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Resilient Network Load Balancing for Datacenters

Thesis Info

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External Link

Author

Irteza, Syed Mohammad

Program

PhD

Institute

Lahore University of Management Sciences

City

Lahore

Province

Punjab

Country

Pakistan

Thesis Completing Year

2019

Thesis Completion Status

Completed

Subject

Computer Science

Language

English

Link

http://prr.hec.gov.pk/jspui/bitstream/123456789/11469/1/Syed%20Mohammad%20Irteza%20computer%20Science%202019%20lums%20lhr.pdf

Added

2021-02-17 19:49:13

Modified

2024-03-24 20:25:49

ARI ID

1676727822933

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Datacenters (DCs) provide the backbone for online services such as web search and social networks. To deliver high bandwidth to such services, modern datacenters are often structured as multi-rooted tree topologies, resulting in multiple paths between every pair of servers. To optimally utilize the available bandwidth, an efficient network load balancing scheme is a critical component. Studies show that datacenters are prone to link failures and switch malfunctions, and this results in congestion asymmetry across network paths. ECMP is a widely deployed load balancing scheme in switches today, which hashes each flow onto one specific path. This leads to hash collisions for elephant flows. On the other side of the spectrum, some schemes spray packets across multiple paths, and while theirperformanceisnear-optimalundersymmetricconditions, theirperformancedegrades significantly under asymmetry, due to packet reordering. In this thesis, we explore how per-packet load balancing can be made efficient in the presence of asymmetry. Thekeycontributionofthisthesisisthedevelopmentofper-packet datacenternetwork load balancing schemes that perform well under asymmetry. Our work is based on the observation that if each flow is provided with a topology that exhibits symmetry in congestion across all its paths, then the flow is able to fully benefit from the bisection bandwidth without facing packet reordering. To this end, we propose SAPS, i.e., Symmetric and Adaptive Packet Spraying. SAPS leverages flow and group tables within OpenFlowenabled switches to create symmetric virtual topologies (SVTs), with each SVT consisting ofpathswithsimilarcapacity. SAPSmapseachflowtoaspecificSVT,withelephantflows mapped to larger bandwidth SVTs, and mice flows mapped probabilistically to any SVT. Experiments conducted involving large-scale packet-level simulations and real testbed settingsindicatethatSAPSimprovesupontheperformanceofseveralexistingloadbalancing schemessuchasECMPandweightedpacketspraying,undervariousfailurescenarios. Under certain scenarios, it also improves upon state-of-the-art schemes such as FlowBender and CONGA. OpenFlow-enabled switches provide the ability to rate limit groups of flows at the switch. By leveraging the rate limiting feature within OpenFlow-enabled switches, we canconstructanSVTbyextractingaspecificsymmetricchunk (orslice)ofresidualcapacity from various paths, rather than the all or nothing path inclusion mechanism in SAPS. 3 Whereas SAPS works well when asymmetry affects a few paths, its performance is adversely affected under higher levels of asymmetry. North-south traffic can lead to a greater number of paths being affected by asymmetry. Rate limiting enables the construction of a set of SVTs that contains the largest possible single SVT. We observe that under greater asymmetry, having an SVT set with the maximum possible SVT significantly enhances performance. This forms the basis of our proposed scheme, Slices, which outperforms other network load balancing schemes (including SAPS) when most paths face asymmetry. Both schemes (SAPS and Slices) are deployable on commonly available OpenFlowenabled switches
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الباب الأول: المقارنة بین عصر نازك الملائكة وعصر

الباب الأول: المقارنة بین عصر نازك الملائكة وعصر

سنتحدث في ھذا الباب عن عصر نازک الملائكة وعصر بروین شاکر وکیف کانت أحوال الأدب في عصرھما، وسنتحدث في الفصل الاْول عن الأدب المقارن بشكل مختصر وما الفرق بين الموازنة والمقارنة، وعن بدایۃ الشعر الحر وماھي حقیقتہُ، عن ثم شعراء عصر النھضۃ الحديثة والتعرف علیھم وماھي مکانۃ نازک الملائکۃ بین شاعرات عصرھا۔
أما في الفصل الثاني فسنتحدث عن الشعر الحديث في شبہ القارۃ الھندیۃ والتعرف علی بعض شعراء وشاعرات هذا العصر وما ھي حقیقۃ الأدب النسائي وما ھي مکانۃ بروین شاکر بین شاعرات عصرھا۔

القاضي عياض: حياته وآرائه في علم الحديث

ABSTRACT: Qazi Ayaz was one of the great scholars in the Knowledge of Hadith. He enjoys a unique status in his memory, narration and understanding of Hadith. He has vast knowledge of chains of Hadith, its transmitters, and their biographies. For acquiring this high position he always travelled to get the Hadith from its well-known experts, and used utmost care in getting the authentic chains of transmitters, so much so that he is considered an authority among the great scholars ofHadith. The methodology of Ayaz in the science of the transmission of Hadith is based upon research, accuracy and authentication ofthe text. He considers the science of transmission and narration. The origin and essence in authenticating the Hadith. He was strict in the criticism of the text of Hadith and emphasized on the narration of the Prophet’s words instead of allowing the narration of the meanings, unlike the other scholars of Hadith. Hence he held some special views, due to his long experience in Hadith. Some of his views are about: The comparison with the original hearing. The appropriate age while transmitting Hadith toothers. The omitting ofrepeated words in Hadith. The usage of the marks of dialect in the text ofHadith. The permission in narration ofthose Hadith about which he himselfdoes not have permission

تحقیق و بررسی شخصیت عرفانی، معنوی و ادبی سید محمد نور بخش و نقش عقائد نور بخشیہ د.

