Re: [Int-area] Continuing the addressing discussion: what is an address anyway?

Brian E Carpenter <brian.e.carpenter@gmail.com> Fri, 04 March 2022 19:57 UTC

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To: Toerless Eckert <tte@cs.fau.de>, Dino Farinacci <farinacci@gmail.com>
Cc: "Int-area@ietf.org" <Int-area@ietf.org>, Dirk Trossen <dirk.trossen=40huawei.com@dmarc.ietf.org>
References: <57c643c667d94a77b9917bb17dc142a5@huawei.com> <7de0956f-3fde-1543-405b-b635f6e69362@lear.ch> <Yh5M18z2/YVfpW7i@faui48e.informatik.uni-erlangen.de> <A771FFF8-43A8-4D84-8B6E-A3E7AF96644E@gmail.com> <YiBhOKIK9bMqwx0a@faui48e.informatik.uni-erlangen.de> <385CF477-C876-482F-ADFE-DAAD6CA7BAEC@gmail.com> <YiH6iHwv+U9QFA06@faui48e.informatik.uni-erlangen.de>
From: Brian E Carpenter <brian.e.carpenter@gmail.com>
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Date: Sat, 05 Mar 2022 08:57:36 +1300
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Subject: Re: [Int-area] Continuing the addressing discussion: what is an address anyway?
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Toerless,

I believe the closest we ever got to agreed definitions was in the
IRTF RFC 6115:

    6.   A "locator" is a structured topology-dependent name that is not
         used for node identification and is not a path.  Two related
         meanings are current, depending on the class of things being
         named:

         1.  The topology-dependent name of a node's interface.

         2.  The topology-dependent name of a single subnetwork OR
             topology-dependent name of a group of related subnetworks
             that share a single aggregate.  An IP routing prefix is a
             current example of the latter.

    7.   An "identifier" is a topology-independent name for a logical
         node.  Depending upon instantiation, a "logical node" might be a
         single physical device, a cluster of devices acting as a single
         node, or a single virtual partition of a single physical device.
         An OSI End System Identifier (ESID) is an example of an
         identifier.  A Fully Qualified Domain Name (FQDN) that precisely
         names one logical node is another example.  (Note well that not
         all FQDNs meet this definition.)

Regards
    Brian

On 05-Mar-22 00:39, Toerless Eckert wrote:
> On Thu, Mar 03, 2022 at 09:28:23AM -0800, Dino Farinacci wrote:
>>> of its address structure helps the underlay to locate the entity (xTR) that the
>>> address is assigned to (xTR). So the name 'locator' is 'just' a good
>>> name for what LISP calls/uses the address for, not for how the under
>>> itself would maybe call the address or use the address for.
>>
>> Well the locator you put in an outer header destination address is called/used/assign to whatever the rules of the underlay are. If the underlay is ethernet, then its a 6-byte address where the high-order 3 bytes is an organizational ID, just to cite an example.
> 
> Indeed.
> 
> I have not seen an answer to the question i posed earlier in the thread:
>   whether and if so what general (not technology specific) definition of locator
> and identifier the IETF may have. But i have seen a lot of confusion about
> it and people shying away from using these terms.
> 
> If (as i think) we do not have a commonly applicable definition of locator/identifier
> (beyond its use in indivdual technologies like LISP), then i think this is because
> folks who tried to apply these terms (incorrectly) may have failed to
> see the difference between what an address is and what someone (like an
> application) calls it (/uses it for). In that respect the reference to
> the White Knight in IEN19 is very helpful to remember.
> 
> Cheers
>      Toerless
> 
>> Dino
>