Subject: Some questions about draft-ietf-l2vpn-evpn-00

From: Martin Pels <[email-masked]>
Date: Mon, 9 Apr 2012 12:59:09 +0200

Hello,

I've been reading the E-VPN draft, and a few questions came up in my
head that the document does not seem to answer.

1) Forwarding packets to a "semi-local" CE

Section 18 describes two load-balancing scenario's: Load-balancing from
a MES to a remote CE, and load-balancing to a local CE. What is missing
here is the situation of a "semi-local" CE.

Consider a case where CE-A is connected to MES-1, and CE-B is
multi-homed to MES-1 and MES-2. If CE-A sends to CE-B, would this
traffic remain local to MES-1, or would it be load-balanced over the
local and the remote path to CE-B?

2) Multi-homing vs. Mac move

According to section 10.2.1, it is possible for a set of MESs to
discover a multi-homed CE with no configuration. I understand this could
be achieved by connecting the CE using LACP, causing both MESs to
generate the same ESI (as specified in section 6, point 2).

In this scenario, how would the requirement that a MES must be able to
distinguish a MAC move from multi-homing (section 19) be satisfied?

3) Handling of more specific MAC Advertisements

Section 11.2.1 describes a method to encode a MAC address as a prefix.
If this is implemented, what should a MES-1 do if it receives a MAC
Advertisement with a prefix from MES-2, and a more specific MAC
Advertisement (a single MAC Address within the prefix) from MES-3?

Kind regards,
Martin

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From: "Henderickx, Wim (Wim)" <[email-masked]>
Date: Mon, 9 Apr 2012 15:36:56 +0200

Martin, in-line with WH>

-----Original Message-----
From: [email-masked] [mailto:[email-masked]] On Behalf Of Martin Pels
Sent: maandag 9 april 2012 12:59
To: [email-masked]
Subject: Some questions about draft-ietf-l2vpn-evpn-00

Hello,

WH> it depends on the BGP Policy applied in the E-VPN. You can either avoid load-balancing such that traffic from/to CE-A only goes via MES1 or allow load-balancing like EIBGP load-balancing in IP-VPNs. 

WH> A MAC move means a MAC address is learned on a different ESI Ctxt, whereas multi-homing means a MAC is learned within an ESI Context. Hope this clarifies. 

WH> the FIB should implement a LPM function like an IP FIB.

Kind regards,
Martin

---

From: sajassi <[email-masked]>
Date: Mon, 09 Apr 2012 10:23:22 -0700

Martin,

In addition to Wim's comments, please see comments below for some additional
clarification ...

On 4/9/12 6:36 AM, "Henderickx, Wim (Wim)"
<[email-masked]> wrote:

> WH> it depends on the BGP Policy applied in the E-VPN. You can either avoid
> load-balancing such that traffic from/to CE-A only goes via MES1 or allow
> load-balancing like EIBGP load-balancing in IP-VPNs.
> 

For unicast traffic, the MES-1 (by default) should load-balanced between
local and remote; however, it can be overwritten so that traffic is only
locally switched. For multicast traffic, it depends on the DF election. If
the local port is selected as DF, then the traffic is locally switched;
however, if the port on the MES-2 is selected as DF, then the traffic goes
over the core. 

> WH> A MAC move means a MAC address is learned on a different ESI Ctxt, whereas
> multi-homing means a MAC is learned within an ESI Context. Hope this
> clarifies. 

And a PE knows that it is a different ESI context, because it learns the MAC
locally from an ESI which is different from the advertised ESI .

> WH> the FIB should implement a LPM function like an IP FIB.

E.g., more specific address should take precedence over coarser one.

Cheers,
Ali

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From: Martin Pels <[email-masked]>
Date: Wed, 11 Apr 2012 19:09:20 +0200

Hi Wim, Ali,

Thanks for your replies.

On Mon, 09 Apr 2012 10:23:22 -0700
sajassi <[email-masked]> wrote:

> locally switched.

That makes sense. It might be useful to clarify this in the draft.

> For multicast traffic, it depends on the DF election. If the local port is 
> selected as DF, then the traffic is locally switched;

Ack.

> locally from an ESI which is different from the advertised ESI .

I understand this would work with statically configured ESIs.

But if the ESI is generated from the CE LACP System Identifier and CE Port key,
it will always be the same, correct? So then when the CE appears behind a second
MES it will always be seen as multi-homing, never as a MAC Move.

> E.g., more specific address should take precedence over coarser one.

Ok. I think this should also be clarified in the text.

Kind regards,
Martin

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From: "Henderickx, Wim (Wim)" <[email-masked]>
Date: Wed, 11 Apr 2012 19:48:41 +0200

Martin, in-line I agree we need to clarify some items.

<<snip>>

<<snip>>

As long as the traffic comes from the same CE this is indeed multi-homing, but I don't see an issue with this. If the traffic comes to another CE with dynamic LACP we will do mac move

-----Original Message-----
From: Martin Pels [mailto:[email-masked]] 
Sent: woensdag 11 april 2012 19:09
To: sajassi; Henderickx, Wim (Wim)
Cc: [email-masked]
Subject: Re: Some questions about draft-ietf-l2vpn-evpn-00

Hi Wim, Ali,

Thanks for your replies.

Ack.

Kind regards,
Martin