This study starts with generalizations such as: statement of the problem, hypothesis, research objectives, formulation of the original question along with sub-questions, research methodology, data and information gathering, research domain, pinpointing of the novel and the original in this research and brief description of obstacles and problems faced during this venture, and then proceeds to introducing the personality of Sayed Muhammad Noor Bakshsh with his academic position and status, his uprising, a brief resume of his outstanding teachers and refutation with proofs of the allegation of the claim of mehdi'ism ascribed to him by his opponents. This is followed by a classificatory detail description of his academic and literary writings and works listed under 84 headings on Quranic exegesis, jurisprudence, ethics, Gnostic science and Sufism, physiognomy, history, etc. — an encyclopedic work subjected to necessary critical introduction. Then there follows in-depth discussion of his Gnostic thought and teachings along with his differentiation between: Gnostic wisdom and science / knowledge, (b) gnosis and Gnostic science, (c) gnosis and Sufism, and (d) the Gnostic and the philosopher — all this followed by his discussion of his views on: (a) the impression of gnosis and Sufism on the mystic journey and behavior, (b) the real Gnostic, (c) the nature of Shariat, tariqat and haqiqat, and their inter-relationship, and then on subjects such as: (a) ten principle, of the mystic journey and behavior, (b) their ranks and gradations, (c) their seven evolutionary states of the 'heart', (d) seven 'presences' and universal realms, (e) illumination and its gradations, (f) levels of phenomenological and intuitive tauhid (state of unity), and (g) dos and don’ts of gnosis. His views and teachings on the foregoing make him figure out as an outstanding original mystic thinker with a highly systematic metaphysics well-integrated and self-consistent mystic ideas and concepts as found emerged out of this phase of the study — all grounded in a gradual phase-wise strictly inductive and empirical process of mystic initiation and orientation, which culminates into a triangular goal of self-purification and growth, self-illumination and discovery and transcendental observation as logical and natural result of the methodology of the theory and practice of the Gnostic science, strictly followed by a Gnostic seeker. In order to make the outsider appreciate the nature of this journey in terms of its trio of initiation, orientation and destination, Allama lqbal has very beautiful summarized its process in the word s of a question-answer correspondence in which a Gnostic seeker and disciple writes to his renowned spiritual master, saying: "Heavens and Earth and God's throne and Hell and Paradise have all ceased to exist for me. When I look around, I find them now where. When I stand in the presence of somebody I see nobody before me; nay even my own being is lost to me. God is infinite. Nobody can encompass Him; and this is the extreme limit of spiritual experience. No saint his been able to go beyond this". To this his master replies: "The experience which is described has its origin in the ever-varying life of the Qalb, and it appears to me that the recipient of it has not yet passed even of one-fourth of the innumerable 'stations' of the Qalb'. The remaining three-fourths must be passed through in order to finish the experience of the first `station' of spiritual life. Beyond this 'station' there are other `stations' known as Ruh, Sirr-e-Khafi and Sirr-e-Akhfa, each of these 'stations' which together constitute what is technically called Alam-e-Amr' has its own characteristics states and experiences. After having passed through these 'stations' the seeker of truth gradually receives the illuminations of 'Divine Names' and 'Divine Attributes' and finally the illuminations of the 'Divine Essence'. This study moves thereafter to an in-depth probe of the spiritual (esoteric) thoughts and teachings of Sayed Muhammad Noor Bakhsh on (I) moral and spiritual virtues such as: (a) steadfastness and endurance, (b) self-accountability, (c) good and homely conduct, (d) sincerity and devotion, (e) self- contentment, (f) humility and meekness (humbleness), (g) forgiveness and ignoring, (h) fear and hope, (i) indifference to and abstinence from worldly things (altruism), piety and cautiousness, (j) departure (from one's homeland, kith and kin and belongings for higher cause), (k) modesty and sense of honor, (1) truth, and on (II) moral vices such as: (a) self-conceit / vanity (egoism), (b) self-aggrandizement, (c) false show, (d) false accusation / slander and double-dealing / duplicity, (e) back-biting, and (f) telling lie. This part of the study highlights the transcendental pragmatism of Sayed Noor Muhammad Bakhsh's esoteric metaphysic in terms of psycho-moral transformation which the seeker of Reality undergoes during his Gnostic journey in the sense of passing through the phase of meditative and contemplative 'thinking' towards the goal of `becoming' and 'doing', that is, moral living. The study thereafter goes ahead towards the realm of art as embedded in the literary thoughts