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ITU-T_G7714-Y1705 - ITU-T Recommendation G

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ITU-T_G7714-Y1705 - ITU-T Recommendation G

INTERNATIONAL TELECOMMUNICATION UNION

ITU-T G.7714/Y.1705

    (11/2001) TELECOMMUNICATION

    STANDARDIZATION SECTOR

    OF ITU

     SERIES G: TRANSMISSION SYSTEMS AND MEDIA, DIGITAL SYSTEMS AND NETWORKS

    Digital sections and digital line system Access networks

    SERIES Y: GLOBAL INFORMATION INFRASTRUCTURE AND INTERNET PROTOCOL ASPECTS

    Internet protocol aspects Operation, administration and maintenance

     Generalized automatic discovery techniques

    CAUTION !

    PREPUBLISHED RECOMMENDATION

    This prepublication is an unedited version of a recently approved Recommendation.

    It will be replaced by the published version after editing. Therefore, there will be

    differences between this prepublication and the published version.

    FOREWORD

    The International Telecommunication Union (ITU) is the United Nations specialized agency in the field of telecommunications. The ITU Telecommunication Standardization Sector (ITU-T) is a permanent organ of ITU. ITU-T is responsible for studying technical, operating and tariff questions and issuing Recommendations on them with a view to standardizing telecommunications on a worldwide basis. The World Telecommunication Standardization Assembly (WTSA), which meets every four years, establishes the topics for study by the ITU-T study groups which, in turn, produce Recommendations on these topics.

    The approval of ITU-T Recommendations is covered by the procedure laid down in WTSA Resolution 1. In some areas of information technology which fall within ITU-T's purview, the necessary standards are prepared on a collaborative basis with ISO and IEC.

    NOTE

    In this Recommendation, the expression "Administration" is used for conciseness to indicate both a telecommunication administration and a recognized operating agency.

    INTELLECTUAL PROPERTY RIGHTS

    ITU draws attention to the possibility that the practice or implementation of this Recommendation may involve the use of a claimed Intellectual Property Right. ITU takes no position concerning the evidence, validity or applicability of claimed Intellectual Property Rights, whether asserted by ITU members or others outside of the Recommendation development process.

    As of the date of approval of this Recommendation, ITU [had/had not] received notice of intellectual property, protected by patents, which may be required to implement this Recommendation. However, implementors are cautioned that this may not represent the latest information and are therefore strongly urged to consult the TSB patent database.

    ; ITU 2001

    All rights reserved. No part of this publication may be reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying and microfilm, without permission in writing from ITU.

    ITU-T RECOMMENDATION G.7714/Y.1705

    Generalized Automatic Discovery Techniques

    (Geneva, 2001)

    Summary

    This Recommendation provides the generic attributes, state diagram and message sets for the

    automatic discovery process.

    Source and history

    DOCUMENT HISTORY

    Issue Notes

    1.0 Version 1.0 of the G.7714/Y.1705.

Keywords

    Auto-discovery, Layer Adjacency Discovery, Physical Media Adjacency Discovery, Service

    Capability Exchange.

ITU-T G.7714/Y.1705 (11/2001) Prepublished version 1

    GENERALIZED AUTOMATIC DISCOVERY TECHNIQUES

1 Scope

    This recommendation describes the specifications for automatic discovery techniques to aid resource management and routing. Other areas such as connection operations, routing of connections within a switched network, are not part of this specification. In this recommendation, two major instances of discovery are addressed, (a) layer adjacency discovery (b) physical media adjacency discovery. In addition the results of either discovery

    processes are also used for establishing logical adjacencies between control entities. 2 References

     ITU-T Rec. G.805 (2000), Generic Functional Architecture of Transport Networks

     ITU-T Rec. G.806 (2000), Characteristics of transport equipment - Description methodology

    and generic functionality

     ITU-T Rec. G.852.2 (1999), Enterprise viewpoint description of transport network resource

    model

     ITU-T Rec. G.853.1 (1999), Common elements of the information viewpoint for the

    management of a transport network

     ITU-T Rec. M.3100 (1995), Generic Network Information Model

    3 Terms and definitions

    Access Point (AP) See G.805

    Connection Termination Point (CTP) See M.3100

    Link See G.85x

    Link Connection See G.85x

    Network Connection See G.805

    Port See G.805

    Subnet Termination Point Pool See G.85x

    Trail See G.85x

    Trail Termination Point (TTP) See M.3100

    Note: In the above references, G.85x represents G.852.2 and G.853.1 4 Abbreviations

AP Access Point

    CELA Control Entity Logical Adjacency

    CTP Connection Termination Point

    Id Identifier

    ITU-T G.7714/Y.1705 (11/2001) Prepublished version 2

LAD Layer Adjacency Discovery

    LC Link Connection

    NC Network Connection

    NE Network Element

    PMAD Physical Media Adjacency Discovery

    Rx Receive

    SCE Service Capability Exchange

    SNTP Sub Network Termination Point

    TTP Trail Termination Point

    Tx Transmit

    UNI User Network Interface

5 Conventions

    SNTP: For purposes of this recommendation, the SNTP is used as a port on a subnetwork. SNTP may be used as an alias to a CTP or TTP. It is understood to have an assigned identifier that would be used for the purposes of routing and resource management.

