ACP 137

UNCLASSIFIED
ACP 137
email service may still be employed in parallel with the MM transport mechanism. This will
allow the directory information necessary to set up the MM service itself to be replicated
between nations, although the mechanism for initially sharing addresses to be employed
between nations would be subject to bilateral agreement, and may include hand carrying of
data.
DATA INTEGRITY
207. There are two primary concerns to be considered in terms of the data integrity of the
transferred LDIF file:
a. There is a need to ensure the LDIF file received by a nation has not been
inadvertently corrupted. Different transport services provide different levels of
capability for ensuring message integrity. In view of this, the Griffin DS will provide
its own internal mechanisms to allow data integrity to be assured. This will be
accomplished using a Hash value calculated from the data before it is sent and carried
in the message to allow its verification at the receiving nation. Note that the Hash is
not intended to protect against malicious changing of data since it is assumed that this
would not happen on Griffin, and hence no further protection of the Hash is provided.
b. There is also a requirement that sending nations may not include LDIF entries
for which they do not hold the master copy. Receiving nations must ensure they
reject the entire file where the sending nation does not hold the master copy of all
entries received (e.g. any nation receiving a UK entry in the US LDIF file should
reject the file, specify the reason for rejection and request a retransmission).
DATA VOLUMES
208. It is anticipated that the Griffin DS will need to support much larger interchange files
than was required with previous DS solutions. It has been identified that proposed messaging
transport mechanisms may not be capable of transferring these large files unchanged.
Additional features which have been added to the protocol to alleviate this problem include:
a. File compression (where allowed by network and security infrastructure). Use
of file compression provides not only the possibility of transporting data files which
exceed the allowed limit, but is also a more efficient use of the network by reducing
network bandwidth requirements (it appears indicate a compression ratio of 10:1 is
achievable). Initially, use of ZIP compression is assumed, but this specification does
not preclude the use of other methods and products as they become available.
b. File Segmentation. The maximum file size limitation requires that a data file
which is larger than a configurable limit is segmented into multiple data files, each
smaller than the limit. These will be sent in separate messages, each with a separate
file name, allowing the original file to be recreated in the correct order by the
receiving nation.
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