1. Jitter Definitions What is what ? Discussion
Roman Krzanowski
IETF Vancouver , CND
November 2005

2. 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

3. 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

4. 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

5. 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, temp
ITU. Clarification to the IP packet delay variation definition in Y Al. Morton
SAA Documentation. Cisco
Brix Documentation. Brix Networks
RFC 3393