Subject: Multiple Multicast Tunnels

From: Hyang-ah Kim <[email-masked]>
Date: Thu, 7 Aug 1997 17:09:09 +0900 (KST)

Hi! 

I am trying to solve the following problem. One approach that now I 
think is to use a probe. However, I am wondering if there is any other
way which is easier or more efficient. If so, please, let me know.  
My another question is if it is possible to get any tool which copies  
all packets passing through a router so that I can apply to make a probe. 

I will greatly appreciate whatever you suggest. 

Best Wishes, 
Hyang-ah Kim

Problem Definition
==================

One of the problems with most of the current backbone networks is 
that they are not multicast-aware. Instead, most of the networks
have a separate multicast routing protocol process running on a 
separate workstation neartby. Tunnels are set up between those 
workstations, and multicast packets are encapsultated into a unicast
packet between two points. 

The problem with these kind of configuration is that there in no way 
to easily tell if there are multiple multicast tunnels between any
two clouds of networks. 

we can simply draw this configuration as follows. There are two net-
work clouds and each is connected to each other through the border
routers denoted BR. The border routers doesn't have multicast routing
protocol abd the workstations A and B configured a tunnel to feed 
multicast traffic. Assume that each cloud's network is multicast-aware.

	/---------\               /----------\
       /    A      \             /   B        \
       |          BR1----------BR2             |
	\   A'     /             \   B'       /
	 \--------/               \----------/

Workstation A' and B' have their multicast connectivity between them,
which is a very undesirable thing since this will suck up your precious
bandwidth. 

How can you tell if there are any duplicate multicast tunnels between
any two network clouds. 

One approach 
============
Attach a probe to each border router. The border router copies all packets
passing through it and sends the copies to the probe. This copy procedure
should not affect the performance of packet delivery since most of 
multicast packets are time-critical. 
The probe looks inside the copied IP payload and again the encapsulated
IP payload to see if this is a multicast packet. If there exist duplicate
multicast tunnels, we could observe an identical characteristic between 
two traffics.

---

From: Dino Farinacci <[email-masked]>
Date: Fri, 8 Aug 1997 18:57:52 -0700

>> to easily tell if there are multiple multicast tunnels between any

    There is an easier way to find out who is tunneling over you. You use
    protocol number based access-lists with violation logging. It will record
    source and destination addresses. Wala!

Dino

---

From: Hyang-ah Kim <[email-masked]>
Date: Mon, 11 Aug 1997 11:10:46 +0900 (KST)

It is very good news for me that there is an easier way.

But I don't understand how this finds out the existence of the
multiple multicast tunnels. Could you give me more detailed 
explanation? 

Thank you very much for your consideration!

- hakim

-- 
Kim, Hyang-Ah					  
System Architecture Lab. CS Dept. KAIST	     
Daejon, Korea

[email-masked]
http://cosmos.kaist.ac.kr/~hakim