<html><head><meta http-equiv="Content-Type" content="text/html charset=utf-8"></head><body style="word-wrap: break-word; -webkit-nbsp-mode: space; -webkit-line-break: after-white-space;" class="">Hey Thomas,<div class=""><br class=""></div><div class="">please see inline<br class=""><div class="">
<br class="Apple-interchange-newline"><span style="color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; display: inline !important; float: none;" class="">Cheers,</span><br style="color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class=""><span style="color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px; display: inline !important; float: none;" class="">Jeff</span><br style="color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class=""><br style="color: rgb(0, 0, 0); font-family: Helvetica; font-size: 12px; font-style: normal; font-variant-caps: normal; font-weight: normal; letter-spacing: normal; orphans: auto; text-align: start; text-indent: 0px; text-transform: none; white-space: normal; widows: auto; word-spacing: 0px; -webkit-text-stroke-width: 0px;" class="">
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<br class=""><div><blockquote type="cite" class=""><div class="">On Mar 20, 2017, at 09:38, Thomas Morin <<a href="mailto:thomas.morin@orange.com" class="">thomas.morin@orange.com</a>> wrote:</div><br class="Apple-interchange-newline"><div class="">
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<div class="moz-cite-prefix">Hi everyone,<br class="">
<br class="">
2017-03-18, Vincent Jardin:<br class="">
</div>
<blockquote cite="mid:15ae0f94d18.27fc.bb328046f2889bc8f44aafa891a44dd2@6wind.com" type="cite" class="">
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<div style="" class=""><p style="margin: 0px 0px 1em;" class="">+Thomas to be on
track.</p>
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</blockquote>
<br class="">
Vincent, you'll tell if what is below helped or not :)<br class="">
<br class="">
<blockquote cite="mid:15ae0f94d18.27fc.bb328046f2889bc8f44aafa891a44dd2@6wind.com" type="cite" class="">
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Le 18 mars 2017 06:19:47 Vivek Venkatraman
<a class="moz-txt-link-rfc2396E" href="mailto:vivek@cumulusnetworks.com"><vivek@cumulusnetworks.com></a> a écrit :</p>
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<div dir="ltr" class="">This is correct. By definition, if a router
is the penultimate hop, it means the actual egress is
downstream and has signaled (advertised) an implicit-null
label to this router. The router doing the PHP knows the
next hop to forward to (the egress) without doing any
additional lookup.
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<br class="">
(Note that with BGP/MPLS VPNs this is the typical behavior, but it
is not a mandatory behavior: the egress router may have advertise a
real label (i.e. not implicit null) in which case the penultimate
router will swap the topmost label of the stack, not seeing/touching
the vpn label. This is also a behavior that relates to the use of
MPLS for transit, but with MPLS-over-GRE or MPLS-over-UDP, MPLS can
be used with IP transit, in which case this behavior is not used).<br class=""></div></div></blockquote>[jeff] to better phrase - no router, beside the one allocating service labels could lookup/touch them, this is true for PHP or any other case. In PHP case, after most outer label has been looked up and a fully resolved adj provided, the rest of the label stack MUST not be looked up (payload)</div><div>In SR case, after Adj-SID has been POPed, the packed must be sent out of the interface associated with the Adj, with no any additional processing<br class=""><blockquote type="cite" class=""><div class=""><div bgcolor="#FFFFFF" text="#000000" class="">
<br class="">
<blockquote cite="mid:15ae0f94d18.27fc.bb328046f2889bc8f44aafa891a44dd2@6wind.com" type="cite" class="">
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<div class="">This behavior should already be supported.</div>
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<br class="">
