Attachment II-16
Procedures for transmitting and collecting
meteorological bulletins on the Internet
A –
Use of electronic mail (e-mail)
Background
Electronic mail (e-mail) can be a very simple and
cost effective way to exchange Meteorological Bulletins, in particular for
collecting meteorological data bulletins. It should be noted however that
e-mail is not an end-to-end service and there is no guarantee of the
timely delivery of messages. E-mail is also inherently insecure.
The following
guidelines describe practices for sending both data collection bulletins
and binary Meteorological Bulletins via e-mail while minimizing security
issues.
Centres implementing this procedure should ensure
that meteorological bulletins to be ingested in the GTS follow the
standard GTS procedures and formats.
Format of messages for sending
Meteorological Bulletins via electronic mail on the Internet:
1.
E-mail messages should use only International Alphabet No. 5. It is recommended that the
Meteorological Bulletin should be contained in the main body of the e-mail
message; as an option it may be contained in an attachment.
Note: ‘attachments' are a part of an
e-mail message that are separate from the main body of the mail message,
and that their display/storage is normally contingent upon some further
action of the user.
2.
It is recommended that only a single bulletin should be sent in each
e-mail message. However, receiving centres may agree to accept multiple
Meteorological Bulletins per e-mail message to a maximum of 5.
3.
The Meteorological Bulletin(s) can be sent either as text in the
main body of the e-mail message, or in the attachment(s) of the e-mail
message, but not in both. Binary
data can only be sent in the attachment(s).
4.
The main body of an e-mail message should follow the following
format:
<Meteorological Bulletin>
NNNN
where,
<Meteorological
Bulletin> is a
standard Meteorological Bulletin starting with the abbreviated header
line, such as
TTAAii CCCC YYGGgg [BBB]
message text
A termination string NNNN is required after every Meteorological
Bulletin.
No other information should be included in the main body of the
e-mail message unless agreed by the receiving centre. For example, automatic
forward and reply informational text should not be allowed in the body of
the message.
Note: The receiving
centre shall validate the AHL before processing the Meteorological
Bulletin.
5.
The total size of all attachments should not exceed 2 MBytes or as
specified in a bilateral agreement. Attachments
should be coded in Base 64 (MIME standard).
6.
The e-mail header “Subject:” field either:
(a) May
contain the AHL if the e-mail message contains a single Meteorological
Bulletin;
(b)
Or a pre-defined <security string>.
Security considerations:
1.
E-mail is inherently insecure. To minimize security issues, all
e-mail input should be pre-authorized by means of a list of valid source
e-mail addresses at the receiving site.
The receiving centre should only process GTS-related e-mails from
the pre-defined list of e-mail addresses. That is, the receiving centre
should validate the e-mail message header “From:” field. To avoid problems with e-mail messages containing manipulated
“From”-fields, centres may optionally agree to implement <security
strings> in the message. If <security strings> are agreed on, and GTS message(s) are included in attachment(s),
then the main body of the e-mail message can only contain the <security
string>. The receiving
centre should validate the “Subject”-field for the AHL or the
pre-agreed string.
2.
No automatic acknowledgements or replies should be sent from the
receiving centres.
3.
It is recommended to use specific mail accounts for GTS data
transfer with bilaterally agreed names and not to receive GTS data in
personal mailboxes.
A
problem with some mail exchanger applications is that by default they
operate as an “open-relay”. An open-relay occurs, for example, if site
A.COM accepts mail from B.NET destined for C.ORG. This means that spammers
can use A.COM’s mail system to distribute their e-mails. Centres should ensure that they do
not operate as an open-relay.
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Publication
No. 9: Volume C1 - Catalogue of Meteorological Bulletins
Notification
from RTH Offenbach [