SPF
SPF
, SPT , . . , G 2001: db8: 3e8: 100 :: / 64. A . - , , (, Ethernet). SPT, ( ) . (IP- - ) (, , - ). SPT.

, [C, E] . ? , C, B D , A . A E. , :
- , E.
- C ( A), , , E , [C, E] .
SPF.
LFA rLFA.
( ) , LFA rLFA. Bellman-Ford , LFA, , , . DUAL . (, , SPF)? , LFA .

- , , . :
- A SPT, SPF .
- A B C, , [A, B] [A, C] .
, A , , - . LFA:
, , LFA.
, :
- NC - .
- BC - .
- LC - .
NC + BC < LC, LFA. A [B, A] [C, A] ( , SPT ). , LFA , LFA? P/Q Space LFA. P/Q Space.
P - , , Q - , . :
SPT , ; SPT. .

E :
- Q, [E, D] SPT , E D.
- P, SPT D ( D ), [D, E], , D E.
- , E, D, [E, D].
SPF - , Shortest Path Trees .