1. Diagnosing PIM Protocol States PIM Working Group
draft-joshi-pim-protocol-state-diag -00.txt
Bharat Joshi
Infosys Technologies Ltd.

2. Motivation
None of the existing mechanisms provide support to diagnose PIM Protocol states.
None of the existing mechanism can be used to diagnose a PIM domain even before the protocol states are created.
This extension can help in identifying the exact type of problem as well as the router where the problem is.
Existing mechanisms:
Multicast connectivity check [ssmping]
Test the multicast connectivity between a client and server.
Multicast traceroute [mtrace]
Trace the multicast path from a source to a destination
Provide additional statistics

3. Possible Tests To carry a dry-run to join a Multicast Group [ASM/SSM]
To calculate approximately the time needed to construct a SPT or RPT.
To test the RP consistency for a Multicast Group in the PIM domain.
To carry a dry-run to check E-BSR consistency in the PIM domain.
To trace the route through which multicast data will traverse, within a pim domain. [Optional]
To carry a dry-run for asserting for a (*,G)/(S,G) state. [To Be Added in the Draft]

4. Join test It works very similar to normal PIM Join messages.
A router receiving the PIM diagnose Request message executes the same code which it would have done if it would have received a normal PIM Join request.
If a router is able to join, it forwards the request towards the RP/Source
Once the request reaches the RP or DR of the source, that router generates a Diagnose Response message and unicast it to the originator address mentioned in the request.
If because of any reasons, a router could not join the group or fails to forward this to previous hop, it would generate a Diagnose Response message with appropriate error code and unicast it to the originator address mentioned in the request.

5. Unicast Response to Originator Unicast Response to Originator
Join Test
Start a ASM Join test
Unicast Response to Originator R6 RP R2 R3 R1 DR R7
Unicast Response to Originator R5 R4
Source
Start a SSM Join test

6. Time in constructing SPT/RPT
The method used in join test can be used to calculate the actual time it takes to construct SPT/RPT.
Time calculated using this method would reflect the time that a SPT/RPT would actually take.
Request message will carry a timestamp option and when DR/RP generates a response message, it would also append a timestamp option. Router interested in this time can take the difference of these two timestamp option.

7. RP Consistency test
It works very similar to how BSMs are flooded in a PIM domain.
A router receiving this PIM diagnose request message finds out if this router will use the RP mentioned in the request message for the Group address mentioned in the request message.
If the RP matches, it forwards this message similar to how it would have forwarded a BSM.
If the RP does not matches, it generates a Response message and unicast it to originator’s address mentioned in the request message.
Once the request message reach to the PIM domain Border router, it generates a unicast response to the originator’s address mentioned in the request message.

8. Unicast Response to Originator
RP Consistency Test
Unicast Response to Originator
Start a RP Consistency Test
Unicast Response to Originator R6 R3 R2
PIM BR R1
PIM BR
PIM BR
Unicast Response to Originator R7 R4 R5
PIM BR

9. Next Step
More review in WG mailing list.
Working group item?