A method for allocating a global label, comprising: receiving, by a controller, a first message sent by a forwarding apparatus, wherein the first message carries a first label range, comprising multiple labels, wherein the multiple labels comprised in the first label range are a subset of multiple labels comprised in a label space of the forwarding apparatus, and the first label range is not equal to the label space of the forwarding apparatus; and allocating, by the controller, a global label to the forwarding apparatus according to the first label range carried in the first message, wherein the global label is a label in the first label range; wherein the first label range comprises a label that has been allocated by the forwarding apparatus to a first label switched path, the forwarding apparatus is a node on the first label switched path, and after the receiving, by a controller, the first message, and before the allocating, by the controller, the global label to the forwarding apparatus, the method further comprises: sending, by the controller, a second message to the forwarding apparatus, wherein the second message comprises a second label range, the second label range comprises multiple labels, the second label range is a subset of the first label range, the second message is used to instruct the forwarding apparatus to allocate a new label to a second label switched path, the new label is used to replace a first label that has been previously allocated by the forwarding apparatus to the second label switched path, the new label is outside the second label range, the second label switched path is a subset of the first label switched path, and wherein the first label that was previously allocated by the forwarding apparatus to the second label switched path was comprised in the second label range; and the allocating, by the controller, the global label to the forwarding apparatus according to the first label range carried in the first message, wherein the global label is a label in the first label range, specifically comprises: allocating, by the controller, the global label to the forwarding apparatus according to the second label range, wherein the global label is a label in the second label range. receiving, by a controller, a first message sent by a forwarding apparatus, wherein the first message carries a first label range, comprising multiple labels, wherein the multiple labels comprised in the first label range are a subset of multiple labels comprised in a label space of the forwarding apparatus, and the first label range is not equal to the label space of the forwarding apparatus; and allocating, by the controller, a global label to the forwarding apparatus according to the first label range carried in the first message, wherein the global label is a label in the first label range; wherein the first label range comprises a label that has been allocated by the forwarding apparatus to a first label switched path, the forwarding apparatus is a node on the first label switched path, and after the receiving, by a controller, the first message, and before the allocating, by the controller, the global label to the forwarding apparatus, the method further comprises: sending, by the controller, a second message to the forwarding apparatus, wherein the second message comprises a second label range, the second label range comprises multiple labels, the second label range is a subset of the first label range, the second message is used to instruct the forwarding apparatus to allocate a new label to a second label switched path, the new label is used to replace a first label that has been previously allocated by the forwarding apparatus to the second label switched path, the new label is outside the second label range, the second label switched path is a subset of the first label switched path, and wherein the first label that was previously allocated by the forwarding apparatus to the second label switched path was comprised in the second label range; and the allocating, by the controller, the global label to the forwarding apparatus according to the first label range carried in the first message, wherein the global label is a label in the first label range, specifically comprises: allocating, by the controller, the global label to the forwarding apparatus according to the second label range, wherein the global label is a label in the second label range.