Integration into global telephone
number system
While the traditional Plain Old
Telephone System (POTS) and mobile phone networks share a common
global standard (E.164) which allocates and identifies any specific
telephone line, there is no widely adopted similar standard for VoIP networks. Some allocate an E.164 number which can be used
for VoIP as well as incoming/external calls. However, there are
often different, incompatible schemes when calling between VoIP providers which use provider specific short codes.