H3C Technologies H3C S12500 Series Switches - Manual (Page 162)

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To configure C-BSR timers:
Step Command Remarks
1. Enter system view. system-view N/A
2. Enter public network PIM view
or VPN instance PIM view. pim [ vpn-instance
vpn-instance-name ]
N/A
3. Configure the BS period. c-bsr interval interval
Optional.
By default, the BS period is
determined by the formula "BS
period = (BS timeout timer – 10) /
2." Because the default BS timeout
timer is 130 seconds, the default
BS period = (130 – 10) / 2 = 60
(seconds). Make sure that the BS
period value is smaller than the BS
timeout timer. Make sure that the
BS period value is smaller than the
BS timeout timer.
4. Configure the BS timeout
timer.
c-bsr holdtime interval
Optional.
By default, the BS timeout timer is
determined by the formula "BS
timeout timer = BS period × 2 +
10." Because he default BS period
is 60 seconds, the default BS
timeout timer = 60 × 2 + 10 = 130
(seconds).
Disabling BSM semantic fragmentation
Generally, a BSR periodically distributes the RP-set information in bootstrap messages within the
BIDIR-PIM domain. It encapsulates a BSM in an IP datagram and might split the datagram into fragments
if the message exceeds the MTU. In respect of such IP fragmentation, loss of a single IP fragment leads
to unavailability of the entire message.
Semantic fragmentation of BSMs can solve this issue. When a BSM exceeds the MTU, it is split to multiple
bootstrap message fragments (BSMFs).
• After receiving a BSMF that contains the RP-set information of one group range, a non-BSR router
updates corresponding RP-set information directly.
• If the RP-set information of one group range is carried in multiple BSMFs, a non-BSR router updates
corresponding RP-set information after receiving all these BSMFs.
Because the RP-set information contained in each segment is different, loss of some IP fragments will not
result in dropping of the entire message.
Generally, a BSR performs BSM semantic fragmentation according to the MTU of its BSR interface.
However, the semantic fragmentation of BSMs originated due to learning of a new PIM neighbor is
performed according to the MTU of the outgoing interface.
The function of BSM semantic fragmentation is enabled by default. Devices not supporting this function
might deem a fragment as an entire message, thus learning only part of the RP-set information. Therefore,
if such devices exist in the BIDIR-PIM domain, you need to disable the semantic fragmentation function on
the C-BSRs.