Re: Proposed response to the Liaison Statement on LMP Link Verifi cation

[Gert Grammel <[e-mail]>]

 - "Fine, send it as is"


Gert


On Tue, 29 Apr 2003, Kireeti Kompella wrote:

>
> > I will formulate a liaison statement in reply to T1X1 regarding
> > draft-ietf-ccamp-lmp-test-sonet-sdh and post it to this list.
>
> Sorry for the tardy follow-up.  Here is the proposed response.
>
> Please send your replies to the list (if you wish to reply privately,
> include the Liaison Coordinator and the ADs in your reply).
>
> Ideally, your reply should say one of:
>  - "Fine, send it as is"; OR
>  - "Please make the following changes", with _specific text_; OR
>  - "Do not send this response".
>
> Please respond by COB Friday, May 16th.
>
> Kireeti.
> =======================================================================
>
> Dear Mr. Biholar,
>
> Regarding the following liaison:
>
> TITLE: Liaison from T1X1 to IETF ccamp regarding
>         draft-ietf-ccamp-lmp-test-sonet-sdh-02.txt
> TO: IETF ccamp Working Group
> CC: ITU-T Q.14/15 (for information)
> SOURCE*: T1X1
> FOR: Action
> DEADLINE: 9 June 2003
> PROJECT: T1X1-01: Optical Interface Standard for Fiber Optic Interconnection
>
> We thank the T1X1 and the ITU-T for their review and the incorporation
> of the LMP Test procedure into G.7714.1.
>
> Based on information contained in the ITU and T1X1 liaison, as well as
> subsequent e-mail exchanges on the CCAMP mailing list, and in order to
> ensure proper interoperability in legacy SDH/SONET networks as well as
> networks in which G.7714.1 is deployed, it will be recommended by the
> editors to the CCAMP community to support only the Jx trace correlation
> procedure and not the in-band Jx procedure.  Pending agreement, the
> draft will be updated.
>
> See inline for more detailed responses to specific points.
>
> > Context of Application Space
>
> <snip>
>
> > It is currently our understanding that the use case
> > scenario for which this procedure is applied encompasses
> > both transport plane connectivity verification as well as
> > correlation of these entities with the control plane.
> > ITU-T G.7714.1 is focused on discovering the transport
> > plane link connection end point relationships and
> > verifying their connectivity.
> > This Recommendation defines two procedures for performing
> > the connectivity verification function, one of which
> > utilizes either the Jx or the DCC bytes of the server
> > signal (termed "in-service"). The other approach in
> > G.7714.1, termed as "out of service", corresponds to
> > inserting a test signal in the payload of the server
> > signal. Based on an analysis of the data link state
> > definitions in draft-ietf-ccamp-lmp-08.txt, we understand
> > that the approach defined in the LMP test for physical
> > connectivity occurs in the context of the "out of service"
> > state (as described in G.7714.1).
> >
> > Please confirm this.
>
> The subject document uses the Jx or DCC bytes to perform the LMP
> Test procedure, but the The LMP Test procedure is done as part of
> GMPLS link intialization, prior to the link being available to
> carry user traffic.
>
> > Usage of Jx Bytes
> >
> > In defining the Jx bytes within G.7714.1, the following
> > was taken into account:
> > 1. One consideration involved the case where the Discovery
> > Agent is located in an external system, and an external
> > interface is used by the Network Element to provision and
> > receive the Trail Trace message. As an existing text-
> > oriented Man-Machine Language, such as TL1, may be reused
> > to provide this interface, it was decided that the
> > discovery message be limited to printable characters.
> > Specifically, the TTI characters should be limited to
> > printable characters as per T.50 with trailing NULLs or
> > SPACEs. Use of arbitrary bit patterns in the lower 7 bits
> > of each byte could prematurely terminate the pattern or
> > trigger fault notification for certain hardware or
> > software implementations. The strategy chosen in G.7714.1
> > avoids the danger by limiting the information content of
> > each byte to 6 bits (84 bits total) and uses a base 64
> > coding according to RFC2045 to place the information in
> > the available bits.
>
> The LMP test procedure described in the subject document defines
> two usages of the Jx bytes.  The first is termed the 'trace
> correlation transport mechanism' and it treats the Jx bytes as
> an opaque bit stream.
>
> This usage is completely consistent with the above.  GMPLS
> identifiers are typically 32 bit numbers and as such are not
> printable characters.  In networks that do not require that the
> Jx bytes be printable, it is also possible to carry the GMPLS
> identifiers directly in the Jx bytes.  This is termed the 'Jx
> transport mechanism'.
>
> > 2. Another consideration involved providing a means for
> > distinguishing this use of the Jx bytes from the
> > traditional use for Trail Trace identifiers in new
> > equipments. As a result, G.7714.1 includes a
> > distinguishing character ("+") as the first non-CRC byte
> > that will never appear as the first character of a TTI.
> > This requires modification of the trail termination
> > functions to prevent the raising of TTI mismatch
> > alarms during the connectivity verification process.
>
> The selection of which LMP transport mechanism use in the LMP Test
> procedure for a given link as well as the time at which the Jx
> bytes are to be used for the LMP Test procedure is under control of
> the GMPLS nodes at either end of the link, so it is well understood
> by those nodes.  It is our understanding, per G.806 section 6.1,
> that the LMP Test procedure would be performed when the link is in
> the NMON (not monitored state), and therefore intermediate SDH/SONET
> equipment would not be performing non-intrusive monitoring.
>
> > While the context for testing the transport plane
> > connectivity is different between the two documents, they
> > both use the Jx bytes of the server signal, and we invite
> > the IETF to determine the appropriateness of the above
> > aspects in their test signal definitions.
>
> The trace correlation transport mechanism is completely consistent
