Re: [mpls-tp] Fwd: I-D Action:draft-fbb-mpls-tp-p2mp-framework-00.txt

[Maarten Vissers <[e-mail]>]

Hi Dave,

> Note that such "bidirectional p2mp connections" (i.e. one unidir p2mp
connection from
> signle root to n leaves, n unidir p2p connections from each leaf to the
root) are
> specified in 802.1Qay; the "Point-to-multipoint TE service instance".
>
> DA> yes, agreed, though I believe with shared forwarding the return path 
> DA> could be constructed more frugally than a literal "leaf x p2p" 
> DA> connections of forwarding state 

The amount of state in the data plane (i.e. switch fabrics) will be indeed
be less due to administrating only a subset of the TESI label values, but
the amount of state in the management system is the same; i.e. each unidir
p2p ESP needs to be administered I assume... Or can this also be done in a
shared manner?

In MPLS one could emulate the administration of PBB-TE ESPs by means of
using two labels to identify a tunnel LSP, i.e. an inner source label plus
an outer destination label. P nodes can now administer the shared
destination label. PE NNI ports need to push/pop now two label stack entry
headers instead of one.

Regards,
Maarten

-----Original Message-----
From: David Allan I [mailto:[e-mail]] 
Sent: donderdag 21 januari 2010 1:09
To: Maarten Vissers; 'Dan Frost'; [e-mail]; 'Loa Andersson'
Subject: RE: [mpls-tp] Fwd: I-D
Action:draft-fbb-mpls-tp-p2mp-framework-00.txt

Hi Maarten: 

> an OAM message to trigger a head end switch could flow from a MIP on 
> the P2P path back to the root.
> This also means that most failure scenarios would result in multiple 
> MIPs originating AIS/LFI traffic back to the root.

MIPs do not generate AIS signals. AIS signals are generated by the
adaptation sink function belonging to the MEP that detects the signal fail
type defect.

DA> poor choice of terms. What I was trying to illustrate was that if
co-routed p2p LSPs were used as a return path to produce a closed OAM system
capable of head end switching, a single failure could result in a number of
sources of failure indication colocated at a node adjacent to the failure
generating PDUs back to the root.

If you need to protect a 1+1 unidir p2mp connection, then this can be done
with unidirectional switching; i.e. with leaf side monitoring only. There is
in such case no need for a return path as there is no APS protocol to run.

DA> Violent agreement.

P2mp connections support a distribution service (e.g. TV signals), and often
associate with duplicated head end systems as well. There are in this case
two roots, which are connected via two diverse rooted unidirectional p2mp
connections to n leafs. A leaf must switch to the standby connection when
the active connection has a signal fail or signal degrade condition (and the
standby connection doesn't have such SF/SD condition). A leaf must also
switch when the connection between the head end system and the p2mp
connection fails, and also when the head end system fails. These two
conditions require that the traditional protection swithcing trigger
conditions (SF,SD) have to be complemented by a client signal fail (CSF)
condition.

I agree with you that 1:n p2mp protection switching would require the set up
of p2p return paths from each leaf to the root (single root). For the
duplicated root case p2p return paths from each leaf to each root would have
to be set up. And in addition a p2p bidir connection between the roots.

DA> More violent agreement....

Note that such "bidirectional p2mp connections" (i.e. one unidir p2mp
connection from signle root to n leaves, n unidir p2p connections from each
leaf to the root) are specified in 802.1Qay; the "Point-to-multipoint TE
service instance".

DA> yes, agreed, though I believe with shared forwarding the return path 
DA> could be constructed more frugally than a literal "leaf x p2p" 
DA> connections of forwarding state

Best regards
Dave




-----Original Message-----
From: [e-mail] [mailto:[e-mail]] On Behalf
Of David Allan I
Sent: woensdag 20 januari 2010 23:30
To: Dan Frost; [e-mail]; Loa Andersson
Subject: Re: [mpls-tp] Fwd: I-D
Action:draft-fbb-mpls-tp-p2mp-framework-00.txt

Happy to oblige, but before I craft some text I think a couple of the
requirements need to be tweaked...

In particular

   o  Recovery techniques used for P2P and P2MP should be identical to
      simplify implementation and operation.

Given we have unidirectional P2P, associated bi-directional P2P and
co-routed bi-directional P2P, and just uni-directional P2MP, apples to
apples would suggest "for uni-directional P2P and P2MP..." should be what is
actally stated.

   o  Unidirectional 1+1 and 1:n protection for P2MP connectivity must
      be supported.

In essence any 1:n system is head end switched. The only way a MEG could be
constructed to meet this requirement and be consistent with the TP
definitions and scope would be an artificial construct of a p2mp path root
to leaves, and a unique co-routed p2p path for each leaf back to the root
such that an OAM message to trigger a head end switch could flow from a MIP
on the P2P path back to the root. This also means that most failure
scenarios would result in multiple MIPs originating AIS/LFI traffic back to
the root. I don't think anything like this is on the drawing board. The only
viable alternative is that non-TP return paths are used, which are optional.
This suggests the requirement should stated as "must" for 1+1 and "should"
for 1:n....

Cheers
Dave

-----Original Message-----
From: [e-mail] [mailto:[e-mail]] On Behalf
Of Dan Frost
Sent: Wednesday, January 13, 2010 12:25 PM
To: [e-mail]; Loa Andersson
Subject: Re: [mpls-tp] Fwd: I-D
Action:draft-fbb-mpls-tp-p2mp-framework-00.txt

Hi,

This is a short document that primarily intends to summarise the P2MP
content from the other frameworks (CP, OAM, Survivability).  The editors
would therefore like to ask the authors of those frameworks to contribute
summary text for the respective sections in this document that is consistent
with the point-to-multipoint architecture described in their frameworks.
We'll be in touch on this topic unless you get to us first.  ;)

Cheers,

-d

On Wed, Jan 13, 2010 at 05:51:28PM +0100, Loa Andersson wrote:
> All,
> 
> we have a new Internet Draft, a framework for mpls-tp p2mp.
> 
> The background is that we broke this out from the generic mpls-tp 
> framework in order to be able to progress both documents independently.
> 
> Please review the document and send comments to mpls-tp mailing list.
> 
> /Loa
> 
> -------- Original Message --------
> 
> 
> A New Internet-Draft is available from the on-line Internet-Drafts 
> directories.
> 
> 	Title           : A Framework for Point-to-Multipoint MPLS in 
> 	Transport Networks
> 	Author(s)       : D. Frost, et al.
> 	Filename        : draft-fbb-mpls-tp-p2mp-framework-00.txt
> 	Pages           : 11
> 	Date            : 2010-01-13
> 
> The Multiprotocol Label Switching (MPLS) Transport Profile (MPLS-TP) 
> is the common set of MPLS protocol functions defined to enable the 
> construction and operation of packet transport networks.  The MPLS-TP 
> supports both point-to-point and point-to-multipoint transport paths.
> This document defines the elements and functions of the MPLS-TP 
> architecture applicable specifically to supporting point-to- 
> multipoint transport paths.
> 
> This document is a product of a joint Internet Engineering Task Force
> (IETF) / International Telecommunication Union Telecommunication 
> Standardization Sector (ITU-T) effort to include an MPLS Transport 
> Profile within the IETF MPLS and PWE3 architectures to support the 
> capabilities and functionalities of a packet transport network.
> 
> Status of This Memo
> 
> This Internet-Draft is submitted to IETF in full conformance with the 
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> 
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