Network Working Group H. Inamura (editor) Internet-Draft NTT DoCoMo, Inc. Expires: January 3, 2002 G. Montenegro Sun Microsystems, Inc. M. Hara M. Hata Fujitsu, Inc. NTT DoCoMo, Inc. W. Gilliam J. James Hewlett-Packard Company Motorola, Inc. R. Ludwig A. Hameed Ericsson Research Fujitsu FNC, Inc. P. Ford R. Garces Microsoft Metricom F. Wills Openwave July 05, 2001 TCP over 2.5G and 3G Wireless Networks draft-ietf-pilc-2.5g3g-03 Status of this Memo This document is an Internet-Draft and is in full conformance with all provisions of Section 10 of RFC2026. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet-Drafts. Internet-Drafts are draft documents valid for a maximum of six months and may be updated, replaced, or obsoleted by other documents at any time. It is inappropriate to use Internet-Drafts as reference material or to cite them other than as "work in progress." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. Comments should be submitted to the PILC mailing list at pilc@grc.nasa.gov. Distribution of this memo is unlimited. Inamura, et. al. Expires January 3, 2002 [Page 1] Internet-Draft TCP over 2.5G and 3G Wireless Networks July 2001 This Internet-Draft will expire on January 3, 2002. Copyright Notice Copyright (C) The Internet Society (2001). All Rights Reserved. Abstract This document describes a profile for optimizing TCP over 2.5G/3G wireless networks. We describe the link characteristics of 3G wireless by using W-CDMA (Wideband CDMA) as an example. We then recommend TCP optimization mechanisms and, finally, present examples of wireless internet services and standardization activities. These potentially will deploy the profile described in this document. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 2. 2.5G and 3G Link Characteristics . . . . . . . . . . . . . . 4 3. TCP over 2.5G and 3G . . . . . . . . . . . . . . . . . . . . 5 3.1 Optimization Mechanisms . . . . . . . . . . . . . . . . . . 5 3.1.1 Large window size . . . . . . . . . . . . . . . . . . . . . 5 3.1.2 Large initial window . . . . . . . . . . . . . . . . . . . . 5 3.1.3 Limited Transmit . . . . . . . . . . . . . . . . . . . . . . 6 3.1.4 Large MTU . . . . . . . . . . . . . . . . . . . . . . . . . 6 3.1.5 Path MTU discovery . . . . . . . . . . . . . . . . . . . . . 6 3.1.6 Selective Acknowledgments . . . . . . . . . . . . . . . . . 7 3.1.7 Explicit Congestion Notification . . . . . . . . . . . . . . 7 3.1.8 Summary . . . . . . . . . . . . . . . . . . . . . . . . . . 8 3.2 Applications . . . . . . . . . . . . . . . . . . . . . . . . 8 3.2.1 i-mode . . . . . . . . . . . . . . . . . . . . . . . . . . . 8 3.2.2 WAP . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9 3.2.3 Ricochet MCDN Network . . . . . . . . . . . . . . . . . . . 9 4. Open Issues . . . . . . . . . . . . . . . . . . . . . . . . 11 5. Security Considerations . . . . . . . . . . . . . . . . . . 12 References . . . . . . . . . . . . . . . . . . . . . . . . . 13 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 16 A. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 18 Full Copyright Statement . . . . . . . . . . . . . . . . . . 19 Inamura, et. al. Expires January 3, 2002 [Page 2] Internet-Draft TCP over 2.5G and 3G Wireless Networks July 2001 1. Introduction Recently, much development and deployment activity has centered around GPRS, UMTS and IMT-2000, also referred to as 2.5G/3G wireless networks. Since a primary motivation for these is data communication, and, in particular, Internet access, TCP performance is a key issue. A number of TCP optimization techniques have been studied to enhance the performance of TCP transmission for various wireless environments [1]. This document proposes a profile of such techniques, derived from previous work at the IETF [34], particularly effective for use with 2.5G and 3G wireless networks. Inamura, et. al. Expires January 3, 2002 [Page 3] Internet-Draft TCP over 2.5G and 3G Wireless Networks July 2001 2. 