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Quality Of Spc Services

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Overview of ICT services QoS management such as SPC

Overview of ICT services QoS management such as SPC

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    Quality Of Spc Services Quality Of Spc Services Presentation Transcript

    • Quality of SPC services Claudio Bortone IV seminar in “ICT Service Oriented Network Architectures“ University of Rome La Sapienza March 24th 2009
    • Table of contents • part 1: – overview on ICT QoS management • definition of a supply contract • definition of an ICT service • definitions and tools for measuring QoS • part 2: – SPC network transport QoS management: • elements for measuring network transport QoS • a network transport service of SPC: always-on • always-on network transport SLA Rome, March 24th 2009 Quality of SPC services
    • ICT QoS management Overview of quality management of complex ICT services’ supply
    • Supply contract
    • Supply contract • a supply contract is a costly deal: – against the financial cost supported by the supplier to provide the supplied object, corresponds a patrimonial benefit for the same supplier due to the object delivery to the counterpart • a supply contract defines: – conditions – subjects – characteristics of supply’s object Rome, March 24th 2009 Quality of SPC services
    • Supply conditions • Supply conditions regulates: – economical aspects – delivery time – mutual responsabilies – involved resources –… – service levels –… Rome, March 24th 2009 Quality of SPC services
    • Supply subjects • three kinds of supply subjects: – supplier: • the economical subject that provides the supply – user: • the user or beneficiary of the object of the supply – contractor: • in some context, it is the direct interlocutor of the supplier instead of the user • a contractor can be a user Rome, March 24th 2009 Quality of SPC services
    • Supply object • the supply object can be: – a product • shoes • food • pencils • personal computers • … – a service: • professional training • catering • library (keeping) • web site hosting • … Rome, March 24th 2009 Quality of SPC services
    • The difference between product and service • product is tangible: – omogeneous – production and distribution differ from consumption – a thing, an object – customers don’t partecipate to the production process – it can be stored – property transfer • service si untangible: – eterogeneous – production and consumption are not separable – an activity, a process – customers partecipate to the production process – it cannot be stored – there’s not property transfer Rome, March 24th 2009 Quality of SPC services
    • Products and services overlapping • a product can include more than one service erogation such as: – for istance: mobile phone • ... • power supply • software • battery • … • often a service can be “realized” by supplying more than one product – for istance: network data transport • … • connection • switch • router • … Rome, March 24th 2009 Quality of SPC services
    • Information and Communication Technology (ICT) services
    • ICT services supply • the contractor is generally the counterpart of an ICT services supplier • some examples of ICT services supply: – connectivity – security – VoIP – system management – web site design – asset management –… Rome, March 24th 2009 Quality of SPC services
    • ICT service supply life cycle: phases • ICT service supply’s life cycle consists in 2 phases: – phase 1: realization • includes activities for implementing the new service and delivery predisposition – phase 2: operation • includes activities for service erogation, change management, problem mangement Rome, March 24th 2009 Quality of SPC services
    • ICT service supply life cycle: transitions • the passage between the 2 life cycle phases is guaranteed by two transitions: – from phase 1 to phase 2: test • service must be realized under the conditions specified in the supply contract (verified and tested) – from phase 2 to phase 1 : design review • information on some troubles resolution or on changes managed in the operation phase, can be used as input for reiterating the realization phase Rome, March 24th 2009 Quality of SPC services
    • ICT service supply life cycle : diagram Rome, March 24th 2009 Quality of SPC services
    • Macro processes for ICT service supply • the international standard ISO/IEC 20000 defines the macro processes necessary to a ICT service supply: – for the realization phase: • Planning and Implementing New or Changed Services • Service Delivery Processes – for the operation phase: • Release Processes • Resolution Processes • Relationship Processes • Control Processes (activate the Design Review) Rome, March 24th 2009 Quality of SPC services
    • Quality of Service (QoS) measure
