Duplicate SID handling

When the IGP issues or receives an LSA/LSP containing a prefix SID sub-TLV for a node SID or a backup node SID with a SID value that is a duplicate of an existing SID or backup node SID, the resolution in Table: Handling of duplicate SIDs is followed.

Table: Handling of duplicate SIDs
	New LSA/LSP
Old LSA/LSP	Backup node SID	Local backup node SID	Node SID	Local node SID
Backup Node SID	Old	New	New	New
Local Backup Node SID	Old	Equal	New	New
Node SID	Old	Old	Equal/Old^¹	Equal/New²
Local Node SID	Old	Old	Equal/Old^¹	Equal/Old^¹

Equal/Old means the following.

If the prefix is duplicate, it is equal and no change is needed. Keep the old LSA/LSP.
If the prefix is not duplicate, still keep the old LSA/LSP.

Equal/New means the following.

If the prefix is duplicate, it is equal and no change is needed. Keep the old LSA/LSP.
If the prefix is not duplicate, pick a new prefix and use the new LSA/LSP.