Subject: [mpls] Clarification reg LSP PING - Draft ver 08- Part 2/3 - First particle

From: "M. elk" <[email-masked]>
Date: Mon, 2 May 2005 14:44:39 +0300

N.B: Sorry , have to partition part 2/3 further into First particle and 2nd particle   

Part 2 of 3 - First Particle  

Appreiate the clarification :

    B. Downstream Mapping TLV , Page 20 

   B1 . For "Only one downstream mapping request may appear in am echo request  "
          change "downstream mapping request" to "downstream mapping object" .  

    B2. For "Otherwise Downstream mapping objects should include a downstream mapping object 
                  ............could be forwarded" .
           The DS TLV do not include DS TLV . May be rewriting the above as 
           "Otherwise ,the echo reply should include a downstream mapping object  .......could be forwarded".

    B3. Moving the "I" Flag  to be global flag . 
           why : The Requirement is to know the Destination " interface and label stack" object .
           Currently: U have to Trace the full path to get those info . 
           what is needed : Just using PING and requesting the "Interface and label Stack" object to be 
            included in the echo reply .        

   B4. Multipath Type , Page 22 

        The Sending LSR have the following to influence the multipath : 
        i) The destination IP , which need to be chosen from the 127/8 range . 
        and/or 
       ii) The Source UDP Port .       

     The Transient LSR (where the TTL expire) have the following info :
      i) the source IP ,Destination IP and the source UDP Port .
      ii) The received label Stack , say {Ln,Ln-1,....L1}
     iii)  The Received DS Mapping TLV 

     Case 1- The "N" Flag set to indicate non-IP Packet 
     
     Sub-case 1a- The LSR consider only the Received Label stack . Run is Hash function (assuming avail of 
                             more than one interface , say intfa and intfb ) on the received label stack to find out on which 
                            interface it will be forwarded , say Intf_a 
                           The LSR reply with DS mapping TLV with intfa details and with "Multipath type" = zero . 
      
    Sub-Case 1b- The LSR consider the Received label Stack and the info of the multipath type 
                             (Multipath Type = 9 or Zero )  received . For simplicity assume no info for the "Multipath Type" 
                             i.e.: "Multipath Type" = Zero . 
                           The LSR run his Hash and find 2 bit-masked label set (say bit_masked_set_1 and bit_masked_set_2). 
                           one which will forward the packet to intfa and the other to intfb . The LSR reply by 2 DS mapping 
                            TLV both with "MultiPath type" = 9 . But : the only possible values for both set (Bit_masked_set_1 , 
                            Bit_masked_set_3) are the Explicit null label or  Router Alert label. is it correct ??? 
                            Say Bit_masked_set_1 resolve to Explicit null , could it be used by the sending LSR more than once . 
                            ex: {Ln,Ln-1,Ln-2,......,Explicit_null,Explicit_null,L1} and still get forwarded to intfa ???.   
                             is it location independent ,ex: {Ln,Explicit_Null,Ln-1,.......L1} same as {Ln,Ln-1,Explicit_null,Ln-2,.....L1} ,
                              both will be forwarded to intfa  ???.

    For Case 1 , Is it sub-case 1a or Sub-case 1b ???  . 

    Case 2 - The "N" Flag cleared to indicate IP Packet .

    Sub-Case 2a- The Transient LSR consider the following when calculating the hash :
                          i) The Source IP Address .
                         ii) The Source UDP port .
                        iii) The multipath info received ( Multipath Type = Zero,or 2 or 4 or 8 )  

    Sub-case 2b- The Transient LSR consider the following when calculating the hash : 
                          i) The Source IP Address .
                         ii) The Source UDP port .
                        iii) The multipath info received ( Multipath Type = zero, or 2 or 4 or 8 )  
                        iv) the received label stack . 

    Sub-Case 2c- The Transient LSR consider the following when calculating the hash : 
                          i) The Source IP Address .
                         ii) The Source UDP port .
                        iii) The multipath info received ( Multipath Type = zero, or 2 or 4 or 8 or 9 )  
                        iv) the received label stack . 

    which sub-case is valid ??? .

