yeah this is what we called teritorial barking where your dog is not sure about the other dog , u have mentoned street dog but it goes same with other new dogs as well , you are doing good in socializing him but the fact remains that " what if he meets dogs whom h doesnt know , what then ?" all i want to suggest you is to mak him meet more dogs often in a distance giving him an idea that its ok for other dogs to be near you ,,to do this u have to follow my steps
1. put your dog leash at his top neck region ( just like the dog show handling)
2. try maintaining a minimum distance of 10ft from the other or new dog
3. walk in a good pace with your dog looking front not the direction where the dog is but the opposite dirction
4. as soon as he looks at the dog snap him out with a sudden pull i the leash so that he sees forward
5. keep walking untill he is calm and is over that dog presence
