# transmission delay in store and forward, what is L/W and how to compute tw [closed]

I don't understand some things in Store and Forward equation:

• D -> Number of channels and switches pairs.
• tr -> Routing time.
• tw -> Transfer time in a channel.

What is the L/W?

And normally exercises provide me tw (time transfer in a link), but now I am doing an exercise in which tw is not provided. I think I should compute with the speed of the links and the data size transferred. But I don't know what should be the size for the data.

Thanks.

## closed as unclear what you're asking by David Richerby, Evil, Yuval Filmus, Juho, Gilles♦Feb 26 '17 at 17:34

Please clarify your specific problem or add additional details to highlight exactly what you need. As it's currently written, it’s hard to tell exactly what you're asking. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

• Welcome to CS.SE! Please edit the question to provide more context. What don't you understand? What do each of the variables mean? You should define all notation in the question, so it is self-contained. Presumably wherever you got the equation from will have defined each of those variables at some point before the equation, so your next step is to start reading backwards until you can find where each one was defined. One further comment: Understanding concepts is usually more important; computer science is much more than just plugging numbers into formulas. – D.W. Jan 13 '17 at 20:24

You ask us what $L$ and $W$ are. But we can't tell you. Only you know where the formula came from (you haven't told us). And only you have access to that book. If the book is any good, it will have defined what $L$ and $W$ represent before using them, so look through the book. If the book uses variables $L$ and $W$ without defining them, then I recommend you look for a better book.

• I am not sure, but could be that L means the size of the packet without the head, and W the Bandwith in the channel? I am not sure because in the previous page it puts w and not W with capital letter. – Quico Llinares Llorens Jan 13 '17 at 22:28