sibling and fallback

sibling (n) 手足 同輩份的人

fallback (v)

1. 撤退 取消戰鬥
2. 備援

相對 sibling 有 parent or child
相對 fallback 則是 peer-to-peer support

In algorithms, the tree traversal is often discussed.
When we withdraw from a node back to its parent or ancestors,
we say we fallback to ancestors;
since no direct links exist between sibling nodes, we have to fallback to the parent then go forward to another sibling.
The vitual path between two sibling nodes may be called peer-to-peer channel.