[vsnet-grb 173610] VOEvent Version 2.0 is now available in GCN/TAN

Bacodine vxw at capella2.gsfc.nasa.gov
Mon Apr 23 03:33:32 JST 2012


TO:  GCN/TAN people interested in VOEvents
RE:  VOEvent Version 2.0 is available
DT:  22 Apr 2012


People not interested in VOEvents can delete this now.


INTRODUCTION:
Recall that last month GCN/TAN started distributing VOEvents
via 3 different servers ( http://gcn.gsfc.nasa.gov/gcn/admin/voevent_server_announce.txt ).
Those 3 servers were distributing Version 1.1 VOEvents.
Now one of the servers (eApps) has been converted to distribute Version 2.0 VOEvents
(now the current IVOA VOEvent version):
    SERVERS                        ORIGINAL CONFIG        NEW CONFIG
                                   VERSIONS               VERSIONS
    209.208.78.170 (Atlantic.net)     1.1                   1.1
    50.116.49.68   (Linode.com)       1.1                   1.1
    68.169.57.253  (eApps.com)        1.1                   2.0

The connection IP_Numbers, port numbers, and read/write protocol
all stay the same for the new 2.0 version.  Only the schema reference changes;
and even that is only in the url pointing to the 2.0 schema -- the contents/formats
of the actual "data" stay the same.  (For most of you, even that schema change
will not affect you.) There are redundant servers for the Ver 1.1 events,
but no redundancy (as yet) for the Ver 2.0 events.

All GCN/TAN notice types are available on all 3 servers;
only the version is different.  (That is 15 GRB_Position notice types,
7 Transient_Position types, 15 non-position types (lc, images, spectra),
4 spacecraft pointing_direction types, and 7 Test types.)

Version 1.1 events have been available within GCN/TAN since June 2009.
As such, a community of 1.1 users has developed.  GCN/TAN policy
has grandfather-ed in ver 1.1 for all distribution methods and formats forever.
If the population of 2.0 users overtakes the 1.1 users (ratio is currently 1 to 3),
then one of remaining 1.1 servers will be converted to 2.0
(but there will always be a 1.1 server until at least a year past
the last 1.1 user connection).  If it does not matter to the Ver1.1 customer,
they are encouraged to change their configuration to version 2.0,
so that I can better/sooner know when to adjust the balance
of the 1.1 vs 2.0 servers and when the last of the version 1.1 customers is gone.

VOEVENT SPECIFICATION:
The IVOA docuement on Version 2.0 VOEvents can be found at:
http://www.ivoa.net/Documents/VOEvent/index.html .  
Version 2.0 is the current version for VOEvents within the IVOA.

OTHER DISTRIBUTION METHODS:
Just like the Ver 1.1, the Ver 2.0 VOEvents are also available via
the GCN/TAN-custom VOEvent sockets and by email (both in the body
of the email and as an attachment).



EXCERPTS FROM THE ORIGINAL/MARCH VOEVENT ANNOUNCEMENT:

DEMONSTRATION CLIENT PROGRAM:
To facilitate quick and easy connection to this new service,
a demo client program (voevent_client_demo) is available.
It can be downloaded from 
    http://gcn.gsfc.nasa.gov/gcn/voevent_client_demo.c
This GCN/TAN client is a clean, simple, standalone client written in C.
It needs no additional libraries or other software packages installed
on your system.  It has the basic parts to (a) establish and maintain
a connection to a server, (b) receive and acknowledge VOEvents, and
(c) tell you when there are problems.

To run this demo, the commandline is:
    voevent_client_demo  <srvr_ip_num>  <port_num>
examples:
    voevent_client_demo  209.208.78.170  8099
All 3 servers are listening on port 8089 for incoming connections:
    209.208.78.170    (on Atlantic.net cloud service) (Ver 1.1)
    50.116.49.68      (on Linode.com cloud service) (Ver 1.1)
    68.169.57.253     (on eApps.com cloud service) (Ver 2.0)

CONNECTION PROTOCOL:
A connection between the client and a server is done using the so-called
"vTCP" protocol.  It is the standand TCP protocol with a "v"OEvent adjustment
involving (a) Imalive packet exchange, (b) a 2-part writing/reading action, and
(c) the explicit ack/nacking-ing of the VOEvents received.  The imalives
allow for both ends to monitor the vitality of the end-to-end connection,
and take corrective action if nothing has been recevied within 2or3 
of the 60-sec intervals the imalives are sent.  The 2-part writing/reading
starts with a 4-byte quantity sent first that indicates the length of the VOEvent
message that will be sent next (so the client reads 4 bytes, then knows
how much to read to get the message).  The acking/nacking allows the server
to keep track that the client has correctly received the full VOEvent message.
The TCP/IP VOEvent protocol is described in
    http://www.ivoa.net/Documents/Notes/VOEventTransport/ .
If you already have a client which implements this vTCP protocol,
you can use it to connect to the GCN/TAN VOEvent servers.
(The voevent_client_demo is just a bare-bones example to get people started
if they have no prior experience with VOEvents.  You can also use
voevent_client_demo to connect to other VOEvent servers using the vTCP protocol.)

