Subject: RE: Questions

From: vishwas <[email-masked]>
Date: Tue, 17 Nov 98 13:10:00 PST

[vishwas]
I thought it may be usefull for PIM implementors.

I'm a student of Changsha Institute of Technology in Changsha,
P.R.China. I have some questions about mobile host issues in IGMP v.2
(RFC 2236).

1) How does a host know it is the first member of that group on the
network ?

[vishwas]
Need Not bother to know that.

2) When a mobile host moves into a new subnet, is it possible to send an
unsolicited version 2 membership report immediatly for each group it
joins ? As the "reports sent by mobile hosts without addresses on the
local subnet will be ignored", a mobile host can send the membership
report messages only after it obtains a local address (care-of address
in mobile IP), doesn't it ?

[vishwas]
Very much TRUE, Provided the new subnet has a multicast router.

3) How about the join latency when a mobile host moves into a new subnet
and need to receive messages from the previous multicast session ? I
noticed that the query interval for the IGMP is by default 125 seconds
(it may be too long in mobile host cases).

[vishwas]
It is an administratively configurable value, U can even set it to 60   
secs. For the latency and Lost packets, U can provide some kind of cache   
agent. But generally U cant help it.

Mean while I was wondering what if the mobile host has moved to a   
location where in the local subnet doesent have a Multicast router..!!   
Then we may have to go for some thing like, Dynamic Tunnelling with the   
nearest Multicast router. In this case MSDP may be of some use (Just a   
hunch). Though it can be thought of joinig the nearest router through   
tunnel somehow, there may be security and administrative issues, which   
cant provide a seamless mobility to a Mobile host.
     If we consider again the Home Agent to redirect the multicast   
traffic to the new location by tunnelling them, again there may be   
Modifications required to the Multicast routing protocol, to support   
MOBILITY extensions.

In general what I would like to ask is, Does Mobility is in the scope of   
Multicast routing...?

Comments pl.
 -vishu

Regards
Vishwanath S. Edavayyanamath
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