Problems with GRQ/GCF messages for the GK discovery

Roy, Radhika R, ALARC rrroy at ATT.COM
Tue May 23 15:26:28 EDT 2000

Hi, Everyone:

Just to remind that we have to address the problems of the GK discovery
using the GRQ/GCF messages in the H.323 mobile environments.

I like point out that an alternative method was suggested to use the MGA

Both GRQ and MGA messages have problems to discover the GK in mobile

However, the meeting report (TD-56, TD-22c) shows that, as if, MGA mechanism
cannot be used in any H.323 mobile communications environment. It is NOT
simply true because H.323 mobile communications environments include:
Wire-line (copper, cable, fiber), Wireless LAN (multi-megabits to
multi-gigabits), and/or Cellular Wireless (picocell, microcell, macrocell)
Networking environments.

The problem for the MGA comes up when the bandwidth is very scarce if the
MGA message is multicast periodically. For example, in the ellular wireless
(macrocell) network, the bandwidth is very scarce. However, this kind of
problem is being addressed by sending the "advertise" message in a UNICAST
fashion. For example, 3GPP has proposed mobile IP's "agent advertisement
message" to be sent in a unicast fashion (instead of multicast) for their
cellular wireless (macrocell) networking environment. The price they are
paying is to make the mobility solution a quasi-dynamic (instead of truly

For all other communications environments [e.g., Wire-line (copper, cable,
fiber), Wireless LAN (multi-megabits to multi-gigabits), and/or Cellular
Wireless (picocell, microcell)] where the bandwidth is NOT scarce, like
mobile IP, the MGA mechanism can be used as appropriate.

However, the use of the MGA message is an OPTION, not mandatory. (This
mechanism will help the mobile H.323 to interwork with the mobile IP should
anyone to implement mobile IP in the lower network layer.)

So, both GRQ/GCF/GRJ and MGA mechanisms can be used in a complementary
manner as appropriate depending on pros and cons of different networking

We will discuss this further. In the meantime, please let me know if you
have any questions.

Best regards,
Radhika R. Roy
+1 732 420 1580
rrroy at

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