Subject: Re: [Int-area] Fwd: New Version Notification for draft-nordmark-intarea-ippl-01.txt

From: Erik Nordmark <[email-masked]>
Date: Mon, 21 Mar 2016 10:36:55 -0700

On 11/5/15 1:28 AM, Mikael Abrahamsson wrote:
> On Thu, 5 Nov 2015, Dave Thaler wrote:
>
>> I notice that currently RFC 4389 is not referenced at all.
>> It’s Experimental since there are many ways of proxying and it just 
>> describes one of them,
>> but I still think it bears referencing informatively, especially 
>> since section 6 of that RFC is
>> very relevant to the discussion on loops in the document.
>
> I have in live networks running spanning tree and HSRP seen issue with 
> the L2 mac learning timeout being 300 second (cisco default) and arp 
> timeout being 4 hours (also cisco timeout) where in certain topologies 
> the L2 switch would not see one of the routers mac address until the 
> arp timeouted, and flooded all traffic to that router to all switches.
>
> The problem was "fixed" by turning down the arp timeout to 270 seconds.
>
> THis is not exactly what your draft describes, but it might still be 
> worth mentioning?

Mikael,

FWIW I've seen similar interaction with VXLAN where there is dataplane 
learning in the underlay and the overlay, both interacting with ARP timers.

But I don't see how to fit in a discussion about MAC learning in the draft.
Any suggestions on how to fit it in?

Thanks,
    Erik

---

From: Erik Nordmark <[email-masked]>
Date: Mon, 21 Mar 2016 10:38:20 -0700

[With better from address]

On 11/5/15 1:24 AM, Dave Thaler wrote:
> but I still think it bears referencing informatively, especially since 
> section 6 of that RFC is
>
Dave,

Sorry for the tardy response. I'll definitely add an explicit reference 
to RFC4389 in the text that currently reads "Hence a NS/NA proxy MUST 
NOT be used with private VLANs."

I don't know if you want some more analysis in the document (in the form 
of an appendix) of why packet proxies don't work.
The short form is that the assumption in RFC4389 is that there is a 
notion of upstream and downstream, but in a PVLAN with multiple routers 
(i.e. promiscuous ports) those ports are peers with no upstream vs. 
downstream notion. Forcing such a notion, e.g., by building a spanning 
tree, would remove the rapid failover and load-balancing benefits that 
motivated having multiple promiscuous ports.

AFAICT this applies to what I'd call "packet proxies" in general. Such 
proxies send a NS (with ttl=255) when receiving a NS.
What we could call "state proxies" do not have such an issue; an example 
of such is DAD proxy (RFC 6957) where a packet received from one host is 
used to build/maintain state which is then used to respond to a NS from 
another host. That approach never emits a NS as a result of receiving an 
NS hence does not have the same looping hazard.

I'll add something along the above lines and submit an update to the draft.

Thanks,
    Erik

*From:*Int-area [mailto:[email-masked]] *On Behalf Of *Erik 
Nordmark
*Sent:* Tuesday, October 20, 2015 3:39 AM
*To:* Internet Area <[email-masked]>
*Subject:* [Int-area] Fwd: New Version Notification for 
draft-nordmark-intarea-ippl-01.txt

This update adds one more issue about Proxy ARP/ND when there are 
multiple routers.

    Erik

-------- Forwarded Message --------

*Subject: *

New Version Notification for draft-nordmark-intarea-ippl-01.txt

*Date: *

Mon, 19 Oct 2015 11:34:04 -0700

*From: *

[email-masked] <mailto:[email-masked]>

*To: *

Erik Nordmark <[email-masked]> <mailto:[email-masked]>

A new version of I-D, draft-nordmark-intarea-ippl-01.txt

has been successfully submitted by Erik Nordmark and posted to the

IETF repository.

Name:          draft-nordmark-intarea-ippl

Revision:      01

Title:         IP over Intentionally Partially Partitioned Links

Document date: 2015-10-19

Group:         intarea

Pages:         11

URL:https://www.ietf.org/internet-drafts/draft-nordmark-intarea-ippl-01.txt 
<https://na01.safelinks.protection.outlook.com/?url=https%3a%2f%2fwww.ietf.org%2finternet-drafts%2fdraft-nordmark-intarea-ippl-01.txt&data=01%7c01%7cdthaler%40microsoft.com%7c8ffc9ba75e0f4c85b95708d2da8f0702%7c72f988bf86f141af91ab2d7cd011db47%7c1&sdata=zj%2b6dMfG1dO5XaChivn3HhaPj5W3m6ppjqDTmFazqz0%3d>

Status:https://datatracker.ietf.org/doc/draft-nordmark-intarea-ippl/ 
<https://na01.safelinks.protection.outlook.com/?url=https%3a%2f%2fdatatracker.ietf.org%2fdoc%2fdraft-nordmark-intarea-ippl%2f&data=01%7c01%7cdthaler%40microsoft.com%7c8ffc9ba75e0f4c85b95708d2da8f0702%7c72f988bf86f141af91ab2d7cd011db47%7c1&sdata=wlAdu3Uoe2o%2bYd2c%2fyUAuSDW5GXpxJO2sFnc6zw5s2U%3d>

Htmlized:https://tools.ietf.org/html/draft-nordmark-intarea-ippl-01 
<https://na01.safelinks.protection.outlook.com/?url=https%3a%2f%2ftools.ietf.org%2fhtml%2fdraft-nordmark-intarea-ippl-01&data=01%7c01%7cdthaler%40microsoft.com%7c8ffc9ba75e0f4c85b95708d2da8f0702%7c72f988bf86f141af91ab2d7cd011db47%7c1&sdata=1ZE87Hn665vt5%2bmIO%2fRS9JjpIqfaD3x%2fCikCWIikA7o%3d>

Diff:https://www.ietf.org/rfcdiff?url2=draft-nordmark-intarea-ippl-01 
<https://na01.safelinks.protection.outlook.com/?url=https%3a%2f%2fwww.ietf.org%2frfcdiff%3furl2%3ddraft-nordmark-intarea-ippl-01&data=01%7c01%7cdthaler%40microsoft.com%7c8ffc9ba75e0f4c85b95708d2da8f0702%7c72f988bf86f141af91ab2d7cd011db47%7c1&sdata=OCw2%2fxbBn1NCymhy6snJXV4g%2f2%2bZce3IWtXEC1Ax1xk%3d>

Abstract:

    IP makes certain assumptions about the L2 forwarding behavior of a

    multi-access IP link.  However, there are several forms of

    intentional partitioning of links ranging from split-horizon to

    Private VLANs that violate some of those assumptions.  This document

    specifies that link behavior and how IP handles links with those

    properties.

Please note that it may take a couple of minutes from the time of submission

until the htmlized version and diff are available at tools.ietf.org.

The IETF Secretariat

---

From: Erik Nordmark <[email-masked]>
Date: Mon, 21 Mar 2016 10:32:54 -0700

Dave,

Thanks,
    Erik

> Dave
> URL:https://www.ietf.org/internet-drafts/draft-nordmark-intarea-ippl-01.txt <https://na01.safelinks.protection.outlook.com/?url=https%3a%2f%2fwww.ietf.org%2finternet-drafts%2fdraft-nordmark-intarea-ippl-01.txt&data=01%7c01%7cdthaler%40microsoft.com%7c8ffc9ba75e0f4c85b95708d2da8f0702%7c72f988bf86f141af91ab2d7cd011db47%7c1&sdata=zj%2b6dMfG1dO5XaChivn3HhaPj5W3m6ppjqDTmFazqz0%3d>