Reply LS on port allocation for the W1 interface
|From Contact||Magnus Westerlund|
|To Groups||3GPP-TSG-CT, 3GPP-TSGCT-CT4|
|Cc||The IETF Chair
|Response Contact||The IESG|
|Liaisons referred by this one||
LS on port allocation for the W1 interface
The IESG apologizes for not providing a more timely reply to your liaison statement. We hope that at least the approval of the assignment of the port for the W1 interface was timely. We positively recognize that 3GPP has initiated work to figure out suitable solutions to handle port usage for network internal interfaces without the need for a static port assignment from IANA. It was further requested by the 3GPP's liaison to IETF that some additional guidance and clarifications in regards to the future possibilities for port registrations by 3GPP with IANA are desirable. Below we will attempt to provide such clarifications. We like to point to the rules and policies documented in BCP 165 (RFC6335 and RFC7605) apply to any future request. The one that is most relevant to 3GPP for any future request is the expectation that assignment of only a single port number per transport protocol will be sufficient across all the future external services, i.e. all 3GPP interfaces that 3GPP defines that use that transport protocol. This can be realized in multiple ways and is something that your own work items should address. Some example of such methods include: * When using (D)TLS one can apply for application-layer protocol negotiation (ALPN) labels (RFC7301) to identify the protocol being used within a (D)TLS session. * Multiple servers with different names can share an IP address and port number when protocols enable demultiplexing by server name. An example is (D)TLS using Server Name Indication (RFC6066). * When using HTTP-based services, use the URI namespace to efficiently separate the different services. * Other protocol-specific methods for upper layer protocol demultiplexing, such as SCTP's Payload Protocol Identifier (PPID) (RFC4960), which enable routing of individual messages to the right consumer on a server. * A 3GPP-defined service discovery solution that redirects to other ports for the individual services. In general we recommend that 3GPP completely avoid the need for port registrations in the system and user range with IANA. Service names (RFC6335) use first-come-first-served registration and have low bars for registration due to the almost unlimited size of the name space, basically only intended to prevent abuse and mass registration. Service names can be combined with DNS and SRV records to look up a service's port number or can be incorporated into a service demultiplexing solution. 3GPP is still requested to apply for a port assignment if you have a need for a port assignment in the user port range (1024-49151). These should meet the rules and policies of the port registry. Further, to enhance any future IANA requests and their handling, the IESG recommends that any future assignment request should be very clear on how this port assignment will ensure that no further port assignments to 3GPP will be necessary for that protocol and have a versioning mechanism to handle future upgrades. In case 3GPP has further questions about a potential port assignment request they are welcome to contact the Transport Area directors per email on <mailto:email@example.com> firstname.lastname@example.org.