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List:       mpls
Subject:    Re: [mpls] [PWE3] Response to Liaison on Clarifying P2MP Combinations
From:       Eric Gray <eric.gray () ericsson ! com>
Date:       2013-11-26 15:59:01
Message-ID: 48E1A67CB9CA044EADFEAB87D814BFF6329A970C () eusaamb104 ! ericsson ! se
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Matthew,

	Your wording is acceptable to me.  It certainly makes the clarification clearer.

:-)
--
Eric

-----Original Message-----
From: Bocci, Matthew (Matthew) [mailto:matthew.bocci@alcatel-lucent.com] 
Sent: Tuesday, November 26, 2013 10:56 AM
To: Eric Gray; Loa Andersson; huubatwork@gmail.com; pwe3@ietf.org
Cc: mpls@ietf.org
Subject: Re: [mpls] [PWE3] Response to Liaison on Clarifying P2MP Combinations
Importance: High

Eric

Theoretically it is possible, but the key is in the word Ścurrentą. The
P2MP requirements/framework was deliberately scoped down after AD review,
from the problem of any P2MP PW over any underlying LSP type. Trying to
define all possible combinations in a single document (when we hadnąt even
characterised the simplest case) was going far beyond the basic
requirements from VPMS.

Maybe we should rephrase the sentence below as follows:

" The only use case for P2MP PWs described in the draft referenced above
is when used with corresponding P2MP
    LSPs. Other more complex use cases are for further study. If required,
participants are encouraged to bring extensions to this architecture to
the PWE3 working group."


Matthew


On 26/11/2013 14:45, "Eric Gray" <eric.gray@ericsson.com> wrote:

>Loa,
>
>	I think you mean on a per-segment basis, where a group of PW-branches
>would traverse the segment using the same segment-ingress/egress pair,
>right?
>
>	If so, this is not logically different from having the same set of
>PW-branches
>traversing a common link.  I guess it is possible that a P2MP MS-PW would
>only use 
>P2P LSPs in every segment; that would require every branching point to be
>at the
>points where the P2P LSP in one domain terminates and two or more P2P
>LSPs are
>used to forward distinct subsets of the P2MP PW through the next domain.
>This
>seems likely (to me, anyway) only if the LSR at the domain boundary
>belongs to
>both domains (not the common case, I believe).
>
>	If there was no branching at domain boundaries, and no P2MP LSPs in any
>domain, it beggars the imagination as to why a P2MP PW would be used in
>the first 
>place, so the overall set of LSPs would effectively be P2MP - wouldn't
>they?
>
>	But, if you think transport of a P2MP PW over a set of P2P LSPs
>exclusively 
>is a valid scenario to consider, why include the text in question at all?
>
>	Since you snipped it, I am adding back the text in question.  It says:
>
>  " The only current valid case for P2MP PWs is when used with
>corresponding P2MP
>    LSPs, as described in the draft referenced above."
>
>	The primary message in this text is that carrying a P2MP PW over
>anything 
>other than a P2MP LSP is invalid.  If that is not the clarification we
>want to provide,
>then we need to change this text, or remove it.
>
>--
>Eric
>
>-----Original Message-----
>From: Loa Andersson [mailto:loa@pi.nu]
>Sent: Monday, November 25, 2013 11:17 PM
>To: Eric Gray; huubatwork@gmail.com; Bocci, Matthew (Matthew);
>pwe3@ietf.org
>Cc: mpls@ietf.org
>Subject: Re: [mpls] [PWE3] Response to Liaison on Clarifying P2MP
>Combinations
>Importance: High
>
>
>
><snip>
>> 2) use of a P2MP PW in conjunction with one or more P2P LSPs is
>>definitely not
>>       valid.
>>
>snip>
>
>Well a MS-PW could do P2MP over P2P LSPs, right?
>
>/Loa
>
>-- 
>
>
>Loa Andersson                        email: loa@mail01.huawei.com
>Senior MPLS Expert                          loa@pi.nu
>Huawei Technologies (consultant)     phone: +46 739 81 21 64

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