Subject: [Fwd: Editorial comments on draft-ietf-pwe3-arch-06.txt Section 8 (was: MIB Doctor (architectural) review needed)]

From: Stewart Bryant <[email-masked]>
Date: Mon, 19 Jan 2004 15:09:18 +0000

The following comments were received from the MIB review process.

Prayon, Tom Nadeau and I talked about this, and it was agreed that
they would re-write section 8 to make it more of an architectural
overview, removing specific PW type MIB references.

The proposed new section 8 is at the end of this mail.

-------- Original Message --------
Subject: Editorial comments on draft-ietf-pwe3-arch-06.txt Section 8 (was: MIB 
Doctor (architectural) review needed)
Date: Thu, 11 Dec 2003 08:58:10 -0800 (PST)
From: C. M. Heard <[email-masked]>
To: Mreview (E-mail) <[email-masked]>
CC: Stewart Bryant <[email-masked]>,        Prayson Pate 
<[email-masked]>

On Thu, 4 Dec 2003, Wijnen, Bert (Bert) wrote:
> Document: draft-ietf-pwe3-arch-06.txt
> 
> Section 8 has a "architectural overview" of how PWE3 related
> MIBs fit in their architecture. We may want to check this out.
> 
> It is on IESG agenda today (Dec 4th)... so probably too late
> to feed any comments into the telechat today. I will take a defer
> so we as MIB doctors can do EARLY review instead of LATE review.

Sigh.  My general reaction to a first read of sections 8.1 and 8.2
was that the proposed MIB architecture seemed reasonable, but since
the devil is in often in the details, and I decided to look at the
reference documents to see how the proposed architecture is actually
realized in the draft PWE3 MIB modules, in particular in the ones
cited in the example shown in Figure 16: the PW-CEM-MIB, PW-TC-MIB,
PW-MIB, and PW-MPLS-MIB.  Alas, this exercise did not come off
entirely trouble-free:  the first problem that I ran into is that
the PW-TC-MIB and PW-MIB drafts have expired (which I got around
by retrieving old versions from the archive at
http://www.watersprings.org/pub/id/index-all.html);  the second
was that the PW-CEM-MIB no longer exists, it is now called the
PW-CEP-STD-MIB;  the third problem was that the reference
[PWMPLSMIB] points to the wrong document.

I'll have some substantive comments on the MIB architecture in
a subsequent message (mainly concerns that the relationship to
the IF-MIB is not discussed), but for now I'd like to get some
editorial comments on record.  Document authors have been cc:'d.

//cmh

Editorial comments on Section 8 of <draft-ietf-pwe3-arch-06.txt>:

Don't use of obsolete term "CEM" in Fig. 15 (Sec. 8.2.1, p.38):
---------------------------------------------------------------

OLD:

                   +-----------+ +-----------+     +-----------+
         Service   |    CEM    | | Ethernet  |     |    ATM    |
          Layer    |Service MIB| |Service MIB| ... |Service MIB|
                   +-----------+ +-----------+     +-----------+

NEW:
                   +-----------+ +-----------+     +-----------+
         Service   |   SONET   | | Ethernet  |     |    ATM    |
          Layer    |Service MIB| |Service MIB| ... |Service MIB|
                   +-----------+ +-----------+     +-----------+

Fix incorrect MIB module names in Fig. 16 (sec. 8.2.1, p.39):
-------------------------------------------------------------

OLD:
                      +-----------------+
                      |    SONET MIB    | RFC2558
                      +-----------------+
                               |
                      +-----------------+
            Service   |SONET Service MIB| pw-cem-mib
             Layer    +-----------------+
           - - - - - - - - - - | - - - - - - - - - - - - - - -
                      +-----------------+
           Generic PW | Generic PW MIBS | pw-tc-mib
             Layer    +-----------------+ pw-mib
           - - - - - - - - - - | - - - - - - - - - - - - - - -
                      +-----------------+
             PSN VC   |   MPLS VC MIBS  | pw-mpls-mib
             Layer    +-----------------+
           - - - - - - - - - - | - - - - - - - - - - - - - - -
                      +-----------------+
              PSN     |    MPLS MIBs    |   mpls-te-mib
             Layer    +-----------------+   mpls-lsr-mib

NEW:
                      +-----------------+
                      |    SONET MIB    | SONET-MIB
                      +-----------------+
                               |
                      +-----------------+
            Service   |SONET Service MIB| PW-CEP-STD-MIB
             Layer    +-----------------+
           - - - - - - - - - - | - - - - - - - - - - - - - - -
                      +-----------------+
           Generic PW | Generic PW MIBS | PW-TC-MIB
             Layer    +-----------------+ PW-MIB
           - - - - - - - - - - | - - - - - - - - - - - - - - -
                      +-----------------+
             PSN VC   |   MPLS VC MIBS  | PW-MPLS-MIB
             Layer    +-----------------+
           - - - - - - - - - - | - - - - - - - - - - - - - - -
                      +-----------------+
              PSN     |    MPLS MIBs    | MPLS-TE-STD-MIB
             Layer    +-----------------+ MPLS-LSR-STD-MIB

Fix incorrect citation/module name (sec. 8.2.2, p. 39)
------------------------------------------------------

OLD:
    adaptation MIB, in this case, it would produce the PW-CEM-MIB
______________________________________________________^^^^^^^^^^
    [PWMPLSMIB] that would be used to adapt SONET services to the
____^^^^^^^^^
    underlying PSN that carries the PWE3 service.

