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  STB’s lack diagnostic interface

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

Customer Premises VoD Cluster Headend IPTV Content Delivery System Core Networ k STB IAD Access Network

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

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

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

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

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

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

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

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

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

Thank you for your attention! Dávid Károly