Lecture4 - Relevant Problems/Network Functionality ECE-CSE...

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1 ECE-CSE 861: Introduction to Computer Communication Networks Ness B. Shroff ECE & CSE Lecture 4 Relevant Problems/Network Functionality Relevant problems (network functionalities) that are to be solved to design networks with high efficiency and good Quality of Service (QoS) Admission Control Scheduling Dimensioning and Resource Allocation Routing Error Detection/Control Congestion Control Fault Management Network Security… Admission Control In the current Internet, all sessions are allowed to enter the network. Instead, the transmission rates of these sessions are throttled (congestion control) resulting in poor quality service Future: Networks may need to provide some level of quality of service (QoS) to ongoing applications (especially important for real-time applications such as voice and video). Admission Control: Network controller admits a session into the network only if it can guarantee QoS to it and at the same time not violate the QoS that it provides to the other users Example: A video session is admitted only if the Pr{packet loss} < 1.0e-09 for each application. Admission Control Question: How to determine that QoS violations won’t take place? Measurements and Estimation. Scalability and complexity We need to be able to predict the congestion in the network and determine how much capacity needs to be allocated. Queueing theory plays a role in developing good control rules of thumb.
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2 Scheduling We may want to differentiate packets or sessions in terms of importance. So we could assign packets as belonging to different classes based on their importance. Scheduling problems : How to serve these packets (or sessions) from different traffic classes. How to serve packets arriving at a switch such that they conform to “interference” constraints within the switching fabric. In wireless systems, the scheduling question may be choosing which user to trasnmit to based on the wireless environment. Scheduling Issues: Will a simple priority mechanism be enough? Should we also worry about the urgency of transmitting a packet? Can we develop optimal scheduling schemes taking both urgency and a measure of importance into account? How to implement efficient heuristics based on these optimal solutions? Note: a packet-level scheduler cannot be very complex because decisions need to made at very high speeds (packet transmission times).
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Lecture4 - Relevant Problems/Network Functionality ECE-CSE...

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