IRTF ANS Working Group J. Lee Internet-Draft S. Singh Expires: March 13, 2004 Y. Roh SAMSUNG AIT September 13, 2003 Interlayer Interactions and Performance in Wireless Ad Hoc Network draft-irtf-ans-interlayer-performance-00.txt 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. This Internet-Draft will expire on March 13, 2004. Copyright Notice Copyright (C) The Internet Society (2003). All Rights Reserved. Abstract Interlayer interaction is the inter-communication between different layers of the network protocol stack. This document provides interlayer interaction metrics and the related information exchange to enhance performance of the wireless ad hoc networks. It also points out the importance of interlayer interaction in determining the scalability of a method. Lee,Singh,Roh Expires March 13, 2004 [Page 1] Internet-Draft Interlayer interaction September 2003 Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Implications of interlayer interactions . . . . . . . . . . 4 3. Interaction metrics . . . . . . . . . . . . . . . . . . . . 5 3.1 Interactions between Lower layer and routing layer . . . . . 5 3.1.1 Signal strength . . . . . . . . . . . . . . . . . . . . . . 5 3.1.2 Interface identifiers . . . . . . . . . . . . . . . . . . . 5 3.1.3 Link failure detection time . . . . . . . . . . . . . . . . 5 3.1.4 Interference . . . . . . . . . . . . . . . . . . . . . . . . 5 3.1.5 Congestion . . . . . . . . . . . . . . . . . . . . . . . . . 6 3.1.6 Bandwidth . . . . . . . . . . . . . . . . . . . . . . . . . 6 3.1.7 SNR information . . . . . . . . . . . . . . . . . . . . . . 6 3.1.8 Link type information . . . . . . . . . . . . . . . . . . . 6 3.2 Interactions between lower layer and transport layer . . . . 6 3.2.1 TCP window size . . . . . . . . . . . . . . . . . . . . . . 7 3.2.2 Link capacity . . . . . . . . . . . . . . . . . . . . . . . 7 3.2.3 The number of retransmissions at MAC layer . . . . . . . . . 7 3.2.4 Link status notification . . . . . . . . . . . . . . . . . . 7 4. Security Considerations . . . . . . . . . . . . . . . . . . 8 5. Future works . . . . . . . . . . . . . . . . . . . . . . . . 9 References . . . . . . . . . . . . . . . . . . . . . . . . . 10 Informative References . . . . . . . . . . . . . . . . . . . 11 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . 11 Intellectual Property and Copyright Statements . . . . . . . 12 Lee,Singh,Roh Expires March 13, 2004 [Page 2] Internet-Draft Interlayer interaction September 2003 1. Introduction Ad hoc networks are infrastructure-less, multi-hop routing, wireless mobile networks formed spontaneously. Multi-hop routing, random movement of the nodes and other features unique to ad hoc networks results in lots of control signal overhead for route discovery and maintenance. This is highly unacceptable in bandwidth-constrained ad hoc networks. Usually these devices have limited computing resources and severe energy constraints. Due to these characteristics, there is lot of research work happening in the performance optimization of ad hoc networks. However, most of the research works are based on optimization at individual layer. [10] indicates that optimizing a particular layer might improve the performance of that layer locally but might produce non-intuitive side effects that will degrade the overall system performance. This draft briefly summarizes the interlayer interaction metrics, points to the information to be exchanged and the benefits of such information exchange between lower layer, routing layer and transport layer. This is useful to design and standardize an adaptive architecture that can exploit the interdependencies among link, medium access, network and application protocols. The architecture where each layer of the protocol stack responds to the local variations as well as to the information from other layers is a major challenge. Lee,Singh,Roh Expires March 13, 2004 [Page 3] Internet-Draft Interlayer interaction September 2003 2. Implications of interlayer interactions Currently ad hoc routing protocols are researched to work mainly on the network layer. It guarantees the independency of the network layer. However each layer need to do redundant processing and unnecessary packet exchange to get information that is easily available to other layers. This increases control signals resulting in wastage of bandwidth, packet collision, etc. By using interlayer interaction, different layers can share locally available information. This will result in substantial amount of performance improvement. Any method is scalable with respect to a (parameter, metric, environment) triple [14]. The interlayer interactions are nothing but the interactions among various environmental parameters. These interactions may affect the fairness of the scalability comparison between different methods. Thus it is important to standardize these parameters as well as interactions among them. Ad hoc network protocol architecture can give optimized performance by exploiting the environmental parameters information flow across different layers. Lee,Singh,Roh Expires March 13, 2004 [Page 4] Internet-Draft Interlayer interaction September 2003 3. Interaction metrics Interlayer interactions schemes that can support adaptability and optimization of the routing protocols are needed. We need to treat the entire stack as a single algorithmic construct in order to improve the performance. Such optimized routing protocol can discover and maintain the routes based on current link status, traffic congestion, signal strength etc. There is need for a general framework to improve performance in scalable ad hoc network. 