and teachings of Sayed Muhammad Noor Bakhsh with a critical discussion in terms of (I) definition of literature with that of (a) its kinds, and (b) the impact of its literary figures on the creation of the history of literature, and (II) glimpses of the Gnostic literature of Sayed Muhammad Noor Bakhsh with glimpse of love and emotion, and (III) glimpses of his educational literature with (a) aesthetics (beauty) of endurance, patience and steadfastness, (b) beauty of faith in human existence, (c) beauty of immortal, everlasting literature, (d) beauty of the Perfect Man, (e) seeking of God, (f) beauty of Godly life, (g) diction of Sayed Muhammad Noor Bakhsh's literary writings, (h) symbolic representation, (i) meaningful benefiting from the scenes and phenomena of Nature, (j) literary styles used and borrowed from the Quran and Hadith, (k) explicit and implicit literary modes, and (1) fluency and intelligibility. Thereafter, this study proceeds to a critical discussion of Sayed Noor Muhammad Bakhsh's scholastic and philosophical thoughts and theories: first (I) the scholastic ones related to: (a) belief in God's tauhid (singularity), (b) belief in Divine pre-destinations (decrees), (c) belief in angels commissioned by God, (d) belief in the institution of prophets, (e) belief in the Sacred revealed books, (f) belief in 'imamatc (g) belief in resurrection, (h) belief in the Mehdi of the ultimate last era, (i) belief in the five holy persons (of the Prophet's family) in the light of the Quranic aya of tathir, (j) a linguistic analysis in the context of 'imamat' from Sayed Muhammad Noor Bakhsh's viewpoint, and (II) second, the philosophic ones related to (a) different and various currents of the Islamic thought, (b) linguistic definition of philosophy, (c) probabilistic unity of existence, (d) classification of existence into (i) necessary existence, (ii) possible (contingent) existence, and (iii) impossible existence (e) the reason for the dependence of the possible existence on the necessary existence, (f) cause and effect, (g) eternity and spatio-temporal occurrence, (h) kinds of the eternal and the spatio-temporal, (i) Sayed M. Noor Bakhsh's view regarding the probable pre-mordial of souls, and (j) classification of the existence. Given this theoretical background of Sayed M. Noor Bakhsh's transcendental metaphysics comprising his Gnostic, spiritual, literary, and scholastico-philosophical plus jurisprudentio-political thoughts, theories and teachings, this study moves onward towards a critical discussion of his practical wisdom based on that theoretical infrastructure, and embedded in his jurisprudentio-political thoughts and theories with (I) first, his jurisprudential thoughts and theories with discussion of (a) distinct and (b) his jurisprudential diction, and (II) second, his politico-social thoughts and theories with linguistic probe of Islam's political jurisprudence. Thereafter, this study moves to an in depth discussion of the impact of Noor Bakhshi's beliefs, first (I) in Iran and Kashmir with special focus on (a) the spread of these beliefs in Kashmir, and (b) some samples of their influence in that region, and (c) building of Noor Bakhshi monastery in Zadi Bal, and second (II) in Pakistan with focus on a sample of the influence of these belief in Baltistan — all this followed by a comparative study of the Noor Bakhshi's of Iran and those of the Indo-Pak subcontinent. This is followed by a discussion of the socio-political conditions of the Noor Bakshis in the contemporary age with a necessary background of (a) the socio-political situation in Iran during Sayed Muhammad Noor Bakhsh's time, and (b) the socio-literary environment of the ninth century, and (c) the socio-political situation in Kashmir and Baltistan at the time of Sayed Muhammad Noor Bakhsh. Given this background, this study moves to a discussion of the current socio-political and literary conditions of the Noor Bakhshis especially (a) their socio-political and linguistic conditions in Baltistan, and (b) their political and linguistic conditions in Kargal and Laddakh with mention of their schools and religious study centers and their mosques and monasteries, followed by an analysis of why the Noor Bakhshis sect did not spread. All this is followed by a logical and natural inference in the form a comprehensive conclusion and brief mention of data collection, and lastly the triple index of subject / persons, places, and libraries visited and utilized, and then a detailed bibliography with a list of books and magazines / journals / periodicals. All these part of the study relieve the keen student of the impression that Sayed Noor Bakhsh's metaphysics may be a barren desert of abstract esoteric ideas and concepts; nay it is a rather a fertile meadow of multidimensional creative thinking and imagination in which there is a happy blend of his Gnostic, spiritual, literary, scholastico-philosophical, and jurisprudentio-political thoughts, theories and teachings, as they bring home the point that Sayed Muhammad Noor Bakhsh was a versatile genius, a linguist scholar and a poet, and a profound mystic philosopher with invaluable academic, literary, and mystico-philosophic erudition.