> This is not semantic addressing in any way
I don't have a background on this term. If one considers it as "embedding
information into an IPv6 address", then it seems ok: there's information
embedded in the address about the position of a node in the network topology.
So no strong opinion on the term.
> Path-Aware Static Addressing
> Path-Aware Systematic Addressing
> Path-Aware Synthetic Addressing
If we need to avoid 'semantic' then maybe also:
Path-Aware Structured Addressing
Path-Aware Spatial Addressing
> But they do move (...).
> ... There should be a change management process, but there will always be
> change.
> ... So the use cases are not truly *static*; they change from time to time
Agree here. Also for the "smart home" scenario devices can get relocated.
> but I believe the draft lacks an important section on what happens when a
> node *leaves* the network (how does the address get reclaimed?) and when a
> node *moves* (how does the node know that it has moved, so that it can
> release its old address and acquire a new one?).
Agree also - even though the topology is largely static over the lifetime of a
system (for use cases in which PASA gets applied), there can still be changes.
A new subsection 6.X could describe maybe how changes are handled - when/if
they occur?
Some cases are:
- Child node gets removed (e.g. broken, or to insert it elsewhere = move)
- Router node gets removed/replaced - new Router might get a different address
- all devices in the tree under it get a new address.
- Node is moved (maybe it reboots, maybe it retains its power due to whatever
reason e.g. battery-backup and it still has its old state at the moment it
detects reattachment of its interface again)
- Root gets replaced (address doesn't change, but maybe it needs to run PASA
again to build its state, and all devices would get the same address again?)
- ...
The document could also declare such change cases as out of scope, but it seems
more useful to describe how PASA handles these cases (to me it seems well able
to handle these) and the impact of it (e.g. IP address changes).
There are some more indirect consequences of IP address change from the
application point of view (e.g. my cached address of a peer suddenly isn't
valid anymore and I need to rediscover its address) but many of those are not
exclusive to PASA, so these can be out of scope mostly.
E.g. a discovery method like unicast DNS-SD or CoRE-RD may be used to
rediscover the IP address of a particular host.
One PASA-specific item that could be added to the Security Considerations is
the following: due to the address structure, it's likely that 1 or more
addresses get "re-used" in case of node changes like listed above.
That is, node 1 could be sending data to IP of node 2 which due to changes now
suddenly arrives at new node 3. In some other address assignment methods like
SLAAC, you would detect this situation due to an ICMPv6 error on the
destination not being reachable, which in turn triggers an IP address
rediscovery.
However with PASA you can't necessarily rely on the ICMPv6 error -- a new/other
node may be re-using that address. Not a show-stopper for PASA, but something
an adopter needs to be made aware of! (Even though it should be obvious
already for some readers.)
Regards
Esko
-----Original Message-----
From: Brian E Carpenter <brian.e.carpen...@gmail.com>
Sent: zondag 15 december 2024 02:23
To: 6lo@ietf.org
Cc: i...@ietf.org
Subject: [6lo] Re: [IPv6]WG Last Call on
draft-ietf-6lo-path-aware-semantic-addressing-09
Hi,
Thanks for the chance to comment.
Firstly, *please* do not use the word "semantic". This is not semantic
addressing in any way. It's a topological addressing scheme, and that's a good
idea. (Semantic addressing is a bad idea that wastes address bits. From the
title, I was expecting to hate this document.)
If you like the PASA acronym, try:
Path-Aware Static Addressing
Path-Aware Systematic Addressing
Path-Aware Synthetic Addressing
(Or change the acronym to PATA: Path-Aware Topological Addressing.)
I realise this affects several drafts, but IMHO "semantic" is just very
misleading.
Some comments about use cases. It is stated that:
> The PASA solution utilizes stable and static topology information...
I think this over-simplifies the real world. Consider for example:
> The smart grid power distribution network forms a typical tree topology...
That's true (although it might be complicated by grid-tied solar generation.)
But that doesn't mean the topology is static - customers can be added or
disconnected at any time. Similarly, topology changes within a home can happen
(new appliance, new power outlet, etc.):
> The Home Gateway, the PLC routers, and most of the home appliance
> are fixed in different locations. They rarely move after setup.
But they do move (in my experience, they can move because of buying new
furniture, or for even smaller reasons).
Similar comments apply to the data center monitoring use case; in a large DC
there will be changes every day. The same is true of industrial networks. There
should be a change management process, but there will always be change.
So the use cases are not truly *static*; they change from time to time. I can
see that the draft covers the case of a node *joining* the network, but I
believe the draft lacks an important section on what happens when a node
*leaves* the network (how does the address get reclaimed?) and when a node
*moves* (how does the node know that it has moved, so that it can release its
old address and acquire a new one?).
Nits:
> 4.2. Smart Home
>
> Smart home or home domotica
"Domotica" is not an English word. It appears to be a trade name of some kind.
> The address assignment described in this document relies on the
> Generic Address Assignment mechanism described in
> [I-D.iannone-6lo-nd-gaao]
Obsolete draft name. Should be draft-ietf-6lo-nd-gaao
Regards
Brian Carpenter (not on the 6lo list)
On 09-Dec-24 22:28, Shwetha wrote:
> Dear 6lo WG,
> (CC'ing 6man.)
>
> This message initiates WG Last Call on the following document:
>
> "Path-Aware Semantic Addressing (PASA) for Low power and Lossy Networks"
> https://datatracker.ietf.org/doc/html/draft-ietf-6lo-path-aware-semantic-addressing-09
>
> <https://datatracker.ietf.org/doc/html/draft-ietf-6lo-path-aware-semantic-addressing-09>
>
> This last call will end on Monday, 23rd of December.
> Please provide your feedback on this document on the mailing list.
>
> Thanks,
> Carles and Shwetha
>
> --------------------------------------------------------------------
> IETF IPv6 working group mailing list
> i...@ietf.org
> List Info: https://mailman3.ietf.org/mailman3/lists/i...@ietf.org/
> --------------------------------------------------------------------
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