RFC 4717, "Encapsulation Methods for Transport of Asynchronous Transfer Mode (ATM) over MPLS Networks", December 2006

Errata ID: 2918
Status: Rejected
Type: Technical
Publication Format(s) : TEXT
Reported By: Alfred Hoenes
Date Reported: 2007-10-17
Rejected by: Stewart Bryant
Date Rejected: 2011-08-05

(1)  incomplete/missing specification of PW types

RFC 4446 (by means of reference update from drafts to published RFCs)
and the IANA "pwe3-parameters" registry refer to this document for
the allocation and description of a couple of (MPLS) Pseudowire Types.
Therefore, this memo should be explicit, precisely give the proper
information, and not leave the reader alone with some apparent
ambiguities in the registry.  (Unfortunately, the RFC uses
descriptive text labels for the PW types that do not match the
text listed as the 'Descriptions' in the MPLS PW Type registry.)

Excluding the PW type 0x001E assigned for the MFA, IANA lists seven
ATM PW types.  I (hopefully) was able to identify most of these in
RFC 4717, but the role of PW type 0x0003 initially remained unclear;
this gap in the meantime has been closed by RFC 4816, taking over
the 'ownership' for that PW type.

To fill in the gap, the following clarifications should be posted
in an RFC errata note for RFC 4717 (please correct if I'm wrong);
because there also is a L2TPv3 Pseudowire Type (sub-)registry
(in the IANA "l2tp-parameters" registry) I also use the precise
term, "MPLS PW Type", in the proposed clarifications.

(1a)  Section 5.1.1

The initial text of Section 5.1.1 (on page 7 of RFC 4717) says:

   This control word is used in the following encapsulation modes:

     - ATM One-to-one Cell Mode
     - AAL5 PDU Frame Mode

It should say:

   This control word is used in the following encapsulation modes:

|    - ATM One-to-one Cell Mode  - MPLS PW types 0x000C and 0x000D
|    - AAL5 PDU Frame Mode       - MPLS PW type 0x000E

(1b)  Section 5.1.2

The initial text of Section 5.1.2 (on page 8 of RFC 4717) says:

   This control word is used in the following encapsulation modes:

     - ATM N-to-one Cell Mode
     - AAL5 SDU Frame Mode

It should say:

   This control word is used in the following encapsulation modes:

|    - ATM N-to-one Cell Mode  - MPLS PW types 0x0009 and 0x000A
|    - AAL5 SDU Frame Mode     - MPLS PW type 0x0002

(1c)  see item (6a) below!

(1d)  missing IANA Considerations

NOTE:
  Would the above clarifications have been included in the RFC,
  it should also have contained an IANA Considerations Section.
  In the meantime, after some complaints and interventions, the
  IANA "pwe3-parameters" registry has been updated to contain the
  proper pointers to RFC 4717 for the abovementioned six PW Types.

======

(7a)  missing applicability statement for PW Types -- also (1c) above

The initial paragraph of Section 8.1 (on page 19 of RFC 4717) says:

   This section describes the general encapsulation format for ATM over
   PSN pseudowires.

According to the expanations in item (1) above, it should say:

   This section describes the general encapsulation format for ATM over
|  PSN pseudowires used with the MPLS PW types 0x0009 and 0x000A (for
|  VCC and VPC transport, respectively) described in Section 5.1.2.

Note: As could be seen later, after the publication of RFC 4816,
this format is reused there.  Thus, it might be even better to say:

   This section describes the general encapsulation format for ATM over
|  PSN pseudowires used with the MPLS PW types 0x0009 and 0x000A (for
|  VCC and VPC transport, respectively) described in Section 5.1.2,
|  and PW Type 0x0003 (transparent cell transport [RFC-to-be-4816]).

Accordingly, an Informative Reference to the work-in-progress
predecessor of RFC 4816 would have to be added to Section 18.


======

Notes:

This was section 1 and section 7(a) of Errata 999
--VERIFIER NOTES--
The ATM PW Encapsulation modes specified are used by multiple ATM PW types and the intent of the working group was to allow new ATM PW types to use these encapsulations without requiring an update or republication of RFC 4717

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