This page describes the use of BGP communities within the network.
|( 64511 : 0 < x < 21 )||Max latency|
|( 64511 : 20 < x < 30 )||Min bandwidth|
|( 64511 : 30 < x < 35 )||Min encryption|
|( 64511 : 40 < x < 54 )||Route Origin|
The following well known communities are implemented.
|( 65535 : 65281 )||No Export||Prefix should not be exported outside of AS4242422601|
|( 65535 : 65282 )||No Advertise||Prefix should not be exported to any peers|
|( 65535 : 65283 )||Local-AS||Prefix should not be exported outside of region|
|( 4242422601 : 120 : host code )||Route learned on this host|
|( 4242422601 : 130 : 1 )||Route is a direct peer|
|( 4242422601 : 140 : DN42 region )||Route learned in this DN42 region|
In a large network like burble.dn42 it can take some time for route updates to be distributed and for the network to settle following changes. As changes ripple through the network it can create a cascade of ghost updates, each with an increasing internal path length, or adjusted latency metric. Worse the cascade of updates can also be re-distributed to peers, creating a significant multiplier for the number of updates from a single change.
To protect against ghost routes, a community is used to track how many internal hops a route has. In a fully meshed network like burble.dn42, a genuine route should never have more than two internal hops, so an export filter is used to prevent distribution of longer paths.
|( 4242422601 : 100 : 1 )||Added on first internal re-distribution|
|( 4242422601 : 100 : 2 )||Added on second re-distribution and prevents further re-distribution within burble.dn42|
The ( 4242422601 : 100 : x ) communities are not exported to peers.