# US 8,751,865 B2 · Network-based service for the repair of IP multicast sessions > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,751,865 B2 - Document ID: US8751865B2 - Status: Granted - Kind: B2 - Application number: 13/954,546 - Filed: 2013-07-30 - Published: 2013-11-28 - Granted: 2014-06-10 - Earliest claimed: 1999-03-17 - Assignees: AT&T Intellectual Property II, L.P. - Applicants: AT&T Intellectual Property II, L.P. - Inventors: Nicholas Frank Maxemchuk; David McManamon; David Hilton Shur; Aleksandr Zelezniak - Web page: https://patentgrep.com/patent/US8751865B2 ## CPC - H04L 12/1868: {Measures taken after transmission, e.g. acknowledgments} - G06F 11/1443: {Transmit or communication errors} - H04L 12/1863: {comprising mechanisms for improved reliability, e.g. status reports (arrangements for detecting or preventing errors by carrying supervisory signal the return channel H04L1/16)} - H04L 12/1886: {with traffic restrictions for efficiency improvement, e.g. involving subnets or subdomains} - H04L 43/0847: {Transmission error} - H04L: TRANSMISSION OF DIGITAL INFORMATION, e.g. TELEGRAPHIC COMMUNICATION (arrangements common to telegraphic and telephonic communication H04M) - G06F: ELECTRIC DIGITAL DATA PROCESSING (computer systems based on specific computational models G06N) ## Abstract A system and method are disclosed for the repair of IP multicast sessions. A repair server polls multiple transmit servers to accumulate as many of the packets missing from the multicast session as possible. A network includes a source of multicast packets in a multicast session and a plurality of multicast recipients in that session. A repair server in the network provides the packets it receives to the recipients. The repair server includes a missing packet detector. There is a plurality of retransmit servers in the network buffering portions of the packets they respectively receive during the session. The repair server maintains an ordered list of the retransmit servers that are most likely to have buffered copies of packets missing from the session. When the repair server detects that there are packets missing from the session it has received, it uses the ordered list to sequentially request the missing packets from respective ones of the plurality of retransmit servers. ## Claims ### Claim 1 A system for repairing multicast sessions in a network, the system comprising: a memory that stores instructions; a processor of a retransmit server that executes the instructions to perform operations, the operations comprising: buffering a portion of packets during a multicast session; receiving, from a repair server, a request for missing packets associated with the multicast session, wherein the request is based on detecting that the missing packets are missing from the multicast session; transmitting, in response to the request for the missing packets, an adaptive enhanced reliability stream of the packets, wherein the retransmit server is selected by the repair server based on a ranking of retransmit servers obtained from a real-time control protocol receiver report. ### Claim 2 (depends on 1) The system of claim 1, wherein the operations further comprise detecting which of the missing packets are in the portion of the packets buffered during the multicast session. ### Claim 3 (depends on 1) The system of claim 1, wherein the operations further comprise receiving a definition of the multicast group session. ### Claim 4 (depends on 1) The system of claim 1, wherein the operations further comprise transmitting the missing packets in a unicast response to the repair server. ### Claim 5 (depends on 1) The system of claim 1, wherein the operations further comprise establishing a retransmission server list. ### Claim 6 (depends on 1) The system of claim 1, wherein the retransmit server is contained within an ordered list of retransmit servers that have a likelihood of having buffered copies of the missing packets of the multicast session. ### Claim 7 (depends on 6) The system of claim 6, wherein the operations further comprise re-ordering the ordered list based on a ranking criterion selected from the group comprising a cumulative number of packets lost field of the report, an interarrival jitter field of the report, a fraction list field of the report, and a round trip delay field from the report. ### Claim 8 (depends on 1) The system of claim 1, wherein adaptive enhanced reliability stream of the packets is supplemented by redundant packets and by block interleaving of the packets. ### Claim 9 A method for repairing multicast sessions in a network, the method comprising: buffering a portion of packets during a multicast session; receiving, from a repair server, a request for missing packets associated with the multicast session, wherein the request is based on detecting that the missing packets are missing from the multicast session; transmitting, by utilizing instructions from memory that are executed by a processor of a retransmit server, an adaptive enhanced reliability stream of the packets in response to the request for the missing packets wherein the retransmit server is selected by the repair server based on a ranking of retransmit servers obtained from a real-time control protocol receiver report. ### Claim 10 (depends on 9) The method of claim 9, further comprising further comprise detecting which of the missing packets are in the portion of the packets buffered during the multicast session. ### Claim 11 (depends on 9) The method of claim 9, further comprising receiving a definition of the multicast group session. ### Claim 12 (depends on 9) The method of claim 9, further comprising transmitting the missing packets in a unicast response to the repair server. ### Claim 13 (depends on 9) The method of claim 9, further comprising establishing a retransmission server list. ### Claim 14 (depends on 9) The method of claim 9, wherein the retransmit server is contained within an ordered list of retransmit servers that have a likelihood of having buffered copies of the missing packets of the multicast session. ### Claim 15 (depends on 14) The method of claim 14, wherein the operations further comprise re-ordering the ordered list based on a ranking criterion selected from the group comprising a cumulative number of packets lost field of the report, an interarrival jitter field of the report, a fraction list field of the report, and a round trip delay field from the report. ### Claim 16 (depends on 9) The method of claim 9, wherein adaptive enhanced reliability stream of the packets is supplemented by redundant packets and by forward error correction coding. ### Claim 17 A non-transitory computer-readable device comprising instructions, which when loaded and executed by a processor of a retransmit server, cause the processor to perform operations, the operations comprising: buffering a portion of packets during a multicast session; receiving, from a repair server, a request for missing packets associated with the multicast session, wherein the request is based on detecting that the missing packets are missing from the multicast session; transmitting an adaptive enhanced reliability stream of the packets in response to the request for the missing packets, wherein the retransmit server is selected by the repair server based on a ranking of retransmit servers obtained from a real-time control protocol receiver report. ### Claim 18 (depends on 17) The non-transitory computer-readable device of claim 17, wherein the operations further comprise detecting which of the missing packets are in the portion of the packets buffered during the multicast session. ### Claim 19 (depends on 17) The non-transitory computer-readable device of claim 17, wherein the operations further comprise transmitting the missing packets in a unicast response to the repair server. ### Claim 20 (depends on 17) The non-transitory computer-readable device of claim 17, wherein the retransmit server is contained within an ordered list of retransmit servers that have a likelihood of having buffered copies of the missing packets of the multicast session.