網路電話品質量測技術

VoIP Quality Measurement

• Course webpage: http://course.ipv6.club.tw/Measurement/
• Time: Thursday 08:10-11:00
• Textbook:
• Reference Book: "Carrier Grade Voice over IP" by Daniel Collins, published by McGraw-Hill.
• Students enroll in this class
• TA:

  Lecture Notes

  • Chapter 1 Introduction
  • Chapter 2 Transporting Voice By Using IP
  • Chapter 5 SIP
  • NAT Traversal
  • Tutorial: Voice Quality (VQ) in Converging Telephony and Internet Protocol (IP) Networks
    • Agilent Technologies, Voice Quality in Converging Telephony and IP Networks
  • I2 E2Epi - End to End Performance Initiative ,Presentations
  • Internet2 End-to-End Performance Initiative (E2E piPEs)

  課程評量方式

  • 作業(20%)
  • 課堂報告(40%)
  • 期中考(20%)
  • 期末考(20%)

  Tools

  1. VoIP TroubleShooter
  2. TestYourVoIP.com
     This site will establish a SIP session with your PC and calculate the MOS value according to the E-Model (ITU-T G.107).
  3. Google Suggest
  4. How to Calculate MOS?
  tools

  Measurement

  1. http://www.internet2.edu/performance/pS-PS/
  2. http://e2epi.internet2.edu/ndt/
  3. CAIDA - Performance Measruement Tools
  4. TWAREN Measurement
  5. SNMP - MRTG
  6. NLANR - National Laboratory for Applied Network Research
     1. Iperf - Measure bandwidth availabity using a client and server model.
     2. Pathchar - determine per-hop bandwidth, propagation delay, queue time and drop rate
     3. Information on creating your own AMP network
  7. Internet End-to-end Performance Monitoring (IEPM) in Stanford
     1. Reverse Traceroute Server
     2. PingER (Ping End-to-end Reporting)
  8. OWAMP (One-Way Latency Measurements)
  9. Firewall Configuration of OWAMP
  10. 構想書
  11. p.800.1.pdf
  12. p.800.pdf
  13. p.862-200102.zip
  14. ITU-T Recommendation P.862, Perceptual evaluation of speech quality (PESQ), an objective method for end-to-end speech quality assessment of narrowband telephone networks and speech CODECs [PDF]
  15. p.862.1-200311.pdf
  16. Reference Paper

  Codec

  • Codec Central

  QoS

  1. DiffServ
  2. RSVP

  OWAMP

  1. IETF IP Performance Metrics (IPPM) working group
  2. RFC 2679 - A One-way Delay Metric for IPPM
     1. This document describes some common errors and uncertainly which you must take into account when performing measurements. However, it is not directly related to OWAMP protocol.
     2. In my opinion, we do not need to "inject" traffic into the network to perform these measurements. We can just collect the results from RTCP.
  3. RFC 3763 - One-way Active Measurement Protocol (OWAMP) Requirements
     1. There should exist two protocols: one for conducting the actual measurement session and another for session setup/teardown/confirmation/retrieval. These protocols are referred to as OWAMP-Test and OWAMP-Control, respectively.
        Comments: This is similar to RTP and SIP!
     2. If OWAMP-Test packets are easy to identify (e.g., they all come to a well-known port number), an intermediate party might place OWAMP-Test traffic into a priority queue at a congested link thus ensuring that the results of the measurement appear better than what would be experienced by other traffic.
  4. RFC 4656 - A One-way Active Measurement Protocol (OWAMP)
     1. TCP well-known port 861 is allocated to OWAMP Control.
     2. OWAMP test traffic is simply a stream of UDP packets from and to negotiated port numbers. If you don't want that the network provider can detect OWAMP traffic easily, you may apply encryption on OWAMP packets.
     3. The goal of encrypted mode is: to make it hard for a party in the middle of the network to make results look "better" than they should be.
     4. because many Internet paths include segments that transport IP over ATM, delay and loss measurements can include the effects of ATM segmentation and reassembly (SAR). Consequently, OWAMP has been designed to allow for small test packets that would fit inside the payload of a single ATM cell (this is only achieved in unauthenticated mode).
     5. OWAMP-Control communications are encrypted with the AES Session-key (using CBC mode) and authenticated with HMAC Session-key
     6. SID is always chosen by the receiver, by concatenation of the 4-octet IPv4 IP number belonging to the generating machine, an 8-octet timestamp, and a 4-octet random value.
     7. Non-zero Accept values indicate a failure of some sort. Zero values indicate normal completion.
     8. Each packet record is 25 octets and includes 4 octets of sequence number, 8 octets of send timestamp, 2 octets of send timestamp error estimate, 8 octets of receive timestamp, 2 octets of receive timestamp error estimate, and 1 octet of Time To Live (TTL), or Hop Limit in IPv6
     9. in encrypted mode both the sequence number and the timestamp are protected to provide maximum data confidentiality and integrity protection, whereas in authenticated mode the sequence number is protected while the timestamp is sent in clear text.
     10. Sending the timestamp in clear text in authenticated mode allows one to reduce the time between when a timestamp is obtained by a sender and when the packet is shipped out. (Encryption causes extra delay, which leads to inaccuracy.)
     11. All of OWAMP-Test AES Session-key, OWAMP-Control AES Session-key, and the SID are comprised of 16 octets. OWAMP-Test HMAC Session-key and OWAMP-Control HMAC Session-key are comprised of 32 octets.
     12. After nine years of IPsec, only 0.05% of traffic on an advanced backbone network, such as Abilene, uses IPsec (for comparison purposes with encryption above layer 4, SSH use is at 2-4% and HTTPS use is at 0.2-0.6%). For numerous reasons in Section 6.6, we decided to use a simple cryptographic protocol (based on a block cipher in CBC mode) that is different from TLS and IPsec.
  5. A Two-way Active Measurement Protocol (TWAMP) draft-ietf-ippm-twamp-00
  6. OWAMP @ Internet2
  7. OWAMP Performance and Interoperability Tests [PDF]
  8. Plug-and-Play (Network) Performance Monitoring
  9. P Calyam, D Krymskiy, M Sridharan, P Schopis, "Active and passive measurements on campus, regional and national network backbone paths", Computer Communications and Networks, 2005. ICCCN 2005
  10. R Kwitt, T Fichtel, T Pfeiffenberger, "Measuring Perceptual VoIP Speech Quality over UMTS
  11. F Michaut, F Lepage, "Application-oriented network metrology: metrics and active measurement tools", Communications Surveys & Tutorials, IEEE, 2005
  12. A Network Monitoring System with a Peer-to-Peer Architecture

