Subject: Re: Wellfleet routers and multicasting :-(

From: Yves Lepage <[email-masked]>
Date: Wed, 26 Jun 1996 20:25:22 -0400 (EDT)

Hi Stephen,

WHat algorythm do you use to determine which routes the router
will be learning and which it will not?

It is simply based on the number of routes there's already in the routing table
or do you check memory consumption (which probably amounts to the same
actually)?

I am asking because I imagine this:

a few thousand people watching a shuttle mission for two full weeks. If
the router has been configured with only the same number of routes
( a few thousands) then I wonder what would happen? WOuld it means that 
no more people behind that router could join existing sessions? If so
it would also mean that people could also not join any newer session
that have appeared, or that new people starting sdr would not receive any 
advertisements... that kind of things. 

Not only it would be easily feasible to perform DOS attacks on the 
sites behind the router but not much control is possible if this is
indeed the algorythm you use. 

Beging able to specify ranges for groups would be nice.

Maybe I am panicing all for nothing :-) 

Thanks.
Yves Lepage

---

From: [email-masked] (Stephen Ostrowski)
Date: Thu, 27 Jun 1996 08:34:32 -0400 (EDT)

The field for limiting the number of routes was only to stop
the flooding of 10k+ routes from being added to our routing table.
We did this as most of our routers in Bay are running with a
little extra memory and when we got a flood of nets from the 
mbone, those routers would run out of memory and crash.  The
ones with enough memory, stayed up, however.

So, we set the limit at 5k routes (still 1k over what is out
there) and when a flood comes in, we will ignore all the 
new routes(which are usually the bogus ones).

If you want to limit the multicast traffic you get on 
an interface, you can use traffic filters to drop
traffic for a group range, group,source address, protocol
or whatever.

I hope this makes sense, and if it doesn't please say so.

- Stephen