# US 10,374,758 B2 · Method and apparatus for controlling handshake in a packet transmission network > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,374,758 B2 - Document ID: US10374758B2 - Status: Granted - Kind: B2 - Application number: 15/303,533 - Filed: 2015-04-10 - Published: 2017-02-02 - Granted: 2019-08-06 - Earliest claimed: 2014-04-15 - Assignees: Signify Holding B.V. - Applicants: Signify Holding B.V. - Inventors: Fulong Ma; Sye Long Keoh - Web page: https://patentgrep.com/patent/US10374758B2 ## CPC - H04L 69/169: {Special adaptations of TCP, UDP or IP for interworking of IP based networks with other networks (protocols for interworking, protocol conversion H04L69/08)} - H04L 1/0016: {involving special memory structures, e.g. look-up tables} - H04L 1/203: {Details of error rate determination, e.g. BER, FER or WER} - H04L 1/206: {for modulated signals} - H04L 5/0055: {Physical resource allocation for ACK/NACK (for physical mapping arrangements in ARQ protocols H04L1/1861)} - H04L 69/164: Adaptation or special uses of UDP protocol - H04L 69/168: specially adapted for link layer protocols, e.g. asynchronous transfer mode [ATM], synchronous optical network [SONET] or point-to-point protocol [PPP] - H04W 24/02: Arrangements for optimising operational condition - H04L 1/0002: {by adapting the transmission rate} - H04L 1/16: in which the return channel carries supervisory signals, e.g. repetition request signals - H04L 67/12: specially adapted for proprietary or special-purpose networking environments, e.g. medical networks, sensor networks, networks in vehicles or remote metering networks - H04L 69/326: in the transport layer [OSI layer 4] (H04L69/16 takes precedence) - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) - H04W: WIRELESS COMMUNICATION NETWORKS (broadcast communication H04H; communication systems using wireless links for non-selective communication, e.g. wireless extensions H04M1/72) ## Abstract The present invention relates to a method and apparatus for controlling a handshake operation. Datagram Transport Layer Security (DTLS) is an important secure protocol in the IP based Internet of things. The performance of DTLS handshake can be significantly affected by network status, traffic and packet loss rate, etc. It is therefore suggested evaluating a package loss rate and estimating causes of packet loss. Then, a DTLS handshake strategy may be changed adaptively based on the detection of packet loss and network status. As a result, the successful rate and delay of DTLS handshake can be improved. An acknowledgement and a non-acknowledgement mode may be used in a hybrid way to evaluate the package loss rate and estimate causes of packet loss and eventually improve performance of DTLS handshake. ## Claims ### Claim 1 An apparatus for controlling handshake in a packet transmission network, the apparatus comprising: a processor to detect packet loss in a handshake-based packet transmission and for estimating a cause of the detected packet loss, and change a handshake strategy of the packet transmission based on the estimated causes, wherein the processor estimates a packet loss rate caused by said estimated cause and to estimate a remaining time for handshake based on the packet loss rate, to compare the remaining time with a predetermined handshake timeout, changes the handshake strategy upon determination that the estimated remaining time is larger than the predetermined handshake timeout, estimates a wireless loss when the detected packet loss is distributed randomly or when delays between each received packet and respective subsequent packet of the received continuous packets are determined by the processor to be equal, and wherein, when the processor has estimated a wireless loss, then the processor estimates a packet loss rate, estimates a remaining time for handshake based on the packet loss rate, to compare the remaining time with a predetermined handshake timeout, and increases a transmission rate of the packet transmission proportional to a ratio between the estimated remaining time for handshake and the predetermined handshake timeout if the estimated remaining time is larger than the predetermined handshake timeout. ### Claim 2 (depends on 1) The apparatus of claim 1, wherein the processor detects the packet loss based on a sequence of received packets. ### Claim 3 (depends on 2) The apparatus of claim 2, wherein the processor detects the packet loss based on a sequence of ClientHello messages of a DTLS handshake signaling. ### Claim 4 (depends on 1) The apparatus of claim 1, wherein the detector processor estimates a congestion loss as the cause of the detected packet loss if a delay between received continuous packets varies or if there is a disorder between received continuous packets. ### Claim 5 (depends on 4) The apparatus of claim 4, wherein, if the processor has estimated a congestion loss, then the processor estimates a packet loss rate, estimate a remaining time for handshake based on the packet loss rate, to compare the remaining time with a predetermined handshake timeout, and to increase a transmission interval and decrease a transmission rate of the packet transmission if the estimated remaining time is larger than the predetermined handshake timeout. ### Claim 6 (depends on 1) The apparatus of claim 1, wherein, when the processor has estimated a congestion loss and when the apparatus is located on a server side of the packet transmission, then the processor notifies a client side of the packet transmission to prolong the handshake timeout. ### Claim 7 (depends on 1) The apparatus of claim 1, wherein the processor estimates the packet loss rate by calculating a total transmission time until receiving the last acknowledgement of a predetermined handshake message and using the equation P L = 1 - 2 N s , wherein NS denotes the calculated total transmission time and PL denotes the estimated packet loss rate. ### Claim 8 (depends on 6) The apparatus of claim 6, wherein said predetermined handshake message is a ClientHello message of a DTLS handshake signaling. ### Claim 9 A method of controlling handshake in a packet transmission network, the method performed by a processor comprising: detecting packet loss in a handshake-based packet transmission; estimating causes of the detected packet loss; estimating a packet loss rate caused by said estimated cause; estimating a remaining time for handshake based on the packet loss rate; comparing the remaining time with a predetermined handshake timeout; and if the estimated remaining time is larger than the predetermined handshake timeout, changing a handshake strategy of the packet transmission based on the estimated causes, and estimating a wireless loss if the detected packet loss is distributed randomly or if delays between each received packet and respective subsequent packet of the received continuous packets are determined by the processor to be equal, and when estimated, by the processor that, a wireless loss exists, estimating a packet loss rate, estimating a remaining time for handshake based on the packet loss rate, to compare the remaining time with a predetermined handshake timeout, and increasing a transmission rate of the packet transmission proportional to a ratio between the estimated remaining time for handshake and the predetermined handshake timeout if the estimated remaining time is larger than the predetermined handshake timeout. ### Claim 10 (depends on 9) A computer program product comprising a plurality of program code portions, stored in a non-transitory computer readable medium, for carrying out the method of claim 9 when run on a computer device. ### Claim 11 (depends on 9) The method according to claim 9, further comprising the following step: if the estimated remaining time is smaller than the predetermined handshake timeout, then do not change a handshake strategy of the packet transmission based on the estimated causes. ### Claim 12 (depends on 1) The apparatus of claim 1, wherein the processor does not change the handshake strategy upon determination that the estimated remaining time is smaller than the predetermined handshake timeout. ### Claim 13 (depends on 5) The apparatus of claim 5, wherein the processor estimates the packet loss rate by calculating a total transmission time until receiving the last acknowledgement of a predetermined handshake message and using the equation P L = 1 - 2 N s , wherein NS denotes the calculated total transmission time and PL denotes the estimated packet loss rate.