2.5G and 3G Link Characteristics The link layer characteristics of 2.5G/3G network affects TCP performance over the link. The characteristics are layer two ARQ (L2 ARQ), FEC (forward error correction) and so on [1]. The justification for L2 ARQ is discussed in [10], [12]. For example, W-CDMA (Wideband CDMA) uses RLC (Radio Link Control) [3] protocol, that is a kind of Selective Repeat and sliding window ARQ. RLC uses protocol data units (PDUs) 336 bits long (including a 16 bit RLC header). This is the unit for retransmission. The SDU (IP packet) is fragmented into PDUs for transmission by RLC. There is also FEC and interleaving. In W-CDMA, one to twelve PDUs (RLC frames) constitute one FEC frame. The actual size of the FEC frame depends on the link conditions and bandwidth allocation. The FEC frame is the unit of interleaving. RLC uses "status report" type acknowledgments. It does not use ack-clocking as in TCP, but rather the poll bit in the header explicitly solicits the peer for a status report containing the sequence number that the peer acknowledged. The use of the poll bit is controlled by timers and by the size of available buffer space in RLC. Also, when the peer detects a gap between sequence numbers in received frames, it can issue a status report invoke retransmission. RLC preserves order of packet delivery The maximum number of retransmissions is a configurable RLC parameter, with a maximum value of 10. Therefore, RLC can be described as an ARQ that can be configured in either HIGH-PERSISTENCE or LOW-PERSISTENCE, not PERFECTLY-PERSISTENT, according to the terminology in [10]. In general, the L2 ARQ and FEC can provide a packet service with a negligibly small probability of undetected error (failure of the link CRC), and a low level of loss (non-delivery) for the upper layer traffic, i.e. IP. The SDU (IP packet) is fragmented into PDUs for transmission. The retransmission by L2 ARQ introduces latency and jitter to the SDU flow, that results in relatively large BDP (Bandwidth-Delay Product) of the 2.5G/3G wireless networks. Inamura, et. al. Expires January 3, 2002 [Page 4] Internet-Draft TCP over 2.5G and 3G Wireless Networks July 2001 3. TCP over 2.5G and 3G 3.1 Optimization Mechanisms 3.1.1 Large window size To achieve the maximum performance in TCP, the advertised receive window size needs to be equal to or greater than the BDP (Bandwidth Delay Product) of the end-to-end path. The wireless link capacity varies by specific technologies used. In 2.5G/3G wireless, the link BDP tends to large. If the end-to-end path contains one or more wireless link, the end-to-end BDP might be larger than the default value of receive window size on many TCP implementations. The receiver must advertise the appropriate receive window size based on the end-to-end BDP. The traditional TCP specification limits the window size to 64 KB. If the end-to-end capacity is expected to be larger than 64 KB, the window scale option [6] can overcome the limitation. TCP over 2.5G/3G should support appropriate window sizes based on the BDP of the end-to-end path. If the estimated path BDP is larger than 64 KB, the window scale option may be deployed. 3.1.2 Large initial window TCP controls its transmit rate using the congestion window mechanism. Traditionally, the initial value of the window is one segment. Because the delayed Ack mechanism is widely deployed, a TCP sender should have an increased initial congestion window of two segments[4]. This effectively cancels the delayed Ack by sending two segments at once in the very first slow start turn, that contributes to avoiding the overhead in the initial phase of the connection. Furthermore, the increased initial window mechanism [5] is also effective, especially for small amounts of data to be transmitted, which is commonly seen in such an application as the Internet-enabled mobile wireless devices. For large data transfer, on the other hand, the effect of this mechanism is negligible. [7] describes evaluations of this mechanism by measurements. Two segments of initial congestion window size is recommended in RFC2581[4]. RFC2414[5] also notes consideration on use of initial window