LDP sessions have been established between three devices on an MPLS network.

LDP establishes and maintains sessions between Label Switching Routers (LSRs) to exchange label bindings and construct Label Switched Paths.

An LDP session relies on a TCP connection established using the transport addresses advertised by its participating routers.

Changing the LDP transport address affects the session ' s transport endpoint and can require the session to be terminated and re-established using the new address.

Changing the label advertisement mode also affects fundamental LDP negotiation and label distribution behaviour. Huawei documentation explicitly states that modifying this mode causes LDP sessions to be re-established.

Configuring Penultimate Hop Popping (PHP) changes label forwarding behaviour rather than the established LDP session itself.

Similarly, changing the MPLS TTL processing mode does not inherently require LDP session renegotiation.

Therefore, changing the LDP transport address and label advertisement mode are the applicable operations.

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