3.1 Interactions between Lower layer and routing layer 3.1.1 Signal strength Usually routing layer is not concerned with signal strength related information handling. Lower layer takes care of signal strength related issues. Signal strength can be useful to know a nodes neighbor, the link to select for best effort packet forwarding etc. Only the link with signal strength above the threshold value can forward the packet.Routing algorithm can exploit signal characteristics related information for such benefits. 3.1.2 Interface identifiers To reduce overhead and bandwidth consumption due to large packet size, lower layer identifier is useful e.g. in source routing based protocols such as DSR, flow state extension is determined to reduce the packet size. If a node uses flow state extension, previous and next nodes interface identifier is recorded in the flow table. 3.1.3 Link failure detection time MAC layer has to go through multiple transmissions before concluding about the link failure resulting in time gap between the occurrence of link failure and its determination. This detection time increases with increasing load in the network. Periodic beacons at the routing layer can be used to reduce this time gap. Lee,Singh,Roh Expires March 13, 2004 [Page 5] Internet-Draft Interlayer interaction September 2003 3.1.4 Interference There is some delay involved between the time when RTS packet is sent and when data packet is received. This delay is high due to the contention of the channel in the region where there is lot of interference from other nodes. Thus interference awareness at the network layer discourages new routes from using such links. 3.1.5 Congestion Delay arising due to queuing of the packet at the MAC layer is a measure of congestion in a node. Congestion aware routing algorithm avoids nodes with large number of queued packets in its buffer. 3.1.6 Bandwidth A link with high bandwidth can naturally carry more traffic. Thus bandwidth aware routing algorithm assigns more route to higher bandwidth link. This helps in uniform link utilizations. 3.1.7 SNR information Transmission rate can be adjusted based on the number of errors in the received packets. At the physical layer, channel estimation is performed to obtain the instantaneous SNR of a link. A transmitter then chooses a transmission rate based on the estimated SNR value. This in turn affects the packet delay of the link. At the network layer, routing decisions are made based on the packet delay associated with each link. The routing decisions in turn affect the offered load distribution in the network and impact the packet delay, transmission rate, and SNR on individual link. 3.1.8 Link type information Some routing protocols (such as AODV) assume that all links between originating node and destination node are symmetric links. So, during route discovery, an additional notification method should be added to efficiently discover the path between source and destination. 3.2 Interactions between lower layer and transport layer Lee,Singh,Roh Expires March 13, 2004 [Page 6] Internet-Draft Interlayer interaction September 2003 3.2.1 TCP window size If TCP sends more packets, probability of false link failures increases. As a result of this, link failures lead to dropping of packets, route failures, unnecessary slow start initiation at TCP sender, possible timeout at TCP sender, and finally decreased overall throughput. Limiting Max. TCP window size results in a reduction of false link failures and throughput improvements. 3.2.2 Link capacity Transport layer protocol such as TCP has its own flow control adapted to network status. Ad hoc networks consist of wireless links with bandwidth constraints. If there is an indication for link overflow at link layer, transport layer can control the sending rate before network congestion in advance. 3.2.3 The number of retransmissions at MAC layer Increasing the number of retransmission results in i) increasing the probability of successful frame transfer, ii) reducing the probability of false link failures, iii) increases a link failure detection time. However, that gives rise to a side effect such as an increasing end-to-end delay and degrading network performance due to TCP RTO timeout. To solve these problems, the notification/feedback from link layer to transport layer is needed to prevent the initiation of congestion control at transport layer. 3.2.4 Link status notification In Ad hoc networks, performance degradation happens mainly due to node mobility. When lower layer detects link failure, a feedback/ notification is needed to prevent packet losses during route re-discovery. If any notification/feedback is not provided, upstream node of failed link must cache on-flight packet. This may cause buffer overflow and waste network resources. Lee,Singh,Roh Expires March 13, 2004 [Page 7] Internet-Draft Interlayer interaction September 2003 4. Security Considerations This document does not specifically address any security concerns. This document does assume that all layers in the node communicate with other layers without any security considerations. But the security concern involved in it must be considered appropriately. Lee,Singh,Roh Expires March 13, 2004 [Page 8] Internet-Draft Interlayer interaction September 2003 5. Future works This document briefly summarizes