Hi Noel,

  My response is inline. Thank you.

[email protected] 写于 2012-11-02 10:22:32:

>     > From: [email protected]
> 
>     > In the third paragraph of Section 10.5.1, you mentioned
> 
>     >  "in addition, since LISP expects all incoming data traffic to be 
on a
>     >   specific port, it was not possible to have multiple ETRs behind 
a
>     >   single NAT (which normally would have only one global 
> address to share,
>     >   meaning port mapping would have to be used, except that... )"
> 
>     > Is something missing here?
>     > Certainly there maybe scenarios such like two or more LISP MN 
connect
>     > behind the same NAT, i.e. two or more ETRs behind a single NAT.
> 
> Maybe I am missing something, but if a NAT has two ETRs behind it, and 
if an
> inbound UDP packet to destination port 4341 arrives at the NAT, how does 
the
> NAT know which ETR to send the packet to?
> 
> (Since the destination IP address in the packet is that of the NAT, and 
port
> 4341 would be used for packets to either ETR.)

I don't understand very clearly.

Consider the scenario that two ETRs behind a single NAT.

When NAT establish states for ETRs who both send packets outbound, it 
could assign
different global IP addresses for them.

As a result, when NAT receives packets inbound, even though packets both 
have Destination
port 4341, their destination addresses are according to different ETRs.

Was there something I misunderstood?

Best Regards
Li Cheng

> 
> Even if you look at the sort host and port, that doesn't necessarily 
help,
> because some source ITR could be sending packets to both ETRs, so 
packets to
> either ETR could also have the identical source host/port.
> 
> In short, there's no way for the NAT to know which ETR the packet is 
for.
> 
> 
> Note that there is a separate "NAT Traversal For LISP" document which
> provides mechanisms to bypass all these issues.
> 
>    Noel
> _______________________________________________
> lisp mailing list
> [email protected]
> https://www.ietf.org/mailman/listinfo/lisp

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