NEW:
    adaptation MIB, in this case, it would produce the PW-CEP-STD-MIB
    [PWCEPMIB] that would be used to adapt SONET services to the
    underlying PSN that carries the PWE3 service.

Eliminate incorrect citation (sec. 8.2.3, p. 40):
-------------------------------------------------

OLD:
    This MIB is used to interconnect the Service Layer MIBs to the PSN VC
    Layer MIBs. The latter will be described in the next section.  This
    layer also provides the PW-TC-MIB [PWTCMIB].  This MIB contains
    common SMI textual conventions [RFC1902] that MAY be used by any PW
___________________________________^^^^^^^
    MIB.

NEW:
    This MIB is used to interconnect the Service Layer MIBs to the PSN VC
    Layer MIBs. The latter will be described in the next section.  This
    layer also provides the PW-TC-MIB [PWTCMIB].  This MIB contains
    common SMI textual conventions that MAY be used by any PW MIB.

Fix incorrect references
------------------------

OLD:
    [PWMPLSMIB] Danenberg et al, "SONET/SDH Circuit Emulation Service
                Over MPLS (CEM) Management Information Base Using
                SMIv2", <draft-ietf-pwe3-cep-mib-01.txt>, work in
                progress, October 2002.

NEW:
    [PWMPLSMIB] Zelig et al, "Pseudo Wire (PW) over MPLS PSN
                Management Information Base",
                <draft-ietf-pwe3-pw-mpls-mib-03.txt>, work in
                progress, October 2003

    [PWCEPMIB]  Danenberg et al, "SONET/SDH Circuit Emulation Service
                Over Packet (CEP) Management Information Base Using
                SMIv2", <draft-ietf-pwe3-cep-mib-03.txt>, work in
                progress, October 2003.

Delete unneeded obsolete reference
----------------------------------

REMOVE:
    [RFC1902]   RFC-1902: Structure of Management Information for
                Version 2 of the Simple Network Management Protocol
                (SNMPv2), Case et al, January 1996.

==========================================================================
==========================================================================

Proposed new section 8:

8. Management and Monitoring

    This section describes the management and monitoring architecture for
    PWE3.

8.1  Status and Statistics

    The PE should report the status of the interface and tabulate
    statistics that help monitor the state of the network, and to help
    with measurement of service level agreements (SLAs). Typical counters
    include:

        o Counts of PW-PDUs sent and received, with and without errors.
        o Counts of sequenced PW-PDUs lost.
        o Counts of service PDUs sent and received over the PSN, with
          and without errors (non-TDM).
        o Service-specific interface counts.
        o One way delay and delay variation.

    These counters would be contained in a PW-specific MIB, and they
    should not replicate existing MIB counters.

8.2  PW SNMP MIB Architecture

    This section describes the general architecture for SNMP MIBs used to
    manage PW services and the underlying PSN.  The intent here is to
    provide a clear picture of how all of the pertinent MIBs fit together
    to form a cohesive management framework for deploying PWE3 services.
    Note that the names of MIB modules used below are suggestions, and do
    not necessarily require the actual modules used to realize the
    components in the architecture to be named exactly so.

8.2.1.  MIB Layering

    The SNMP MIBs created for PWE3 should fit the architecture shown in
    Figure 15.  The architecture provides a layered modular model into
    which any supported emulated service can be connected to any
    supported PSN type. This model fosters reuse of as much functionality
    as possible. For instance, the emulated service layer MIB modules do
    not redefine the existing emulated service MIB module; rather, they
    only associate it with the pseudowires used to carry the emulated
    service over the configured PSN. In this way, the PWE3 MIB
    architecture follows the overall PWE3 archiecture.

    The archtecture does allow for the joining of unsupported emulated
    service or PSN types by simply defining additional MIB modules to
    associate these new types with existing ones. These new modules can
    subsequently be standardized. Note that there is a separate MIB
    module for each emulated service as well as one for each underlying
    PSN.  These MIB modules may be used in various combinations as
    needed.

