Subject: Re: Question on scopes involving IPv6 addresses

From: "Alex R n" <[email-masked]>
Date: Tue, 06 Mar 2001 05:07:34 -0700

>>> JINMEI Tatuya / _神*B** <[email-masked]> 03/06/01 04:24PM >>>
>>>>> On Tue, 06 Mar 2001 09:38:40 +0100, 
>>>>> Alain Ritoux <[email-masked]> said:

>> Is the following a valid configuration in IPv6. The
>> addresses represented in as (L) are either all site
>> local or all link local addresses

>> A(L1)---------(L2)B(L1)----------(L2)C
>> 
>> B is connected to two different links / sites. The
>> addresses are unique within their respective scopes.

> For me this seems correct

Yes, this is correct.

> But I wonder if we can push as far as :
>     A(L1)---------(L2)B(L2)----------(L1)C
>     the assumptions being the same.

This is correct, too, provided that the B's two interfaces belong to
different links.  For more details about the scoped addresses
(including link-local and site-local ones) architecture, see 
draft-ietf-ipngwg-scoping-arch-xx.txt
(the 01 version is the latest one, which has already expired, but the
02 version has been submitted and will soon be out.)

Going through scoped address architecture it provides a mechanism to distinguing the same address belonging to different scopes. What I am wondering is that 

a) Couldnt the scope index have been part of the IPv6 address.
b) For upper layers like UDP which identifes a connection based on addresses wouldnt it be better to put the scope index into the address itself.
  One scenario is that we could have the same [source src port destination dst port ]  pairs from different scopes as in the scenario earlier seen. Is the upper layer suppose to handle this in a different manner like having scoped tables.

Thanks
Alex

---

From: [email-masked]
Date: Tue, 6 Mar 2001 08:52:05 -0600

Having the scope be part of the IPv6 address or having other distinguishing
attribute in the NLA (which is null now) was discussed and rejected. 
I was supportive of this idea.   But it does add an entire address space
management part to IPv6 site local addresses.  My input is don't go there.
Implementations will have to have scoping code following the scope-arch-02
draft architecture.  How that is done is and should be implementation
specific.  I think maintaining tables in an implementation is a question of
the type of implementation.  I think its better to extend existing OS kernel
protocol control block structures and search algorithms to be scope aware.
This also means that information can be extracted by user space applications
for management of scopes and for source/destination address selection.  But
all should use the assumption that FF05 prefixes will only exist within a
site and will not overlap sites, because they can be duplicated.
 
/jim

 
Going through scoped address architecture it provides a mechanism to
distinguing the same address belonging to different scopes. What I am
wondering is that 
 
a) Couldnt the scope index have been part of the IPv6 address.
b) For upper layers like UDP which identifes a connection based on addresses
wouldnt it be better to put the scope index into the address itself.
  One scenario is that we could have the same [source src port destination
dst port ]  pairs from different scopes as in the scenario earlier seen. Is
the upper layer suppose to handle this in a different manner like having
scoped tables.
 
Thanks
Alex

---

From: [email-masked]
Date: Tue, 6 Mar 2001 12:30:10 -0600

whoops FF05 below should have been FF05 and FEC0.  the new
addr-scope-arch-02 draft takes care of this too nicely.  I am not sure in
that draft using different routing tables for each zone is best in ALL
iimplementation cases.  I can think of several where it is not.
/jim