    6 Instances of discovery

    6.1 Layer Adjacency Discovery

    Layer Adjacency Discovery can be described as a process that is used for deriving an association between two SNTPs that form a link connection in a particular layer network. The association created through layer adjacency discovery is valid so long as the trail supporting the link connection is valid.

    6.2 Physical Media Adjacency Discovery

    Physical media adjacency discovery can be described as a process that is used for verifying the physical connectivity (connected over fiber or any other physical media) between two ports on physical media adjacent network elements in the network. For example, physical media adjacency discovery can aid in improving inventory of network resources, verifying port characteristics of physically media adjacent network elements, etc.

    6.3 Control Entity Logical Adjacency Establishment

    Control Entity Logical Adjacency Establishment is the process of creating a logical adjacency between two control entities that control SNTPs that are associated through layer adjacency discovery.

    7 Layer adjacency discovery

    In Section 6, layer adjacency discovery was defined as the association between two SNTPs that forms a link connection.

    Layer adjacency discovery will be used for (a) building layer network topology to aid routing decisions, (b) creating logical adjacencies between control entities and (c) for identifying link ITU-T G.7714/Y.1705 (11/2001) Prepublished version 3

    connection endpoints for purposes of connection management. Figure 7.1 shows an example scenario.

    Client layer Link

    Client layer LC

    Server layer trailSNTP

    CTP

    AP

    Server layer NC

    Figure 7.1/G.7714/Y.1705 Example figure to illustrate layer adjacency discovery.

    In this example, we have two APs that are associated over a server layer NC to form a trail at the server layer and this trail supports the association of three SNTPs in the client layer to form a client layer link composed of three LCs. The layer adjacency discovery process in this example associates the two SNTPs in the server layer (alias to the corresponding network TTPs) and the three SNTPs in the client layer (alias to the client layer CTPs). The purpose served by the server layer NC is to ensure the validity of the trail and hence the validity of the supported client layer LCs. Thus, the associations established at the two layers are valid only as long as the supporting server layer NC is valid.

    For the discovery process to be effective in establishing the associations, it is necessary to provide suitable identification to the end points of the associations, i.e., SNTP IDs have to be assigned. Based on the application that uses the results of the discovery process, the SNTP IDs may be different, e.g.,

    a. Routing: This requires knowledge of the layer network topology. The information relevant to

    the building of the topology are the links and link connection endpoint identifiers. b. Connection Management: This requires knowledge of the CTPs that are associated with the

    SNTPs and the CTP IDs need to be discovered for this application. The CTP ID could be the

    same as the routing address or could be different, e.g., timeslot number, tributary number, etc. Note that although SNTP-SNTP associations are referred to, as link connections, this has to be understood to be “potential link connections” because the SNTP-SNTP association becomes an LC

    only when CTPs that are bound to SNTP get instantiated.

    Note that the SNTP-SNTP associations that exist over an UNI reference point may not be exposed to the user for security of operator proprietary information.

    Although in the above example, it is mentioned that two discovery processes are used to identify the topology of the two layer networks, this is not necessary and methods shown in Annex A and Appendix I may be used to reduce the number of discovery tests.

    ITU-T G.7714/Y.1705 (11/2001) Prepublished version 4

7.1 SNTP Control Entity Logical Adjacency Establishment

    In this phase of discovery, a logical adjacency is established between control entities that control SNTPs that are associated via layer adjacency discovery. The procedures for establishing these adjacencies are beyond the scope of this recommendation, however, for establishing these logical adjacencies it may be necessary to communicate the control entity identifiers as identification attributes as part of the layer adjacency discovery process. After the logical adjacency is established service capability exchange (described in Annex A) can take place.

    8 Physical media adjacency discovery

    In Section 6, physical media adjacency discovery is described as the process of verifying physical connectivity between two ports on physical media adjacent network elements. Depending on the physical packaging of the functions within a network element, different types of associations may need to be discovered as part of physical media adjacency discovery. This is illustrated in Figure 8.1.

    Client Layer Link

    Bound SNTPsBound SNTPs

    Media Layer

    Trail

    TTPTTP

    Media Layer NC

    Permanent Connection

    Figure 8.1/G.7714/Y.1705 Example to illustrate physical media adjacency discovery.