size of more than two. Although the increased initial congestion window is experimental status, the impact of use of it to the majority of the Internet can be mitigated if the split architecture[36] is deployed that terminates TCP connection between the mobile node and the gateway and could set the CWND > 2 segments only to the TCP connection to the mobile node. Be careful on the Inamura, et. al. Expires January 3, 2002 [Page 5] Internet-Draft TCP over 2.5G and 3G Wireless Networks July 2001 implications caused by the use of the transport gateway, which includes end-to-end argument, mobility and security[36]. Due to the fact that the delayed Ack mechanism is the standard and that the increased initial window option is especially effective for the small data transfer that is common for mobile wireless devices, TCP over 2.5G/3G should use initial CWND (congestion window) = 2 segments. It may use CWND > 2 segments if a gateway is present. When applying CWND > 2 segments, it may also be applicable to the restart window. 3.1.3 Limited Transmit RFC3042[30], Limited Transmit, is extending Fast Retransmit/Fast Recovery for TCP connections with small congestion windows that is not enough to generate three duplicate acknowledgements. The mechanism calls for sending a new data segment in response to each of the first two duplicate acknowledgments that arrive at the sender. This mechanism is effective when congestion window size is small or if a large number of segments in a window are lost. This may reduce the retransmission due to TCP round trip timeout. As the discussion in Section 3.1.2, this mechanism is useful for small amounts of data to be transmitted. TCP over 2.5G/3G implementations should implement Limited Transmit. 3.1.4 Large MTU One of the link layer parameters is MTU (Maximum Transfer Unit). In TCP, the slow start mechanism tries to find an adequate rate for the network path. The larger MTU allows TCP to grow the congestion window faster [11], because the window is counted in unit of segments. In the link with error, smaller link PDU size is better in terms of the chance of successful transmission. With layer two ARQ and transparent link layer fragmentation, the network layer can enjoy larger MTU even in a relatively high BER (Bit Error Rate), condition. Without these features in the link, smaller MTU is better. TCP over 2.5G/3G should allow freedom for designers to choose MTU from a small value (such as 576B) to a large value (up to 1500B). 3.1.5 Path MTU discovery Path MTU discovery allows a sender to determine the maximum end-to-end transmission unit for a given routing path. RFC1191[21] and RFC1981[23] describe the MTU discovery procedure for IPv4 and IPv6 respectively. This allows TCP senders to employ larger segment sizes (without causing IP layer fragmentation) instead of assuming the default MTU. TCP over 2.5G/3G implementations should implement Path MTU Discovery. Path MTU Discovery requires intermediate routers Inamura, et. al. Expires January 3, 2002 [Page 6] Internet-Draft TCP over 2.5G and 3G Wireless Networks July 2001 to support the generation of the necessary ICMP messages. RFC1993[22] provides recommendations that may be relevant for some router implementations. 3.1.6 Selective Acknowledgments The selective acknowledgment option (SACK), RFC2018[8], is effective when multiple TCP segments are lost in a single TCP window [13] . In particular, if the end-to-end path has a large BDP and a certain amount of packet loss rate, the probability of multiple segment losses in a single window of data grows high. In such cases, SACK performs better than traditional and Reno TCP [9]. TCP over 2.5G/3G should support SACK. 3.1.7 Explicit Congestion Notification Explicit Congestion Notification, RFC2481[25], allows a TCP receiver to inform the sender of congestion in the network by setting the ECN-Echo flag; a receiver will set this flag on receiving an IP packet marked with the CE bit. The TCP sender MUST then reduce its congestion window. The use of ECN is believed to provide performance benefits [24]. TCP