Re: [ns] a multicast question

[adolfo@us.ibm.com]

Are you sure that your ACK is getting out of the receiving node BEFORE it
receives the data?  That doesn't seem like it's possible.

Anyway, regardless of that, it seems to me that your protocol MUST handle
the situation of receiving the ACK for a packet it has not yet received.
That is, say that A and B are receiving a packet sent from S.  If the link
between S and B is very slow while all other links are extremely fast, then
A could receive the packet and ACK it to S and B before B even gets the
original data packet.  This is perfectly legal in IP and your protocol
should handle it to be complete.  Because of this (and not knowing your
topology), I would guess that what you are seeing is normal.....  Of
course, more information is needed to be absolutely sure....

good luck,


Adolfo F. Rodriguez

adolfo@us.ibm.com
Advisory I/T Specialist
ITSO Raleigh, IBM
razor@cs.duke.edu
PhD Student, Computer Science
Duke University




Shuju Wu <swu@mail.sis.pitt.edu>@ISI.EDU on 08/08/2000 05:29:02 PM

Sent by:  owner-ns-users@ISI.EDU


To:   ns-users@mash.cs.berkeley.edu
cc:
Subject:  [ns] a multicast question



HI,

I attached a multicast agent to a node.
After this node receives a data packet,
this node will multicast an ACK to the whole
group. But in NAM, when I check the packets,
the ACK packet is multicast to whole group
earlier than the data packet, that means
other nodes receive the ACK packet first, receive
the data packet after the ACK packet.

Can anyone tell me why this happends?
Did I set up something wrong?

Thanks

Shuju