This protocol is designed to be flood routed in a meshed network in
as efficient a manner as possible.
-The protocol consists of a L<Routing Section> and a L<Command Section>.
-The two sections are separated with the '|' character.
-
-Most of this document is concerned with the L<Routing Section>, however
-some L<Standard Commands> which all implementation should issue and
+Each message consists of a L</Routing Section> and a L</Command Section>.
+The two sections are separated with the '|' character and the whole
+message is terminated in the standard RFC/Internet manner with the
+ascii <carraige return><linefeed> characters. It follows that these
+characters (as well as a small number of other reserved characters)
+can only be sent escaped. This is described further in the
+L</Command Section>.
+
+Most of this document is concerned with the L</Routing Section>, however
+some L</Standard Commands> which all implementation should issue and
must accept are described.
-=head2 Routing Section
+=head1 Routing Section
The application that implements this protocol is essentially a line
oriented message router. One line equals one message. Each line is
It is assumed that nodes are connected to
each other using a "reliable" streaming protocol such as TCP/IP or
-AX25. Having said that: in context, elements of the protocol could be
-multi or broadcast, either "as is" or wrapped in some other framing
+AX25. Having said that: in context, messages in this protocol could be
+multi/broadcast, either "as is" or wrapped in some other framing
protocol.
Because this is an unreliable, best effort, "please route my packets
discontinuity either caused by outage or deliberate filtering.
However, as it is envisaged that most messages will be flood routed or,
-in the case of directed messages (those that have a E<lt>tonodeE<gt> or
-E<lt>touserE<gt>) down all interfaces showing a route for that
+in the case of directed messages (those that have L</To> and/or
+L</ToUser> fields) down all interfaces showing a route for that
direction, it is unlikely that messages will be lost in practice.
-=head3 Field Description
+=head2 Field Description
-Only the first three fields in the L<routing section> are compulsory
+Only the first three fields in the L</Routing Section> are compulsory
and indicate that this is a broadcast to be sent to all nodes coming
-from the L<Origin>. If the message needs to be identified as coming
-from a user on a node, then the L<FrmUser> field is added.
+from the L</Origin>. If the message needs to be identified as coming
+from a user on a node, then the L</FrmUser> field is added.
-Adding a L<To> and/or L<ToUser> field will restrict the destinations
+Adding a L</To> and/or L</ToUser> field will restrict the destinations
or recipients that receive this message.
-The L<Hop> field is incremented on receipt of a message on a node.
+The L</Hop> field is incremented on receipt of a message on a node.
Fields are separated by the comma ',' character with the last field
required followed by the vertical bar '|' character.
originating node. It is incremented immediately on receipt and
before determining its value.
-So the originating node sends a message with a L<Hop> of 0, the
+So the originating node sends a message with a L</Hop> of 0, the
neighbouring nodes must increment this field before passing
it on to higher layers for onward processing.
Implementations may have an upper limit to this field and may
-silently drop incoming messages with a L<Hop> count greater than the
+silently drop incoming messages with a L</Hop> count greater than the
limit.
=item FrmUser
This field is used either to indicate particular node destination
or to differentiate this broadcast in some way by making this
-message as a member of a L<Channel>. Any message can be sent
-down any L<Channel>. The names of L<Channel>s and their usage
+message as a member of a L</Channel>. Any message can be sent
+down any L</Channel>. The names of L</Channel>s and their usage
is entirely up to the implementor.
It is assumed that node names can be differentiated from user
-names and L<Channel> names.
+names and L</Channel> names.
If the field is set to a particular node destination, it will
be routed (rather than broadcast) to that node. However, any
this further.
Conventionally this field is used to indicate the user to whom
-this message is directed. In an ideal world the L<To> field
+this message is directed. In an ideal world the L</To> field
will be set, by the originating node, to the identifier of the node
on which this user resides.
-If the L<To> field is not set then this message will be
+If the L</To> field is not set then this message will be
broadcast. However, should a node become apparent (on route)
-then nodes are free to fill in the L<To> field and proceed
+then nodes are free to fill in the L</To> field and proceed
with a more directed approach.
If it becomes apparent (on route) that there may be more than
-one possible L<To> destination for a L<ToUser> then a node
-may duplicate the message (keeping the same L<TimeSeq>) and
-route it onwards. Because of the L<deduplication> inherent in
+one possible L</To> destination for a L</ToUser> then a node
+may duplicate the message (keeping the same L</TimeSeq>) and
+route it onwards. Because of the L</DeDuplication> inherent in
the system, it is indeterminate as to which destination will
receive the message. It is possible for all or just some
-destinations to receive the message. The tuple (L<Origin>,
-L<TimeSeq>) will determine uniqueness.
+destinations to receive the message. The tuple (L</Origin>,
+L</TimeSeq>) will determine uniqueness.
-This field can, in the case where L<To>
-is set to the name of a node, be set to a L<Channel>. If this
+This field can, in the case where L</To>
+is set to the name of a node, be set to a L</Channel>. If this
is the case then this will cause this message to be sent to
-a L<Channel> on the L<To> node only.
-
+a L</Channel> on the L</To> node only.
+
=back
-=head3 Channel
+=head2 Channel
Channels are a concept very similar to that on IRC. It is a
way of segregating data flows in a network. In principle, subject
to local policy or application requirements, any data (or
-L<Command Section>) can be sent down any channel.
+L</Command Section>) can be sent down any channel.
It is up to the implementation whether to use this feature or not.
