Energy Efficient Fragment Recovery Techniques for Low-power and Lossy Networks
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Energy Efficient Fragment Recovery Techniques for Low-power and Lossy Networks

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    Energy Efficient Fragment Recovery Techniques for Low-power and Lossy Networks Energy Efficient Fragment Recovery Techniques for Low-power and Lossy Networks Presentation Transcript

    • Energy Efficient Fragment Recovery Techniques for Low-power and Lossy Networks Ahmed Ayadi , Pascal Thubert† IT/TELECOM Bretagne Rennes, France † Cisco Systems 12 January 2011Ahmed Ayadi (IT/TELECOM Bretagne) IP and Wireless Sensor Networks’2011 Lyon, 12-13 January 2011 1 / 19
    • Motivation The IETF Working Group 6LoWPAN has recently introduced an adaptation layer that provides header compression and fragmentation/reassembly mechanisms to allow sending/receiving IPv6 packets over LLNs (e.g., IEEE 802.15.4), The IPv6 length is larger than 1280 bytes while an 802.15.4 frame can have a payload limited to 74 bytes A IPv6 packet might end up fragmented into as many as 18 fragments at the 6LoWPAN layer. If a single one of those fragments is lost in transmission, all fragments must be resent.Ahmed Ayadi (IT/TELECOM Bretagne) IP and Wireless Sensor Networks’2011 Lyon, 12-13 January 2011 2 / 19
    • Outline 1 Link Layer Error Control Mechanisms 2 Simple Fragment Forward and Recovery Fragment Recovery proposal Recoverable Fragment: Dispatch type and Header Fragment Acknowledgement Dispatch type and Header An SFFR scenario 3 Performance evaluation Impact of SFFR on the energy consumption of TCP Impact of SFFR on the energy consumption of UDP The SFFR rounds improve the energy efciency When it is better to used SFFR? 4 Conclusion and perspectivesAhmed Ayadi (IT/TELECOM Bretagne) IP and Wireless Sensor Networks’2011 Lyon, 12-13 January 2011 3 / 19
    • Link Layer Error Control Mechanisms Automatic Repeat reQuest (ARQ) ARQ uses the cyclic redundancy check (CRC) error-detecting code that is added to the data: the receiver uses the error-detecting code number to check the integrity of the received data After receiving a correct frame, the receiver replies by an ACK. If the sender does not receive an ACK before the timeout, it re-transmits the frame/packet until the sender receives an acknowledgment or exceeds a predefined number of re-transmissions. Forward Error Correction (FEC) The main idea of FEC is to add redundancy to the original frame, to allow the destination node to detect and correct some bit errors. The FEC algorithm adds (α × K) redundancy bits to form a frame of length D. FEC can adapt to multihop by adopting more redundancy bits, but.Ahmed Ayadi (IT/TELECOM Bretagne) IP and Wireless Sensor Networks’2011 Lyon, 12-13 January 2011 4 / 19
    • Link Layer Error Control Mechanisms If the wireless network becomes very lossy, ARQ would increase the transmission delay between the source and the receiver. Using ARQ, the source continues to send the remaining fragments, even if one fragment is already lost. The reliable transport layer (e.g., TCP) MUST retransmit the segment and thus all the fragments. FEC requires more CPU energy and the amount of overhead is difficult to predict for the rapidly changing conditions of real-world LLNs .Ahmed Ayadi (IT/TELECOM Bretagne) IP and Wireless Sensor Networks’2011 Lyon, 12-13 January 2011 5 / 19
    • Simple Fragment Forward and Recovery SFFR is a new end-to-end recovery algorithm recently proposed by Thubert et Hui for 6LoWPANs. SFFR allows the sender to recover easily and quickly the lost fragments. SFFR uses the datagram ”tag” as a switchable label. SFFR minimize the acknowledgement overhead by applying a compressed acknowledgement bitmap SFFR takes into support the out-of-order fragment delivery.Ahmed Ayadi (IT/TELECOM Bretagne) IP and Wireless Sensor Networks’2011 Lyon, 12-13 January 2011 6 / 19
    • Fragment Recovery proposal SFFR uses 32 bits as SACK Bitmap SFFR defines 4 new dispatch types: RFRAG: regular fragments, RFRAG-AR: the last fragment which request an acknowledgment, RFRAG-ACK: an new fragment that inform the sender about the received fragments form the lost one. Figure: Additional Dispatch Value Bit PatternsAhmed Ayadi (IT/TELECOM Bretagne) IP and Wireless Sensor Networks’2011 Lyon, 12-13 January 2011 7 / 19
