Packet Design interview questions

First I had a online written round having 3 different sections related to Data Structures, Linux/Unix and C/C++. 10 questions in each section this needs to be finished in 30 mins. If round is qualified and second round was coding round they gave me one question on C++ which I had to correct and write a function and submit in max 2 hrs. After this round I had Skype round in which they based basic data structure questions from Linked list and Trees. This round went for almost 2 hrs. I cleared this round also then I had face to face interview at their Pune office. This F2F interview went for 4 hrs.

Its a rigorous interview with multiple rounds (only technical). I had 6 rounds where almost all of their senior guys asked datastructure/puzzle questions. Since they are into networking, most of the questions were graph related