Subject: [NSIS] closing GIST issue 14 (Service Demultiplexing in MA Protocol Stacks)

From: "Hancock, Robert" <[email-masked]>
Date: Fri, 2 Sep 2005 14:22:40 +0100

Dear all,

There's been a long-standing open issue about how to convey
higher layer addressing information (e.g. TCP port numbers)
during association setup when there might be several different
configurations needed (e.g. TCP with or without TLS). See also:

http://nsis.srmr.co.uk/cgi-bin/roundup.cgi/nsis-ntlp-issues/issue14

There was some discussion of this during the interop event and
also at the WG session in Paris, and the end result is the
following:

revised text in 5.7.1:

   A Stack-Proposal object is simply a list of profiles; each profile is
   a sequence of MA-Protocol-IDs.  A Stack-Proposal is generally
   accompanied by a Stack-Configuration-Data object which can carry
   higher-layer-addressing information elements for any protocol listed
   in the Stack-Proposal which needs it.  A higher-layer-addressing
   information element may apply globally (to all instances of the
   protocol in the Stack-Proposal) or be tagged as applying to a
   specific instance; for example, this can be used to carry different
   port numbers for TCP depending on whether it is to be used with or
   without TLS.  A higher-layer-addressing information element may also
   be flagged as 'not usable'; for example, a NAT which could only
   handle TCP would set this for higher-layer-addressing about SCTP.

and a new bit format in C.4.5:

   The higher layer information fields are formatted as follows:

    0                   1                   2                   3
    0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   |MA-Protocol-ID |    Proposal   |    Length     |D|  Reserved   |
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   //                   Higher-Layer-Addressing                   //
   +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
   MA-Protocol-ID = Protocol identifier as described in
   Section 5.7
   .
   Proposal  = Tag indicating which proposal from the accompanying
               Stack-Proposal object this applies to. Proposals
               are numbered from 1 upwards; the special value 0
               indicates 'applies to all proposals'.
   Length    = the byte length of higher layer addressing
               information that follows. This information will be
               zero-padded up to the next word boundary.
   D flag    = If set, this protocol should not be used for a
               messaging assocation.

This seems the right balance between simplicity and efficiency.

robert h.

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