> with this.  The JX transport mechanism requires additional
> identifiers (i.e., the Verify ID).
>
> > Even if these considerations are not relevant to this
> > context, it will be necessary to augment G.783 equipment
> > functions to recognize this new usage of Jx messages.
>
> We would be happy to provide assistance to T1X1/ITU-T in augmenting
> G.783 equipment functions to recognize the additional capability
> for supporting GMPLS networking elements.
>
> > Required Updates to SDH Equipment Specifications
> >
> > SDH equipment specifications as they currently exist reflect
> > the usage of the Jx bytes prior to the development of
> > G.7714.1. ITU-T Study Group 15 has as a work item to
> > revise these equipment functions to include support for
> > these new functions. Specifically, this will involve
> > updates to trail termination functions to generate and
> > receive the new messages and to avoid unnecessary alarms in
> > the case where the new messages are received.  In addition,
> > non-intrusive monitoring functions will need to be revised
> > so that unnecessary alarms are not raised when the
> > messages are observed en-route.  Whether or not there is
> > further alignment between the message formats used in
> > G.7714.1 and the subject draft, the new functions to
> > support the subject draft will also need to be reflected
> > in the atomic functions in G.783.  The sending and
> > receiving of these messages can be reflected in the trail
> > termination functions in a similar way to what we plan to
> > do for support of G.7714.1 functions.
>
> We would be happy to provide assistance to T1X1/ITU-T in augmenting
> G.783 equipment functions to recognize the additional capability
> for supporting GMPLS networking elements.
>
> > Terminology Differences
>
> <snip>
>
> > Based upon draft-ietf-ccamp-lmp-08.txt, Section 11.3.1,
> > the "up/free (in-service)" data link state appears to
> > correspond with what G.7714.1 refers to as "out-of-
> > service".  This difference in terminology has resulted in
> > different interpretations of the context.  Explaining the
> > scenarios further in the lmp test document would be
> > beneficial in establishing a translation between the
> > differing uses of the same terms.  Within ITU-T, work is
> > being initiated of draft Rec. G.fame, Framework for ASON
> > Management, where control plane/management plane
> > interactions will be addressed.
>
> We agree that terminology differences between IETF and ITU-T wrt
> GMPLS have been confusing.  There is an ongoing effort within
> CCAMP to work together with T1X1/ITU-T on bridging the terminology
> gaps.  For example, there is a new Internet draft
> (draft-aboulmagd-ccamp-transport-lmp-00.txt) being considered in
> CCAMP to do this mapping for LMP.
>
> > Further Study Items
> >
> > Following are some areas where further contributions are
> > requested:
> > 1.     For SDH equipment functions in G.783, it needs to
> > be understood whether the application of the lmp test
> > message requires revision of NIM (non-intrusive
> > monitoring) functions.  The reason for this is that the
> > test procedure is initiated between control entities at
> > the end-points of the trail, and intermediate points are
> > not necessarily aware that the test is taking place.  For
> > G.7714.1, it was felt important for any termination or NIM
> > function to easily distinguish between the various uses of
> > the Jx bytes.  It may be necessary for the subject draft
> > to use a similarly easily recognizable format.  If no
> > revision to NIM functions is required for the context of
> > this draft, the architecture of the context for this
> > application (demonstrating why the NIM functions are not
> > required) should be reflected in G.803 and/or G.807/G.8080.
>
> It is our understanding, per G.806 section 6.1, that
> the LMP Test procedure would be performed when the link is in the
> NMON (not monitored state), and  therefore intermediate SDH/SONET
> equipment would not be performing non-intrusive monitoring.
> As described, the trace correlation procedure use of Jx bytes is
> consistent with the current standards.
>
> > 2.Determination of whether it would be possible to use the
> > identical message formats in the subject draft as in
> > G.7714.1 for the connectivity verification function.
>
> The trace correlation transport mechanism is completely consistent
> with this.  The Jx transport mechanism requires additional
> identifiers (i.e., the Verify ID).
>
> > 3.Determination of whether it would be possible to use the
> > same overall structure (distinguishing character, 4 bit
> > message type, 80 bit message body) if a different message
> > format or information content is required.
>
> This is certainly possible (not applicable for the trace correlation
> procedure).
>
> > 4.Work is needed to clarify under what
> > configurations/states (for example: no VC-n signals
> > carrying client traffic) the lmp test message is
> > applicable over J0.  If the signal can be framed and J0
> > can be recovered, the Regenerator Section is considered
> > as "in service" from a transport plane perspective.  So
> > unlike the J1/J2 case, the application of the lmp test
> > message at the Regenerator Section does not occur in an
> > "out of service" state (from a transport plane
> > perspective).
>
> Section 6.1 of G.806 refers to a "termination function part of a
> trail, which is in the process of set-up" as in the NMON state.
> LMP link verification is based on pre-service testing.  Please let
> us know if we can be of any assistance in updating the appropriate
> Recommendations to support the GMPLS network element LMP capability.
> This is not applicable for the trace correlation procedure.
>
> > 5. Clarification of the usage of transport and control
> > names for transport resources in the subject draft, as
> > described in G.8080 Amendment
>
> The trace correlation transport mechanism supports a separation of
> the transport and control plane identifiers.
>
> > 6. Consideration of the ANSI 64-byte J1.
>
> This was mistakenly deleted from the latest version of the draft.
> This will be included in the next version.
>
> Sincerely,
> Kireeti Kompella and Ron Bonica,
> Chairs of the CCAMP WG/IETF.