  B5. The Filed "Depth Limit" ,page 22 
         Guess this filed should be ignored (or set to zero) when the DS mapping TLV is part of Echo request . 
         This field is populated by the LSR sending the echo reply to indicate the number of labels out from 
         the received label stack considered in the hash . is it correct ?. 
         if yes : consider 
         the Transient LSR received label stack {L3,L2,L1} and DS Mapping TLV 
         The transient LSR reply with DS mapping TLV with label field {L4,L2,L1} and Depth-limit=2 
         is it mean that LSR will do the hah over {L3,L2} or {L2,L1} or even {L3,L1} ??? 

  B6. Protocol , page 23 
        Consider  PE1----P1----P2----PE2 .
        The PE1 send echo request with TTL=1 and DS mapping TLV. 
         The DS mapping TLV contain the 2 label , {(L1,LDP),(L2,IP VPN)}  
         P1 send echo reply with DS mapping TLV . 
         The DS mapping TLV contain the 2 label as :
         i) {(L3,LDP),(L2,IP VPN)} 
         or
         ii) {(L3,LDP),(L2,Unknown)}   

        In the first case , P1 copy the protocol of L2 from the DS mapping TLV received . 
        In the 2nd case ,P1 have no self info which protocol issued L2 so it mark L2 with Unknown protocol 
        irrespective of what protocol was associated with L2 in the received DS mapping TLV . 
        
        so which case the draft is calling for ?? .

   B7. Multipath info encoding , page 23 

    B7.1 For the first Para  "The multipath info encodes labels ..........". 
            The sentence "The contents of the fields are shown in the table above", 
            It seems the table is missing .  
            The sentence "Label and Address pairs .....", in this ver of the draft the "multipath type" = 1 = label 
            is deprecated . Also , what it meant by "pairs" ??? . 

   B7.2 For "multipath type" = 8 or 9 encoding . could we have an example to make it clear . 

   B7.3  For the Para " if the received multipath information is ........".
            For the sentence "  if the received multipath information is non-null," , is it mean 
            "If their is DS mapping TLV received " ???.  
            
            For " if the received multipath information is null" , is it mean 
            " If their is no DS mapping TLV received  " .

           For "The type must be set to 0" , is it Zero or 7 (no-match) ??

           Re-writing the Para as : 

           "If their is Downstream Mapping TLV received ,the labels and IP address MUST be picked from 
            the set provided . if none of these labels or addresses map to a particular downstream interface ,
            then in the downstream mapping TLV for that interface in the echo reply ,the multipath type must 
            be set to 7 (no match) . If their is no DS mapping TLV received ,the receiver LSR simply return no 
           Downstream mapping TLV in the echo reply ".

  B7.4 for the Para  "For Example ,suppose ..........." .
          my understanding that the address should be in the 127/8 range ???.
          
           For " with Hash key Type 7 " , in this ver of the draft the Hash key is renamed multipath Type . 
          Also , in this ver multipath-Type = 7 is not defined (only 0 ,2,4,8 and 9 ). 
           
           For " The Head end reflects ...." , could we elaborate in the draft how this is done  .guess this 
           will make it clearer  for the reader . 

          An example of using label to exercise path ,will be very useful . 

 B7.5 For the Para "Note that computing .....". 
         Could we have it as explicit notification(instead of implicit)  ,say by setting certain global flag in the 
         echo reply . 

 B7.6 For " If a packet was originated with TTL n>1 arrived with outermost label L at LSR X ....". 
            Guess it could be more clear as :
        " If a packet was originated with TTL n>1 arrived with outermost label L with TTL=1 at LSR X ..." 

 B7.7 For "Note that there are multiple downstream label fields in each TLV as the incoming label L may be 
                   swapped with a  label stack ". 

         Consider PE1----P1---Tunnel1--P2---PE2 
          testing for IP VPN LSP using trace .
          Case 1 :
          PE1 send echo request with DS mapping TLV with label fields :  {(L1,LDP),(L2,IP VPN)}
          P1 reply include DS mapping TLV with label fields {(L3,RSVP-TE),(L4,LDP),(L2,IP VPN)}.

         OR 
         Case 2 : 
         PE1 send echo request with DS mapping TLV with label fields :  {(L1,LDP)} 
          P1 reply include DS mapping TLV with label fields {(L3,RSVP-TE),(L4,LDP)}.

          is it case 1 or 2 ?? 
          The above note in the draft could be understood that it is case 2 ??. 
          while the definition of "downstream label " in page 23 ,indicate it is case 1 .   

 Brgds 

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