Performance Evaluation of Concurrent Multipath Transfer Using SCTP Multihoming in Multihop Wireless Networks Ilknur Aydin Chien-Chung Shen Department of Computer and Information Sciences University of Delaware Newark, DE 19716, USA E-mail: {aydin,cshen}@cis.udel.edu Abstract—A transport layer protocol supporting multihoming allows an application to transmit data via multiple paths si- multaneously (termed concurrent multipath transfer, or CMT for short). SCTP is an IETF-supported transport layer protocol with built-in multihoming capability. Earlier work by Iyengar et. al. proposed a CMT protocol using SCTP multihoming for im- proving application throughput, which studied the performance of CMT over wired networks using ns-2 simulations. Given recent advances in multiple radio nodes, multichannel radios, and multipath routing we believe that we will see more multihomed nodes in the wireless networks context. This motivates us to study the SCTP-based CMT over wireless networks. In this paper, we investigate the throughput of the applications using the SCTP- based CMT over IEEE 802.11 static multihop wireless networks with QualNet simulations. I. I NTRODUCTION Today, more and more devices (laptops, PDAs, mobile phones, etc.) come equipped with multiple wireless interfaces to connect to the networks. For instance, it has been a norm for PCs and laptops to have one Ethernet interface and one Wi-Fi interface. Mobile phones and network interface cards that inte- grate multiple wireless technologies (such as 3G/UMTS/GPRS and Wi-Fi) have been widespread. In addition, nodes with multiple radios and radios operating over multiple channels are being developed [1], [2]. A host is multihomed if the host has multiple network addresses [3]. All these advances and technological enablers motivate the use of multihoming, especially in the context of wireless networks. A multihome-capable transport layer protocol allows each endpoint of a single transport layer connection to have multiple network addresses. When each network address is associated with a different network interface card which is connected to a different network, multiple (physical) paths between the multihomed hosts become feasible. Therefore, a multihome- capable transport layer protocol can support the (simulta- neously) transfer of application data through multiple paths between multihomed hosts within a single transport layer connection. That is, a multihome-capable transport protocol can technically support concurrent multipath transfer (CMT). This work is supported in part by the National Science Foundation under grant CNS-0347460. CMT can be used for different purposes such as increasing ap- plication throughput, fault-tolerance, bandwidth aggregation, load balancing, etc. The current transport layer workhorses of the Internet, TCP and UDP, do not support multihoming. However, the emerging Stream Control Transmission Protocol (SCTP) [4], [5] has built-in multihoming support. SCTP is originally designed to transport telephony signaling messages over IP networks. Later on, SCTP is supported by the IETF and found useful as a general purpose, reliable trans- port protocol for the Internet. SCTP provides services similar to TCP’s (such as connection-oriented, reliable data trans- fer, ordered data delivery, window-based and TCP-friendly congestion control, flow control, etc.) and UDP’s (such as unordered delivery, message-oriented, etc.). In addition, SCTP provides other services neither TCP nor UDP offers (such as multihoming, multistreaming, protection against SYN flooding attacks, etc.) [6]. In the SCTP jargon, a transport layer connec- tion is called an association. Each SCTP packet, or generally called SCTP protocol data unit (SCTP-PDU), contains an SCTP common header and multiple data or control chunks. One of the most prominent features of SCTP is its built-in multihoming where an association can be established between a set of local and a set of remote IP addresses as opposed to a single local and a single remote IP address as in a TCP connection. In an SCTP association, each SCTP endpoint chooses a single port. Although multiple IP addresses are possible to reach one SCTP endpoint, only one of the IP addresses is specified as the primary IP address to transmit data to the endpoint (destination). Therefore, although standard SCTP is multihome-capable, the standard SCTP in reality do not support CMT. Iyengar et. al. [7], [8] introduced CMT to the standard SCTP to achieve increased application throughput and studied the performance of this SCTP-based CMT in various wired scenarios. Our objective is to study the performance of SCTP-based CMT 1 over multihop wireless networks (MWNs). In this 1 From here on, any mention of SCTP-based CMT or CMT refers to the CMT protocol as in [7].