Re: suites vs. a la carte and IPcomp in IKEv2-05

[Henry Spencer <henry@spsystems.net>]

On Fri, 28 Feb 2003, Dan Harkins wrote:
>   You do have to agree on something. Namely, which of the 3 possible
> compression algorithms you will be using to uncompress the data
> you receive...

No, there is no need for negotiated agreement on that.  It suffices that
the other end sends with an algorithm you have advertised your willingness
to uncompress with.  (Since compression is *always* at the sender's option,
the receiver can never require it.)

Only if the algorithms involve non-trivial parameters that the two ends
must agree on (and which there is no reasonable default for) is actual
negotiation more or less required.

> and what CPI will be used in the IPcomp header that
> encapsulates that compressed data.

There is no need for negotiated agreement on that either, since there are
pre-assigned CPIs for the standard algorithms. 

                                                          Henry Spencer
                                                       henry@spsystems.net