0
Ensuring QoS in Your VoIP Development Choon Shim CTO and Senior VP of Engineering [email_address]  ,  http://www.qovia.com
VoIP problems <ul><li>Outage: </li></ul><ul><li>- Infrastructure: switch, router, bridge, UPS, etc </li></ul><ul><li>- VoI...
Roots of the problems <ul><li>IP is not designed for carrying real-time media stream. </li></ul><ul><li>Management was not...
VoIP ready network <ul><li>Fast network: low latency and jitter </li></ul><ul><li>Clean network: few packet loss and retra...
Bandwidth <ul><li>Required bandwidth per call (bps): </li></ul><ul><li>BW = (V + I + L) * 8 * P </li></ul><ul><li>Where, V...
To reduce bandwidth requirement <ul><li>Bandwidth requirement by codec and duplex </li></ul><ul><li>cRTP reduces 2-5 bytes...
Clean network <ul><li>Reduce hop counts </li></ul><ul><li>Reduce complexity of network topology </li></ul><ul><li>Remove d...
QoS ready network <ul><li>Layer 3: </li></ul><ul><ul><li>Type of Service (TOS) </li></ul></ul><ul><ul><li>RSVP signaling (...
Fault tolerant network - Outage detection <ul><li>Carrier failure: T1, E1, Analog </li></ul><ul><li>- No incoming or outgo...
Fault tolerant network – Outage detection (cont) <ul><li>Infrastructure failure: </li></ul><ul><li>- No dial tone or bad v...
Fault tolerant network –  Outage detection (cont) <ul><li>VoIP element failure: </li></ul><ul><li>- No dial tone. </li></u...
Outage detection issues <ul><li>Lack of alarm implementation. </li></ul><ul><li>Too many consoles to monitor: NMS, vendor ...
Alarm – Event driven Switch Router T1/E1 UPS GK GW TE Bridge Analog Environ Server Management  Server  SNMP Trap Email/Pag...
Checking vital signs <ul><li>Blind polling: send a ping to every elements every x minutes. It triggers extra network traff...
Manageable VoIP Network – Voice quality measurement <ul><li>MOS (Mean Opinion Score):  </li></ul><ul><li>- Subjective meas...
Voice quality measurement <ul><li>PSQM (Perceptual Speech Quality Measurement, ITU-T P.861):  </li></ul><ul><li>- A utomat...
Voice quality measurement <ul><li>PAMS (Perceptual Analysis and Measurement System): </li></ul><ul><li>-  Designed an intr...
Voice quality measurement <ul><li>PESQ : PESQ (ITU–T P.862): </li></ul><ul><li>-  The latest standard for assessing voice ...
Voice quality measurement <ul><li>Delay guideline: ITU-T G.114 </li></ul>Acceptable Acceptable under conditions Unacceptab...
Quality problem detection <ul><li>Interpret RTCP and RTCP XR.  </li></ul><ul><li>Packet monitoring by Layer2 switch taping...
Problem isolation procedure Central QoS server RTCP Packet monitoring SNMP ALARM Console VoIP Network 1 2 3 4 5 6
Central QoS management server <ul><li>Discover VoIP components/elements dynamically. </li></ul><ul><li>Create a topology a...
Console <ul><li>Display overall call quality. </li></ul><ul><li>Display topology and status display. </li></ul><ul><li>Dis...
Q & A <ul><li>Thank you! </li></ul><ul><li>Any questions? </li></ul>
Upcoming SlideShare
Loading in...5
×

Ensuring QoS in Your VoIP Development

440

Published on

0 Comments
0 Likes
Statistics
Notes
  • Be the first to comment

  • Be the first to like this

No Downloads
Views
Total Views
440
On Slideshare
0
From Embeds
0
Number of Embeds
0
Actions
Shares
0
Downloads
8
Comments
0
Likes
0
Embeds 0
No embeds

No notes for slide

Transcript of "Ensuring QoS in Your VoIP Development"

