Alarm clocks should only be used in emergencies or if there is no other option because they

The open systems interconnection (osi) reference model: defines standards for many aspects of computing and communications within a network. is a generic description for how computers use multiple layers of protocol rules to communicate across a network. defines standards for wireless local area network (wlan) communication protocols. details the advantages and disadvantages of various basic network cabling options.

The idea that, for each pair of devices v and w, there’s a strict dichotomy between being “in range” or “out of range” is a simplified abstraction. more accurately, there’s a power decay function f (·) that specifies, for a pair of devices at distance δ, the signal strength f(δ) that they’ll be able to achieve on their wireless connection. (we’ll assume that f (δ) decreases with increasing δ.) we might want to build this into our notion of back-up sets as follows: among the k devices in the back-up set of v, there should be at least one that can be reached with very high signal strength, at least one other that can be reached with moderately high signal strength, and so forth. more concretely, we have values p1 ≥ p2 ≥ . . ≥ pk, so that if the back-up set for v consists of devices at distances d1≤d2≤≤dk,thenweshouldhavef(dj)≥pj foreachj. give an algorithm that determines whether it is possible to choose a back-up set for each device subject to this more detailed condition, still requiring that no device should appear in the back-up set of more than b other devices. again, the algorithm should output the back-up sets themselves, provided they can be found.\

What need most led to the creation of the advanced research projects agency network? darpa wanted scientists to be able to collaborate and share research easily. darpa wanted american and russian politicians to be able to communicate. darpa wanted astronauts to be able to contact nasa and the white house. darpa wanted factory owners to be able to coordinate supply chains.