dave martin vice president, product management [email protected] 408.351.7209...
TRANSCRIPT
Agenda
Challenges for converged networks Quality of Service Monitoring VoIP performance Troubleshooting
Solutions and best practices
Deployment examples Service Provider Enterprise
Wrap-up/summary
Quality Of Service - Why Is It Necessary?
PSTN has set the bar - VoIP as a replacement technology must offer the same quality experience
Users will tradeoff voice quality for mobility - not true for fixed line services
VoIP has very stringent jitter, latency and packet loss requirements…best effort IP forwarding is insufficient
“Becauszzzz wit_o_t it _sers w__l be unha_py!”
Ensuring A High Quality Voice Experience: Design Considerations
Prioritize voice over data traffic Take advantage of DiffServ routing if available in the network…
but remember… TOS bit setting is NOT traffic management !!
Implement traffic shaping
Provide call admission control
Route media shortest path
Pay Close Attention To Access Links
T-1/E-1Router
LAN and network core tend to be over-provisioned
Congestion Point
OC-x Multi-Gigabit
100Mbps
Managing Access Links
Traffic shapingPriority queuingDiffserv packet markingCall Admission Control
VideoData
T1 WAN Link1.544Mbits/Sec
•Video calls established•Data “shaped”
•New calls are blocked•Data not starvedcompletely
Data allowed to consume available bandwidth as calls are completed
High Priority Queue
Low Priority Queue
time
High PriorityQueue Low Priority
Queue
WAN/LAN Link
Route Media Shortest Path: Hosted PBX Scenario
Service Provider
Atlanta
San Francisco
Dallas
LegendSignaling path
Media path
Softswitch
VoIP Monitoring Issues
Distributed nature of IP networking means no natural demarcation point for problem resolution
I just had a poor quality call…...but why?
Difficult to monitor long term call performance and identify consistently poor performers
Create Demarcation Points
Location #1IP
network
Softswitchor
IP PBXIP Phone
Location #2
IP Phone
SignalingMedia
A
B CD
VoIP ManagerLocation #3
Mean Opinion Score (MOS) provides a simple listening quality scale the represents the user experience
Monitoring at points A, B, C and D provides a demarcation point between LAN and WAN
Use Call Quality Statistics To Isolate Network Problems
Common causes of jitter:
• Ethernet link set at half duplex• Ethernet link set to autonegotiate• Congestion in upstream router
Provide Proactive Support
Trend analysis at the network level can spot persistent problems
Set quality thresholds for advanced notification
Deployment Examples
• QoS • Monitoring
• QoS• Monitoring
• VPN
Best Practices Summary
Quality of Service Implement prioritization, traffic shaping, call admission
control Route calls shortest path to minimize jitter, latency, and
packet loss
Monitoring Create demarcation points Build quality monitoring into the network Use tools that report on the user experience and send
proactive notification of VoIP quality problems
