In the following exercise, we are going to study the CoAP protocol (Constraint Application Protocol ) used in Wireless Sensor Network (WSN), to simplify implementation in Sensor Nodes which have very limited resources in term of memory, computing power and energy. The standard is generic and does not make any assumption on Layer 2, but in our case we will suppose that layer 1 and 2 are IEEE 802.15.4. At layer 3, the 6LoWPAN protocol compresses the 40 bytes of the IPv6 header into 20 bytes. Another characteristic of WSN, is the high error rate on the radio link which leads to frame losses.

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RES1 Data Link Layer (9/12)

Data Link Layer The exercises shown that Send and Wait protocol does not offer good performances when propagation delay is long compared to transmission time. In that case it is better to send several unacknowledged frames instead of waiting for acknowledgments before sending another frame. We study HDLC protocol which can be view as the ancestor of … Read moreRES1 Data Link Layer (9/12)