draft-ietf-idmr-pim-sm-spec-07.txt   draft-ietf-idmr-pim-sm-spec-08.txt 
skipping to change at line 1630 skipping to change at line 1630
Value(G,M,C(i))= Value(G,M,C(i))=
(1103515245 * ((1103515245 * (G&M)+12345) XOR C(i)) + 12345) mod 2^31 (1103515245 * ((1103515245 * (G&M)+12345) XOR C(i)) + 12345) mod 2^31
where M is a hash-mask included in Bootstrap messages. where M is a hash-mask included in Bootstrap messages.
This hash-mask allows a small number of consecutive groups This hash-mask allows a small number of consecutive groups
(e.g., 4) to always hash to the same RP. For instance, (e.g., 4) to always hash to the same RP. For instance,
hierarchically-encoded data can be sent on consecutive hierarchically-encoded data can be sent on consecutive
group addresses to get the same delay and fate-sharing group addresses to get the same delay and fate-sharing
characteristics. characteristics.
In standard C, this corresponds to:
srand(G & M);
srand(rand() ^ Ci);
value = rand();
This assumes the use of the BSD rand, which generates
32-bit numbers, rather than the System-V rand which
only generates 16-bit numbers.
2 The candidate with the highest resulting value is then 2 The candidate with the highest resulting value is then
chosen as the RP for that group, and its identity and hash chosen as the RP for that group, and its identity and hash
value are stored with the entry created. value are stored with the entry created.
Ties between C-RPs having the same hash value, are broken Ties between C-RPs having the same hash value, are broken
in advantage of the highest address. in advantage of the highest address.
Estrin,Farinacci,Helmy,Thaler,Deering,Handley,Jacobson,Liu,Sharma,Wei [Page 37] Estrin,Farinacci,Helmy,Thaler,Deering,Handley,Jacobson,Liu,Sharma,Wei [Page 37]
The hash function algorithm is invoked by a DR, upon reception The hash function algorithm is invoked by a DR, upon reception
of a packet, or IGMP membership indication, for a group, for of a packet, or IGMP membership indication, for a group, for
 End of changes. 

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