Re: [mpls] Last Call: <draft-ietf-mpls-ldp-ipv6-14.txt> (Updates to LDP for IPv6) to Proposed Standard

[Mark Tinka <[e-mail]>]

On Wednesday, December 17, 2014 03:26:54 PM Aissaoui, 
Mustapha (Mustapha) wrote:

> It is actually testing against existing LDP IPv4
> implementations when the LSR compliant to this draft
> sends LDP IPv6 FECs and LDP IPv6 addresses over the LDP
> IPv4 session.
> 
> Here is a brief summary of the issues as I described to
> the list this summer: "
> When an LSR which supports LDP IPv6 according to this
> draft is in a LAN with a broadcast interface, it can
> peer with LSRs which support this draft and LSRs which
> do not. When it peers using IPv4 LDP control plane with
> an LSR which does not support this draft, we have seen
> during our testing an issue that the advertisement of
> IPv6 addresses or IPv6 FECs to that peer will cause it
> to bring down the IPv4 LDP session.
> 
> In other words, there are deployed LDP implementations
> which are compliant to RFC 5036 for LDP IPv4 but are not
> compliant to RFC 5036 when it comes to handling IPv6
> address or IPv6 FECs over an LDP IPv4 session. This is
> making us very concerned that when users enable
> dual-stack LDP IPv4/IPv6, they will bring down LDP IPv4
> sessions which have been working in a multi-vendor
> environments for so many years. "

Thanks for the explanation, Mustapha.

Operationally, sounds a bit like IS-IS in a mixed single and 
dual stack environment, but with IS-IS running in ST (Single 
Topology) mode.

Of course, the IS-IS solution is to support MT (Multi-
Topology) so that adjacencies between a single stack and 
dual stack device work just fine.

I realize I'm simplifying things a bit, but not sure if we 
can borrow a leaf from the IS-IS solution, if we are going 
to implement an integrated LDPv4/LDPv6 in the same code 
base.

One more question - are you implying that this issue is not 
present in a point-to-point topology?

Mark.