  Reference Slides

  1. Better Illustration of E2E piPEs in 2003.2.4 Miami Joint Tech BOF
  2. 2003.5.15. Almost the same presentation as the previous one.
  3. Network Measurement Tools Summary of ESnet, 2006.02.
  4. Presentation of IEPM Group in ESCC 2003.02 Miami Meeeting. It appeals that a common monitoring infrastructure is necessary. See http://www-iepm.slac.stanford.edu for more tools developed by IEPM.
  5. IETF IPPM WG Meeting in 2006.03
  6. Some Management and Diagnostic Tools mentioned by UCLA NOC.
  7. 2005.10 Active and Passive Measurements by OARnet
     • Active Measurements
       • Require injecting test packets into the network to determine network topology or end-to-end performance of network paths
       • +)Better characterize end-user perceived application-quality since they emulate experience of actual end-application traffic using a few test packets
       • -)They consume bandwidth required by actual application traffic
     • Passive Measurements
       
       Do not inject test packets in the network but require capturing of packets and their corresponding timestamps transmitted by applications running on network-attached devices over various network links
       • +)Do not inject test traffic and data is obtained from devices that are involved in the functioning of the network
       • -)They impose large overhead on network devices to keep track of such information in addition to their core functionality of forwarding packets
     • "Delay" is a metric for active measurement, not passive measurement.
     • Ohio State developed their own toolkit: ActiveMon
     • H.323 Beacon is recommended as "An easy to install and use tool that is open source" to evaluate video/audio stream MOS values.
  8. 2006.4.5 OWAMP and BWCTL: Installation and Configuration by Jeff Boote (boote@internet2.edu) @ Network Performance Workshop
     • Hyperlinks to the cookbook of OWAMP and BWCTL are given.
     • Detailed configuration steps are illustrated.
  9. 2006.5.29 Jeff, Internet2 E2EPI
     • By defining clean APIs and protocols between each layer, the diagnostic costs can be reduced.
     • Users can access the statistics of network data from Abilene Observatory. TANet can try to establish similar mechanism to allow researchers requesting similar data from TANet.
     • Encourage people to deploy open source tools BWCTL/Iperf, OWAMP, NDT.
     • Set DSCP (a.k.a. first 6 bits of the TOS byte).
  10. The Performance Bottleneckpplication, Computer, or Network
      1. Measurement Tools are VERY important!
      2. Case Study at SC'04
         • Team spent over 1 hour looking at Win XP config, trying to verify Buffer size
         • Single NDT test verified this in under 30 seconds
      3. Full to Half mismatch detection - Asymmetric throughput (opposite direction is less)
      4. Three major tools:
         1. BWCTL (Bandwidth Control wrapper for NLANR Iperf)
         2. OWAMP: One-Way Active Measurement
         3. NDT: Network Diagnostic Tool
  11. User-Perceived Performance Measurement on the Internet
      • This talk addresses several network measurement projects:
        1. NIMI (National Internet Measurement Infrastructure)
        2. E2E piPEs (of course)
        3. Proxy-Based Tools: Liston Proxy / Medusa Proxy
        4. AMP
        5. Network Weather Service
      • Because the Internet was designed following the end-to-end principle, end-to-end performance is ultimately the most meaningful to measure
      • Network users see end-to-end performance directly and could be effectively used as monitor points

  Presentation List

  1. RFC 3611 - RCTP Extended Reports

  Podcast

  1. Five Critical Issues for VoIP Implementation.
     1. What to do with your existing device
     2. Assessing your network status
     3. Redesign your network
     4. Pilot Strategy
     5. Training