This presentation provides an overview of the BGP MED attribute:

• What are MEDs?
• Potatoes (cold, hot, mashed)
• Deriving MED values
• Why MEDs break with aggregation
• MEDs from different ASes
  • Different policies
  • Different IGPs
  • Implementation caveats
    • No MED v. MED 0
    • MEDs with confeds
    • To advertise or not to advertise (BGP spec adv. rules)
• MEDs and persistent route oscillation (RFC 3345)
• The effect of MEDs on BGP updates
  • IGP link flap = MED churn, domino effect
• Effects of attributes on BGP update packing and convergence