Two Company switches are connected via a trunk link. In this network, the original frame is encapsulated and an additional header is added before the frame is carried over a trunk link. At the receiving end, the header is removed and the frame is forwarded to the assigned VLAN. This describes which technology?()
A. DISL
B. ISL
C. DTP
D. IEEE 802.1Q
E. MPLS
F. None of the other alternatives apply
6岁男孩,咳嗽4个月,痰不多,常于凌晨咳醒,活动后也咳嗽,一直无发热,曾服用红霉素等多种抗生素均无效,加用氨茶碱后症状明显减轻。既往无湿疹史,体检:两肺呼吸音粗糙。考虑最可能的诊断是()
A. 支气管哮喘
B. 支气管异物
C. 咳嗽变异型哮喘
D. 支气管淋巴结结核
E. 支气管炎