This thesis analyzes the performance of Quantized Congestion Notification (QCN) during data access from clustered servers in data centers. The reasons why QCN does not perform adequately in these situations are examined and several modifications are proposed to the protocol to improve its performance in these scenarios. The causes of QCN performance degradation are traced to flow rate variability, and it is shown that adaptive sampling at the switch and adaptive self-increase of flow rates at the QCN rate limiter significantly enhance QCN performance in a TCP Incast setup. The performance of QCN is compared against TCP modifications in a heterogeneous environment, and it is shown that modifications to QCN yield better performance. Finally, the performance of QCN with the proposed modifications is compared with that of unmodified QCN in other workloads to show that the modifications do not negatively affect QCN performance in general.

The aim of this work is to take the methodology developed by Ernest Cowell, and further refined by James R. Royse, of cataloging singular readings of Greek scribes and seek to apply it to Coptic scribes. This study focuses on the text of John found in P. Mich Inv. 3521 and the singular readings of that manuscript. In order to have a basis of comparison, singular readings from two other Coptic versions of John are cataloged as well.1 In total 1619 singular readings have been identified in the three manuscripts. Following Colwell and Royse, the readings have been further divided into orthographic, sensible and nonsense readings. The sensible and nonsense readings have been further divided and categorized into additions, omissions, substitutions, transpositions and verbal prefixes. All of these entries are then noted in the accompanying database with appropriate commentary so that the reader may format and use the information in a variety of ways. In addition to the database, detailed commentary has been provided on the singular readings of P. Mich. Inv. 3521 with the following conclusions: Like Greek scribes, Coptic scribes are more likely to omit something than to add something; The category of "transpositions as corrected leaps" which James Royse found useful in his work, has proved unhelpful when dealing with this papyrus; and finally some preliminary analysis about the scribe of P. Mich. Inv. 351 is given. 1 Elinor Husselman, The Gospel of John in Fayumic Coptic (P. Mich. Inv. 3521), The University of Michigan Kelsey Museum of Archaeology Studies (Ann Arbor: University of Michigan, 1962); Rodolphe Kasser, Papyrus Bodmer III: Évangile de Jean et Genèse I-IV, 2 en Bohaïrique (Louvain: Secrétariat du CorpusSCO, 1958); Herbert Thompson, The Gospel of St. John According to the Earliest Coptic Manuscript (London: British School of Archaeology in Egypt, 1924).