Subject: Re: [mpls] Comment on draft-ietf-mpls-tp-ethernet-addressing

From: Stewart Bryant <[email-masked]>
Date: Mon, 03 Dec 2012 14:30:13 +0000

Joel

I have changed the text to:

Another approach which may be considered is to use the Ethernet 
broadcast address FF-FF-FF-FF-FF-FF as the destination MAC address in 
frames carrying MPLS-TP packets over a link that is known to be 
point-to-point. This may, however, lead to excessive frame distribution 
and processing at the Ethernet layer. Broadcast traffic may also be 
treated specially by some devices and this may not be desirable for 
MPLS-TP data frames.

In view of the above considerations, the approach which SHOULD be used, 
is therefore to configure both nodes to use the method descibed in this 
document which uses, as a destination MAC address, an Ethernet multicast 
address reserved for MPLS-TP for use over point-to-point links. The 
address allocated for this purpose by the Internet Assigned Numbers 
Authority (IANA) is 01-00-5E-90-00-00. An MPLS-TP implementation MUST 
process Ethernet frames received over a point-to-point link with this 
destination MAC address by default.

Which I think should address your concern

- Stewart

On 26/11/2012 16:49, Joel M. Halpern wrote:
> Stewart,
>     Your description is what I would have expected.
>  However, sectio 2 of this document recommends that implementations 
> use this multicast address on pt-to-pt MLS-TP links.  There is no 
> discussion of negotiation, discovery, or even configuration.  The text 
> as written seems to simply assume that using this multicast address 
> will work. Your description clearly says that it won't work.
>
> Yours,
> Joel
>
> On 11/26/2012 5:59 AM, Stewart Bryant wrote:
>> On 16/06/2012 20:10, Joel M. Halpern wrote:
>>> In reviewing this document (sorry I am a day late for the WG LC end),
>>> a question occurred to me regarding the material in section 2.
>>>
>>> Is there reason to believe that existing implementations will process
>>> received frames on pt-to-pt Ethernet links where the destination
>>> address is 01-00-5E-90-00-00?  If so, should that reason be mentioned
>>> (or am I just missing the obvious here?)  If not, is this a safe
>>> recommendation?
>>>
>>> Otherwise, this is clear and useful.
>>> Thank you,
>>> Joel
>>
>> Hi Joel, I only just noticed that I did not reply on this.
>>
>> An MPLS-TP LSR  will reject all ethernet packets received on addresses
>> that it is not configured to receive packets on. This is how Ethernet
>> interfaces work. Thus an existing implementation will ignore packets
>> sent with a MAC address of 01-00-5E-90-00-00, since the address is not
>> meaningful to it and thus will not have been configured for reception.
>>
>> Regards
>>
>> Stewart
> .
>

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From: "Joel M. Halpern" <[email-masked]>
Date: Mon, 03 Dec 2012 10:57:24 -0500

That suffices.
Thank you,
Joel

PS: My personal guess is that on a link known correctly to be 
point-to-point FF-FF-FF-FF-FF-FF would work fine.  But that is a WG 
call, and the new text is sufficient.