Style question: It seems odd and cumbersome to refer to R' Yishmael this way - "bno shel", why not refer to him as R' Yishmael ben Yochanan or R' Yishmael b'R' Yochanan like R' Yishmael b'R' Yosi Hagalili?
Menachem Weiman, St. Louis USA
Shalom Menachem,
Thank you for your interesting question! I assume the reason for this odd reference to Rebbi Yishmael derives from the fact that there are around 15 Tana'im called Rebbi Yochanan, and a shorter list, called Rebbi Yishmael. Since it is needed to mention the name of Rebbi Berokah in order to identify which Rebbi Yochanan was Rebbi Yishmael's father (so that we will know which Rebbi Yishmael it is), it might be more comfortable to use the term "Beno" for the first mention and then "Ben" the second time. Another possibility is that Rebbi Yochanan was his son's Rebbi Muvhak, so perhaps "Beno Shel" implies an extreme closeness between the father and his son since he taught him most of his Torah.
I hope this helps,
Aharon Steiner