Folks,

It is much more simple than this.

According to RFC 8200, an IPv6 Destination Address is the “128-bit address of 
the intended recipient of the packet (possibly not the ultimate recipient, if a 
Routing header is present). See [RFC4291] and Section 4.4.”

Therefore, if a packet does not contain a Routing header, its IPv6 Destination 
Address is the 128-bit address of its *ultimate recipient*.

Therefore, a node MUST have billions of IPv6 addresses in order to consume a 
packet:

- that does not have a Routing header
- whose IPv6 destination address is a 128-bit carrier C-SID

This is because billions of carrier CSIDs can be used to route the packet to 
that node.

The vast majority of those addresses are not configured on the node.

I am pretty sure that this is not what RFC 8200 had in mind.

                                                Ron





Billions of unique 128-bit CSID containers can steer a packet to a particular 
node. Therefore, that node must have billions of addresses, the vast majority 
of which are not configured on the node!!

                                                   


Juniper Business Use Only

-----Original Message-----
From: ipv6 <ipv6-boun...@ietf.org> On Behalf Of Brian E Carpenter
Sent: Saturday, October 9, 2021 4:02 PM
To: Robert Raszuk <rob...@raszuk.net>; 6MAN <6...@ietf.org>
Cc: SPRING WG <spring@ietf.org>
Subject: Re: [spring] draft-filsfilscheng-spring-srv6-srh-compression-02

[External Email. Be cautious of content]


On 10-Oct-21 00:39, Robert Raszuk wrote:
> Hi Brian,
>
>> Which means: 64 bits.
>
> Sorry but what is so magic about /64 here ?

It is mandated by the current IPv6 addressing architecture. Despite many 
discussions, there has never been consensus to change it. So if /64 is not the 
boundary between the routeable part and the host-specific part, it's not IPv6.

   Brian

>
> Is this coming from the longest routable IPv6 prefix ? Sort of analogy to /24 
> in the IPv4 world ? Or something else ?
>
> I think LPM and CIDR techniques are pretty well established.
>
> Any fixed length of the address block with the meaning - do not use those 
> bits inter or intra domain for anything useful even if your prefix+node can 
> happily fit in /32 seems just dead wrong to me. And that is irrespective of 
> any SRv6 discussion.
>
> In my books if I get allocated say /48 or /40 from RIR what I do with the 
> remaining bits is my own business.
>
> Best,
> R.
>
>
>
>     > Sorry, but it is a little bit late – RFC 8986 is already published.
>
>     "Locators are assigned consistent with IPv6 infrastructure allocation."
>
>     Which means: 64 bits.
>
>     I have no time to study compressed SIDs, but if they trample on the
LOC they are not IPv6 addresses.
>
>        Brian
>
>
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