Comments about Multicast and Access Grid
- My institution has not
successfully deployed multicast.
- in my experience, the
multicast issues usually occurs in this order. 1 - Department LAN 2 -
Campus / Organization LAN 3 - Campus/Org connection to I2 4 - I2 WAN.
- When it works, it's great.
Fortunately, for us it usually works.
- MC issues are almost always
local issues. Our host institution resists allowing widespread usage of
multicast. We have 2 specific ports at our facility that the
institutional networking support allows MC traffic to go to. This is
almost always workable. When we have problems, it's typically a 1-way
MC issue; we can get audio and video in, but can't trasmit both. These
types of issues tend to disappear on their own, over the course of a
day. We've not been very sucessful in identifying the actual problem
when this behavior is observed. Fortunately, the bad behavior is
infrequent and most of the venues that we visit are bridged for the
occasion when MC fails.
- Everyone who shows an
interest in AccessGrid must be told in clear firm terms that multicast
is a necessity and that using crutches like a unicast bridge should
only be done as necessary to convince upper management of the value of
- it's gotten better but,
we're a long way out from it being a simple task :(
- I am able to multicast,
however some of the sites that I connect to have a lot of problems
- The AG's need (preference)
for multicast is a great technology driver - in that network engineers
are driven to make their networks operated properly. Unicast bridges
are a convenient workaround, enabling network engineers to not do their
job (of configuring their routers etc to accomodate multicast).
- The media tools launch and
run better when using multicast.
- Normally works OK for us on
AG2.3 - main issue is in the bridging other sites use, particularly
between Insors nodes in the US & us in the UK.
- Multicast is important for
performance, primarily efficient use of bandwidth. Because of from what
I see as its limited availability, unicast bridging is critical to the
success of a collaboration tool such as AG.
- Would be nice to have a
clear document stating what ports to open up for firewall folks (uni
- Multicast has been totally
unreliable, with two years' experience. We rarely can have a conference
without dropping connections at least once--which is very disruptive.
We sometimes use bridged mode via inSORS.
- Multicast is the source of
about 99% of our problems. And since we don't have any control of the
entire network, end to end quality of service is a best effort of the
- Somewhere upstream outside
of our state there is a few folks we can not send multicast to, but
generally 95% of the time it is not a problem. I train my operators to
always be prepared to work around a potential multicast problem,
fortunately it's usually working and we advise sites who do have
multicast issues how to connect to use utilizing unicast.
- I am only able to use
multicast to connect to a locally based venue-server. When connecting
to an overseas venue-server, I am always forced to use a unicast
- I am a developer and I can
use multicast for my test locally. However, none of the events
transmitted in the US I have been able to receive in multicast. It
seems to be broken somewhere along the way from the US to the UK...
- Always works for me.
- Sometimes when meeting with
people who are using a bridge we seem to have trouble, meeting with
other straightforward multicast sites is usually good.
- The main problem is that
Multicast is not set up by default at most institutions.
- There was a problem with
Multicast within XXXXX University's network, but this has now been
fixed with a router upgrade. Since then Multicast has been functioning
- We have router problems
here. We can receive multicast but cannot transmit outside our
- Although the university has
multicast from outside to the border router, there is still no
multicast on the LAN (Problems with the backbone switches). Its on
their todo list, but is a low priority.
- Ultimately people need to
get multicast sorted. I'm amazed at how slow the adoption of multicast
has been, especially at the normal ISP level, as potentially it could
save a shedload of bandwidth.
- We used to use multicast 95%
of the time. Then a fault on a site router which affected the whole
site was fixed, and since then multicast has suffered frequent (e.g.
every 30 seconds) dropouts, so for the last 9 months we've had to use
unicast and bridges. The router manufacturer hasn't been able to fix
- As known well, multicast
reachability is not available to common PC users. Even now, only
advanced research institutes can have multicast. Our organization
fortunately could prepare multicast but it has not been working
reliably. I feel, in 50% of important meetings, we have had a
- Normally great, but problems
are extremely hard to track down. Not network ops are weak on
understanding MC and/or MC diagnostic tools.
- Needs more
- my I2 connection is not
multicast enabled, so i must connect unicast.
- I have gone to great efforts
to have my laptops ip address added to the routed mcast address range
and getting our site properly configured for mbgp. Not easy. For adding
new or occational users to an AG session unicast will be invaluable and
is something I intend to look into. I have also as yet not been able to
use AG form home :(
- Great solution to the
problem... but it needs to be _much_ more consistent.
- Am not clear on how to
- We use unicast only on
networks that do not support multicast or where there is a multicast
- Public bridges and a more
unified 'home' venue would help proliferate AccessGrid technology.
- Often the network converges
to a multicast tree slowly, so it takes a while for my video and audio
to start to be received by other nodes.
- We also have running a
Unicast to Multicast Bridge Server
- The network does need to be
open and good communication with networking on site. We had a few
problems getting them to understand what ports should be open, what is
really a multicast problems, etc.
- multicast is definitely nice
and the way to go with multipoint conferencilng, to eliminate MCU type
requirements. but the unicast option needs to be there since edu
networks at least are in flux and sometimes mcast is not available; and
some users don't have mcast but should be accommodated (the user/use is
more important than the technology).
- Occassional glitches with
international multicast between Australia (home) and oversease
- multicast is a state of the
grid which is needed for effective and efficient grid computing. The
Accessgrid emerged in 99 as a tool to debug multicast for this effort.
In it's current role as a video conferencing system, multicast is
helpful but not mandatory. The underlying premise of the AccessGrid,
however, is as an interface to enable grid computing.
- Multicast on the WAN is ok,
on our Lan is a problem.
- all we can say that
multicast is good to use for the accessgrid than unicast.
- need debug tool
- Using multicast is good, but
I usually cannot find out how to enable multicast through Venue Client,
the interface is not so user friendly.
- It's rather new that we can
use multicast. In the past we only could use unicast.
- Makes sense as long as it
- We've had some (very few)
occasions when multicast wasn't working on one of the routers
connecting us to our gigapop. Some times we've resorted to unicast with
an endpoint that didn't have multicast. Other than these very few
times, multicast has worked.
- I have to use unicast
because I am behind a firewall and on a commodity Internet connection
that doesn't support multicast.