    • Recoverable Fragment: Dispatch type and Header Upon the first fragment, the routers lay an label along the path that is followed by that fragment (that is IP routed), and all further fragments are label switched along that path. Figure: Recoverable Fragment Dispatch type and HeaderAhmed Ayadi (IT/TELECOM Bretagne) IP and Wireless Sensor Networks’2011 Lyon, 12-13 January 2011 8 / 19
    • Fragment Acknowledgement: Dispatch type and Header A 32 bits uncompressed bitmap is obtained by prepending zeroes to the XXX in the pattern below. else, Figure: Compressed acknowledgement bitmap encodingAhmed Ayadi (IT/TELECOM Bretagne) IP and Wireless Sensor Networks’2011 Lyon, 12-13 January 2011 9 / 19
    • Expanded bitmap examples (a) Expanding 1 octet encoding (b) Expanding 3 octets encoding Figure: Expanded bitmap encodingAhmed Ayadi (IT/TELECOM Bretagne) IP and Wireless Sensor Networks’2011 Lyon, 12-13 January 2011 10 / 19
    • An SFFR scenario Sender Receiver RFRA G RFRA G RFRA G-AR . RFRAG-ACK RFRA G-AR RFRAG-ACK Figure: End-to-end simple fragment forwarding and recoveryAhmed Ayadi (IT/TELECOM Bretagne) IP and Wireless Sensor Networks’2011 Lyon, 12-13 January 2011 11 / 19
    • Parameters Table: Network parameters. Parameter Value Hop number 5 Application data size 1048 kbytes TCP MSS/ UDP payload size 512/1024 bytes NHC header 1 bytes TCPHC header 8 bytes 6LoWPAN header 3 bytes IEEE 802.15.4 header 23 bytes IEEE 802.15.4 acknowledgment size 10 bytes Transmit Energy 0.24 µJ/bit Receive Energy 0.21 µJ/bitAhmed Ayadi (IT/TELECOM Bretagne) IP and Wireless Sensor Networks’2011 Lyon, 12-13 January 2011 12 / 19
    • Impact of SFFR on the energy consumption of TCP (1/2) 103 103 No ARQ, No SFFR No ARQ, No SFFR No ARQ, SFFR No ARQ, SFFR ARQ=3, No SFFR ARQ=3, No SFFR Consumed energy (J) Consumed energy (J) ARQ=3, SFFR ARQ=3, SFFR 102 102 10−5 10−4 10−3 10−5 10−4 10−3 BER BER (a) MSS = 1024 bytes (b) MSS = 512 bytes Figure: Energy Consumption of an TCP data transfer with vs without SFFR (number of hops is equal to five).Ahmed Ayadi (IT/TELECOM Bretagne) IP and Wireless Sensor Networks’2011 Lyon, 12-13 January 2011 13 / 19
    • Impact of SFFR on the energy consumption of TCP (2/2) 103 1024, No SFFR 1024, SFFR 512, No SFFR Consumed Energy (J) 512, SFFR 102 2 4 6 8 10 Number of hops Figure: Energy Consumption of an TCP data transfer with vs without SFFR SFFR (ARQ=3, B = 5 × 10−4 ).Ahmed Ayadi (IT/TELECOM Bretagne) IP and Wireless Sensor Networks’2011 Lyon, 12-13 January 2011 14 / 19
    • Impact of SFFR on the energy consumption of UDP (1/2) control congestion 10−1 10−1 Energy Efficiency Energy Efficiency 10−2 10−2 No ARQ, No SFFR No ARQ, No SFFR No ARQ, SFFR No ARQ, SFFR ARQ=3, No SFFR ARQ=3, No SFFR ARQ=3, SFFR ARQ=3, SFFR 10−3 −5 10−3 −5 10 10−4 10−3 10 10−4 10−3 BER BER (a) UDP payload size = 1024 bytes (b) UDP payload size = 512 bytes Figure: Energy Efficiency of an UDP data transfer with vs without SFFR.Ahmed Ayadi (IT/TELECOM Bretagne) IP and Wireless Sensor Networks’2011 Lyon, 12-13 January 2011 15 / 19
    • Impact of SFFR on the energy consumption of UDP (2/2) 1024, No SFFR 1024, SFFR 512, No SFFR 512, SFFR Energy Efficiency 10−1 10−2 2 4 6 8 10 Number of hops Figure: Energy Efficiency of an UDP data trasfer with and without SFFR (ARQ=3, B = 5 × 10−4 ).Ahmed Ayadi (IT/TELECOM Bretagne) IP and Wireless Sensor Networks’2011 Lyon, 12-13 January 2011 16 / 19
    • The SFFR rounds improve the Energy Efficiency 10−1 Energy Efficiency 10−2 No SFFR SFFR=1 SFFR=2 SFFR=3 10−3 −5 10 10−4 10−3 BER Figure: Energy Efficiency of an UDP data transfer with different SFFR rounds (ARQ=3, 5 hops).Ahmed Ayadi (IT/TELECOM Bretagne) IP and Wireless Sensor Networks’2011 Lyon, 12-13 January 2011 17 / 19
    • When it is better to used SFFR? 10−3 MSS=256 BER MSS=512 MSS=768 MSS=1024 MSS=1280 10−4 2 4 6 8 10 Number of Hops (h) Figure: SFFR in a multi-hop TCP transmission: prefer SFFR above the curves (ARQ=3).Ahmed Ayadi (IT/TELECOM Bretagne) IP and Wireless Sensor Networks’2011 Lyon, 12-13 January 2011 18 / 19
    • Conclusion and perspectives Conclusion SFFR is a new energy-efficient end-to-end fragment recovery, Simulations results show that SFFR reduces significantly the consumed energy. Perspectives Congestion control due to fragmentation, Reduces the PER of RFRAG-AR and RFRAG-ACK.Ahmed Ayadi (IT/TELECOM Bretagne) IP and Wireless Sensor Networks’2011 Lyon, 12-13 January 2011 19 / 19