From: Yoav Nir <ynir.ietf@gmail.com>
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Date: Mon, 28 Apr 2014 16:47:48 +0300
To: draft-ietf-opsawg-large-flow-load-balancing.all@tools.ietf.org,
 "<secdir@ietf.org>" <secdir@ietf.org>, "<iesg@ietf.org> IESG" <iesg@ietf.org>
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Archived-At: http://mailarchive.ietf.org/arch/msg/secdir/MNAntvFB8zf9WqHP-Bk8k67IikQ
Subject: [secdir] Secdir review of
 draft-ietf-opsawg-large-flow-load-balancing-11
Precedence: list

Hi

I have reviewed this document as part of the security directorate's
ongoing effort to review all IETF documents being processed by the
IESG.  These comments were written primarily for the benefit of the
security area directors.  Document editors and WG chairs should treat
these comments just like any other last call comments.

tl;dr version: the document is ready.

I was a little surprised by the way the document is organized, and I=92m =
not sure who the target audience is. On the one hand it is very verbose =
on explanations (that=92s a good thing!) and I could very well =
understand it even though I lack any background on the matter.  On the =
other hand, the order in which things are explained seems strange:

The introduction talks about large flows vs small flows, long-lived =
flows vs short-lived flows, and Large flows vs Small flows (no, I=92m =
not repeating myself, capitalize Large is different from lower-case =
large and in fact means both =93large=94 and =93long-lived=94).  But =
three things are totally missing: What is a flow? How large does a flow =
have to be to be considered =93large=94 (lower case), and how long must =
a flow continue to be considered =93long-lived=94. Even the terminology =
section (1.2) defines Large, Small and small again, but not what a flow =
is.  These concepts are finally explained in sections 4.1, 4.3.1, and =
4.3.2.

The document describes how load balancing can be achieved by moving =
large flows around between links and by removing loaded links from the =
hash table, so that Small (or actually un-classified) new flows will not =
go to overloaded links. This is an improvement over the assumed default =
that is statically assigning flows to links based on a hash.

The document has a short security considerations section that says that =
it does not impact the security of the Internet infrastructure or =
applications. I tend to agree, because the parts of the network where =
these protocols tends to be mostly stateless, so moving flows from one =
component to another should not make a difference. It would be different =
if there were supposed to be firewalls on the nodes.
The security considerations also says that load balancing might help in =
resisting DoS attacks, for example if an attacker can create traffic =
where the hash would collide with some Large flow. With load balancing =
either the attacker=92s flow or the Large flow is moved, eliminating the =
contention. Again, I tend to agree, although this will allow a more =
powerful attacker to overload all the links, not just the ones they can =
target with the hash function. Still, an attacker powerful enough to =
overload all the links is likely to be able to create traffic that =
collides with all links anyway.

I don=92t think there=92s anything missing from the security =
considerations.

Hope this helps

Yoav