Subject: Multicast address

From: Zhai Mingyu <[email-masked]>
Date: Sat, 11 Mar 2000 14:32:40 +0800

Hi,
  about Multicast address allocation I have some questions,i.e., whether

the following two situations can appear or not.
1)In the same TTL scope,there are two sessions which all use the same
multicast
address( for example 233.7.117.2) ,but they use different Transport
protocols,
for example,one using UDP and another using XTP.
2)Likely there are two sessions which all use the same multicast
address( for example 233.7.117.2) ,and same Transport protocol,
for example using UDP.But these two session use different Destination
Port,for example one using port number 22222 and another using 33333.

I think these two situations can exist in Multicast address allocaton,
is it right?

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From: Pavlin Ivanov Radoslavov <[email-masked]>
Date: Fri, 10 Mar 2000 23:19:32 -0800

> I think these two situations can exist in Multicast address allocaton,

Theoretically, yes, same multicast address with different transport
protocol (or different port number) would mean different
session. However, at the network level, IP multicast uses only the
multicast address to make difference between the
sessions/groups. E.g. the multicast routers uses only the multicast
address to route the packets to the receivers. Otherwise, if you
allow the Transport protocol and/or the port number to be a part of
the session ID, the routers would need to lookup the protocol number
and the port number of each packet as well.

malloc tries to solve the address allocation problem only at the IP
level by handling unique addresses to each session, and therefore it
doesn't consider the protocol and the port numbers.

Pavlin