Re: [Enum] ENUM Query

Bernie Hoeneisen <> Sat, 07 March 2020 10:55 UTC

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Date: Sat, 7 Mar 2020 11:55:01 +0100 (CET)
From: Bernie Hoeneisen <>
To: Wayne Cutler <>
cc: Brian Rosen <>, "" <>
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Subject: Re: [Enum] ENUM Query
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Hi Wayne

Thanks for your response.

I think I am getting closer to understand the challenges reagarding ENUM 
in IMS. (It's been a while since my last 3GPP/IMS meeting, which dates 
back to year 2002:ish.)

In the following a preliminery assessment of your options (incl. further 

> · Enhance the current ProtocolBasedClass of SIP as defined in RFC 3764 
> to add a sub-type - e.g. "SIP/MMTEL" & "SIP/RCS" - with the absence of 
> a sub-type meaning "all services".

This is a no-go, as RFC 6117 does not forsee to use subtype strings other 
than different URI Schemes for Protocol-Based Enumservices. cf.

> · Re-use (or perhaps re-interpret?) an existing result (e.g. 
> ApplicationBasedClass of IM or unifmsg) to mean RCS Messaging - but this 
> feels like a kludge,


- What are the differences between im (Enumservice) and RCS as used in 

- What are the differences between unifmsg (Enumservice) and RCS as used 
in IMS?

> · Define a new ENUM registry entry to identify RCS Messaging.

Given the information I currently have/understand, this appears to be the 
cleanest approach, i.e.  to define a new Application-Based Enumservice:

- "rcs:sip" with URI Schemes "sip" and "sips"

or both

- "rcs:sip" with URI Scheme "sip"
- "rcs:sips" with URI Scheme "sips"

(depending on the implementation, see also: )

If we go down this road, you may also want to consider the same for MMTEL, 
to replace your legacy approach that uses the Protocol-Based Enumservice 
"sip", e.g.:

- "mmtel:sip" with URI Schemes "sip" and "sips"

Note that anything I write here is pre-liminery and MUST NOT be 
interpreted in any way as "decision by the Dedicated Expert for ENUM" (or 
alike), but rather help you to find the right direction for a possible 
upcoming formal IANA registration process.


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