Yes, I can confirm that forwarding via a neighbor on an interface
based on the incoming MPLS label is supported.<br class="">
This is what we use in bagpipe IP VPN 'linux' driver [1].<br class="">
<br class="">
<blockquote cite="mid:15ae0f94d18.27fc.bb328046f2889bc8f44aafa891a44dd2@6wind.com" type="cite" class="">
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<div class="">What is not supported (if I remember right) is the
ability on the egress to terminate a label and perform a
(route) lookup. That is needed to really be able to
support any L2/L3 VPN service properly.</div>
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<br class="">
I think it is a requirement to have something efficient to trigger a
lookup in any {routing table, vrf interface, netns}.<br class="">
<br class="">
I hadn't tried (because no need). I thought we might achieve
something like that by forwarding the packet on 'lo', or on a vrf
interface, or on a veth device: wouldn't this kind of next hop
specification trigger a re-enter of the packet in the IP stack after
the pop operation ?<br class=""></div></div></blockquote>[jeff] would’t this be a tad inefficient? :) </div><div><blockquote type="cite" class=""><div class=""><div bgcolor="#FFFFFF" text="#000000" class="">
<br class="">
-Thomas<br class="">
<br class="">
[1]
<a class="moz-txt-link-freetext" href="http://git.openstack.org/cgit/openstack/networking-bagpipe/tree/networking_bagpipe/bagpipe_bgp/vpn/ipvpn/mpls_linux_dataplane.py#n194">http://git.openstack.org/cgit/openstack/networking-bagpipe/tree/networking_bagpipe/bagpipe_bgp/vpn/ipvpn/mpls_linux_dataplane.py#n194</a><br class="">
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<blockquote cite="mid:15ae0f94d18.27fc.bb328046f2889bc8f44aafa891a44dd2@6wind.com" type="cite" class="">
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<div class="gmail_extra"><br class="">
<div class="gmail_quote">On Thu, Mar 16, 2017 at 10:45 AM,
Jeff Tantsura <span dir="ltr" class="">
<<a moz-do-not-send="true" href="mailto:jefftant@gmail.com" target="_blank" class="">jefftant@gmail.com</a>></span>
wrote:<br class="">
<blockquote class="gmail_quote" style="margin:0 0 0
.8ex;border-left:1px #ccc solid;padding-left:1ex">
Donald,<br class="">
<br class="">
Wrt PHP, this is incorrect, PHP node MUST not perform
IP lookup, or in fact any lookup after POP. In most
cases (labeled services, L2/L3 VPN) there's another
label(s) in the stack, looking it up would be fatal.<br class="">
<br class="">
Regards,<br class="">
Jeff<br class="">
<br class="">
> On Mar 15, 2017, at 08:05, Donald Sharp <<a moz-do-not-send="true" href="mailto:sharpd@cumulusnetworks.com" class="">sharpd@cumulusnetworks.com</a>>
wrote:<br class="">
><br class="">
> David/Roopa -<br class="">
><br class="">
> Olivier asked me about these two issues yesterday
in the FRR Technical<br class="">
> Meeting. I just wanted to make sure I didn't
loose track of these<br class="">
> questions that he had:<br class="">
><br class="">
> 1) More than 2 labels in the kernel at a time,
when will this be<br class="">
> allowed in the kernel?<br class="">
><br class="">
> -> David is currently working on this
issue. When he is done it<br class="">
> will be upstreamed. So soonish(tm).<br class="">
><br class="">
> 2) PenUltimate Hop Popping:<br class="">
><br class="">
> I know this issue is not trivial to solve. In
fact, once the POP<br class="">
> instruction perform, the packet must re-enter in
the IP packet<br class="">
> processing to determine what action must apply. A
possible solution<br class="">
> would be to process this packet as a new incoming
IP packet when<br class="">
> output interface is the loopback disregarding the
IP address value.<br class="">
> But, this issue is less urgent than the first
one. Our OSPF Segment<br class="">
> Routing implementation could announce if the
router works in<br class="">
> PenUltimate Hop Poping mode or not. So, for the
moment, the option is<br class="">
> force to yes.<br class="">
><br class="">
> thanks!<br class="">
><br class="">
> donald<br class="">
><br class="">
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