[libvirt] migration: why did we choose port 49152-49215 for migration as default?

[Zhangbo (Oscar)]

Hi all:
    As we know,  "32768~61000" are random ports reserved for customized use. 49152-49215 is in that range. 
	We think that setting migration port into this range, is a little risky. Because other applications may have already taken these ports before we migrate a guest, then the migration job would fail.

    So, why did we choose "49152-49215" as the default port range for migration, any specific purpose? Thanks in advance.

Oscar.