M I 07 I 15