Yea I did alot of debugging of the networks hardest problems, and the crossover is especially true with telecom systems since all the inter-connectivity comes from the standards bodies, which share a lot of the same base and history. But some stuff differed as well, it was difficult for a bunch of the hardened circuit switched folks to move to an all IP world, and I only had a cursory view into the circuit switched world which was on it's way out when I was in industry.