H3C Technologies H3C SecPath F1000-E - Manual (Page 644)

619
CAUTION:
In configuration, make sure the BS period value is smaller than the BS timeout value.
5. Disabling BSM semantic fragmentation
Generally, a BSR periodically distributes the RP-set information in bootstrap messages within the
PIM-SM 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 PIM-SM domain, you need to disable the
semantic fragmentation function on the C-BSRs.
To disable the BSM semantic fragmentation function:
Step Command Remarks
1. Enter system view. system-view N/A
2. Enter public network PIM view. pim N/A
3. Disable the BSM semantic
fragmentation function.
undo bsm-fragment enable
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.
Configuring administrative scoping
When administrative scoping is disabled, a PIM-SM domain has only one BSR. The BSR manages the
whole network. To manage your network more effectively and specifically, partition the PIM-SM domain
into multiple admin-scoped zones. Each admin-scoped zone maintains a BSR, which serves a specific
multicast group range. The global-scoped zone also maintains a BSR, which serves all the remaining
multicast groups.
1. Enabling administrative scoping
Before you configure an admin-scoped zone, you must enable administrative scoping first.
Perform the following configuration on all routers in the PIM-SM domain.
To enable administrative scoping: