Track 2 - Internet Routing and IP Network management (7-Oct-96)
Autonomous Systems and EGP
2) New BGP Features
D) Route Damping in GateD
- The purpose of Route Damping is to control routing instability at receiving peers
- Peers monitor received route announcements and
Retain history of flap (up/down) routes
- Weighted based on Number of flaps
- greater the number of flaps, greater the time routes held down
- A metric of instability at current time is maintained
- This metric is decayed over time so that after an extended period of stability it tends to 0
- An exponential decay algorithm is used for maintaining the metric
- Cost
- Need to remember history for a long interval
- Want to increase delay in proportion to number of flaps over the interval
- Recent history of stability of a route is taken to be a predictor of
future behavior
- Decay of unstable route history entries is done in an efficient manner by queuing all
history entries eligible for reuse at the same time in the same slot of a slotted timing array.
- In general, the damping algorithm (based upon a now expired internet draft
by Curtis Villamizar) is highly efficient in terms of processing and storage requirements.