over 2.5G/3G may support ECN. RFC2481[25] also places requirements on intermediate routers (e.g. active queue management and setting of the CE bit in the IP header to indicate congestion). Thus the use of ECN on the TCP connections is dependent on the necessary support from the relevant routers. Inamura, et. al. Expires January 3, 2002 [Page 7] Internet-Draft TCP over 2.5G and 3G Wireless Networks July 2001 3.1.8 Summary Items Qualifier ---------------------------------------------------------------- Large window size based on end-to-end BDP Window scale option Window size>64KB [RFC1323] Large initial window (CWND = 2 segments) [RFC2581] Large initial window (CWND > 2 segments) Behind a gateway [RFC2414] Limited Transmit [RFC3042] Selective Acknowledgment option (SACK) [RFC2018] Path MTU discovery [RFC1191,RFC1981]M MTU larger than default IP MTU Explicit Congestion Notification(ECN) [RFC2481] 3.2 Applications We introduce wireless services deploying (or capable of deploying) the recommendation we discuss here. Net-enabled portable phones and wireless ISPs are the two major applications. 3.2.1 i-mode Mobile terminal users want to enjoy the Internet experience on their handset. This market is emerging and growing rapidly. A deployment example is i-mode [27], a wireless Internet service. As of this writing, it is the largest single wireless internet service in the world, with 25 million subscribers in Japan. The next version of i-mode that operates over W-CDMA, that is called FOMA [28], is launched at the end of May 2001. It deploys the profiled TCP that is described in this document. The browser embedded in the handset utilizes the higher speed of 3G infrastructure that can provide up to 384kbps packet mode service. From the perspective of transport layer, the underlying W-CDMA network can be viewed as a network with a relatively large BDP and jitter. The loss rate of IP packets is low due to the ARQ, but the recovery in the layer two appears as jitter to the higher layers. The i-mode infrastructure directly conveys IP packets to the gateway for accessing the Internet. In addition to the operation by the Inamura, et. al. Expires January 3, 2002 [Page 8] Internet-Draft TCP over 2.5G and 3G Wireless Networks July 2001 embedded browser, the i-mode handset can be connected to a computer, a PDA and the like as a wireless modem. In this mode, most of data communication facilities can be controlled via AT modem commands. The W-CDMA infrastructure, whose core network uses GPRS (General Packet Radio Service), can be viewed as a large PPP link to GGSN (Gateway GPRS Supporting Node). The other side of GGSN is connected to fixed networks of ISPs using, for example, leased lines. 3.2.2 WAP The WAP Forum [14] is an industry association that has developed standards for wireless information and telephony services on digital mobile phones and other wireless terminals. In order to address WAP functionalities for high speed networks such as 2.5G and 3G networks and to aim at convergence to the Internet standards, the WAP Forum has been addressing adoption of TCP as its transport protocol, benefiting from relevant documents and discussions within IETF and, in particular, its PILC working group. WAP Forum is releasing a new generation of specifications. The WAP specifications include a set of the recommended TCP options that is described in this submission. The specification of the profiled TCP is available for public review [20]. 