7. State-managed PCE needed

The PCE in request/response mode presented above is a stateless PCE, i.e. it doesn't memorize requests and responses.

This mode of operation, without state conservation, leads to limitations in the use of PCE. Indeed, the problems of calculating dependent paths using different sources cannot be addressed with this mode of operation. Indeed, considering a path request A → B and a path request C → D to be disjoint, a PCE without state conservation will never be able to ensure that path C → D is disjoint from path A → B if it does not memorize the previously computed path A → B.

To enable the PCE to memorize the states of calculated paths (this is known as stateful PCE), the PCE will need to maintain a new database called LSPDB (Label Switched Path DataBase).