-=head3 Routing
+=head2 Routing
It is assumed that nodes will be connected in a looped network with
more than one route available (in many cases) to another node.
In anycase, most traffic is not directed, but broadcast to all users
on all nodes.
-Each message is uniquely identified by the (L<Origin>,L<TimeSeq>)
+Each message is uniquely identified by the (L</Origin>,L</TimeSeq>)
tuple. The basic system will learn which interfaces can see what nodes
-by looking at the tuple and merging that with the L<Hop> count.
-Each interface remembers the latest L<TimeSeq> with the lowest L<Hop>
-for each L<Origin> that arrives on that interface. It also remembers
-the number of messages for that L<Origin> that has been received on
+by looking at the tuple and merging that with the L</Hop> count.
+Each interface remembers the latest L</TimeSeq> with the lowest L</Hop>
+for each L</Origin> that arrives on that interface. It also remembers
+the number of messages for that L</Origin> that has been received on
that interface.
Any message for onward broadcast is duplicated and sent out on all
is more than one possible route then, depending on network or local
policy, the message may be duplicated and sent on other interfaces
as well.
-
-=head3 DeDuplication
-On receipt of a message, its unique tuple (L<Origin>,L<TimeSeq>) is
+=head2 DeDuplication
+
+On receipt of a message, its unique tuple (L</Origin>,L</TimeSeq>) is
checked against a hash table. If it exists: the message is silently
dropped. If it does not exist in the hash table then the tuple is
added.
This mechanism only ensures that a message broadcast around the network
travels the least distance and through the fewest nodes possible. It
is up to higher layers to make sure that data carried is not, itself,
-duplicated!
-
-=head2 Command Section
+duplicated!
+
+=head2 Examples
+
+ # on link startup
+ GB7TLH,3D02350001,0|HELLO
+
+ # on user startup
+ GB7TLH,3D042506F2,0,G1TLH|HELLO
+
+ # on user disconnection
+ GB7TLH,3D9534F32D,0,G1TLH|BYE
+
+ # a talk (actually 'text') message to a user (some distance away
+ # from the origin node)
+ GB7TLH,3D03450019,3,G1TLH,GB7BAA,G8TIC|T,Hiya Mike what's happening?
+
+ # a talk/chat/text message to a channel or group
+ GB7TLH,0413525F23,2,G1TLH,VHF|T,2m is opening on MS
+
+ # a ping to find the whereabouts and distance of a user from a node
+ # the hex number on the end is the ping ID
+ GB7TLH,1512346543,0,,,G7BRN|PING,9F4D
+
+ # the same from a user on GB7TLH
+ GB7TLH,1512346543,0,G1TLH,,G7BRN|PING,23
+
+ # this effectively asks whether the user is on-line on a particular node
+ GB7TLH,1512346543,0,G1TLH,GB7DJK,G7BRN|PING,35DE
+
+ # A possible reply, same ID as ping followed by the no of hops on the
+ # received ping
+ GB7DJK,1512450534,3,G7BRN,GB7TLH,G1TLH|PONG,35DE,3
-The Command Section of the message contains the actual data being
+
+=head1 Command Section
+
+The L</Command Section> of the message contains the actual data being
passed. It is called the Command Section because all commands
-are identified with a L<Command Tag> which is implemented by
+are identified with a L</Tag> which is implemented by
the software using this protocol.
-=head3 Command Tag
+The L</Tag> is separated from its data by a comma ','. All fields
+in any subsequent data shall be separated by a comma ','.
+All fields shall
+be HTTP encoded such that reserved characters (comma ',',
+vertical bar '|',
+percent '%',
+equals '='
+and non printable characters less than 127 (or %7F in hex)
+[including newline and carraige return] are tranlated to
+their two hex digit equivalent preceeded by the percent '%' character.
+
+For example:
+
+ "%0D%0A" is "<carriage return><linefeed>".
+ "hello%2C there" is "hello, there"
+
+This is not standard CSV, fields are not quoted (delimited with either
+' or ").
+
+All national characters above 127 are UTF8 encoded in the
+standard perl 5.8.x way. It follows that all (perl) programs that
+are written according to this specification must say:
+
+ use UTF8;
-The Command Tag consists of string of uppercase letters and digits, starting
+A message (or line) is terminated with <carriage return><linefeed>
+0x0d 0x0a. Incoming messages must be accepted even when terminated
+with just <linefeed>.
+
+Care must be taken to make sure that fields have any reserved characters
+encoded. In particular: it is perfectly permissible to have <linefeed>
+characters in a field - so long as they are escaped.
+
+Fields come in two styles: either simple fields (just containing
+data) or B<key>=B<value> pairs. Each pair must be separated from
+the next by a comma ','. The B<key> must consist of the set of
+characters [a-z0-9_] (ie lowercase letters, digits and underscore),
+with a leading letter. The B<value> must be HTTP encoded as
+specified above and can otherwise contain any character.
+
+There is no maximum size specified for a message. It is up to each
+implimentation to enforce one (if only for their own protection).
+
+=head2 Tag
+
+The L</Tag> consists of string of uppercase letters and digits, starting
with a leading, uppercase, letter. Tags should be as short as is meaningful.
Valid tags would be:
dx
Ann
-There are a number of standard commands which must be accepted by
+=head2 Standard Commands
+
+There are a number of L</Standard Commands> which must be accepted by
all implementations.
=head1 AUTHOR
projects / spider.git / commitdiff