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PORT ALLOCATION

FOR NEW 3GPP INTERFACES

By Giorgi Gulbani, CT4 Rapporteur
for the PortAl Work Item

Since 2015, The Internet Assigned Numbers Authority (IANA) When the IANA assignment request cannot be justified, one
has encouraged 3GPP to find and implement a solution of the alternative solutions described in clause 4 of TR 29.941
for the port assignments for protocols only used in 3GPP should be adopted. This is especially true for 3GPP interfaces
networks, as an alternative to IANA assigned port numbers. that would be used only in intra-domain scenarios.
In the meantime, IANA and the Internet Engineering
Steering Group (IESG) have continued processing In scenarios, when IANA allocated default port numbers cannot
applications for new port allocations and do grant numbers, be used, while a new 3GPP interface application may require
so long as their recommendations given in IETF RFC 7605 a pre-defined specific server port number, 3GPP becomes
are followed. responsible for allocating a server port number (solution#6 in
3GPP TR 29.941).
A friendly parting of the ways The 3GPP registry for Service Names and Port

Now, from Release 17 onwards a 3GPP CT4 Working Group Numbers
study has identified possible options for scenarios when
a new default port number allocation is required, but for Port numbers should be assigned from a sub-range of the
certain technical reasons requesting the number from IANA Dynamic/Private Port range [49152 - 65535]. Working Group CT4
is not seen as the best way forward. decided to set aside further sub-range of 101 ports from 65400 to
65500. 3GPP allocated port numbers are documented in 3GPP
The study produced eight solution proposals and respective TS 29.641.
guidelines, which are documented in 3GPP TR 29.941. Any
3GPP working group can now rely on these guidelines and From Release 17, when a new application requires a pre-defined
select the solution that is the most suitable for achieving server port number, during the application initialization the
their objectives. operating system will tell the new application if the port is
already in use or not. If the port is in use by another, legacy
It is still strongly recommended that 3GPP groups should application, the new application or operating system shall ensure
apply to IANA for assigned service name and port number that the legacy application stops using the port.
for any protocol potentially supported by roaming and inter-
domain interfaces, when no other service port discovery is It is up to the implementation to decide if the legacy application
applicable (e.g. DNS-based solutions). will be forced to stop using the port immediately, or if the legacy
application will be granted some period of time for gracious
removal of the port from use.
“Any 3GPP working group can now rely on For more information, please check WG CT4’s Technical Report
these guidelines and select the solution and Specification on this topic:
that is the most suitable for achieving their • 3GPP TR 29.941 - Guidelines on Port Allocation for New 3GPP
objectives.” Interfaces
• 3GPP TS 29.641 - 3GPP registry for Service Names and Port
Numbers

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