Subject: OSPFv3 TE draft

From: "Manral, Vishwas" <[email-masked]>
Date: Fri, 11 Oct 2002 05:17:37 -0400

Hi folks,

We are in the process of putting down a document for adding IPv6 TLV's for
TE purposes and an LSA type in OSPFv3 for the same. We would want the
opinion of the group regarding the setting of the U-bit in the TE-LSA type
field.

My opinion is that the U-bit should be set to 0, so that any router not
recognizing the TE LSA would not forward the LSA any further. This I feel
would help in the case where some routers in the area do not recognize the
TE LSA while others do. This way redundant TE information would not be
flooded in the entire area topology in case only part of the area
understands the TE LSA.

Thanks,
Vishwas

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From: Acee Lindem <[email-masked]>
Date: Fri, 11 Oct 2002 10:29:42 -0400

Hi Vishwas,

> flooded in the entire area topology in case only part of the area

My opinion is that the U-bit should be set to 1 in all OSPFv3 opaque LSAs.
By doing this, all OSPF implementations that support RFC 2740 will support
opaque LSAs. I can appreciate your point on minimizing the flooding of TE
opaque LSAs. However, the setting of the U-bit is based solely on
the function code in the LS type.

Thanks,
--
Acee

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From: Kireeti Kompella <[email-masked]>
Date: Fri, 11 Oct 2002 08:02:58 -0700

Hi Vishwas,

> My opinion is that the U-bit should be set to 0

Consider the following case:

        ... A ----- B ----- C ...

A & B and B & C form OSPF adjacencies and exchange "regular" LSAs.
Say A and C are TE-aware and B isn't.  A advertises TE properties
of the A->B link, and C advertises TE properties of the C->B link.

Suppose B did in fact flood A's TE LSA to C and C's TE LSA to A.
Anyone other router building a TE database would immediately
understand that there isn't a TE path from A to C.

Suppose now that there is another direct link A<->C, but no OSPF
adjacency over that link.  A advertises the A->C link in its TE
LSA, and C advertises C->A in its TE LSA.  The TE topology would be:

        ... A ===== C ...

This is a situation that is likely to arise in GMPLS, for example.

If B doesn't forward A's TE LSA to C (and vice versa), the above TE
topology will not be visible to others in the network.

So, to summarize: there is no harm is allowing non-TE aware routers
to forward TE LSAs, but there may be much to gain.  My suggestion:
set the U bit to 1.

Kireeti.

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From: Kunihiro Ishiguro <[email-masked]>
Date: Fri, 11 Oct 2002 12:23:03 -0700

>to forward TE LSAs, but there may be much to gain.  My suggestion:

I agree.  Let's keep current draft value (which says U bit to 1).
--
Kunihiro Ishiguro