[c-nsp] SPT <-> RPT threshold switchover

[Vladimir Litovka]

Colleagues hi,

can anybody clarify the following issue - I can't make router to
switch back to Shared Tree (Rendezvous Point Tree, RPT) from Shortest
Path Tree (SPT) after traffic goes below configured threshold:

1) lead router configured with the following threshold: ip pim
spt-threshold 14 (i.e. 14Kbps)
2) while traffic rate below threshold, RPT is in use, you see 8Kbps
rate on RP-tree:
===================
D0#sh ip mroute count
IP Multicast Statistics
Forwarding Counts: Pkt Count/Pkts per second/Avg Pkt Size/Kilobits per second
Other counts: Total/RPF failed/Other drops(OIF-null, rate-limit etc)

Group: 239.1.1.1, Source count: 0, Packets forwarded: 123, Packets received: 123
  RP-tree: Forwarding: 123/1/1044/8, Other: 123/0/0
===================

3) after traffic goes above threshold, router switches to SPT:
===================
D0#sh ip mroute count
IP Multicast Statistics
Forwarding Counts: Pkt Count/Pkts per second/Avg Pkt Size/Kilobits per second
Other counts: Total/RPF failed/Other drops(OIF-null, rate-limit etc)

Group: 239.1.1.1, Source count: 1, Packets forwarded: 322, Packets received: 323
 RP-tree: Forwarding: 312/1/1044/15, Other: 312/0/0
>>>>>>  Source: 100.2.0.2/32, Forwarding: 10/0/1044/0, Other: 11/1/0 <<<<<<<
====================

4) then, I drop traffic rate again to 8Kbps and actually nothing happens:
====================
D0#sh ip mroute count
IP Multicast Statistics
Forwarding Counts: Pkt Count/Pkts per second/Avg Pkt Size/Kilobits per second
Other counts: Total/RPF failed/Other drops(OIF-null, rate-limit etc)

Group: 239.1.1.1, Source count: 1, Packets forwarded: 565, Packets received: 566
>>>>  you see although there is 8Kbps on SPT (i.e. below threshold), RP-tree still not in use; SPT is active <<<<<
 RP-tree: Forwarding: 312/0/1044/0, Other: 312/0/0
 Source: 100.2.0.2/32, Forwarding: 253/1/1044/8, Other: 254/1/0
====================

any comments on this? config is pretty simple - "ip pim sparse-mode"
on all interfaces and threshold configured using "ip pim spt-threshold
14" statement.
RP identification done through BSR.

Cisco IOS Software, 7200 Software (C7200-ADVIPSERVICESK9-M), Version
12.2(33)SRD3, RELEASE SOFTWARE (fc3)

Thanks.

--
/doka
~~~~~~~~
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