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.

Consider a slotted aloha system, where the time slot equals the fixed duration of each packet. assume that there are 4 stations a,b,c,d sharing the medium. (a) stations a,b,c,d receive one packet each from higher layers at times 1.3, 1.5, 2.6,5.7 respectively. show which transmissions take place when, according to the slottedaloha protocol; describe all transmissions until all four packets have been successful.when needed, each station has access to the following sequence of random number, provided by a random number generator and drawn uniformly between 0 and 1: (1) station a draws numbers: 0.31, 0.27, 0.78, 0.9, 0.9, 0.11, 0. (2) station b draws numbers: 0.45, 0.28, 0.11, 0.83, 0.37, 0.22, 0. (3)station c draws numbers: 0.1, 0.2, 0.3, 0.4, 0. (4) station d draws numbers: 0.36, 0.77, 0.9, 0.1, 0.1, 0.1, 0.1, 0. (b) in slotted aloha, a station transmits in each time slot with a given probability. what probabilities would you assign to each of the four stations so as to: (i) maximize the efficiency of the protocol? (ii) maximize fairness among the four stations? (c) will the efficiency increase or decrease if we modify slotted aloha as follows: (i) get rid of slots and allow stations to transmit immediately? (ii) implement carrier sensing? (iii) implement collision detection? (iv) implement collision avoidance?

This chapter lists many ways in which becoming computer literate is beneficial. think about what your life will be like once you’re started in your career. what areas of computing will be most important for you to understand? how would an understanding of computer hardware and software you in working from home, working with groups in other countries and contributing your talents.

Select the correct answer. peter has launched a website that features baby products. however, clients often find they are unable to access the website because the server is down. which feature of cybersecurity should peter focus on for his website? a. data authenticity b. data privacy c. data availability d. data integrity e. data encryption