Subject: "Pw type" clarification needed in draft-martini-pwe3-MH-PW-requir ements-00.txt

From: "Kulkarni, Hrishikesh (Hrishikesh)" <[email-masked]>
Date: Thu, 27 Jan 2005 10:21:35 +0530

Hi all,

I would like to bring notice the following sections in the requirement text
which mentions pw type or encapsulation. The usage of pw type is a bit
unclear 
in these sections.

in bullet 1, we say that pw type MUST be same across the hops of the same
MH-PW
and in bullet 3, we allow pw types or encapsulation to be changed by S-PE.
one definition of pw type is given in the text referred by bullet 2.

Could the editor's please help clarify the meaning of pw type in each
context?

1. Section 3.2 The paragraph which describes Figure 2.

"
   PW1
   and PW3 are segments of the same MH-PW while PW2 and PW4 are segments
   of another pseudowire. PW segments of the same MH-PW (e.g., PW1 and
   PW3) MUST be of the same PW type, but PSN tunnels (e.g., PSN1 and
   PSN2) can be the same or different technology.
"

2. Section 6.1. Architecture, requirement #"i"
     
"
   That is, the PW type (i.e. ATM, Ethernet, etc) MUST be
   transparent to the S-PEs in the forwarding plane, except for
   the functions needed for interworking PW transport over
   different PSN types. 
"

3. Section 6.1. Architecture, requirement #"v"

"
        -v. S-PEs MAY change the type or encapsulation mode of a PW.
            This enables the establishment of a MH-PW between two PEs
            with different encapsulation capability.

"

Thanks
Rishi.

-----Original Message-----
From: [email-masked] [mailto:[email-masked]]On Behalf Of
David McDysan
Sent: Wednesday, January 26, 2005 11:58 PM
To: 'Scott W Brim'; [email-masked]
Cc: [email-masked]; [email-masked]
Subject: RE: [PWE3] Re: I-D
ACTION:draft-martini-pwe3-MH-PW-requirements-00.txt

Scott,

Are you impliying that the TAI contains information on which a routing
decision can be made, or only that it (in combination with the node's (IP)
address) is a globally unique PW endpoint identifier?

Dave

> -----Original Message-----
> From: [email-masked] [mailto:[email-masked]] On 
> Behalf Of Scott W Brim
> Sent: Wednesday, January 26, 2005 5:30 AM
> To: [email-masked]
> Cc: [email-masked]; [email-masked]; [email-masked]
> Subject: Re: [PWE3] Re: I-D 
> ACTION:draft-martini-pwe3-MH-PW-requirements-00.txt
> 
> 
> On 1/25/2005 13:39, [email-masked] allegedly wrote:
>  >> There are 2 cases here wrt MPLS and GMPLS and they are 
> quite  >> different. However, in all cases the functional 
> architecture rule  >> of nested layer networks holds, ie a 
> client layer link-connection  >> (ie the 'line' we draw 
> between adjacent nodes in some layer  >> network) is 
> supported by a trail in a lower layer network...this is  >> 
> the essence a 'truth' of topology creation and it's a 
> relationship  >> that recurses to the duct. Now let's look at 
> the 2 cases in a bit  >> more detail:  >>  >> MPLS - this is 
> a digital wrapper in the data-plane, ie 'just add a  >> label 
> and create a lower level LSP at will'.  Each LSP however does 
>  >> NOT create a new layer network.  Those familiar with the 
> functional  >> arch modelling of MPLS will probably also 
> realise that each LSP, no  >> matter where it appears in a 
> nested stack of LSPs, belongs to the  >> SAME layer network 
> (perhaps not so easy to visualise?).  It's not  >> the IP 
> layer network however despite using IP structured addresses  
> >> for LSPs....just like using IP structured addresses for 
> the access  >> points of a SDH VC4 layer network does not 
> make the SDH VC4 layer  >> network part of the IP layer 
> network!  However, there is still  >> something not quite 
> right here...all LSPs SHOULD use the SAME  >> access point 
> addressing no matter how they are created (be it via  >> 
> signalling protocol X, Y or Z or NMS manual provisioning).  
> This is  >> because THIS address belongs to the data-plane 
> and it should be  >> agnostic to the control-plane used.  Not 
> the case in MPLS.  This  >> issue becomes rather important 
> for (OAM) Connectivity Verification  >> when there are 
> misconnectivity defects between LSPs created by  >> different means.
> 
> Neil,
> 
> The IP addresses are used for control messages.  The control messages 
> themselves refer to LSP endpoints (and intermediate points for 
> MH-PWs), and do so in terms of TAIs.  In this particular use of MPLS 
> -- multi-hop pseudowires -- TAIs are the layer network endpoint 
> identifiers.  Also, unlike single-hop pseudowires, multi-hop 
> pseudowires do create a new layer network with trails based on 
> concatenated PWs.
> 
> Scott
> 
> _______________________________________________
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> 

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