Hi there:)

Cisco IP SLA has a feature Path-jitter.

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router#show ip sla statistics
IPSLAs Latest Operation Statistics

IPSLA operation id: 1
Type of operation: udp-jitter
        Latest RTT: 44 milliseconds
Latest operation start time: 11:40:36.392 MSD Thu Aug 5 2010
Latest operation return code: OK
RTT Values:
        Number Of RTT: 100              RTT Min/Avg/Max: 19/44/72 milliseconds
Latency one-way time:
        Number of Latency one-way Samples: 100
        Source to Destination Latency one way Min/Avg/Max: 5/30/58 milliseconds
        Destination to Source Latency one way Min/Avg/Max: 13/14/21 milliseconds

Jitter Time:
        Number of SD Jitter Samples: 99
        Number of DS Jitter Samples: 99
        Source to Destination Jitter Min/Avg/Max: 0/16/45 milliseconds
        Destination to Source Jitter Min/Avg/Max: 0/2/8 milliseconds
Packet Loss Values:
        Loss Source to Destination: 0           Loss Destination to Source: 0
        Out Of Sequence: 0      Tail Drop: 0
        Packet Late Arrival: 0  Packet Skipped: 0
Voice Score Values:
        Calculated Planning Impairment Factor (ICPIF): 0
        Mean Opinion Score (MOS): 0
Number of successes: 14
Number of failures: 0
Operation time to live: Forever
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There is no Average two way jitter value but I can get it via SNMP.

SNMP OID is:
1.3.6.1.4.1.9.9.42.1.5.2.1.46 - rttMonLatestJitterOperAvgJitter
Avg of Positive and Negative Jitter in SD & DS direction

How does this value calculate?
What formula has been used in IOS for this calculation?

I've tried to calculate this value by myself with the method from
RFC 3550 and I get different result than IOS gets me via
1.3.6.1.4.1.9.9.42.1.5.2.1.46 OID.

Can anyone shed some light on this?