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FW: CR LDP Local repair
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From: "Vijayanand C - CTD, Chennai." <vijayc@ctd.hcltech.com>
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Date: Tue, 18 Dec 2001 13:28:40 +0530
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Cc: mpls@UU.NET
Title: RE: CR LDP Local repair
Don,
I
understand that CR LDP basically uses LDP signalling procedures. According
to that when there is a next hop change the label with the old next hop is
released, because CR LDP uses Dod Conservative retention mode.Then the request
is sent to new NH.
The issue I am asking is how does the LSR at node D
behave when it receives another request for existing LSP(same LSPID) from B.
Remember the request is not a modification request. Will LSR at node D give a new mapping to node B
when LSP with same LSPID exists through
BCD.
Vijay
Vijay
You
said this was a loose path. Loose paths take the shortest hops. Mapping
messages may arrive unsolicited or a new mapping is solicited based on
that IP forwarding changing. This is all under control of the LSP. If the path
is not pinned then it accepts the new mapping and releases the old.
Don
Don,
If
node D receives a new request with same LSPID from B will it return a
mapping for that, given that an LSP with same ID exists in D with C as
upstream. So , should 'nt the existing CR-LSP be released
first.
Vijay
Vijay
A couple logic flaws.
1) don't release B-C before new B-D mapping is
received.
2) Loose hops shouldn't have bandwidth
constraints, think about it, a loose hop has to follow the best route and
can't do admission control.
Don
> -----Original Message-----
> From: Vijayanand C - CTD, Chennai. [mailto:vijayc@ctd.hcltech.com]
> Sent: Friday, December 14, 2001 12:48 AM
> To: mpls@UU.NET
>
Subject: CR LDP Local repair
>
>
> Hello all,
> I have a question on the signalling funcionality in CR LDP
> for local repair.
>
> Consider the topology
below.
>
>
---------- C ------------
>
|
|
>
--A --- B ---------------------- D--
>
>
>
> Assume a tunnel exist across A-B-C-D( loose ER Hops as B
D )
> Suppose a
> route update happens at node B with the next hop for node D
> being node D
>
itself(may be due to BW constraints the CSPF has taken this
> decision and LSP
>
is now going straight through). At this point node B sends a
> release along
> CD
to release the old segment and a request to D. In case,
> the request
>
(which has to travel just one hop) arrives earlier than the
> release( which
>
has to be processed at CR LDP at node C ) at node D, then
> the request would
> be rejected by node D because the request is not a
> mdification request but a
> request for existing LSP itself !!
>
> This situation would occur more
consistently if the original
> path that
is
> released were more longer than the new
path.
>
> How
does CR LDP handle such a signalling scenario?
>
> Thanks in advance,
> Regards,
> Vijay
>
>
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