I too have posted my personal attack by 2 dogs, not even considered "vicious" breeds, but large none the less. I carry a Kershaw pocket knife for a multitude of reasons, but was thankful I had it when they attacked. The little ankle biting "Toto's" are
usually are more bark than bite, but can usually be dealt with by a swift kick. Kinda like trying to make a 40yd Field Goal....Or just scruff them and throw them across the street, room, what have you,...
Big dogs however, regardless of breed, especially on the street/hiking trail/backroads,etc,.. in "pack" mode, or in a poorly fenced in yard in uber "protection/attack" mode, are a lethal threat.
Regardless, if the owner is there, and can't control them, you will have about 2-3 seconds to make your decision, the dog(s) if in "attack" mode will usually make the decision for you. They size you up, and instinct takes over almost instantly.
Two things will happen if you stand your ground, as running just triggers the "chase" response.
1: They will bark, lower their tail, and not attack.
2: They won't bark, growl in a low pitch, face you head on and charge.
At that point it's game over, you defend yourself, as Alf posted with any means you have. Knife, pistol, gouge eyeballs, death grip on throat, rip testicles, whatever it takes. The initial attack by a big dog is to get you down and go for your face and throat, and it is blindingly fast and ruthless, defensive bites come from reflexively putting your hands, arms in front of your face. The dogs "fight/attack" response is balls to the wall, full tilt, 110% attack. There is no "moderate" dog attack.
If there is more than one dog getting ready to attack you, and I was legally carrying, I would not hesitate,.... shoot em'. I'll apologize to my daughter, owner, whoever, but I won't go down without a fight, whether their on 4 legs, or 2.
Good question, and of course, my humble opinion.
This response is not PETA approved.