FILTERING:
Even though GCN/TAN votan is a server and you can connect anonymously,
if you register with GCN/TAN, you can receive all the regular
filtering capabilities of the original GCN system.
Votan is able to accomplish this by checking your IP Number (IPN)
when you connect.  If your IPN matches an entry in the votan sites.cfg file,
then it uses that configuration to determine which Notice types
you want to receive plus all 16 filtering rules.
(See  http://gcn.gsfc.nasa.gov/gcn/tech_describe.html#tc25
for a list of all the filtering functions available.)
If you register, you can have only one client running on the specified
machine (ie the IP Number), because votan uses only the IP Number
to identify you (ie no additional port_number like in original GCN).
Two clients on the same machine have the same IP Number.
Registration is simple -- a 'configuration' is built using the same
GCN/TAN config_builder webpage (see below).
If you choose not to register, there can be no filtering
so then your connection will receive all Notices of all the types
(currently ~2000 per day; this does not count the 1440 imalive
transport-protocol messages sent per day).

ACTION ITEM:
a) If, after reviewing the information above/below, you want to receive
the GCN/TAN VOEvents, you need to decide if you want to have the filtering 
capabilities or not.
If you want filtering, then go to:
    http://gcn.gsfc.nasa.gov/gcn/config_builder.html
and select "#1 Create a new config" specifying the "VO_EVENT" selection
in the Distribution method pull-down menu (plus making selections for all
the other items that make up sites's configuration); 
or select "#2 Modify an existing config" and (at the least) change your current
distribution method to the VO_EVENT method. 
Of course, if you do not want filtering, then you can just connect anonymously
to the server and receive all Notices the GCN/TAN produces.
b) Then you need to get a client (either voevent_client_demo or another client program)
and connect to one of the VOEvent servers listed above.
If you do not want filtering, then just connect with a client progrqam.

THE FUTURE:
The following items/functions will be implemented in the future
(in semi-prioritized order):
a) Add version 2.0.  DONE.
b) Add capability for vetted authors to publish to these servers.
c) Allowing anonymous connections to publish.
d) Having a database of past VOEvents that is queriable.




Sincerely,
Scott

Scott Barthelmy                      NASA-GSFC, Code 661, Greenbelt, MD   20771
PHONE:  301-286-3106                 (office)       CELL:   301-346-3733
EMAIL:  scott at lheamail.gsfc.nasa.gov
PAGER:  3013463733 at cingularme.com
WEB:    http://gcn.gsfc.nasa.gov/gcn


(You can take this opportunity to review your current configuration
and request changes (see http://gcn.gsfc.nasa.gov/gcn/config_builder.html
Selection #2) or your can just tell me what you want changed, but please
include your config below so (a) I know your site_name, and (b) you mark the
differences/changes.)
//////////////////////////////// Your Current Configuration /////////////////////////

BEGIN_SITE
SITE_NAME  VSNET
DATES      25jun05   23oct07
SITE_LON_LAT   135.75   35.00
DIST_METHOD   EMAIL
DIST_ADDRESS  vsnet-grb at ooruri.kusastro.kyoto-u.ac.jp
POC_NAME      Daisaku Nogami
POC_ADDRESS   vsnet-grb at ooruri.kusastro.kyoto-u.ac.jp
DAILY_REPORT_ENABLE   0
DAILY_REPORT_ADDRESS  vsnet-grb at ooruri.kusastro.kyoto-u.ac.jp
# Site-specific items:
TRIGGER_ID     0
INTENSITY      -1.0
ERROR          360.1000
DELAY          999.9
SIGNIFICANCE   0.00
CONF_LEVEL     0.00
OBSERVABILITY  ALL
ATTACHMENT     NONE
SIMBAD_NED     0
# Type-specific items:
IPN_POS
INTEGRAL_SPIACS
INTEGRAL_WAKEUP
INTEGRAL_REFINED
INTEGRAL_OFFLINE
KONUS_LC
SWIFT_BAT_GRB_ALERT
SWIFT_BAT_GRB_POS  trig_id=0
SWIFT_BAT_GRB_NACK_POS
SWIFT_BAT_GRB_LC  trig_id=0
SWIFT_FOM_2OBS  trig_id=0
SWIFT_SC_2SLEW  trig_id=0
SWIFT_XRT_POS
SWIFT_XRT_NACK_POS
SWIFT_XRT_IMAGE
SWIFT_XRT_PROC_IMAGE
SWIFT_UVOT_POS  inten=99.00
SWIFT_UVOT_IMAGE
SWIFT_UVOT_PROC_IMAGE
SWIFT_UVOT_SRCLIST
SWIFT_UVOT_PROC_SRCLIST
SWIFT_POINTDIR
SWIFT_TOO_FOM
SWIFT_TOO_SLEW
END_SITE


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