Re: [Int-area] I-D Action: draft-ietf-intarea-frag-fragile-06.txt

On Thu, Jan 31, 2019 at 5:03 PM Templin (US), Fred L
<Fred.L.Templin@boeing.com> wrote:
>
>
>
> > -----Original Message-----
> > From: Int-area [mailto:int-area-bounces@ietf.org] On Behalf Of Tom Herbert
> > Sent: Thursday, January 31, 2019 4:40 PM
> > To: Joe Touch <touch@strayalpha.com>
> > Cc: Ron Bonica <rbonica@juniper.net>; int-area <int-area@ietf.org>
> > Subject: Re: [Int-area] I-D Action: draft-ietf-intarea-frag-fragile-06.txt
> >
> > On Thu, Jan 31, 2019 at 3:10 PM Joe Touch <touch@strayalpha.com> wrote:
> > >
> > >
> > >
> > >
> > >
> > > On 2019-01-31 13:56, Tom Herbert wrote:
> > >
> > > On Thu, Jan 31, 2019 at 7:59 AM Joe Touch <touch@strayalpha.com> wrote:
> > >
> > >
> > > The problem with dropping the entire paragraph is the section title - talking about stateless firewalls begs the question of stateful
> > ones. This is reinforced later in the recommendations. The sentences you remove were the only thing that tied the two together,
> > which IMO is important.
> > >
> > >
> > > Joe,
> > >
> > > The term "Stateless firewalls" is unambiguous in this context. In a
> > > stateless firewall, each packet is inspected and judge based solely on
> > > it's content.
> > >
> > >
> > > My statement above has no relation to any potential ambiguity in the term.
> > >
> > > ---
> > >
> > > However, the term stateless is inaccurate in a few places:
> > >
> > > (Sec 4.6) NAT is a stateful procedure for an otherwise stateless protocol as well. The same could be argued for load balancers that
> > retain similar state through a connection for a flow (i.e., not just hashing the flow or tuple, but doing round-robin per-flow/tuple
> > 'sticky' routing)
> > >
> > > (Sec 7.3) The problem is not just stateless middle boxes, but also certain stateful ones (e.g., NATs, some load balancers, etc.)
> > >
> > > ---
> > >
> > > Thus "stateful" actually is both ambiguous and inaccurate here.
> > >
> > > You appear to want to distinguish between the state needed for virtual reassembly and the state needed to maintain NAT
> > translations or sticky round-robin load balancing, but there's no simple term that differentiates them. They're both content-
> > dependent, context-dependent, and stateful.
> > >
> > >
> > > Further, as you note there are no *specified* algorithms for virtual reassembly, nor are there any *specified* for NAT translation
> > table maintenance or sticky load balancing. Everyone comes up with their own and the basic concept is well enough defined as to not
> > need a specification.
> > >
> > In that case, if it's so obvious and well defined then there shouldn't
> > be any issue in either providing a reference to a description or
> > specifying it in the draft (if authors do choose discuss virtual
> > reassembly in the draft).
>
> I have been telling everyone about virtual fragmentation reassembly for
> years. You will find it in many of my docs. Here is what cisco says about it:
>
> https://www.cisco.com/c/en/us/td/docs/ios/sec_data_plane/configuration/guide/12_4/sec_data_plane_12_4_book/sec_virt_frag_reassm.html

Hi Fred,

It does seem that Cisco configuration manuals and marketing materials
are the best source of information on virtual reassembly.

https://www.cisco.com/c/en/us/td/docs/ios-xml/ios/ipaddr_frre/configuration/xe-3s/frre-xe-3s-book/virt-frag-reassembly.html
is a little more interesting in that it provides a few more details.
In particular the requirement that all fragments must traverse the
same intermediate device is mentioned:

"The reassembly process requires all fragments within an IP datagram.
If fragments within an IP datagram are sent to different devices due
to load balancing VFR may fail and fragments may be dropped."

Tom

>
> Fred
> >
> > Tom
> >
> > > Joe
> >
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