            Native
         Service MIBs    ...           ...               ...
                          |             |                 |
                    +-----------+ +-----------+     +-----------+
          Service   |    CEP    | | Ethernet  |     |    ATM    |
           Layer    |Service MIB| |Service MIB| ... |Service MIB|
                    +-----------+ +-----------+     +-----------+
                            \           |             /
                              \         |           /
        - - - - - - - - - - - - \ - - - | - - - - / - - - - - - -
                                  \     |       /
                    +-------------------------------------------+
         Generic PW |            Generic PW MIBs                |
           Layer    +-------------------------------------------+
                                 /             \
        - - - - - - - - - - - - / - - - - - - - - \ - - - - - - -
                              /                     \
                            /                         \
                    +--------------+             +----------------+
          PSN VC    |L2TP VC MIB(s)|             | MPLS VC MIB(s) |
           Layer    +--------------+             +----------------+
                           |                              |
          Native     +-----------+                  +-----------+
           PSN       |L2TP MIB(s)|                  |MPLS MIB(s)|
           MIBs      +-----------+                  +-----------+

                  Figure 15: MIB Module Layering Relationship

    Figure 16 shows an example for a SONET PW carried over MPLS Traffic
    Engineering Tunnel and an LDP-signaled LSP.

                             +-----------------+
                             |    SONET MIB    |  RFC2558
                             +-----------------+
                                      |
                        +------------------------------+
             Service    | Circuit Emulation Service MIB|
              Layer     +------------------------------+
            - - - - - - - - - - - - - | - - - - - - - - - - - - -
                             +-----------------+
            Generic PW       | Generic PW MIB  |
              Layer          +-----------------+
            - - - - - - - - - - - - - | - - - - - - - - - - - - -
                             +-----------------+
              PSN VC         |   MPLS VC MIBs  |
              Layer          +-----------------+
                                |           |
                   +-----------------+  +------------------+
                   | MPLS-TE-STD-MIB |  | MPLS-LSR-STD-MIB |
                   +-----------------+  +------------------+

        Figure 16: SONET PW over MPLS PSN Service-specific Example

8.2.2.  Service Layer MIB Modules

    This conceptual layer in the model contains MIB modules used to
    represent the relationship between emulated PWE3 services such as
    Ethernet, ATM, or Frame Relay and the pseudo-wire used to carry that
    service across the PSN. This layer contains those corresponding MIB
    modules used to mate or adapt those emulated services to the generic
    pseudo-wire representation, which are represented in the "Generic PW
    MIB" functional block in Figure 16 above.  This working group should
    not produce any MIB modules for managing the general service; rather,
    it should produce just those modules that are used to interface or
    adapt the emulated service onto the PWE3 management framework as
    shown above. For example, the standard SONET-MIB [RFC2558] is
    designed and maintained by another working group. The SONET-MIB is
    designed to manage the native service without PW emulation.  However,
    since the PWE3 working group is chartered to produce standards which
    show how to emulate existing technologies such as SONET/SDH over
    pseudo-wires rather than re-inventing those modules.

8.2.3.  Generic PW MIB Modules

    The middle layer in the architecture is referred to as the Generic PW
    Layer.  MIB in this layer are responsible for providing pseudo-wire
    specific counters and service models used for monitoring and
    configuration of PWE3 services over any supported PSN service. That
    is, this layer provides a general model of PWE3 abstraction for
    management purposes. This MIB is used to interconnect the MIB modules
    residing in the Service Layer to the PSN VC Layer MIBs (see section
    8.2.4).

8.2.4.  PSN VC Layer MIB Modules

    The third layer in the PWE3 management architecture is referred to as
    the PSN VC Layer. It is comprised of MIBs that are specifically
    designed to associate pseudo-wires onto those underlying PSN
    transport technologies that carry the pseudo-wire payloads across teh
    PSN.  In general this means that the MIB module provides a mapping
    between the emulated service that is mapped to the pseudo-wire via
    the Service Layer and Generic PW MIB Layer onto the native PSN
    service. For example, in the case of MPLS for example, it is required
    that the general VC service be mapped into MPLS LSPs via the MPLS-
    LSR-STD-MIB [LSRMIB] or Traffic Engineered (TE) Tunnels via the
    MPLS-TE-STD-MIB [TEMIB]. In addition, the MPLS-LDP-STD-MIB [LDPMIB]
    may be used to reveal the MPLS labels that are distributed over the
    MPLS PSN in order to maintain the PW service. As with the native
    service MIB modules described earlier, the MIB modules used to manage
    the native PSN services are produced by other working groups that
    design and specify the native PSN services. These MIBs should contain
    the appropriate mechanisms for monitoring and configuring the PSN
    service such that the emulated PWE3 service will function correctly.

8.3 Connection Verification and Traceroute

    A connection verification mechanism should be supported by PWs.
    Connection verification as well as other alarm mechanisms can alert
    the operator that a PW has lost its remote connection.  The opaque
    nature of a PW means that it is not possible to specify a generic
    connection verification or traceroute mechanism that passes this
    status to the CEs over the PW.  If connection verification status of
    the PW is needed by the CE, it MUST be mapped to the native
    connection status method.

    For troubleshooting purposes, it is sometimes desirable to know the
    exact functional path of a PW between PEs. This is provided by the
    traceroute service of the underlying PSN.  The opaque nature of the
    PW means that this traceroute information is only available within
    the provider network, e.g., at the PEs.