IEEE1588v2解析（5）--PTP的传输方式

PTP报文一般采用multicast方式传输，也可以用unicast方式传播（如果能实现类似multicast的效果）；

PTP报文支持的传输类型有：

PPP over UDP over IPV4 

The UDP destination port of an event message shall be 31.

The UDP destination port of a multicast general message shall be 320.

The UDP destination port of a unicast general message that is addressed to a clock shall be 320. 

PPP over UDP over IPV6

The UDP destination port of an event message shall be 31.

The UDP destination port of a multicast general message shall be 320.

The UDP destination port of a unicast general message that is addressed to a clock shall be 320. 

 PPP over Ethernet

all PTP implementations directly using Ethernet format packets with the #88F7 Ethertype