  1. 1. Ensuring QoS in Your VoIP Development Choon Shim CTO and Senior VP of Engineering [email_address] , http://www.qovia.com
  2. 2. VoIP problems <ul><li>Outage: </li></ul><ul><li>- Infrastructure: switch, router, bridge, UPS, etc </li></ul><ul><li>- VoIP element: call server, SIP server, GW, GK, MCU, handsets. </li></ul><ul><li>- Carrier: T1/E1, analog signal trunk lines. </li></ul><ul><li>Voice Quality: </li></ul><ul><li>- Delay: network bandwidth, processing power </li></ul><ul><li>- Echo: hybrid, acoustic </li></ul><ul><li>- Jitter: jitter buffer calculation, variable delay </li></ul><ul><li>- Packet loss: sender base, receiver base </li></ul><ul><li>- Out of order: complex topology </li></ul>
  3. 3. Roots of the problems <ul><li>IP is not designed for carrying real-time media stream. </li></ul><ul><li>Management was not considered by System/Elements Vendors. </li></ul><ul><li>Too many moving parts. </li></ul><ul><li>Too many protocol layers. </li></ul><ul><li>Too many API layers. </li></ul><ul><li>Multi vendor products. </li></ul>
  4. 4. VoIP ready network <ul><li>Fast network: low latency and jitter </li></ul><ul><li>Clean network: few packet loss and retransmit </li></ul><ul><li>QoS ready network: Voice packet has priority </li></ul><ul><li>Fault tolerant network: redundancy and backup </li></ul><ul><li>Manageable network: monitoring and management </li></ul>
  5. 5. Bandwidth <ul><li>Required bandwidth per call (bps): </li></ul><ul><li>BW = (V + I + L) * 8 * P </li></ul><ul><li>Where, V is size of voice sample, </li></ul><ul><li>I is IP/UDP/RTP overhead, </li></ul><ul><li>L is data link overhead and </li></ul><ul><li>P is packets generated per second. </li></ul><ul><li>Example) (160 + 40 + 18) * 8 * 50 = 87.2 kbps </li></ul><ul><li>Required bandwidth total: </li></ul><ul><li>Total BW = BW * N </li></ul><ul><li>Where, N is total number of simultaneous calls </li></ul><ul><li>Example) 87.2 * 50 = 4.36 Mbps </li></ul><ul><li>=> Increase bandwidth </li></ul>
  6. 6. To reduce bandwidth requirement <ul><li>Bandwidth requirement by codec and duplex </li></ul><ul><li>cRTP reduces 2-5 bytes overhead </li></ul><ul><li>VAD reduces up to 50% payload </li></ul>29.4 87.2 110.4 Full duplex 78.4 174.4 220.8 Half duplex G.729 (20 ms) G.711 (20 ms) G.711 (10 ms) Link Type (Sample time)
  7. 7. Clean network <ul><li>Reduce hop counts </li></ul><ul><li>Reduce complexity of network topology </li></ul><ul><li>Remove duplex mismatch </li></ul><ul><li>Remove black hole and loop </li></ul><ul><li>Avoid half duplex link </li></ul><ul><li>Use common sense for cabling </li></ul>
  8. 8. QoS ready network <ul><li>Layer 3: </li></ul><ul><ul><li>Type of Service (TOS) </li></ul></ul><ul><ul><li>RSVP signaling (RFC 2205) </li></ul></ul><ul><ul><li>DiffServ (RFC2474) </li></ul></ul><ul><ul><li>Multiprotocol Label Switching (MPLS) </li></ul></ul><ul><li>Layer 2: </li></ul><ul><li>- 802.1p and 802.1q </li></ul><ul><li>- Ethernet Class of Service (COS) </li></ul>
  9. 9. Fault tolerant network - Outage detection <ul><li>Carrier failure: T1, E1, Analog </li></ul><ul><li>- No incoming or outgoing calls. </li></ul><ul><li>- Checking the module LED. </li></ul><ul><li>- Checking the event log, management console. </li></ul><ul><li>- Running a loop back test for T1/E1. </li></ul><ul><li>- Checking with T1 tester. </li></ul><ul><li>- Receiving an alarm from the call server. </li></ul>
  10. 10. Fault tolerant network – Outage detection (cont) <ul><li>Infrastructure failure: </li></ul><ul><li>- No dial tone or bad voice quality </li></ul><ul><li>- Checking NMS console </li></ul><ul><li>- Checking SNMP Traps </li></ul><ul><li>- Testing cables </li></ul><ul><li>- Testing switches, routers, bridges, etc </li></ul><ul><li>- Checking UPS power load, power level, connection </li></ul>
  11. 11. Fault tolerant network – Outage detection (cont) <ul><li>VoIP element failure: </li></ul><ul><li>- No dial tone. </li></ul><ul><li>- Checking SNMP trap. </li></ul><ul><li>- Checking NMS console. </li></ul><ul><li>- Checking with the vendor management console. </li></ul><ul><li>- Checking event log, trace, etc. </li></ul>
  12. 12. Outage detection issues <ul><li>Lack of alarm implementation. </li></ul><ul><li>Too many consoles to monitor: NMS, vendor supplied management, third party software, carrier OSS/EOSS. </li></ul><ul><li>Too many elements could go wrong. </li></ul><ul><li>Carriers are not monitoring the CSU or CPE. </li></ul>