3.2.3 Ricochet MCDN Network Metricom, Inc. is a high-speed wireless data company. Its high-speed Ricochet mobile access delivers user speeds of 128 kbps, and is currently available in 15 metropolitan areas and 15 airports in the United States serving over 50 million potential customers. Ricochet acts like, feels like, and works like a high-speed wired network connection. It provides wireless access to information from outside the confines of an office or any single location. Ricochet is a wide-area wireless packet data network. The architecture for the Ricochet system is based on Metricom's Micro Cellular Data Network (MCDN) technology. This architecture has seven physical components: 1) wireless modems or subscriber devices; 2) a cluster of MicroCells; 3) Wired Access Points; 4) a nation-wide wired backbone; 5) a MCDN Name Service; 6) a Network Management System; 7) and MCDN gateways. The MCDN system architecture is based on a mesh of MicroCells deployed throughout a metropolitan area and operates in accordance with FCC part 15.247 rules and regulations for the ISM band [26]. When the user's computing device attempts to negotiate a PPP connection to the network, the radio modem establishes a virtual connection, analogous to TCP, to the MCDN gateway, which ensures that all of the packets from the user's computing device are routed Inamura, et. al. Expires January 3, 2002 [Page 9] Internet-Draft TCP over 2.5G and 3G Wireless Networks July 2001 to the Internet. The Wired Access Point provides the actual connection from the wireless cloud to the wired Ethernet. The data is place onto a high bandwidth wired backbone and routed to a central collection point, the Network Interface Facility (NIF.) The user's device then appears to the rest of the Internet as if it is physically located at the PPP termination point. Inamura, et. al. Expires January 3, 2002 [Page 10] Internet-Draft TCP over 2.5G and 3G Wireless Networks July 2001 4. Open Issues Other ideas to enhance the performance of TCP over the 2.5G/3G networks may include the ROHC (RObust Header Compression) for TCP [18], RFC2309[17] (Active Queue Management). We have been interested in T/TCP (Transaction/TCP), RFC1644[16], because the Web browsing on a smart phone tends to require short TCP connection duration and small amount of data transfer. The pattern of such use is more transactional rather than streaming. Because T/TCP is regarded as being weak security-wise [35], and not widely deployed, we did not recommend T/TCP in this document. Experimental RFC2414[5] describes a mechism for using intial values of CWND greater than 2. This approach has not yet been proven safe for widespread use in the Internet. However, implementers are encouraged monitor research in this area (for example [15]) because larger initial values for CWND will reduce the time it takes to perform TCP data transfers. Eifel algorithm [19] is an enhancement to TCP's error recovery scheme. It eliminates the retransmission ambiguity, thereby solving the problems caused by spurious timeouts and spurious fast retransmits. It is promising for wireless networks where spurious retransmissions may occur, the algorithm can improve the end-to-end throughput, because it reduces the penalty of a spurious timeout to a single (in the common case) spurious retransmission. D-SACK (Duplicated SACK), RFC2883[29], specifies how to use the SACK option when acknowledging duplicate segments. Using D-SACK, sender can know what order the segments arrived and infer more precisely the cause for the situations where duplicate packets received, including early retransmit timeout. Because the delay-jitter seen in the 2.5G/3G networks may cause such early retransmit timeout, this extension can be useful for adjusting the RTO calculation to reduce the case of spurious retransmissions. We should watch more evaluation and deployment/standardization status of Eifel and D-SACK in the wireless environment. RFC2988[37] specifies standard algorithm to use to compute the retransmit timer in TCP. The RFC states that the TCP sender should set the initial RTO value less than three seconds. To avoid spurious time out in very first exchange of packets, subnetwork designer/operator should be carefull about the link layer behavior. The use of highly persistant ARQ and multiple hop of such links in the end-to-end path may result in too large delay. In general, subnetwork designers should minimize all three parameters delay, delay variance and packet loss) as much as possible [12]. Inamura, et. al. Expires January 3, 2002 [Page 11] Internet-Draft TCP over 2.5G and 3G Wireless Networks July 2001 5. Security Considerations In 2.5G/3G