help3002

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help3002

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UWA week 14 (1st semester, non-teaching week) ↓

Lab 3 Piggybacking implementation (both)

3:53am Thu 4th Apr, Christopher M.

ANONYMOUS wrote:

> I'm struggling a lot trying to implement the piggybacking in stopandwait.c. When it comes to the concepts I'm able to pinpoint where I need to implement the code and how the code should look like, but I'm unable to use things like #define EV_PIGGYBACK_TIMER EV_TIMER2 or CNET_start_timer(EV_PIGGYBACK_TIMER, PIGGYBACK_TIMEOUT, 0);.

Hi, I'm not sure how to answer your question as I'm not sure what you mean by "I'm unable to use things..." The approach to piggybacking requires two timers, one supporting the retransmission of unacknowledged (outgoing) data, and one to force the sending of an acknowledgement 'by itself' if we have no data to send. The header file cnet.h defines 10 timers, named EV_TIMER0..EV_TIMER9, but doesn't define the constant EV_PIGGYBACK_TIMER (as cnet tries not to force you to write your protocols or data structures in any way). But it makes protocols easier to ready if we give the timers more meaningful names, as with:

#define EV_PIGGYBACK_TIMER      EV_TIMER2