Remember when learning IE's always wanted to have the opportunity in an existing network equipment under more contact. After all, to the session will be in contact with every day, because the objective conditions I later found some video B station is also good. At least give this line of network engineers do have a general awareness. For example: what kind of room fiber patch panels, optical patch cord type, optical module type and parameters. Some have said that the main UP doing video when there is great heart, take care of some of the newcomers did not take their own environmental conditions. Here affixed to a few links to your reference;
https://www.bilibili.com/video/BV1F4411V725?from=search&seid=11182762461493290785
(UP above the main comparative determined by doing new instructions can give an intuitive understanding)
https://www.bilibili.com/video/BV1M7411V7vY/?spm_id_from=333.788.videocard.2
following UP Lord cow B, wired networks, wireless devices are also get together the two servers. These devices did not see that spend less on learning very heart.