Which protocol is required for end-to-end signaling in an IntServ QoS architecture?

IntServ is a per-flow QoS model that guarantees bandwidth by reserving resources at every hop in the network path. RSVP is the signaling protocol that carries PATH and RESV messages between endpoints to establish and maintain these reservations end-to-end. Without RSVP, IntServ cannot communicate bandwidth requirements to intermediate nodes and cannot function.

DSCP (Differentiated Services Code Point) is a packet marking mechanism used in DiffServ, not a signaling protocol and not part of the IntServ architecture.

ToS (Type of Service) is an older IP header field for marking precedence and is not a signaling protocol used for end-to-end reservation.

LLQ (Low Latency Queuing) is a queuing mechanism that combines priority queuing with CBWFQ and operates independently of IntServ signaling.

DiffServ is a separate, competing QoS architecture that uses per-hop behaviors and packet marking rather than end-to-end signaling and resource reservation.