AS path length


primary knob of BGP hammer  (default metric)
All AS versus unique AS count:
prepending - repeating of AS 
makes AS path look longer
reduces traffic via this path
bumps at AS path lengths 12,14 
e.g., 202.183.247.0/24  3561 5400 5400 5727 4651 7568 7568 7568 7568 7568
5 unique + 5 repeated ASes == AS path length 10

routes are compared/chosen locally 
other metrics: 
multiexit discriminator (MED)
communities