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

Brian E Carpenter <> Fri, 04 March 2022 19:57 UTC

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To: Toerless Eckert <>, Dino Farinacci <>
Cc: "" <>, Dirk Trossen <>
References: <> <> <Yh5M18z2/> <> <> <> <>
From: Brian E Carpenter <>
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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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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

         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.)


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