    In this example, there are two TTPs are associated through a media layer network connection which is a permanent connection (so long as there are no fault conditions on the media layer, e.g., fiber break). A media layer trail is supported over this media layer NC. The client layer link contains three link connections which are the associations between the instantiated CTPs or the bound SNTPs. If the bound SNTPs are contained within the same network element that contains the media layer termination function, then the SNTP to CTP association is internal to the network element and does not require any discovery tests to be performed. This is illustrated in Figure 8.2 ITU-T G.7714/Y.1705 (11/2001) Prepublished version 5

    Client Layer Link

    Media Layer

    Trail

    TTPTTP

    Media Layer NC

    Network ElementNetwork ElementPermanent Connection

    Figure 8.2/G.7714/Y.1705. Example to illustrate physical media adjacency discovery when SNTPs and

    associated CTPs are contained within the same network element.

    8.1 Port Control Entity Logical Adjacency Establishment

    In this phase of discovery, a logical adjacency is established between control entities that control ports that are associated via physical media adjacency discovery. The procedures for establishing these adjacencies are beyond the scope of this recommendation, however, for establishing these logical adjacencies it may be necessary to communicate the control entity identifiers as identification attributes as part of the physical media adjacency discovery process. After the logical adjacency is established service capability exchange (described in Annex A) can take place. 9 Discovery attributes list

    Attribute

    LAD Attributes

    A-end SNTP Id

    B-end SNTP Id

    A-end SNTPpool Id

    B-end SNTPpool Id

    A-end SNTP control entity Id

    B-end SNTP control entity Id

    PMAD Attributes

    A-end Port Id

    B-end Port Id

    A-end Port control entity Id

    B-end Port control entity Id

ITU-T G.7714/Y.1705 (11/2001) Prepublished version 6

9.1 LAD Attributes

    A-end SNTP Id Identifier of near end SNTP of the association

     to be discovered.

B-end SNTP Id Identifier of far end SNTP of the association

     to be discovered

A-end SNTPpool Id Identifier of near end SNTPpool of the

     association to be discovered

B-end SNTPpool Id Identifier of the far-end SNTPpool of the

     association to be discovered.

A-end SNTP control entity Id Identifier of the control entity that controls the

     A-end SNTP.

B-end SNTP control entity Id Identifier of the control entity that controls the

     B-end SNTP.

9.2 PMAD Attributes

    A-end Port Id Port Identifier for the A-end of the media layer

     association.

B-end Port Id Port Identifier for the B-end of the media layer

     association.

A-end Port control entity Identifier of the control entity that controls the A-

    Id end port. Note that this Port control entity

     identifier need not be the same as the SNTP

     control entity identifier used in the LAD

     attributes.

B-end Port control entity Identifier of the control entity that controls the B-

    Id end port. Note that this Port control entity

     identifier need not be the same as the SNTP

    control entity identifier used in the LAD

    attributes.

10 Discovery message

    The LAD, and PMAD processes can be effected using a message based scheme which exchanges identity attributes. Note that neither the actual protocol specific attributes nor the protocol mechanisms are discussed here. There is no assumption made on whether the same or different protocols are needed for the different instances of discovery. The actual protocol may operate in either an acknowledged or unacknowledged mode. In the acknowledged mode the discovery message might carry the near end identity attributes and the acknowledgement can carry the far end identity attributes in response to the received near end attributes. Additionally, the service ITU-T G.7714/Y.1705 (11/2001) Prepublished version 7

    capability information may also be carried as part of the acknowledgement. In the unacknowledged mode either end send their respective identity attributes and service capability exchange is done at a different time. In either mode the messages are expected to be sent at least until the discovery process is completed. Section 10.1 and 10.2 show the attributes for an acknowledged discovery process.

    10.1 HELLO: Discovery

    Attribute

    LAD Attributes

    A-end SNTP Id

    A-end SNTPpool Id

    A-end SNTP control entity Id

    PMAD Attributes

    A-end Port Id

    A-end Port control entity Id

10.2 HELLO_ACK: Discovery Response

    Attribute

    LAD Attributes

    B-end SNTP Id

    B-end SNTPpool Id

    B-end SNTP control entity Id

    PMAD Attributes

    B-end Port Id

    B-end Port control entity Id

    11 Discovery process flow

    The overall discovery process flow (shown in Figure 11.1) is a generic process that is applicable to both LAD and PMAD. However, LAD and PMAD occur at different times in the network. The detailed state machines for the LAD and PMAD processes are shown in the subsections. The state machines for CELA and SCE are not discussed in this recommendation.

    ITU-T G.7714/Y.1705 (11/2001) Prepublished version 8

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