wireless network, data transmission in ciphertext is limited only over the air, but cleartext between RAN and core network. For the end to end security, IP security RFC2411[33] or TLS RFC2246[32] could be deployed. If you use the transport gateway as mentioned in Section 3.1.2, note that it introduces several issues which impact security, which includes the conflict with IPsec. For example, WAP protocol stack is considering to deploy TLS [31] because of its gateway architecture. Inamura, et. al. Expires January 3, 2002 [Page 12] Internet-Draft TCP over 2.5G and 3G Wireless Networks July 2001 References [1] Montenegro, G., Dawkins, S., Kojo, M., Magret, V. and N. Vaidya, "Long Thin Networks", RFC 2757, January 2000. [2] Third Generation Partnership Project, "3GPP Specifications", 1999, . [3] Third Generation Partnership Project, "RLC Protocol Specification (3G TS 25.322:)", 1999. [4] Allman, M., Paxson, V. and W. Stevens, "TCP Congestion Control", RFC 2581, April 1999. [5] Allman, M., Floyd, S. and C. Partridge, "Increased TCP's Initial Window", RFC 2414, September 1998. [6] Jacobson, V., Bdaden, R. and D. Borman, "TCP Extensions for High Performance", RFC 1323, May 1992. [7] Allman, M., "An Evaluation of TCP with Larger Initial Windows 40th IETF Meeting -- TCP Implementations WG. December", December 1997. [8] Mathis, M., Mahdavi, J., Floyd, S. and R. Romanow, "TCP Selective Acknowledgment Options", RFC 2018, October 1996. [9] Fall, K. and S. Floyd, "Simulation-based Comparisons of Tahoe, Reno, and SACK TCP", Computer Communication Review, 26(3) , July 1996. [10] Fairhurst, G. and L. Wood, "Link ARQ issues for IP traffic", Internet draft , November 2000, . [11] Dawkins, S. and G. Montenegro, "End-to-end Performance Implications of Slow Links", Internet draft , November 2000, . [12] Karn, P., Falk, A., Touch, J., Montpetit, M., Mahdavi, J., Montenegro, G., Grossman, D. and G. Fairhurst, "Advice for Internet Subnetwork Designers", Internet draft , November 2000, . Inamura, et. al. Expires January 3, 2002 [Page 13] Internet-Draft TCP over 2.5G and 3G Wireless Networks July 2001 [13] Dawkins, S., Montenegro, G., Magret, V., Vaidya, N. and M. Kojo, "End-to-end Performance Implications of Links with Errors", Internet draft , November 2000, . [14] Wireless Application Protocol, "WAP Specifications", 2000, . [15] Allman, M., "A Web Server's View of the Transport Layer", ACM Computer Communication Review 30(5), October 2000, . [16] Braden, R., "T/TCP -- TCP Extensions for Transactions", RFC 1644, July 1994. [17] Braden, R., Clark, D., Crowcroft, J., Davie, B., Deering, S., Estrin, D., Floyd, S., Jacobson, V., Minshall, G., Partridge, C., Peterson, L., Ramakrishnan, K., Shenker, S., Wroclawski, J. and L. Zhang, "Recommendations on Queue Management and Congestion Avoidance in the Internet", RFC 2309, April 1998. [18] IETF, "Robust Header Compression", 2001, . [19] Ludwig, R. and R. H. Katz, "The Eifel Algorithm: Making TCP Robust Against Spurious Retransmissions", ACM Computer Communication Review 30(1), January 2000, . [20] Wireless Application Protocol, "WAP Wireless Profiled TCP", WAP-225-TCP-20010331-p, April 2001, . [21] Mogul, J. and S. Deering, "Path MTU Discovery", RFC 1191, November 1990. [22] Knowles, S., "IESG Advice from Experience with Path MTU Discovery", RFC 1993, March 1993. [23] McCann, J., Deering, S. and J. Mogul, "Path MTU Discovery for IP version 6", RFC 1981, August 1996. [24] Hadi Salim, J. and U. Ahmed, "Performance Evaluation of Explicit Congestion Notification (ECN) in IP Networks", RFC 2884, july 2000. [25] Ramakrishnan, K. and S. Floyd, "A Proposal to add Explicit Inamura, et. al. Expires January 3, 2002 [Page 14] Internet-Draft TCP over 2.5G and 3G Wireless Networks July 2001 Congestion Notification (ECN) to IP", RFC 2481, January 1999. [26] FCC Rules and Regulations, "Part 15", October 1997. [27] NTT DoCoMo, Inc., "i-mode", 2001, . [28] NTT DoCoMo, Inc., "FOMA", 2001, . [29] Floyd, S., Mahdavi, J., Mathis, M. and M. Podolsky, "An Extension to the Selective Acknowledgement (SACK) Option