عنوان مقاله
عملکرد SCTP در شبکه های Wi-Fi و وایمکس با موبایل های چند مرکزی
فهرست مطالب
چکیده
مقدمه
SCTP
شبیه سازی ها
کارهای وابسته
نتیجه گیری
بخشی از مقاله
کنترل ازدحامSCTP
الگوریتم های کنترل ازدحام بکاررفته توسطSCTP بر اساس کنترل ازدحام TCP توصیف شده در RFC2581 می باشند. از کنترل ازدحامSCTP همیشه برای کل پیوند (لینک) و نه رشته های انفرادی استفاده شده است.
مکانیسم کنترل ازدحام پیشرفته SCTP از شروع کند، اجتناب از ازدحام و الگوریتم های انتقال مجدد سریع تشکیل می شود. برای تنظیم نرخ انتقال داده ها نقاط انتهایی سه متغیر را حفظ می کنند: گیرنده تبلیغ شده (rwnd)، پنجره ازدحام (cwnd) و آستانه شروع کند(ssthresh). SCTP نیازمند یک متغیر کنترل دیگر به نام (pba)partial-bytes-acked می باشد که در طول اجتناب از تراکم برای تسهیل تنظیم cwnd بکاربرده می شود.
کلمات کلیدی:
Performance of SCTP in Wi-Fi and WiMAX networks with multi-homed mobiles Vicuña Nelson INRIA and LIA/Université d’Avignon 339, chemin des Meinajaries, 84911 Avignon, France nelson.vicuna@etd.univavignon.fr Jiménez Tania LIA/Université d’Avignon 339, chemin des Meinajaries, 84911 Avignon, France tania.jimenez@univavignon.fr Hayel Yezekael LIA/Université d’Avignon 339, chemin des Meinajaries, 84911 Avignon, France yezekael.hayel@univavignon.fr ABSTRACT This paper provides an exhaustive performance analysis by simulation of the SCTP transfer protocol in WiMAX and Wi-Fi networks. We provide also a comparison of SCTP with both transfer protocols UDP for VoIP applications and TCP for FTP sessions, as SCTP can support these two types (elastic and non-elastic) of traffic. Finally, we study how SCTP performs when a mobile is multi-homed, i.e. connected simultaneously to two wireless networks (Wi-Fi and WiMAX). Categories and Subject Descriptors C.2.5 [Computer-Communication Networks]: Local and Wide-Area Networks; C.2.6 [Computer-Communica-tions Networks]: Standards; C.4 [Performance of Systems]: Performance attributes General Terms Performance Keywords Wireless, SCTP, NS-2, VoIP, Multi-homing. 1. INTRODUCTION The Stream Control Transmission Protocol (SCTP) has similar congestion control and retransmission mechanisms to those of TCP, which were designed for wired networks. Wireless networks have some particularities that can create problems when adaptive protocols as TCP and SCTP are used. We study the performance of SCTP in wireless networks to see the behavior of this protocol with different parameters and compare it with other transport protocols, like TCP and Permission to make digital or hard copies of all or part of this work for personal or classroom use is granted without fee provided that copies are not made or distributed for profit or commercial advantage and that copies bear this notice and the full citation on the first page. To copy otherwise, to republish, to post on servers or to redistribute to lists, requires prior specific permission and/or a fee. WNS2, October 24, 2008, Athens, Greece Copyright 2008 ACM 1-59593-504-5 ...$5.00. UDP. We used two types of traffic: elastic (i.e, FTP transfers or HTTP) and non-elastic (VoIP). We use NS-2 to study SCTP through extensive simulations. We compare the behavior of the three transport protocols (SCTP, UDP, and TCP) over three different technologies (Wired, IEEE 802.11 and IEEE 802.16) as well as multi-homing between the two wireless technologies. Flexibility and diversity of modules in NS-2 allows us to design heterogeneous scenarios evaluating their performance. We made the necessary adjustments in the source code to achieve the interconnection of the modules and operation between them. Modules like SCTP of Protocol Engineering Laboratory (PEL) at the University of Delaware, WiMAX and Wi-Fi extentions developed at the National Institute of Standards and Technology (NIST) of the United States, have been used at the same time with different kinds of traffic and topologies to do the performance evaluation study. The rest of this paper is organized as follows. In section 2, we have a short description of SCTP with an emphasis on the differences it has with respect to TCP and UDP. In section 3, the simulation scenarii are explained and in section 4 the performance analysis is presented. In section 5, we provide an overview of the related work in SCTP performance evaluation and compare it with our work. Finally, section 6 concludes the paper. 2. SCTP SCTP is a transport protocol defined in RFC4960 [14]. It was designed by the Signaling Transport (SIGTRAN) group of the Internet Engineering Task Force (IETF). Initially, it was introduced to serve as a reliable signaling and control transport protocol for telecommunications traffic running over IP networks via a number of proposed adaptation layers, but has since evolved for more general use to satisfy the needs of applications that require a message-oriented protocol with all the necessary TCP-like mechanisms [4]. SCTP provides sequencing, flow control, reliability and full-duplex data transfer like TCP. In addition, SCTP has unique features including multi-homing and multi-streaming. Based on these two features, SCTP was originally designed to provide a reliable transport between two end hosts using multiple, independent control of streams. SCTP belongs to the transport layer in the IP architecture, like TCP and UDP. SCTP is also richer in functionality and more tolerant to network and component failures than TCP [15]. Like TCP,