    • General consideration on the quality of service • the International Standardization Organization (ISO), definines quality as: – “the level with which a set of charateristics (of product, of system, or process) satisfies the requirements” • the satisfation level of a user/contractor can be evaluated in two ways: – subjectively – objectively Rome, March 24th 2009 Quality of SPC services
    • Subjective quality • the subjective QoS can be defined as the deviation between perceived QoS and desired QoS: – QoS desired: • it is the quality level determined by explicit or implicit needs or by user desire – QoS perceived: • it is the quality level that the user can be evaluate by using service and by comparing the (actual or potential) service performance with his desire Rome, March 24th 2009 Quality of SPC services
    • Objective quality • the objective quality can be defined as deviation between designed QoS and erogated QoS: – designed QoS: • it is the quality level taken as reference (project requirement) during the realization; it regulates the organizational system, the service realization modalities, and the functioning conditions – erogated QoS: • it is the quality level objectively measured in the operational phase by adeguated measuring tools Rome, March 24th 2009 Quality of SPC services
    • Key Performance Indicators • the Key Performance Indicators (KPIs) are tools used to objectively measure QoS, during the life cycle of the supply: – one or more KPIs can be determined for each supply sub-process – KPIs can be put together to built another KPI • constant monitoring of KPIs is an important activity: – it allows the supplier to identify precisely the processes that need to be fine tuned to increase the satisfaction level – it allows the user/contractor to measure more objectively the erogated QoS Rome, March 24th 2009 Quality of SPC services
    • KPI determination • the determination of a significant KPI often is a challenging activity: – it is necessary to avoid that: • it consists in a statistic data that is not rappresentative • it is defined in a vage and interpretable way – the requirements for a good KPI designer are: • technical and managerial skills which must be reliable and horizontal • capability analysis and affective reporting for all the factors which affect the indicator evaluation Rome, March 24th 2009 Quality of SPC services
    • Service Level Agreement (SLA) • in a service supply, the SLA is a condition that establishes: – the thresholds within which the objective quality aspects (measured by KPI) are accettable – the penalities agreed with the supplier in case of established thresholds are exeded Rome, March 24th 2009 Quality of SPC services
    • Minimal requirements for SLA • Minimal requirements for SLA are: – service characterization – involved KPIs list – KPIs aggregation algorithm – SLA target – the referencing time slot – modality of evaluation and penalty payment – reporting modalities Rome, March 24th 2009 Quality of SPC services
    • SLA target • the SLA target represents the acceptable threshold value within which the objective quality aspects are measured by one or more KPIs • the supplier uses the SLA targets as quality level reference (project requirements) during the relization phase Rome, March 24th 2009 Quality of SPC services
    • SLA target rappresenting desired QoS • it is crucial that the contractor defines SLA targets in line with desired QoS: – strict SLA targets imply an increase of referring desired quality levels while designing – strict project requirements imply a non proportional increase of performance price Rome, March 24th 2009 Quality of SPC services
    • SLA refining • other useful information that can enrich the SLA definition are: – the erogation time slot (time during which the service are erogated) – SLA updating modalities –… Rome, March 24th 2009 Quality of SPC services
    • SLA classification • the classification of a SLA in accordance with the process that are involved in KPI is a best practice • some example of classification are: – delivery – assurance – performance –… Rome, March 24th 2009 Quality of SPC services
    • SPC network transport QoS management QoS management of the network transport service included in the SPC supply
    • Elements for measuring quality of network service
    • Tipical metrics • Packet Loss – percentage of packets that do not reach their destination • Delay – One-Way-Delay • the time elapsing between the packet departure and arrival – Round-Trip-Delay • the time elapsing between the packet departures and its acknowledgement • Jitter – delay variation between two subsequent packets Rome, March 24th 2009 Quality of SPC services
    • Packet loss contributes • network malfunctions – link error • significant bit error probability • congestion – network equipement that does not have enough resources to manage incoming packets – memory resource shortage of interface output queue • transients – transient and incoherent network configurations due to routing protocol convergence • packets dropped for TTL zero value Rome, March 24th 2009 Quality of SPC services
