M/M/1 vs G/G/1 vs G/M/1 I am using queuing theory to model a router.
I have a model that assumes Poisson traffic and I need to modify it as my actual traffic is not Poisson  
I want to ask what's the main difference between Poisson arrivals and general arrivals  in terms of results ? 
ie what are the formulas that don't hold if we don't have Poisson assumption ?

For general inter-arrival times instead of Possion, the formulas are expressed in terms of a general cumulative distribution function $F(x)$ so to use them you need to have a distribution in mind.  
Look at Introduction to Probability Models Eleventh Edition by Sheldon M. Ross
for reference. 