the interaction metrics. More detail information is needed about these metrics. Also the exact information flow between lower layer and routing layer is needed. How the routing layer or lower layer should use information received from lower layer or routing layer and its effect on performance optimization remain a challenge to achieve. Lee,Singh,Roh Expires March 13, 2004 [Page 9] Internet-Draft Interlayer interaction September 2003 References [1] W. H. Yuen, H. Lee, and T. D. Andersen, "A Simple and Effective Cross Layer Networking System for Mobile Ad Hoc Networks," Proc. of IEEE PIMRC'02, pp. 1952-1956, Sep. 2002 [2] J. Li, C. Blake, D. De Couto, H. I. Lee, and R. Morris, "Capacity of Ad Hoc Wireless Networks", Proc. of ACM Mobicomí¯01, pp. 61- 69, July 2001 [3] Johnson, D., Perkins, C. and J. Arkko, "Mobility Support in IPv6", draft-ietf-mobileip-ipv6-24 (work in progress), July 2003. [3] O. Dousse, F. Baccelli, and P. Thiran, "Impact of interferences on connecitivity in ad hoc networks", Proc. of IEEE Infocom'03, Vol. 3, pp. 1724-1733, March 2003 [4] S. Roy, D. Saha, S. Bandyopadhyay, T. Ueda, and S. Tanaka, "A Network-Aware MAC and Routing Protocol for Effective Load Balancing in Ad Hoc Wireless Networks with Directional Antenna", Proc. of ACM MobiHoc'03, pp. 88-97, June 2003 [5] C. Barrett, M. Drozda, A. Marathe, M. V. Marathe, "Characterizing the interaction Between Routing and MAC Protocols in Ad-Hoc Networks", Proc. of ACM MobiHoc'02, pp. 92-103, June 2002 [6] M. Takai, J. Martin, and R. Bagrodia, "Effects of Wireless Physical Layer Modeling in Mobile Ad Hoc Networks", Proc. of ACM MobiHoc'01, pp. 87-94, Oct. 2001 [7] D. Perkins, H. Hughes, and C. Owen, "Factors affecting the performance of ad hoc networks", Proc. of IEEE ICC'02 Vol. 4, pp. 2048-2052, April 2002 [8] R. Jiang, V. Gupta, and C. V. Ravishankar, "Interactions Between TCP and the IEEE 802.11 MAC Protocol", Proc. of IEEE DISCEXí¯03, April 2003 [9] A. J. Goldsmith and S. B. Wicker, "Design Challenges for Energy- constrained Ad Hoc Wireless Networks", IEEE Wireless Comm. Mag., Lee,Singh,Roh Expires March 13, 2004 [Page 10] Internet-Draft Interlayer interaction September 2003 Vol. 9, No. 4, pp. 8-27, Aug. 2002 [10] E. M. Royer, S. J. Lee, and C. E. Perkins, "The effects of MAC protocols on ad hoc networks communication", Proc. of IEEE WCNC'00, Vol. 2, pp. 543-548, Sept. 2000 [11] A. Safwat, H. Hassanein, and H. Mouftah, "Optimal cross-layer designs for energy-efficient wireless ad hoc and sensor networks", Proc. of IEEE IPCCC'03, pp. 123-128, 2003 [12] A. Misra and S. Banerjee, "MRPC: maximizing network lifetime for reliable routing in wireless environments", Proc. of IEEE WCNC'02, Vol. 2, pp. 800-806, March 2002 [13] M. Grossglauser and D. C. Tse, "Mobility Increases the Capacity of Ad Hoc Wireless Networks", IEEE/ACM Trans. On Networking, Vol. 10, No. 4, pp. 477-486, Aug. 2002 [14] O. Arpacioglu, T. Small, Z. J. Haas, í—Notes on Scalability of Wireless Ad Hoc Networksí˜, , August, 2003 Authors' Addresses Ji-Hoon Lee SAMSUNG Advanced Institute of Technology i-Networking Laboratory San 14-1, Nongseo-ri, Giheung-eup Yongin-si, Gyeonggi-do 449-712 KOREA Phone: +82 31 280 9552 EMail: vincent.lee@samsung.com Shubhranshu Singh SAMSUNG Advanced Institute of Technology i-Networking Laboratory San 14-1, Nongseo-ri, Giheung-eup Yongin-si, Gyeonggi-do 449-712 KOREA Phone: +82 31 280 9552 EMail: shubhranshu@samsung.com Yong-Sung Roh SAMSUNG Advanced Institute of Technology i-Networking Laboratory San 14-1, Nongseo-ri, Giheung-eup Yongin-si, Gyeonggi-do 449-712 KOREA Phone: +82 31 280 9593 EMail: yongsung.roh@partner.samsung.com Comments Please send comments to shubhranshu@samsung.com Lee,Singh,Roh Expires March 13, 2004 [Page 11] Internet-Draft Interlayer interaction September 2003 Intellectual Property Statement The IETF takes no position regarding the validity or scope of any intellectual property or other rights that might be claimed to pertain to the implementation or use of the technology described in this document or the extent to which any license under such rights might or might not be available; neither does it represent that it has made any effort to identify any such rights. Information on the IETF's procedures with respect to rights in standards-track and standards-related documentation can be found in BCP-11. Copies of claims of rights made available for publication and any assurances of licenses to be made available, or the result of an attempt made to obtain a general license or permission for the use of such proprietary rights by implementors or users of this specification can be obtained from the IETF Secretariat. The IETF invites any interested party to bring to its attention any copyrights, patents or patent applications, or other proprietary rights which may cover technology that may be required to practice this standard. Please address the information to the IETF Executive Director. Full Copyright Statement Copyright (C) The Internet Society (2003). 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 assignees. 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 Lee,Singh,Roh Expires March 13, 2004 [Page 12] Internet-Draft Interlayer interaction September 2003 HEREIN WILL NOT INFRINGE ANY RIGHTS OR ANY IMPLIED WARRANTIES OF MERCHANTABILITY OR FITNESS FOR A PARTICULAR PURPOSE. Acknowledgment Funding for the RFC Editor function is currently provided by the Internet Society. Lee,Singh,Roh Expires March 13, 2004 [Page 13]