System and signal monitoring for iptv set top box systems
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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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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

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


Contents

Contents

  • IPTV Network Architecture

  • Set top box architecture

  • MPEG-2 Transport Stream Monitoring

  • Implementation

  • Test results

  • Conclusions, future work


Iptv content delivery system

IPTV Content Delivery System

Headend

Customer Premises

Core Network

IAD

VoD Cluster

Access Network

STB


Set top box architecture

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

Transport Stream Monitoring

  • Raw UDP encapsulation

  • TS packets

    • Header, Adaptation Field

    • PID’s, metadata, Elementary Streams

    • Timestamps: PCR, PTS, DTS


Transport stream monitoring ii

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

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

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

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

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

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

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

Thank you for your attention!

Dávid Károly

[email protected]


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