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

Zouwenyu <> Mon, 26 May 2014 02:29 UTC

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From: Zouwenyu <>
To: Donald Eastlake <>
Thread-Topic: [trill] [TRILL FGL] A question about RFC7172
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Date: Mon, 26 May 2014 02:29:04 +0000
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Subject: Re: [trill] [TRILL FGL] A question about RFC7172
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Hi Donald,

From: Donald Eastlake []
Sent: Saturday, May 24, 2014 22:31
To: zouwenyu 06026
Subject: Re: [trill] [TRILL FGL] A question about RFC7172

>Hi Wenyu,

>On Sat, May 24, 2014 at 4:00 AM, Zouwenyu <> 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.

  In [RFC7172], Section 4.1.1, it says this words, "Ingress as a TRILL multi-destination data packet (TRILL Header M bit = 1) on a distribution tree rooted at a nickname held by an FGL RBridge or by the pseudonode of an FGL link. ". In this descriptions, does the FGL RBridge mean both FGL RBridge and FGL-safe RBridge? In this way, for a native multi-destination frame which is FGL ingressed, the ingress RB must select a tree root held by a RBridge whose flag 1 in the TRILL-VER sub-TLV is set, and do not care whether a RBridge is FGL or FGL-safe.
Does it work like this?


>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?

> Donald E. Eastlake 3rd   +1-508-333-2270  (cell)
> 155 Beaver Street, Milford, MA 01757 USA

>> Thanks.
>> Regards,
>> wenyu
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