Re: [Idr] WG LC draft-ietf-idr-flowspec-path-redirect-10.txt [11/17/2019 to 12/2/2019]

Robert Raszuk <robert@raszuk.net> Fri, 29 November 2019 09:34 UTC

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From: Robert Raszuk <robert@raszuk.net>
Date: Fri, 29 Nov 2019 10:34:26 +0100
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To: "Van De Velde, Gunter (Nokia - BE/Antwerp)" <gunter.van_de_velde@nokia.com>
Cc: Jeffrey Haas <jhaas@pfrc.org>, Sue Hares <shares@ndzh.com>, "idr@ietf.org" <idr@ietf.org>
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Subject: Re: [Idr] WG LC draft-ietf-idr-flowspec-path-redirect-10.txt [11/17/2019 to 12/2/2019]
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Gunter,

To your and Jeff's point regarding multiple redirect rules I have a bit
different perspective.

First let's observe that redirect could be realized in two forms (both are
valid and used in practice):

-A- redirect of the original flow
-B- redirect of copy of the flow

See while in -A- clearly one redirect must be used, in -B- on the
other hand multiple redirects should be supported. One span, one security
TAP, one TCP analyzer etc ...

Your draft defines -A-. To add -B- all what is needed is just one bit flag.

Would you consider it ?

Cheers,
R.





On Fri, Nov 29, 2019 at 4:51 AM Van De Velde, Gunter (Nokia - BE/Antwerp) <
gunter.van_de_velde@nokia.com>; wrote:

> Hi Jeff,
>
> Thanks for the feedback and suggestions.
>
> See inline: *GV>*
>
> -----Original Message-----
> From: Idr <idr-bounces@ietf.org>; On Behalf Of Jeffrey Haas
> Sent: Thursday, November 28, 2019 20:21
> To: Sue Hares <shares@ndzh.com>;
> Cc: idr@ietf.org
> Subject: Re: [Idr] WG LC draft-ietf-idr-flowspec-path-redirect-10.txt
> [11/17/2019 to 12/2/2019]
>
> Sue,
>
>
>
> > On Nov 18, 2019, at 12:41 AM, Susan Hares <shares@ndzh.com>; wrote:
> >
> > This begins a 2 week WG Last call on
> draft-idr-flowspec-path-redirect-10.txt from [11/17/2019 to 12/2/2019].
> >
> > You can obtain the draft at:
> >
> > https://datatracker.ietf.org/doc/draft-ietf-idr-flowspec-path-redirect/
> >
> > Consider in your review whether this draft:
> >
> > 1)      Is compatible with draft-ietf-rfc5575bis-17.txt?
>
> Yes.  (Close enough.)  The current version of the draft is implementable.
>
> > 2)      Whether the draft is useful for deployments of flow specification
>
> It can be useful.
>
> > 3)      Is this technology ready for deployment?
> > 4)      Is the write-up of this technology in
> draft-ietf-idr-flowspec-path-redirect clearly written and ready for
> publication?
>
> Ready with minor issues, IMO:
>
> Procedure-wise, there needs to be a bit more text covering cases about
> interactions with other traffic actions.  This was a known headache for
> similar drafts such as redirect-to-ip.  In particular, interaction with
> redirect-to-ip and redirect-to-vrf is needed.
>
> GV> Section “6. Validation Procedures” gives input on this. We discussed
> this with you long ago and hence this text was added.
>
> “
>    While it MUST NOT happen, and is seen as invalid combination, it is
>    possible from a semantics perspective to have multiple clashing
>    redirect actions defined within a single flowspec rule.  For best and
>    consistant compatibility with legacy implementations, the redirect
>    functionality as documented by rfc5575bis MUST NOT be broken, and
>    hence when a clash occurs, then rfc5575bis based redirect MUST take
>    priority.
> “
>
> This means that redirect-to-VRF will take absolute priority to not break
> rfc5575bis behavior.
> Having also redirect-to-ip will result in an invalid
>
>
> The text "A single flowspec rule MUST NOT have more as one indirection-id
> per S-ID.  On a flowspec client the indirection-id with lowest S-ID MUST be
> imposed first for any given flowspec entry."  There's no procedure for what
> happens in error handling when you do have more than one of the same S-ID.
> The text about the case for S-ID of 0 is also a bit ambiguous.  It feels
> like it's reading "there is no sequence", but what do you do when you then
> have ones that do?
>
> *GV>* What about the following rewrite:
>
> Original:
>    The 'S-ID' field identifies a 4 bit Sequence ID field.  This field is
>    used to provide a flowspec client an indication how and where to
>    sequence the received indirection-ids.  The Sequence ID value 0
>    indicates that Sequence ID field is NOT set and SHOULD be ignored.  A
>    single flowspec rule MUST NOT have more as one indirection-id per
>    S-ID.  On a flowspec client the indirection-id with lowest S-ID MUST
>    be imposed first for any given flowspec entry.
>
> New:
>    The 'S-ID' field identifies a 4 bit Sequence ID field.  This field is
>    used to provide a flowspec client an indication how and where to
>    sequence the received indirection-ids.  The Sequence ID value 0
>    indicates that Sequence ID field is NOT set and *****all** other
> sequence ID's***
>    SHOULD be ignored.  A
>    single flowspec rule MUST NOT have more as one indirection-id per
>    S-ID.  On a flowspec client the indirection-id with lowest S-ID MUST
>    be imposed first for any given flowspec entry.
>
> *GV>* In section *6. Validation procedure" there is text to handle the
> error condition when the flowspec rule results in an invalid redirection,
> that prescribe what needs to happen when the “redirect to indirection-id”
> does not result in a valid redirection:
>
> "
>    While it MUST NOT happen, and is seen as invalid combination, it is
>    possible from a semantics perspective to have multiple clashing
>    redirect actions defined within a single flowspec rule.  For best and
>    consistant compatibility with legacy implementations, the redirect
> *   functionality as documented by rfc5575bis MUST NOT be broken*, and
>    hence when a clash occurs, then *rfc5575bis based redirect MUST take*
> *   priority*.  Additionally, if the "Redirect to indirection-id" does not
>    result in a valid redirection, then the flowspec rule MUST be
>    processed as if the "Redirect to indirection-id" community was not
>    attached to the flowspec route.
> "
>
> *GV>* Is there more to add to this? (We could add a line to detail that
> “redirect-to-ip” is incompatible with “redirect to indirection-id” and
> result in invalid redirection rule, however to me that is already implied
> with enough detail in the text above)
>
> A few IANA issues:
> I see the type registry is currently registered with IANA (code point
> 0x09).  However, the sub-type registry is not established for some reason?
> The ID-Type field likely needs its own IANA registry.  Values 1-5 are
> defined in this draft.
>
> *GV>* Correct. There is a reason for this. When we asked IANA the
> code-points they informed me that once the document get to RFC the sub-type
> registry will be established by IANA.
>
> The flags field (one octet) currently has 3 bits reserved.  In the past,
> we've not done a registry for such cases (c.f. graceful restart) until we
> need to start carving out those reserved bits for future extensions.  I
> leave it to the chairs' opinion whether we want this a priori or not.
>
> *G/*
>
>
> >
> > Thank you for considering this draft.
> >
> > Cheerily, Susan Hares
> >
> > _______________________________________________
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