ICMP is a link layer protocol. ICMP messages are triggered by the physical layer, and response messages are provided by the IP layer or upper layer protocol.

(single) Is the following description correct? EPON packets are variable length. The GPON downstream frame is fixed length.

LAN computers in judging the received broadcast frame is the method whether they should receive, judge whether the source MAC address of the frame is the same as the hardware address of the machine.

(Single) The UA5000 narrowband main control board PVM and the broadband main control board IPM are connected to each other to provide voice services and broadband services. The voice service is transmitted to the IPM board through the internal IP channel, and then transmitted to the upper layer by the uplink interface of the IPM board. Network, which command should be used to configure the system networking mode?

(single) How many message commands are there in the H.248 protocol?