|The direction of data flow on an Label Switched Path (LSP)
segment with respect to the head of the LSP.
Where an LSP is signaled using a conventional signaling
protocol, the 'head' of the LSP is the source of the signaling
(also known as the ingress) and the 'tail' is the destination
(also known as the egress). For unidirectional LSPs, this
usually matches the direction of flow of data.
For manually configured unidirectional LSPs, the direction of
the LSP segment matches the direction of flow of data. For
manually configured bidirectional LSPs, an arbitrary decision
must be made about which LER is the 'head'.