[AG-TECH] Bridge availability chances.
Christoph Willing
willing at vislab.uq.edu.au
Mon Apr 9 16:06:11 CDT 2007
On 10/04/2007, at 5:38 AM, Derek Piper wrote:
>
> I'm having a (possibly) similar problem with a participant in
> Tokyo, Japan. I'm not sure of the way that bridges are chosen, but
> it seems that from this participant's location, no bridges are
> available at all. I'm not sure if it's firewalling or what that
> might prevent even the LIST of bridges appearing, or what it is.
At present, all AG3 bridges are "advertised" via a single bridge
registry (at ANL) and collected into the VenueClient's bridge list
when it starts up. If the bridge registry is not contactable, for
whatever reason, at startup then the VenueClient will have an empty
bridge list. Often, restarting the VenueClient will result in a
usable bridge list - it depends on why the registry wasn't
contactable; it could be that the registry was down, or maybe a local
network problem. As long as the bridge registry isn't contactable,
there'll be an empty bridge list.
AG3.1 (real soon now) caches bridge lists so that the cached version
can be used when the bridge registry is not reachable at start up. It
also has an update facility i.e. update bridge list while VenueClient
is running.
The AG2 bridge mechanism is quite different - for a particular venue,
a site somehwere must be running a bridge server which explicitly
targets that particular venue in its configuration file (AG3 bridges
bridge all venues).
chris
> Jimmy Miklavcic wrote:
>> I'm working with Kansas University Medical Center to get a small
>> Access Grid node running. They most certainly don't have
>> multicast available on their campus so we are stuck with unicast.
>> They have a "very" stringent security policy and I'm forced to
>> narrow down the number of bridges that they will allow through
>> their fire wall.
>> So the question is, if I give them a list of ten bridges, what
>> are the chances that one or two of them will be listed in the
>> bridge registry? Should they increase their bridge locator
>> function from 10 to say 20 to increase their chances of seeing any
>> of the ten? Also, if a bridge is not listed in the registry, does
>> it mean that it is not available?
>> -- Jimmy Miklavcic
>> Multimedia Specialist
>> Jimmy.Miklavcic at utah.edu
>> UNIVERSITY OF UTAH
>> CTR FOR HIGH PERFORM COMPUTING
>> 155 SOUTH 1452 EAST RM 405
>> SALT LAKE CITY, UT 84112-0190
>> Office: 801.585.9335
>> Fax: 801.585.5366
>> http://www.anotherlanguage.org
>>
>
> --
> Derek Piper - dcpiper at indiana.edu - (812) 856 0111
> IRI 323, School of Informatics
> Indiana University, Bloomington, Indiana
>
Christoph Willing +61 7 3365 8350
QCIF Access Grid Manager
University of Queensland
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