Subject: Draft-ietf-mpls-lsp-ping-02.txt: How to handle the "Target FEC Stack" ?

From: lidefeng <[email-masked]>
Date: Fri, 09 May 2003 16:04:21 +0800

Hi,all,

In Section "3.1. Target FEC Stack " of draft-ietf-mpls-lsp-ping-02.txt,there
is an example as following,

   "If LSR X wanted to verify that a label stack of <1001, 23456> is the
   right label stack to use to reach an IP VPN prefix of 10/8 in VPN foo
   on an egress LSR with loopback address 192.168.1.1 (learned via LDP),
   X has two choices.  X can send an MPLS echo request with a FEC Stack
   TLV with a single FEC of type VPN IPv4 prefix with a prefix of 10/8
   with the Route Distinguisher for VPN foo.  Alternatively, X can send
   a FEC Stack TLV with two FECs, the first of type LDP IPv4 with a
   prefix of 192.168.1.1/32 and the second of type of IP VPN with a
   prefix 10/8 in VPN foo.  In either case, the MPLS echo request would
   have a label stack of <1001, 23456>.  (Note: in this example, 1001 is
   the "outer" label and 23456 is the "inner" label.)"

I want to know that in the alternative choice,whether to add the Route
Distinguisher to the IPV4 with the prefix 10/8 to make the device along the
path between the two CE(source and sink CE concerning the prefix 10/8 in the
VPN foo ) identify the VPN foo? If that is true,then the first FEC element
in the above alternative choice is 192.168.1.1/32(IPV4 type),and its
corresponding label is 1001,and the second FEC element is FEC of type VPN
IPv4 prefix with a prefix of 10/8 with the Route Distinguisher for VPN
foo,the corresponding label is 23456.Right?

That is 192.168.1.1/32(FEC) ---->1001(LABEL),and
RD:10/8(FEC)--->23456(LABEL),Could you please tell me whether my
understanding is right?

TIA and Regards!

Li Defeng