Subject: Re: mboned: AMT SSM addressing

From: Venketesan <[email-masked]>
Date: Fri, 15 Sep 2006 10:32:22 -0700

Sachin,
In SSM connections relays are not involved, gateways talk to each 
other directly. So when one gateway at source fails, the recivers 
gateway shud be able to find the backup source gateway using the 
anycast address. 
But the issue is when the new source gateway takes over the old one, 
the existing SSM group addresses (that are binded to the unicast 
address of old gateway) are no more valid. The SSM  group address that 
the new gateway supports will be corresponding to its own unicast 
address (see section 6.3 in the draft). This essentially means the 
reciver "applications" need to shift to the new addresses and all the 
obvious complications associated.. i mean how do u co-ordinate the 
move and stuff...

Hence as John said if u have to source SSM traffic u shud have the 
gateway functionality running in the source itself and not in a 
router. If this source fails anyway u cant help it then.

regards,
Venkat

----- Original Message -----
From: Sachin K <[email-masked]>
Date: Friday, September 15, 2006 8:40 am
Subject: Re: mboned: AMT SSM addressing

> Hi Venkat,
> 
> Even if another gateway tries to backup the failed gateway, the 
> relay may
> drop the packets from the new gateway, as it has no state 
> information for
> this new gateway.
> 
> IMO: another tunnel (through a 3-way handshake) has to be established
> between the new gateway and the relay. But according to the AMT 
> draft the
> 3-way handshake is initiated by the receiver and not the source.
> Also SSM itself does not have any fault tolerant mechanism for this
> scenario. Correct me if I am wrong on this.
> 
> Thanks,
> Sachin
> 
> 
> On 9/14/06, Venketesan <[email-masked]> wrote:
> >
> > Hi,
> > I had a question about the functioning (fault tolerence) of AMT 
> in a
> > certain situation in SSM described below. If one of the authors or
> > someone could answer it..
> >
> > Suppose the unicast address of the gateway is a.b.c.d and is 
anycast
> > prefix is x.y/16. thats makes the possible group addresses 
available
> > for SSM to be 232.c.d/24. Now suppose that this gateway for this
> > domain fails and we have another gateway avaialble with unicast
> > address a.b.c.e. Now since the G in (S, G) is coupled with the 
> unicast> address of the gateway, what happnes to the existing 
> connections i.e
> > (x.y.a.b, 232.c.d/24). How would they be recovered, how would the
> > applications in hosts in remote domains be made aware of the 
changed
> > Group address pool i.e. 232.c.e/24.
> >
> > Thanks,
> > Venkat
> > _______________________________________________________________
> > user interface: http://darkwing.uoregon.edu/~llynch/mboned.html
> > web archive:  http://darkwing.uoregon.edu/~llynch/mboned/
> >
> 
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