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System and Signal Monitoring for IPTV Set-Top-Box Systems

System and Signal Monitoring for IPTV Set-Top-Box Systems. Dávid Károly Tivadar Szemethy Árpád Bakay. The need for end to end monitoring. Telcos are rolling out IPTV 3-play Must ensure high availability, QoS, QoE Importance of CPE monitoring Last mile problems

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System and Signal Monitoring for IPTV Set-Top-Box Systems

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  1. System and Signal Monitoring for IPTV Set-Top-Box Systems Dávid Károly Tivadar Szemethy Árpád Bakay

  2. The need for endtoend monitoring • Telcos are rolling out IPTV • 3-play • Must ensure high availability, QoS, QoE • Importance of CPE monitoring • Last mile problems • STB’s lack diagnostic interface

  3. Contents • IPTV Network Architecture • Set top box architecture • MPEG-2 Transport Stream Monitoring • Implementation • Test results • Conclusions, future work

  4. IPTV Content Delivery System Headend Customer Premises Core Network IAD VoD Cluster Access Network STB

  5. Set top box architecture • Hardware • RISC GPP • Video decoding with DSP or ASIC • Ethernet, SCART, IR interface • Software • Embedded Linux • Media player • User interface, browser

  6. Transport Stream Monitoring • Raw UDP encapsulation • TS packets • Header, Adaptation Field • PID’s, metadata, Elementary Streams • Timestamps: PCR, PTS, DTS

  7. Transport Stream Monitoring (II) • Characteristics to measure • Bandwidth, Packet loss • Also per stream type (audio/video/metadata) • UDP-level Jitter, inter-arrival gap min/max/avg • PCR characteristics • PCR Jitter • PCR discontinuities, missing PCR

  8. Naive implementation • AF_PACKET raw sockets • Packet filter • Not feasible • Inaccurate • Eats up CPU cycles, UI responsiveness is hindered • 10 Mbps HDTV stream: 23% CPU usage

  9. Packet capture inside the kernel • Register a callback • Dev_add_pack() • Callback runs in softirq context • Gets skbuf with timestamp • Eliminates kernel to user copies • Results can be accessed via /proc filesystem

  10. User mode portion • SNMP agent based on Net-SNMP • Turn on/off with SNMP row creation/deletion • Sends TRAP in cast of threshold violation • Repeatedly reads the proc-file • Only aggregated values: averages, counters • Read once per second • Can be remotely queried, turned on/off • Also provides diagnostic parameters • Load average, free memory • CPU load imposed by SNMP agent

  11. Test results • Tests conducted in two settings • Corporate intranet • IPTV test network of a service provider • The approach is workable • No extra CPU load imposed (even with HDTV, up to 10 Mbps) • Accurate measured values, compared to a standalone PC probe

  12. Further findings • PCR behavior is codec-dependent • Usefulness of diagnostic parameters • Headend misconfiguration causes small subtle errors (like metadata discontinuity) • This results in high STB load and frequent reboots

  13. Conclusions and future work • Interpreting acquired data • Further experiments are needed • Compare metrics with opinion score • Data mining • Other parameters worth analyzing • MDI per RFC1889 • IGMP channel zap delay • Integrate into IAD or bridging probe

  14. Thank you for your attention! Dávid Károly David.Karoly@netvisor.eu

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