Subject: Re: I-D ACTION:draft-riegel-pwe3-tdm-requirements-01.txt

From: Maarten Vissers <[email-masked]>
Date: Mon, 23 Dec 2002 14:32:48 +0100

I would like to propose to extend the requirements document with a more specific
identification of the ingress/egress points of a PW. I.e. a PW connects
essentially two (ITU-T G.805) Connection Points (CP) within a layer network.

E1 PW connects two P12x_CPs for case of transparent (unstructured) service:

   P12x_CP      P12x Link Connection     P12x_CP
 ---- O ----------------------------------- O -----
        |<-------------PW---------------->|

E1 PW connects two P12s_CPs for case of transparent frame-synchronous service:

   P12s_CP      P12s Link Connection     P12s_CP
 ---- O ----------------------------------- O -----
        |<-------------PW---------------->|

T1 PW connects two P11x_CPs for case of transparent (unstructured) service:

   P11x_CP      P11x Link Connection     P11x_CP
 ---- O ----------------------------------- O -----
        |<-------------PW---------------->|

E3 PW connects two P31x_CPs for case of transparent service:

   P31x_CP      P31x Link Connection     P31x_CP
 ---- O ----------------------------------- O -----
        |<-------------PW---------------->|

T3 PW connects two P32x_CPs for case of transparent service:

   P32x_CP      P32x Link Connection     P32x_CP
 ---- O ----------------------------------- O -----
        |<-------------PW---------------->|

VC-n (n=11,12,2,3,4,4-4c,4-16c,4-64c) PW connects two Sn_CPs for case of
transparent service:

    Sn_CP        Sn Link Connection       Sn_CP
 ---- O ----------------------------------- O -----
        |<-------------PW---------------->|

ATM VP PW connects two VP_CPs for case of transparent service:

    VP_CP        VP Link Connection       VP_CP
 ---- O ----------------------------------- O -----
        |<-------------PW---------------->|

ATM VC PW connects two VC_CPs for case of transparent service:

    VC_CP        VC Link Connection       VC_CP
 ---- O ----------------------------------- O -----
        |<-------------PW---------------->|

DS0 PW connects two P0_CPs for case of transparent service:

    P0_CP       P0s Link Connection       P0_CP
 ---- O ----------------------------------- O -----
        |<-------------PW---------------->|

The information transported is the Characteristic Information (CI). 
E.g. over the VC-n CP and VC-n PW flows the VC-n CI.
These CPs and CIs are explicitly defined in ETSI EN 300 417-4-1, EN 400 417-5-1,
Rec. G.705, G.783, I.732 and can as such be referred to from the PWE3 RFCs.

P0_CI:   17/G.705
P11x_CI: 15/EN 300 417-5-1
P12x_CI: 14/EN 300 417-5-1
P12s_CI: 7/EN 300 417-5-1 and 12/G.705
P31x_CI: 12/EN 300 417-5-1
P32x_CI: 11/EN 300 417-5-1
P11x_CI: 15/EN 300 417-5-1
Sn_CI:   4,5,6,7/EN 300 417-4-1, 5/EN 300 417-9-1 and 12,13/G.783
VP_CI:   D.3/I.732
VC_CI:   D.5/I.732

For the case a PW supports multiplexing, the PW is a Link with multiple Link
Connections.
Example VC-n PW with 5x VC-n:

    Sn_CPs       Sn Link Connections      Sn_CPs
 ---- O ----------------------------------- O -----
 ---- O ----------------------------------- O -----
 ---- O ----------------------------------- O -----
 ---- O ----------------------------------- O -----
 ---- O ----------------------------------- O -----
        |<-------------PW---------------->|

The PW connects via the CPs at its edge to atomic functions defined in G.705,
G.783, I.732, etc. This can be an adaptation function or a connection function.
Example: VC-4 PW with STM-1 and STM-4 interfaces and no flexibility in STM-4
interface

                                                      -----------
                                                      --------- |
                                                      ------- | |
                                                            | | |
               S4_CP                             S4_CP      | | |
       ----------O------------              -------O------- | | |
       |                     |              |             | | | |
    MS1/S4_A                 ------ PW ------             MS4/S4_A
       |                                                     |
     MS1_TT                                                MS4_TT
       |                                                     |

When there would be flexibility in the selection of the VC-4 in the STM-4
interface, a VC-4 connection function (S4_C) is included and connected to the
VC-4 PW

                                           -----------------------
                                           |         S4_C        |
                                           -----------------------
               S4_CP                        |             | | | |
       ----------O------------        S4_CP O      S4_CPs O O O O
       |                     |              |             | | | |
    MS1/S4_A                 ------ PW ------             MS4/S4_A
       |                                                     |
     MS1_TT                                                MS4_TT
       |                                                     |

The PW can be modelled as well with similar atomic functions... in this example
there would be a MPLS-VC/S4_A function at each edge of the PW connected via a
MPLS-VC trail...

                                           -----------------------
                                           |         S4_C        |
                                           -----------------------
               S4_CP                        |             | | | |
       ----------O------------        S4_CP O      S4_CPs O O O O
       |                     |              |             | | | |
    MS1/S4_A            MPLS-VC/S4_A   MPLS-VC/S4_A       MS4/S4_A
       |                     |              |                |
     MS1_TT              MPLS-VC_TT     MPLS-VC_TT         MS4_TT
       |                     |              |                |
                             ----------------

For transparent (unstructured) E1 connection this model would be:

              P12x_CP                            P12x_CP
       ----------O------------              --------O---------
       |                     |              |                |
   E12/P12x_A          MPLS-VC/P12x_A MPLS-VC/P12x_A      E12/P12x_A
       |                     |              |                |
     E12_TT              MPLS-VC_TT     MPLS-VC_TT         E12_TT
       |                     |              |                |
                             ----------------

Adding these network architecture models to the PWE3 architecture document,
would connect existing specifications in ITU-T with the PWE3 specifications not
leaving any ambiguity about the actual signals transported via a PW. 
It also adds implicitly the interface specifications of the interfaces that
provide access to these PWs. Example: G.705 specifies how to access the P12x_CP
(via e.g. E12_TT and E12/P12x_A functions), while G.783 specifies access to this
P12x_CP via OSn, RSn, MSn, S4 and finally S12_TT and S12/P12x_A functions.

When the PW is able to multiplex multiple signals, the MPLS-VC/Client_A function
will have multiple Client_CPs. E.g. for case of PW capable to multiplex 5 VC-12
signals:

             | | | | | 
             O O O O O S12_CPs
             | | | | |
           MPLS-VC/S12_A
                 |
             MPLS-VC_TT
                 |

Regards,

Maarten

---

From: Max Riegel <[email-masked]>
Date: Mon, 23 Dec 2002 23:18:23 +0100

Maarten,

you mentioned a E1 frame-synchronous (= structured ?) service, but what 
about a T1 frame-synchronous service?

Bye
Max

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