faults and congestion in high-end computing systems, supporting multiple network communication paths is becoming increasingly important. However, multi-path communicationcomeswiththedisadvantageofout-oforderarrivalofpackets(becausepacketsmaytraverse differentpaths).Whilemodernnetworkingstackssuchas theInternetWide-AreaRDMAProtocol(iWARP)over 10-GigabitEthernet(10GE)supportmulti-pathcommunication, their current implementations do not handle out-of-order packets primarily owing to the overhead onin-ordercommunicationthatitadds.Specifically,in iWARP,supportingout-of-orderpacketsrequiresevery packettocarryadditionalinformationcausingsignificant overheadonpacketsthatarrivein-order.Thus,inthis paper,weanalyzethetrade-offsindesigningafeaturecompleteiWARPstack,i.e.,onethatprovidessupport forout-of-orderarrivingpackets,andthus,multi-path systems,whilefocusingontheperformanceofin-order communication.Weproposethreefeature-completedesignsofiWARPandanalyzetheprosandconsofeach ofthesedesigns usingperformanceexperimentsbased onseveralmicro-benchmarksaswellasaniso-surface visualrenderingapplication.Ouranalysisrevealsthat theiWARPdesignprovidingthebestoverallperformance dependsontheparticularcharacteristicsoftheupper layersandthatdifferentdesignsareoptimalbasedon themetricofinterest.

Earlier generation protocols such as TCP/IP have traditionally been implemented in the host kernel space and have not been able to scale with the increasing network speeds. Accordingly, they form the primary communication bottleneck in current high-speed networks. In order to allow existing TCP/IP applications that had been written on top of the sockets interface to take advantage of high-speed networks, researchers have come up with a number of solutions including highperformance sockets. The primary idea of high-performance sockets is to build a pseudo sockets-like implementation which utilizes the advanced features of highspeed networks while maintaining the TCP/IP sockets interface; this allows existing TCP/IP sockets based applications to transparently achieve a high performance. The Sockets Direct Protocol (SDP) is an industry standard for such highperformance sockets over the InfiniBand (IB) network and the Internet Wide-Area RDMA Protocol (iWARP) over Ethernet networks. In this thesis, we focus on designing and enhancing SDP over iWARP and IB.

In the past decade several high-speed networks have been introduced, each superseding the others with respect to raw performance, communication features and capabilities. However, such aggressive initiative is accompanied by an increasing divergence in the communication interface or “language” used by each network. Accordingly, portability for applications across these various network languages has recently been a topic of extensive research. Programming models such as the Sockets Interface, Message Passing Interface (MPI), Shared memory models, etc., have been widely accepted as the primary means for achieving such portability. This dissertation investigates the different design choices for implementing one such programming model, i.e., Sockets, in various high-speed network environments (e.g., InfiniBand and 10-Gigabit Ethernet). Specifically, the dissertation targets three important sub-problems: (a) designing efficient sockets implementations to allow existing applications to be directly and transparently deployed on to clusters connected with high-speed networks; (b) analyzing the limitations of the sockets interface in various domains and extending it with features that applications need but are currently