Subject: Re: I-D ACTION:draft-khosravi-forces-tcptml-01.txt

From: Robert Haas <[email-masked]>
Date: Tue, 1 Mar 2005 20:10:19 +0100

Hormuzd, All,

Khosravi, Hormuzd M wrote:

>Regarding this shim/TML header containing the length for redirected
>packets,
>I believe the ForCES PL header already has a length field that can be
>used for this purpose.
>The redirected packets are also transported within a ForCES PL message
>so the shim/TML header is really not needed if they are sent on a
>different connection/channel.
>  
>

I think we also have to provide a way to transport redirected packets 
from the FE to the CE _without_ any encapsulation, i.e. _raw_ redirection.

The bad-length case raised by Joel could be supported with 
encapsulation, as it anyway remains a corner case. And I don't think it 
is difficult to distinguish such raw redirected packets from PL 
messages, nor to prevent DoS by setting shapers in the FE. My main 
motivation is to free the FEs from an unnecessary encapsulation load.

>BTW, Jamal, I agree very much with your design philosophy regarding
>doing away with TML messages/ header and keeping it simple. Just need to
>analyze further if this is viable.
>
>  
>
That has been my thinking as well. As Jamal described, some additions to 
the FE LFB can replace special mcast control TML messages.

Regards,
-Robert

-- 
Dr. Robert R. Haas
IBM Zurich Research Laboratory
Säumerstrasse 4
CH-8803 Rüschlikon/Switzerland
phone +41-44-724-8698  fax +41-44-724-8578  http://www.zurich.ibm.com/~rha

---

From: "Khosravi, Hormuzd M" <[email-masked]>
Date: Wed, 2 Mar 2005 11:26:52 -0800

Robert,

Thanks for your feedback! Pls see my comments inline below... 

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

I think we also have to provide a way to transport redirected packets 
from the FE to the CE _without_ any encapsulation, i.e. _raw_
redirection.

[HK] The biggest issue that I see for not encapsulating the redirected
packets in the PL header is interoperability. This is clearly a
tradeoff, you might get slightly better performance if you avoid any
encapsulation (although we haven't noticed any performance issues here)
but at the cost of Interoperability, bad-length case that Joel pointed
out, loss of protocol-inbuilt DoS prevention mechanisms, etc. IMHO,
Interoperability alone clearly out weighs any performance benefits here
(not considering the other issues, which are also significant).

BTW, if you have any performance nos here, pls do share them with us. I
would be very interested to know since we didn't see any such issues in
our implementation.

[HK] Good, we are all on the same page here...we will definitely strive
to achieve this goal of minimal TML overhead...it should be achievable.

Regards
Hormuzd