dogs in the 7th century

I don't know much about dogs; my sister had one when I was seven, but I'm a cat person. Nothing against dogs, I've just always lived in cities, which I think is a hostile environment for large dogs (and small dogs, in my experience--small though it is--tend to yap). So, regarding dogs: utterly ignorant. I've been researching the 7th century for a while now (for my Hild novel), but find I still don't know much about it. So, in this regard too: utterly ignorant. Now I'm faced with writing about dogs in the 7th century and my mind has gone terrifyingly blank.

Here's how I imagine the dog situation in the north of England circa 627:

• There are herd dogs--large, loyal protectors of flocks (sheep, cows, goats, maybe even geese) that run with the flock to protect it from predators but don't herd the flock under commands from the shepherd/cowherd/goosegirl. These dogs (sometimes just one, occasionally a pair) would spend much more time with the beasts than the humans. They eat, sleep, even play with the cows/sheep. Perhaps they were imprinted as puppies and mostly think they *are* cows/sheep.
  

• There are sight hounds, coursers and so on, like deerhounds--probably largely under royal or at least 'noble' control.

• Bulldogs would control large animals going to slaughter.
  

• There are hounds of war: huge things that perhaps wear spiked collars and are trained to do one thing: kill. These would most likely be kept in royal kennels because they might not be safe to allow anywhere else.

• Perhaps isolated farmsteads or small settlements would have a couple of dogs-of-all-trades.

• Perhaps people would form bonds with some of these dogs. Perhaps that would be discouraged. Perhaps not.

I read about Cuchulain and his hound, and I wonder, Did they care for each other? Or was the dog just a tool--an important and precious tool, like a sword, but not something to devote feeling to? If dogs were, to some degree, pets, how would they be trained? Would women be allowed to keep dogs? Would they want to?

Hild has basically had a puppy forced upon her by the queen, Æthelburh, who wants a dog for herself (I've yet to work out why) and thinks that if at least one other female at the royal vill--even a child, like Hild--has a dog, Æthelburh won't seem like such a foreign weirdo.

So now I'm trying to figure out how it all works: what would the dog (a bitch, I've decided) look like? Would it have a leash? How would it be trained? I'm thinking a cross between a wolfhound and a Molossian-type herd dog--big, but not as heavy as a Molossian or as tall as a wolfhound--that has protective but not herding instincts, with an urge (though not an overwhelming one) to chase prey. It would hit maturity around 18 months.

So my question for both dog-lovers and medievalists is: does any of that make sense? Do you have suggestions?