[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [dccp] port numbers and DCCP

Hey all!

Let's talk about this for just a second.

Caveats:
* We will probably end up doing what SCTP did, since it is the simplest, so in some sense this mail is academic.
* Some of the original coauthors don't like the well-known port concept anyway.

But I am not 100% sure that automatic registration of the TCP port space is the right answer.

The port space is finite. The well-known ports list already has anomalies, where the TCP port is one service and the UDP is another (port 2014), where only SCTP is registered (3097), where TCP and SCTP are registered but not UDP (3565). Do we borrow the UDP port space? The TCP port space? The SCTP port space? There is no easy way to find out what TCP registrations were "current" at the time of SCTP's publication, so there's no way to know what ports are really reserved.

I would prefer that we start afresh with DCCP, at least notionally. Maybe some language like this:

DCCP connections may make use of well known port numbers, as in TCP and UDP, although the Service Code may lessen this requirement somewhat. IANA SHOULD maintain registrations for well-known DCCP port numbers using similar mechanisms as for TCP, UDP, and SCTP. When a port number is not explicitly reserved for DCCP, implementations SHOULD use any existing registration for UDP. However, implementers are encouraged not to rely on this fallback, and explicitly reserve well-known ports as they are used.

Eddie


On Nov 15, 2005, at 3:39 PM, Colin Perkins wrote:

On 15 Nov 2005, at 22:34, Sally Floyd wrote: 
Colin reported last week at IETF that the main DCCP internet-draft
didn't make any assignments about port numbers.  RFC 2969
says the following, for SCTP:

This protocol will require port reservation like TCP for the use of
"well known" servers within the Internet. All current TCP ports
shall be automatically reserved in the SCTP port address space. New
requests should follow IANA's current mechanisms for TCP.

Our suggestion is that we will add this language to the DCCP spec
when the draft reaches AUTH48, the authors' 48 hours just before
the document is issued as an RFC.  And in this way all TCP ports
will automatically be reserved in the DCCP port address space as
DCCP ports also, without the need for modifying the IANA registry.

Does this seem fine to everyone?

Yes, assuming it follows UDP port registrations and rules, rather than TCP.

Colin