This paper deals with the issue of providing performance guarantee such as throughput, delay, and jitter for real-time multimedia applications in packet switched networks. Generally, video demands very high bandwidth in such applications [1,2]. To achieve greater efficiency in video transmission, we propose a scheme based on the semantics of the video represented as a MPEG stream. All existing service disciplines such as Delay Earliest-Due-Date, Virtual Clock, Stop-and-Go, etc., are generic in their approach and do not differentiate among picture types of a video stream. These disciplines assume that the packets of a stream are independent and assign priority for all packets on an equal basis to provide performance guarantee. The packets exceeding the specification, are marked as low priority and receive best effort service only. Low priority packets get dropped if insufficient resources are available, leading to the los of vital information in a video stream such as I picture on which the other information (P or B picture) depend. In this paper, we introduce a concept called, Differential Priority, which exploits the interdependency among pictures by assigning different priorities to different picture types, to minimize the loss of vital information. The simulation studies confirm that the loss is less in our approach compared to the existing (single priority) approach. Further, the existing service disciplines provide performance guarantee on a per packet basis. But it is the set of packets such as a slice, in a video stream, will be more meaningful compared to a single packet during reconstruction of image at the destination. Based on this semantics, we propose yet another concept known as Slot, which is typically the transmission time of one slice of a video stream. The delay guarantee known as Slotted Deadline Guarantee (SDLG), is associated with it to provide guarantee to a set of packets in a slot rather than a single packet. The advantages of SDLG are: (a) reduced work load for the scheduler in updating the priority data-structure and (b) better statistical performance guarantee due to flexibility of deadline of packets within a slot. These two results are established through analysis and simulation. These motivated us to propose a semantics-based approach to provide performance guarantee. The adaptive rate service discipline proposed in this paper, exploits the semantics of the video stream, viz., the differential priority and the slot, to provide slotted deadline guarantee. © 1997 Elsevier Science B.V.