We have big dogs around here and up North all the time running around. Recently one ran up the outside stairs and jumped me and almost knocked me down(we have a leash law here)...I walk with a hiking pole for stabilization. I gave the owner "what for"... and we continued for a few months this way until I called the police, which I was forced to do...as the dog was huge... a Louisiana hound hunting creature. He was being friendly but I could have fallen down the concrete steps that day! The dog responded to the calm--go home. The owner was another story!
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I do what Cesar Milan does on his shows and it always works for me. I stand calmly and try to project this "calm submissive attitude". The dogs stop and stare and when they do, I say GO HOME... and slowly point away from us to where I want them to go. You can do the gesture just with your chin and eyes, and not need to point. I even did this thru a window. Two big dogs from our cousins came, one day, when our old cats were out 3 summers ago upNorth. The one looked at me, and I did the "calm" thing, and she got confused and I said "go home" all the while looking at her.
She not only made some wuff sound, but called the other to her and they BOTH left, looking over their shoulders once or twice.

Anger, waving arms, raising the voice, any sign of fear, and it is over! It is a stoic thing you do, instead. If you take ownership of your immediate area, they will leave unless they are "sick" or "crazy". If you know for sure they have attacked humans, that is another story. And I would have the pepper spray in that event. Dogs in general will defer to a "leader". Just hold your ground, and try not to keep walking-- as this shows weakness. You don't want to appear to be running away. So stay there as long as you need to take ownership of the area.
Any fear, or weakness and it is over IMO. Really aggressive dogs are another story... if I were you I'd have a cane or stick with me just in case and a cell phone.