Subject: RE: A question on mpls-te-mib: mplsTunnelHopEntryPathComp

From: "Kota, Ravikumar" <[email-masked]>
Date: Tue, 28 Aug 2001 11:18:06 -0400

Hi Li,
in the draft draft_ietf_mpls_te_mib_07.txt

mplsTunnelHopEntryPathComp OBJECT-TYPE
   SYNTAX        INTEGER {
                      dynamic(1),    -- CSPF computed
                      explicit(2)    -- strict hop
                  }
   MAX-ACCESS    read-create
   STATUS        current
   DESCRIPTION
"If this value is set to dynamic, then the user
          should only specify the source and destination of
          the path and expect that the CSPF will calculate
          the remainder of the path.  If this value is set to
          explicit, the user should specify the entire path
          for the tunnel to take.  This path may contain
          strict or loose hops.  Each hop along a specific
          path should have this object set to the same value"
   ::= { mplsTunnelHopEntry 14 }

 So if u want to mention other location along with sourse and destination ,
u can not use 
dynamic option . U have to use "explicit" path option with sub option
"loose".
For this the object in the MIB is as follow:(from the same draft )

mplsTunnelHopType OBJECT-TYPE
   SYNTAX        INTEGER {
                      strict(1),
                      loose(2)
                     }
   MAX-ACCESS    read-create
   STATUS        current
   DESCRIPTION
        "Denotes whether this tunnel hop is routed in a
          strict or loose fashion."
   ::= { mplsTunnelHopEntry 11 }

so with the option "explicit" and "loose" ur LSP will be established.
For the other LSR s which u have not mentioned explicity , i think CSPF will
calculate them based on the TUNNEL resource requirement.( caqn be corrected
if it is wrong ).

Regards
Ravikumar Kota

-----Original Message-----
From: Ling Li [mailto:[email-masked]]
Sent: Tuesday, August 28, 2001 11:08 AM
To: [email-masked]'
Subject: A question on mpls-te-mib: mplsTunnelHopEntryPathComp 

I was confused by the description of mplsTunnelHopEntryPathComp as bellow:

mplsTunnelHopEntryPathComp OBJECT-TYPE
SYNTAX INTEGER {
	dynamic(1), -- CSPF computed
	explicit(2) -- strict hop
}
MAX-ACCESS read-create
STATUS current
DESCRIPTION
"If this value is set to dynamic, then the user
should only specify the source and destination of
the path and expect that the CSPF will calculate
the remainder of the path. If this value is set to
explicit, the user should specify the entire path
for the tunnel to take. This path may contain
strict or loose hops. Each hop along a specific
path should have this object set to the same value"
::= { mplsTunnelHopEntry 14 }

My question is: what if a user want to use CSPF to find a route from Boston
to San Francisco, but specifically he/she wants the route to go through
Chicago.

The description seems suggesting that this operation is not allowed, because
1. The user specified not only the source and destination, but an extra
loose hop (Chicago). Therefore mplsTunnelHopEntryPathComp  cannot be dynamic
2. The user wanted to enable CSPF to calculate the path, so explicit is not
appropriate for mplsTunnelHopEntryPathComp.

Could anyone clarify on this doubt?

Thanks, 

Ling Li 

Axiowave Networks, Inc. 
Email: [email-masked] 
========================