for TCP", RFC 2883, July 2000. [30] Allman, M., Balakrishnan, H. and S. Floyd, "Enhancing TCP's Loss Recovery Using Limited Transmit", RFC 3042, January 2001. [31] Wireless Application Protocol, "WAP TLS Profile and Tunneling", WAP-219-TLS-20010411-p, May 2001, . [32] Dierks, T. and C. Allen, "The TLS Protocol Version 1.0", RFC 2246, January 1999. [33] Thayer, R., Doraswamy, N. and R. Glenn, "IP Security Document Roadmap", RFC 2411, November 1998. [34] Mitzel, D., "Overview of 2000 IAB Wireless Internetworking Workshop", RFC 3002, December 2000. [35] de Vivo, M., O. de Vivo, G., Koeneke, R and G. Isern, "Internet Vulnerabilities Related to TCP/IP and T/TCP", ACM Computer Communication Review 29(1), January 1999, . [36] Border, J., Kojo, M., Griner, J., Montenegro, G. and Z. Shelby, "Performance Enhancing Proxies Intended to Mitigate Link-Related Degradations", Internet draft , May 3 2001, . [37] Paxson, V. and M. Allman, "IP Security Document Roadmap", RFC 2988, November 2000. Inamura, et. al. Expires January 3, 2002 [Page 15] Internet-Draft TCP over 2.5G and 3G Wireless Networks July 2001 Authors' Addresses Hiroshi Inamura NTT DoCoMo, Inc. 3-5 Hikarinooka Yokosuka Shi, Kanagawa Ken 239-8536 Japan EMail: inamura@mml.yrp.nttdocomo.co.jp URI: http://www.nttdocomo.co.jp/ Gabriel Montenegro Sun Microsystems, Inc. EMail: gab@sun.com Max Hata NTT DoCoMo, Inc. EMail: hata@mml.yrp.nttdocomo.co.jp URI: http://www.nttdocomo.co.jp/ Masahiro Hara Fujitsu, Inc. EMail: mhara@FLAB.FUJITSU.CO.JP Joby James Motorola, Inc. 33-A, Ulsoor Road, Bangalore 560042 India EMail: joby@MIEL.MOT.COM William Gilliam Hewlett-Packard Company Cupertino, California EMail: wag@cup.hp.com Inamura, et. al. Expires January 3, 2002 [Page 16] Internet-Draft TCP over 2.5G and 3G Wireless Networks July 2001 Alan Hameed Fujitsu FNC, Inc. EMail: Alan.Hameed@fnc.fujitsu.com Reiner Ludwig Ericsson Research Ericsson Allee 1 52134 Herzogenrath Germany EMail: Reiner.Ludwig@Ericsson.com Rodrigo Garces Metricom EMail: RGarces@Metricom.com Peter Ford Microsoft EMail: peterf@Exchange.Microsoft.com Fergus Wills Openwave EMail: fergus.wills@openwave.com Inamura, et. al. Expires January 3, 2002 [Page 17] Internet-Draft TCP over 2.5G and 3G Wireless Networks July 2001 Appendix A. Acknowledgements The authors gratefully acknowledges the valuable advises from following individuals: Gorry Fairhurst (gorry@erg.abdn.ac.uk) Mark Allman (mallman@grc.nasa.gov) Aaron Falk (afalk@PanAmSat.com) Inamura, et. al. Expires January 3, 2002 [Page 18] Internet-Draft TCP over 2.5G and 3G Wireless Networks July 2001 Full Copyright Statement Copyright (C) The Internet Society (2001). All Rights Reserved. This document and translations of it may be copied and furnished to others, and derivative works that comment on or otherwise explain it or assist in its implementation may be prepared, copied, published and distributed, in whole or in part, without restriction of any kind, provided that the above copyright notice and this paragraph are included on all such copies and derivative works. However, this document itself may not be modified in any way, such as by removing the copyright notice or references to the Internet Society or other Internet organizations, except as needed for the purpose of developing Internet standards in which case the procedures for copyrights defined in the Internet Standards process must be followed, or as required to translate it into languages other than English. The limited permissions granted above are perpetual and will not be revoked by the Internet Society or its successors or assigns. This document and the information contained herein is provided on an "AS IS" basis and THE INTERNET SOCIETY AND THE INTERNET ENGINEERING TASK FORCE DISCLAIMS ALL WARRANTIES, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO ANY WARRANTY THAT THE USE OF THE INFORMATION HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Acknowledgement Funding for the RFC editor function is currently provided by the Internet Society. Inamura, et. al. Expires January 3, 2002 [Page 19]