Subject: Clarification on lsp-ping-02.txt

From: "M. ELK" <[email-masked]>
Date: Tue, 15 Apr 2003 09:27:29 +0000

Hi

Appreciate to calrify the following :

1- For "Ping Mode" (ie: TTL=255) , understood that the echo request
   COULD not include the "Downstream Mapping" TLV as the ingress have
   mo knowledge to fill this TLV (the only exception if the egress
   is a direct neighbor ) .
   IF YES : Could we indicated explicitly in the doc .

  Pls comment .

2- In section 4.3 " Recieving an MLPS Echo Request"

   Quote
    If the echo request is good, X then checks whether it is a valid
   transit or egress LSR for the FEC in the echo request.  If not, X MAY
   log this fact.  If it is, X notes that interface I over which the
   echo was received, and the label L with which it came.  X checks
   whether it actually advertised L over interface I for the FEC in the
   echo request.
   Unquote

The recieving node could recieve "Stack of FEC TLV" and the recieved
labeled packet could have a "stack of label" .
As an example :
PE1--P1---P2---PE2

Ping from PE1 to PE2 for  FEC 10.10.10/24 on VPN green
Case 1 : No PHP
PE1 insert stack of FEC (First is PE2 FEC , 2nd is the VPN FEC)
PE2 have asdvertised a Label L1_lpd to P2 for FEC=PE2
PE2 have advertised a label L2_MPBGP to PE1 for FEC VPN
The ECHO request labeled packet is recieved at PE2 with label stack 
<L1_lpd,L2_MPBGP> . The FEC stack < FEC PE1 , FEC VPN>

case 2 : with PHP

PE1 insert stack of FEC (First is PE2 FEC , 2nd is the VPN FEC)
PE2 have asdvertised a Label Implicit_Null to P2 for FEC=PE2
PE2 have advertised a label L2_MPBGP to PE1 for FEC VPN
The ECHO request labeled packet is recieved at PE2 with label stack 
<L2_MPBGP> . The FEC stack < FEC PE1 , FEC VPN>

Case 3 :
PE1 insert single FEC ,the VPN FEC)
PE2 have asdvertised a Label Implicit_Null to P2 for FEC=PE2
PE2 have advertised a label L2_MPBGP to PE1 for FEC VPN
The ECHO request labeled packet is recieved at PE2 with label stack 
<L2_MPBGP> . The FEC stack <FEC VPN>

My question :

A- para 4.3 should highlight/explain in explicit term how to match a
    stack of FEC versus a recieved stack of label taking into account
    the case of the depth of FEC stack could be different of
     the depth of the label stack .

B- For checking interface "I" .
    Quote
    X checks whether it actually advertised L over interface I for
    the FEC in the echo request.
    Unquote

    For case 3 , this check will fail despite it is the correct
    behaviour .

    May be we need to consider :
    1- The type of label distribution ruunning over interface I .
       If "Per_interface" :
       do interface check for the TOP label only.
       if "Plateform_wide":
         If the top FEC say FEC1 is IPV4  :
           Then {If the label advertised for FEC1 over interface "I" is
                "implicit_null" :
                Then  skip "check interface".
                else  Do "Check Interface" }

           Else {Skip "Check Interface" ) .

3-For Hash key type

  A- For "Type 6" :
     Understood that such type is used to indicate :
     "This Path will only forward unlabeled packet"
     is it correct ??

  B- For "Type 7" , Could U pls explain it's usage .

Brgds

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