Subject: Re: CR-LDP

From: [email-masked]
Date: Tue, 28 Mar 2000 22:28:24 +0800

Please refer to draft-ietf-mpls-atm-02.txt  section 9 (Encapsulation) which
details the use of MPLS label stack for ATM based implementation.

The top label is carried in the ATM VPI/VCI, and is therefore replicated on
every cell header for that packet.  The (rest of the) label stack appears
in the packet's shim header and NOT in any cell header.

-- Ajith

|   Ajith Narayanan <[email-masked]>
---

"Santosh Gupta" <[email-masked]> on 03/28/2000 05:07:15
PM

Please respond to "Santosh Gupta" <[email-masked]>

To:   Ajith Narayanan/Singapore/IBM@IBMSG
cc:   [email-masked]
Subject:  Re: CR-LDP

Hi Ajit
    The label stacking scenario that you mentioned is possible in MPLS, but
if  we implement it on ATM then how can it be done as the  ATM cell has a
fixed header size (5 bytes) and there is just 12+16 bits allocated for
label (VPI/VCI ). Any suggestions.
santosh
  ----- Original Message -----
  From: [email-masked]
  To: Santosh Gupta
  Cc: [email-masked] ; Ashish Monga ; [email-masked]
  Sent: Tuesday, March 28, 2000 1:03 PM
  Subject: Re: CR-LDP

  LSP-IDs become part of the "traffic engineering state" of the network.
So
  it is legitimate to define a CR-LSP, whose ingress is LER2,  stacking or
  splicing with an existing CR-LSP whose ingress is LER1,  the latter being
  specified by its LSP-ID.   The entity which does traffic engineering can
be
  thought of as "higher" than the LSR, and it knows these LSP-IDs.  At that
  level, there is global (or, supra-local) knowledge.

  However, from the point of view of LSRs, local knowledge is sufficient.
  LSRs need to know only the LSP-IDs they participate in.

  In your example,  LER2 and LSR5 do not need to know the spliced/stacked
  CR-LSP's LSP-ID because all they do with it is, just pass it downward.
  That remains true as we go down the request path till we hit LSR3, for
  which it is intended.   So there is no need for non-participating LSRs to
  be aware of the LSP-ID.

  -- Ajith

  --

  "Santosh Gupta" <[email-masked]> on 03/28/2000 12:45:39
  PM

  Please respond to "Santosh Gupta" <[email-masked]>

  To:   [email-masked], [email-masked]
  cc:   "Ashish Monga" <[email-masked]> (bcc: Ajith
        Narayanan/Singapore/IBM)
  Subject:  Re: CR-LDP

  Hi Sumit
      The concerned section of CR-LDP draft is as below.
  4.7.4. ER-Hop 4: LSPID

  The LSPID is used to identify the tunnel ingress point as the next
  hop in the ER. This ER-Hop allows for stacking new CR-LSPs within an
  already established CR-LSP. It also allows for splicing the CR-LSP
  being established with an existing CR-LSP.
  If an LSPID Hop is the last ER-Hop in an ER-TLV, than the LSR may
  splice the CR-LSP of the incoming Label Request to the CR-LSP that
  currently exists with this LSPID. This is useful, for example, at
  the point at which a Label Request used for local repair arrives at
  the next ER-Hop after the loosely specified CR-LSP segment. Use of
  the LSPID Hop in this scenario eliminates the need for ER-Hops to
  keep the entire remaining ER-TLV at each LSR that is at either
  (upstream or downstream) end of a loosely specified CR-LSP segment
  as part of its state information. This is due to the fact that the
  upstream LSR needs only to keep the next ER-Hop and the LSPID and
  the downstream LSR needs only to keep the LSPID in order for each
  end to be able to recognize that the same LSP is being identified.

  In this it clearly states that it is not only the Ingress LER and the
LSRs
  in the path of this LSP but other LERs also need to know the LSP-ID of
  different LSPs. The scenario is something like

                  LER1 ------> LSR2-------->LSR3------>LSR4

                  LER2-------->LSR5

  there is an LSP setup as shown from LER1 thru LSR2,LSR3, LSR4. Now LER5
  receives a ER-TLV which says it has to make an  LSP for which the next
hop
  is LSR3 and the already existing LSP with the LSP-ID is to be used. Now
the
  question is how does LSR5 or LER2 come to know about this particular
LSP-ID
  which actually originated at LER1?

  santosh

  [email-masked]

  ----- Original Message -----
  From: Sumit Garg
  To: 'ashish'
  Sent: Tuesday, March 28, 2000 3:49 A
  Subject: RE: CR-LDP

  Hi,

  LSD-ID is a TLV defined by the CR-LDP draft. It is a combination of the
  LSR-ID and a 2 octect number assigned by the ingress/ initiating LSR.
This
  would typically be an administor assigned/ monitored quantity and thereof
  known a priori for LSP splicing/ tunneling.

  The LSPID is propagated to downstream LSRs in the LSP setup request.

  Regards
  Sumit

    -----Original Message-----
    From: ashish [mailto:[email-masked]]
    Sent: Monday, March 27, 2000 03:58 AM
    To: [email-masked]
    Subject: CR-LDP

    In CR-LDP draft-03, one of the ER-HOP TLV types contain LSPID field
that
  is used for tunneling thru some existing LSP having that LSPID field.
    This means that that LSPID should be known in advance .
    How is that done.
    Does information regarding each LSP being created each having unique
  LSPID is propagated to all LSR's.
    Please clarify.