Subject: RE: [Isis-wg] draft-martin-neal-policy-isis-admin-tags-05.txt - a dditions and c orrections

From: "Martin, Christian" <[email-masked]>
Date: Wed, 17 Apr 2002 13:23:18 -0400

Tony,

>>
>yes, you _cannot_ change other people LSPs and if you change 
>yours, you 
>need new version number and
>checksum anyway.

Agreed.  The tag changes can only occur at area boundaries where TLV 135 is
copied into the new area's LSP.

>
>Comment for deletion and I'm getting picky here, you may not 
>want to go 
>into this matter. What you specified
>is an ordered set or a chain but one could also think of an array, to 
>give you an example, assume I send you
>version 1 with 3 tags for a route {X,Y,Z}. The next version contains 
>{X,Z}. The interpretation could be either
>
>a) the route has a tag X that preceeds tag Z which could e.g. 
>mean that 
>tag X overrides certain properties
>    of tag Z or any such thing.
>
>or
>
>b) the route had a first tag X, then a second tag Y, then a 
>third tag Z 
>and now it has a
>    firs tag X and a _second_ tag Z.  First tag e.g. always encodes an 
>extended community,
>    second is a customer tag,
>    third is tag indicating that route is a summary as example.
>
>What does it mean? In a second interpretation, the semantics of {X,Z} 
>and {X,NULL-TAG,Z} are different,
>in the first interpreation both constructs mean the same.
>
>IMO, think what you want to have or say that both are possible and 
>interpretation depends on application.

Ok, I see the issue.  How about this:

6. Ordering of Tags

   The semantics of the tag order are implementation-dependent.  That
   is, there is no implied meaning to the ordering of the tags that
   indicates a certain operation or set of operations need be performed,
   based on the order of the tags.  Each tag SHOULD be treated as an
   autonomous identifier that MAY be used in policy to perform a policy
   action.  Whether or not tag A preceeds or succeeds tag B SHOULD not
   change the meaning of the tag set.  However, an implementation MAY
   wish to preserve tag ordering such that an ordered set of tags has
   meaning to the local policy.

   Each IS that receives an LSP with TLV(s) 135 and/or 235, that have
   associated SubTLV(s) 1 and/or 2, MAY operate on the tag values as
   warranted by the implementation.  If an implementation needs to
   change tag values, for example, at an area boundary, then the TLV(s)
   SHOULD be copied to the newly generated Level-1 or Level-2 LSP at
   which point, the contents of the SubTLV(s) MAY change as dictated by
   the policy action.  In the event that no change is required, the
   SubTLV(s) SHOULD be copied in order into the new LSP, such that
   ordering is preserved.

>And oh, you misspelled Verizon in the header unless it's a different 
>company ;-)

Whoops.  Good catch - actually that was an old nroff that I reused - we've
reorged since so I was working for a non-existent subsidiary of an
non-existent company!  ;)

Thanks for the suggestions!
-chris
>    thanks
>    -- tony
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---

From: Tony Przygienda <[email-masked]>
Date: Wed, 17 Apr 2002 10:50:34 -0700

>    meaning to the local policy.

ok, vague enough to not specify much but make people to understand there
are possible issue when they play with stuff. I hope more people get vocal
here if they need that stuff

        thanks

    -- tony