Re: [trill] [TRILL FGL] A question about RFC7172

[Donald Eastlake <[e-mail]>]

Hi Wenyu,

On Sat, May 24, 2014 at 4:00 AM, Zouwenyu <[e-mail]> wrote:
> Hi Donald,
>
>     In RFC7172, there are three types of RBridge: VL RBridge, FGL-safe
> RBridge and FGL RBridge.
>
>     As specified in [RFC7172], Section 8.2, the flag 1 in the TRILL-VER
> sub-TLV should be set to indicate that a RBridge is FGL-safe.
>
>     For FGL-edge RBridge, the Interested Labels and Spanning Tree Roots
> Sub-TLV which is specified in [RFC7176], Section 2.3.8, could indicate that
> a RBridge is FGL RBridge.
>
>     But how to decide whether a RBridge is FGL or not, which is only a
> transit FGL RBridge? I have not seen any TLV or flags to indicate that.

Generally all FGL RBridges are also FGL-safe. The only difference is
that an FGL RBridge can ingress a native frame to an FGL TRILL data
packet and it can egress an FGL TRILL data packet to a native frame.

If an FGL RBridge is a transit RBridge, then it is not ingressing or
egressing, so why would any other RBridge in the TRILL campus care if
it is an FGL RBridge or not? As long as the other RBridges know that
it is FGL-safe, they know they can route TRILL data through it.

Presumably the network manager knows because the network manager knows
what the equipment they are managing can do. So if some FGL-safe
RBridge is not advertising interest in any FGL labels in an Interested
Labels sub-TV, the network manager would know if it could be
configured to ingress/egress to/from FGL -- and if it was so
configured it would then start advertising interest in one or more FGL
labels with the Interested Labels sub-TLV.

Does this answer your question?

Thanks,
Donald
=============================
 Donald E. Eastlake 3rd   [phone] (cell)
 155 Beaver Street, Milford, MA 01757 USA
 [e-mail]

> Thanks.
> Regards,
> wenyu