TAILIEUCHUNG - Lecture note Networking - Theory and fundamentals: Delay models in the network layer

It is important in data communication settings to be able to characterise the delay that individual packets are subjected to in their sojourn through the system. Delays can be traced to four main causes: Processing delay, propagation delay, transmission delay, queueing delay. | Lecture note Networking - Theory and fundamentals: Delay models in the network layer TCOM 501: Networking—Theory and Fundamentals Class Notes University of Pennsylvania Santosh S. Venkatesh ° c 1997 Delay Models in the Network Layer It is important in data communication settings to be able to characterise the delay that individual packets are subjected to in their sojourn through the system. Delays can be traced to four main causes. • Processing delay: This is the time it takes to process a frame at each subnet node and prepare it for retransmission. These delays are deter- mined by the complexity of the protocol and the computational power available at each subnet node. • Propagation delay: This is the time it actually takes a frame to prop- agate through the communication link. These delays are dictated by the distance or length of the communication pathway. They can be significant, for instance, in satellite links and in high-speed links when the propagation delay can be a significant fraction of the overall delay. • Transmission delay: This is the time it takes to transmit an entire frame, from first bit to last bit, into a communication link. These delays are dictated primarily by link speed, for example, a 9600 bps link occasions only half the delay of a 4800 bps link. • Queueing delay: This is the time a frame has to wait in a queue for ser- vice. These delays are occasioned by congestion at the subnet nodes. Propagation delays are determined by the physical channels and are inde- pendent of the actual traffic patterns in the link; likewise, processing delays are determined by the available hardware and again are not affected by traf- fic. We hence focus on the transmission and queueing delays endemic at any subnet node. The discussion ignores the possibility of retransmissions, which of course add to the overall delay. In practice, however, retransmis- sions are rare in many data networks so .

• Quản trị mạng
• Processing delay
• Networking theory
• Delay models
• Network layer
• Propagation delay
• Transmission delay
• Queueing delay