Re: [trill] [rbridge] Query on draft-ietf-trill-esadi-00

Donald Eastlake <> Mon, 01 October 2012 03:49 UTC

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From: Donald Eastlake <>
Date: Sun, 30 Sep 2012 23:49:01 -0400
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To: somnath chatterjee <>
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Subject: Re: [trill] [rbridge] Query on draft-ietf-trill-esadi-00
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Hi Somnath,

On Thu, Jul 12, 2012 at 8:32 AM, somnath chatterjee
<> wrote:
> Hi Authors,
> I have few comments and a query about  draft-ietf-trill-esadi-00.
> 1> Section 4.2 Receipt of ESADI PDUs
>    "Because all ESADI instance for VLAN-x are adjacent, when RB1
> receives an ESADI-CSNP from RB2 and detects that it has ESADI-LSPs
> that RB1 is missing, it sets the transmission flag only for its own
> ESADI-LSPs that RB1 is missing. Missing ESADI-LSPs originated by other
> ESADI instances will be detected by those other instances."
>    I am not able to understand the quoted sentences.Could you please clarify?

Usually there are only a few RBridges on a link so, if the DRB sends
an IS-IS CSNP that shows it is missing some LSP, other RBridges on the
link will update the DRB by sending the missing LSP -- and that
missing LSP can easily be for some other RBridge that is not on the
link and could not have seen the DRB's CSNP.

But in the ESADI protocol, all the participating RBridges are on the
same physical link so they should all see a CSNP. So there is no
reason for an ESADI RBridge to respond to a CSNP with missing LSPs
that it has that are not its own.

> 2> The figure 2 and 3 in Section 2. ESADI Protocol Overview have the
> Inner MAC DA as "Next Hop Dest. Address"   which should be
> "All-Egress-RBridges" (formerly called "All-ESADI-RBridges")

A new version will be posted soon fixing that.

> 3> In Section 6. ESADI-LSP Contents
>    "ESADI-LSP number zero MUST NOT exceed 1470 minus 24 bytes in
> length (1446 bytes) but if received longer, it is still processed
> normally."
>    should be changed to
>    "The ESADI payload for ESADI-LSP number zero MUST NOT exceed 1470
> minus 24 bytes in length  (1446 bytes) but if received longer, it is
> still processed normally."


> Also should it be 1470-24 or Sz-24 ? Sz being the campus wide MTU.

Because, in the current ESADI draft, LSP number zero is used for
sending the priority of RBridges participating in a particular ESADI
instance, it seemed important to but extra careful that LSP number
zero got through. So it should be 1470-24 just like the Hello maximum
is 1470.

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

> Thank you,
> Regards,
> Somnath