  13. 13. Alarm – Event driven Switch Router T1/E1 UPS GK GW TE Bridge Analog Environ Server Management Server SNMP Trap Email/Pager Carrier console VoIPm Console
  14. 14. Checking vital signs <ul><li>Blind polling: send a ping to every elements every x minutes. It triggers extra network traffics. Total number of packets per hour N = e * x / 60, where e = number of elements, x is minutes. </li></ul><ul><li>Severity base polling: send a ping to critical elements more often. For example) GW: every 5 mins, GK: every 6 mins, Switch: every 10 mins, Terminal element: 30 mins, etc. </li></ul><ul><li>Dynamic polling: recalculates number of pings based on the previous faults, traffic or volume. Number of packets N =  f(1)..f(e), where f is the function being used for calculating faults, traffic and volume. </li></ul>
  15. 15. Manageable VoIP Network – Voice quality measurement <ul><li>MOS (Mean Opinion Score): </li></ul><ul><li>- Subjective measurement of VoIP. </li></ul><ul><li>- Pre selected voice sample over different media, replayed to mixed group of men and woman, who rate them from 1 to 5. </li></ul><ul><li>4 – 5: Toll Quality </li></ul><ul><li>3 – 4: Communication quality </li></ul><ul><li>< 3 : Synthetic quality </li></ul>
  16. 16. Voice quality measurement <ul><li>PSQM (Perceptual Speech Quality Measurement, ITU-T P.861): </li></ul><ul><li>- A utomated scoring process using an algorithm that enables computer-derived scores to correlate to MOS scores. </li></ul><ul><li>- Designed for circuit-switched network and does not take into effect important parameters such as jitter and packet loss, which affect voice quality on a VOIP network adversely. </li></ul>
  17. 17. Voice quality measurement <ul><li>PAMS (Perceptual Analysis and Measurement System): </li></ul><ul><li>- Designed an intrusive listening speech quality assessment tool where speech quality is computed by injecting a speech like signal at one end and analysing the degraded signal at other end of the network. </li></ul>Parameter SCORE 1 2 3 4 5 Latency (ms) <50 50-75 75-100 100-200 >200 Packet/Loss (%) 0 0-1 1-2 2-3 >3 Jitter (ms) <5 5-10 10-50 50-100 >100
  18. 18. Voice quality measurement <ul><li>PESQ : PESQ (ITU–T P.862): </li></ul><ul><li>- The latest standard for assessing voice quality and is expected to eventually replace PSQM. </li></ul><ul><li>- It builds on the PSQM and PAMS algorithms by adding additional processing steps to account for signal-level differences and the identification of errors associated with packet loss. </li></ul>
  19. 19. Voice quality measurement <ul><li>Delay guideline: ITU-T G.114 </li></ul>Acceptable Acceptable under conditions Unacceptable 0 150 400 0 – 150 ms: Good quality and no echo 151 – 400 ms: Acceptable under certain conditions and echo canceling is needed 401+: Unacceptable for real-time voice traffic and planning and testing purposes only
  20. 20. Quality problem detection <ul><li>Interpret RTCP and RTCP XR. </li></ul><ul><li>Packet monitoring by Layer2 switch taping or port mirroring. </li></ul><ul><li>Probing and active monitoring by injecting a test packet. </li></ul><ul><li>SNMP, RMON or sFlow gathering. </li></ul>
  21. 21. Problem isolation procedure Central QoS server RTCP Packet monitoring SNMP ALARM Console VoIP Network 1 2 3 4 5 6
  22. 22. Central QoS management server <ul><li>Discover VoIP components/elements dynamically. </li></ul><ul><li>Create a topology and aggregate multiple call servers, GW, GK, MCU, SIP Servers, etc. </li></ul><ul><li>Collect performance/delay data from various sources. </li></ul><ul><li>Calculate variable polling period and injects an active packet. </li></ul><ul><li>Make a statistical model to use for assign QoS. </li></ul><ul><li>Organize elements/QoS data in the relational DBMS. </li></ul><ul><li>Detect voice quality problem and send an alarm to console. </li></ul><ul><li>Inject an active test packet to isolate the problem as per console. </li></ul>
  23. 23. Console <ul><li>Display overall call quality. </li></ul><ul><li>Display topology and status display. </li></ul><ul><li>Display drill down to detail elements with MOS/PESQ. </li></ul><ul><li>Display real time status and quality changes. </li></ul><ul><li>Trigger the problem isolation procedure. </li></ul>
  24. 24. Q & A <ul><li>Thank you! </li></ul><ul><li>Any questions? </li></ul>
  1. A particular slide catching your eye?

    Clipping is a handy way to collect important slides you want to go back to later.

×