Jitter Definitions What is what ? Discussion Roman Krzanowski

Jitter Definitions What is what ? Discussion

• Roman Krzanowski

• IETF Vancouver , CND

• November 2005

What is the Problem ?

• There are two operationalized definitions of jitter

• IETF RFC based (RFC 3393)
• Statistics on interpacket delay variation; usually implemented as the variation of the delay on consecutive packets
• Also implemented by MEF
• Used by most North American SP in SLAs definition
• Used in RTP protocol
• Used in Video buffer sizing
• ITU definition (Y.1541, Y.1540)
• Difference between the DV(99%)-DV(0%) over a sample set
• This is one of the DV definitions but most strongly supported by the providers
• Any other jitter metrics we should discuss ?
• Note: several alternative definitions in IETF RFC and ITU Y.1450 exist; presented shorthand definitions are selected on the basis of operational implementations and they do not exhaust all the options specified in RFC and ITU documents

What is the Problem ?

• European and Australasian providers support strongly ITU definition claiming that it is the only right one and the only needed one

• My contention is that both are a bit different (see AT&T paper) telling us different things about network events; Thus, there is a place for both metrics with necessary understanding that both have specific applications, advantages and disadvantages

What I am proposing ?

• Have a discussion on merits and limitations of two (maybe more) jitter metrics

• Develop UC where specific metrics are applicable
• Develop test cases/models demonstrating the uses and abuses of both metrics

• Develop recommendations (best practices) on the use of both metrics for:

• The monitoring of the network performance
• Which metrics and why and how
• For VoIP, Video, network buffer sizing
• Measuring burstness of the network traffic for VoIP and Video applications
• Sizing de-jitter buffers based on each measure
• Diagnosing network events based on both jitter measures

• Create a team to work with on this issue

Selected References

• ITU SG-12. Analysis, measurement and modeling of Jitter. January 2003

• ‘Standardized active measurements on Tier I active IP backbone’, IEEE Communications Magazine, June 2003

• ITU Y.1540 (12/2002)

• ITU- Y.1541 Oct, 2005. temp

• ITU. Clarification to the IP packet delay variation definition in Y.1540 . Al. Morton

• SAA Documentation. Cisco

• Brix Documentation. Brix Networks

• RFC 3393