Subject: Re: comments on protocol draft

From: "Khosravi, Hormuzd M" <[email-masked]>
Date: Thu, 15 Jul 2004 22:19:09 -0700

Furquan,

Thanks for your comments. I think these are all very good points and we
will definitely work to address them in the future revs of the draft.
Pls see a few comments below... 

-----Original Message-----
From: Forwarding and Control Element Separation
[mailto:[email-masked]] On Behalf Of Furquan Ansari

4) ForCES data and control packet paths:
   - From the text in the draft, it certainly looks like the same
     association/channel is used for carrying both the control and the
data
     packets. I believe that this shouldn't be the case. The control
     packets and the data packets should use two independent  channels
     (associations) for sending and receiving messages between  the CE
and
     the FE. Any effect on one channel should not effect the other.

[HK] I completely agree on this. This has been a design principle that
we have pushed for and has been well received by the WG. #1 in section 4
(TML Reqs) talks about Reliability by referencing RFC 3654 in which the
reliability requirements for Data and Control messages are clearly
differentiated as you have stated below.

     a) The control channel setup between the CE and the FE may (will)
have
     totally different requirements from the data channel. E.g. we may
     choose to use TCP as the TML layer to tranfer data from the FE to
CE
     (and vice-versa). However, the data channel may not require TCP, or
     in fact, should not use TCP. The data delivery reliability of the
     forces data packets (e.g. routing packets) is independently taken
     care of by the routing protocols themselves. The effect on some
protocols
     of reliably delivering data, but that is not timely may be
disastrous -
     i.e. the effects are unknown.

     b) Irrespective of packet priority, if TCP is employed between the
     CE/FE then packets will be delivered in order. The data packets can
     overwhelm the control packets and can lead to DoS. Not being able
to
     deliver the data (routing) packets should not prevent the forces
control packets from reaching CE/FE.

     The bottom line is, one should be able to independently choose the
     transport mechanism (TML) between the CE and FE for the forces
control
     and data packets.

[HK] We have done more analysis, experimentation in our Labs on
separation of Data and Control (in the ForCES protocol) using separate
Transport connections and have found that using Transport protocols with
congestion/flow control for both data and control and help significantly
during a DoS attacks. We have conducted experiments using TCP for both
data and control as well as a combination of TCP and UDP for control,
data respectively.

Either myself or a colleague will be presenting our experimentation
results at the IETF meeting in San Diego. I will make sure to share this
more widely with the WG.

Thanks
Hormuzd

---

From: Furquan Ansari <[email-masked]>
Date: Fri, 16 Jul 2004 11:07:30 -0400

Hormuzd,
    Thanks for the reply. It certainly would be great if you can share
your experimentation results with
the WG. I hope you would be doing a comparison study of the two methods
as well.

Thanks,

--
Furquan Ansari
Bell Labs Research                      Ph : 732-949-5249
Holmdel, NJ                             Fax: 732-949-4556