H3C Technologies H3C S10500 Series Switches - Manual (Page 180)

165
NOTE:
About the BS period:
• By default, the BS period is determined by the formula “BS period = (BS timeout – 10) / 2.” Because the
default BS timeout is 130 seconds, the default BS period = (130 – 10) / 2 = 60 (seconds).
• If this parameter is manually configured, the system will use the configured value.
About the BS timeout timer:
• By default, the BS timeout value 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).
• If this parameter is manually configured, the system will use the configured value.
CAUTION:
Ensure that the BS period value is smaller than the BS timeout value.
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 maximum transmission unit (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.
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.
Follow these steps to disable the BSM semantic fragmentation function:
To do… Use the command… Remarks
Enter system view system-view —
Enter public network PIM view or
VPN instance PIM view pim [ vpn-instance
vpn-instance-name ]
—
Disable the BSM semantic
fragmentation function
undo bsm-fragment enable
Required
By default, the BSM semantic
fragmentation function is enabled.
NOTE:
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.