Subject: per-connection config and destination address selection

From: JINMEI Tatuya / 神明達哉<[email-masked]>
Date: Tue, 30 Jul 2002 14:29:25 +0900

draft-ietf-ipv6-default-addr-select-08.txt mentions two per-connection
configuration switches for source address selection.  One is for home
vs care-of addresses, and the other is for temporary vs public
addresses.

The value of the switches may affect destination address selection,
because it depends on the expected source address corresponding to
each candidate of destination address.

I have a feeling that the current draft is not very clear about the
dependency.  For example, Section 8 (Implementation Considerations)
indicates that the destination address selection algorithm can be
implemented inside getaddrinfo().  However, the library function
does not always know the value of per-connection switches in advance.
An application may even not open a socket for the actual connection
when calling getaddrinfo().

This may rather be an implementation issue, so I don't think we need a
major revise of the draft just due to this.  But I also think it would
be good to add some note about the dependency in Section 8 before
publishing the draft.

					JINMEI, Tatuya
					Communication Platform Lab.
					Corporate R&D Center, Toshiba Corp.
					[email-masked]
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From: "Richard Draves" <[email-masked]>
Date: Tue, 30 Jul 2002 13:03:19 -0700

Yes, this is an issue with per-socket configuration of source address
selection. I haven't figured out a great solution. Obviously one can
imagine passing flags to getaddrinfo but that isn't so attractive.

For the temporary vs public addresses, this isn't a big deal because the
temporary vs public rule 7 is so low on the list and usually the choice
won't affect the common prefix length of the source address with the
possible destination addresses. In other words, the choice of the
destination address will not be affected if the source selection that
happens inside destination address ordering is not configured properly
for temporary vs public.

For the home vs care-of addresses, it is more of a problem. I don't have
enough operational experience with that aspect to have much preference
for a solution.

Rich

> -----Original Message-----
> From: [email-masked] 
> [mailto:[email-masked]] 
> Sent: Monday, July 29, 2002 10:29 PM
> To: [email-masked]
> Subject: per-connection config and destination address selection
> 
> 
> draft-ietf-ipv6-default-addr-select-08.txt mentions two 
> per-connection configuration switches for source address 
> selection.  One is for home vs care-of addresses, and the 
> other is for temporary vs public addresses.
> 
> The value of the switches may affect destination address 
> selection, because it depends on the expected source address 
> corresponding to each candidate of destination address.
> 
> I have a feeling that the current draft is not very clear 
> about the dependency.  For example, Section 8 (Implementation 
> Considerations) indicates that the destination address 
> selection algorithm can be implemented inside getaddrinfo().  
> However, the library function does not always know the value 
> of per-connection switches in advance. An application may 
> even not open a socket for the actual connection when calling 
> getaddrinfo().
> 
> This may rather be an implementation issue, so I don't think 
> we need a major revise of the draft just due to this.  But I 
> also think it would be good to add some note about the 
> dependency in Section 8 before publishing the draft.
> 
> 					JINMEI, Tatuya