-------------o-------------------o--------o--- bus __________ | __________ __|__ | | Transmit |->o->| Receiver | | UART| ... | |_____| | |_____| | UART | __|||__ |___________________________| | Host | __|||||||||__ |_______| | Host | | Computer | |_____________|From the point of view of the host computers, the UART offers the usual serial device interface. Assume that the bus is arranged so that the start bit is a 1 and the bus passively or's together all of the outputs from all of the UARTS to compute the value all UARTS will receive. Assume all UARTS use the same data rate
Aside: From a software perspective, the Apple Localtalk bus works roughly like this. At a lower level, however, the Localtalk bus uses inductive coupling between the local UART and the bus, and a synchronous protocol is used instead of an asynchronous protocol.
The Problem: Outline the interrupt service routine(s) and low level software needed to implement the CSMA-CD (Ethernet) protocol on this hardware. Assume that each machine has a unique 8-bit address, and that the interface to higher level software is through send_packet( d, a ), which sends the fixed size packet of data d, to user a, and receive_packet( d, a ), which awaits a packet from any user and returns the packet in d and the address of the sender a. The constant packet_size is given in bytes.
The Problem: Tannenbaum uses a different definition of transparency in Section 9.4.1, without ever giving a general definition of the term, although he gives many examples in the distributed system context. Write a page or so that a) Gives a general definition of transparency as the term is used by Tannenbaum, b) contrasts this with Parnas's use of the term, and c) attempts to find the relationship between these two usages. Here, items a) b) and c) are not sub-parts of the problem, but issues you must address, not necessarily in that order.
The Problem: Discuss the impact of this on the whole idea of protocol hierarchies outlined in section 10.1 of the text.