A comment on <draft-ksinant-v6ops-isp-analysis-00.txt>

["Francois Le Faucheur (flefauch)" <flefauch@cisco.com>]

Hello Vladimir,

In section 3.3, I noticed the following:

"  When MPLS is already deployed in the backbone, it may be desirable 
   to provide IPv6-over-MPLS connectivity. However, the problem is that
   setting up an IPv6 Label Switched Path (LSP) requires some signaling
   through the MPLS network. Currently, there is no direct mechanism to
   do this for IPv6. A workaround is to use BGP for signaling and/or 
   perform IPv6-over-IPv4-over-MPLS encapsulation, as described in 
   [BGPTUNNEL].  More analysis is needed on what is the right approach 
   in this case.
"

Well, there actually are mechanims specified to set up IPv6 LSPs: both
LDP and RSVP-TE specifications cover both label binding for IPv4 and for
IPv6. 

However, in the considered networks where IPv4 MPLS is already deployed,
the situation is that :
	- (i) there is a control place in place which establishes IPv4
LSPs across the core, providing connectivity among all the Edge boxes
(Provider Edges)
	- (ii) these LSPs are already used for transport of multiple
services (IPv4, IPV4-VPNs, Layer 2 VPNs, ...)
	- (iii) there is strong operational pressure to keep core stable
for these services
	- (iv) the LSPs can be used to carry yet another service which
is IPv6 (and BTW IPv6-VPNs next)
	- (iv) this can be achieved without any change to the core
neither in terms of software, nor in terms of hardware, nor even in
terms of configuration.

So, I believe operators see transport of "IPv6 over IPv4/MPLS" more as
an opportunity to add services with no impact on the core, than as a
workaround to circumvent protocol limitation.

Also, while [BGP-TUNNEL] does allow the IPv6-over-IPv4-over-IPv4/MPLS
encapsulation option, it also allows the direct IPv6-over-IPv4/MPLS
encapsulation option which is the one commonly deployed today.

I may be jumping into the "more analysis is needed" discussion you
announced, but I thought it may be useful to try converge on the problem
description.

I hope this is useful.

Francois

PS: looking forward to seeing you in Minneapolis.