    • Delay contributes • sending delay – time between packet receiving and queuing on output interface • queuing delay – time elapsed while packets remain in queue • line delay – time needed to write a packet on the line • it depends on the packet dimension and from the bit rate (technological facility) • it can be reduced increasing resources • propagation delay – time needed for the signal to cover the distance from source to destination • it depends on the light speed • it cannot be decreased • ritrasmission delay – time needed to ritransmit a lost packet • only for links that provide ritrasmission feature Rome, March 24th 2009 Quality of SPC services
    • Jitter • mathematical jitter – standard deviation of one-way-delay • it is the square root of variance (average of squares of average deviation) • inter-packet delay variation – defined in RFC 3393 – average of interarrival times difference • let ti the time necessary to a packet i to reach destination, it will be calculated the average of |ti+1 – ti| Rome, March 24th 2009 Quality of SPC services
    • Inter-packet delay variation T1 T4 T5 T8 Source (Querier) P1 R1 P2 R2 Destination (Responder) T2 T3 T6 T7 • Jitter SD = (T2 – T1) – (T6 – T5) • Jitter DS = (T2 – T1) – (T6 – T5) Rome, March 24th 2009 Quality of SPC services
    • Charatteristics of SPC transport service always-on
    • Always-on service • technical specifications definition: – “transport services allow linking to the supplier’s network by a technology that provides permanent access (link xDSL, SDH, etc.)” • technical specifications also define the service access point “Punto di Accesso al Servizio” (PAS) such as: – “every service will be erogated by one or more phisical user interface called PAS” Rome, March 24th 2009 Quality of SPC services
    • Transfer component • different applications need different data transport requirements: – for each application and for each PAS the supplier can provide one or more transfer components “Componente di Trasferimento “ (CdT) – every CdT is characterized by: • a scope • guaranteed amount of access bandwidth “Banda Massima in Accesso” (BMA) • a service class “Classe di Servizio” (CdS) Rome, March 24th 2009 Quality of SPC services
    • Service class (CdS) • 4 desired quality of transport requirement for a CdT can be associated to 4 CdS: – real time (RT) • low delay and low jitter – mission critical (MC) • low delay and low packet loss – streaming (ST) • low jitter – best effort (BE) • no specific requirements Rome, March 24th 2009 Quality of SPC services
    • Always-on network transport SLA
    • Minimal requirements of SLA • minimal requirements of SLA are: – service characterization – involved KPIs list – KPIs aggregation algorithm – SLA target – the referencing time slot – modality of evaluation and penalty payment – reporting modalities Rome, March 24th 2009 Quality of SPC services
    • Service characterization • one always-on service characterization: – supply: • Public Connectivity System – service: • always-on (AON) – service characteristic: • one transport component with a real time service class Rome, March 24th 2009 Quality of SPC services
    • Involved KPIs • three tipical KPIs used for measuring quality of transport services from source to destination: – one way delay (OWD) – packet loss – jitter • KPIs measuring modalities: – each equipement that realizes the PAS will measure constantly sending 10 packets with a 40 bytes dimension toward the QXN border router – this measure will be done for each minute of the day, and for each CdT with a RT CdS Rome, March 24th 2009 Quality of SPC services
    • Aggregation algorithm and SLA target • the measures must be aggregated in “survey intervals” with 24 hours duration (for CdT BGA) • SLA target for each KPI in each “survey interval” is: – for OWD: • < 40 ms for 99% of packets – for Packet Loss: • < 0,15% of packets – for Jitter: • average value < 15 ms Rome, March 24th 2009 Quality of SPC services
    • Reference time slot and penalties • for each four-month period: – SLA considers survey intervals out of SLA target for each KPI • the penalty for each four-month period under check will be: – 1% of monthly charge of each survey interval out of SLA target in four months Rome, March 24th 2009 Quality of SPC services
    • Reporting modalities • for each four-month period will be produced a report that represents: – the four-month period under check – the identificative of service – the measure of each KPI (PL, OWD, Jitter) – the number of intervals out of SLA target – monthly charge – percentage of monthly charge used for calculating penalty – economical value of penalty Rome, March 24th 2009 Quality of SPC services
    • Thanks Claudio Bortone e-mail: claudio@bortone.it web-site: http://www.linkedin.com/in/claudiobortone