Subject: [NSIS] Incremental deployement story for draft-ietf-nsis-nslp-natfw-20

From: Magnus Westerlund <[email-masked]>
Date: Fri, 27 Nov 2009 13:56:47 +0100

Hi,

I am reviewing the NAT/FW NSLP and have some high level questions about
this work regarding incremental deployment.

When reading the document I get the impression that it starts out in
world where the majority of the nodes have been upgraded and focus on
mechanism in that world. It is not that it needs to work, but to me the
main focus would be to ensure that the signaling protocol works well
when deploying it only in one access network, or even subnet and then
starts to grow the deployment.

I am missing this story and how to get good performance out of the NSLP
in such settings. The proxy mode enables this to some degree but seems
to lack some functionality to allow for incremental deployment. The main
issue seems to be sender proxying that seems to lack a method to
indicate: Please proxy this but also try end to end. That allows for
quick setup of the egress to public path, and allows for opening all the
way if the end-to-end actually works.

I would like to have a section that describes how one can start out with
some end-hosts and edge-NAT/FW that support proxying. Then probe the
path towards end-to-end to see if there are additional NATFW aware
entities on the path allowing for a increase functionality scope.

I am also a bit worried about the assumption that edge devices must be
correctly configured. Consider the case of an ISP that does NAT44, i.e.
the customer - ISP edge has one NAT that may have been the edge
initially, but then the ISP has run out of addresses and decides to
deploy its own NAT. For the application running in an end-host the gain
with the NATFW signalling is lost until the customer edge device is
reconfigured to not any longer be the edge. I don't know if there is a
simple solution to this problem. If not I would defer the inclusion but
it should be noted as a short coming.

Comments?

Cheers

Magnus Westerlund

IETF Transport Area Director
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