[单选] Data transfer is slow between the source and destination. The quality of service requested by the transport layer in the OSI reference model is not being maintained. To fix this issue, at which layer should the troubleshooting process begin?（）

供给学派为什么把减税作为其政策主张的中心？ 标杆学习 票据上有伪造，变造的签章的，将影响到票据上其他真实的签章的效力。 OSPF路由协议在多路访问的网络中，需要选择DR和BDR，那么其在那种状态进行了DR和BDR的选举？（） Init状态。 2way状态。 Exstart状态。 Exchange状态。 对于贴现发行债券而言，到期收益率与当期债券价格正向相关。 Data transfer is slow between the source and destination. The quality of service requested by the transport layer in the OSI reference model is not being maintained. To fix this issue, at which layer should the troubleshooting process begin?（）