A method and system are provided for opportunistic request-grant switching. If an ingress has no granted payload segment to send, and a flow exists which requires a request to be sent, an opportunistic payload segment is sent including a request and a payload segment related to the request. If an opportunistic payload segment is sent and the payload is dropped, the request is kept and is then treated as a regular request-grant request. The ingress port consequently only has to transmit the payload a maximum of twice. Ingress ports can thus opportunistically exploit the low latency available when egress ports are not contended for, and yet fall back on the strong fairness and quality of service (QoS) assurances of request-grant semantics. Buffering in the switch core can optionally be implemented to extend performance gains, but fairness and QoS are not dependent on this buffering.