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PCE Working Group                                                H. Chen
Internet-Draft                                       Huawei Technologies
Intended status: Standards Track                                  M. Toy
Expires: March 15, 2018                                          Verizon
                                                                  X. Liu
                                                                   Jabil
                                                                  L. Liu
                                                                 Fujitsu
                                                                   Z. Li
                                                            China Mobile
                                                      September 11, 2017


                      PCEP Link State Abstraction
                   draft-chen-pce-h-connect-access-03

Abstract

   This document presents extensions to the Path Computation Element
   Communication Protocol (PCEP) for a child PCE to abstract its domain
   information to its parent for supporting a hierarchical PCE system.

Status of This Memo

   This Internet-Draft is submitted in full conformance with the
   provisions of BCP 78 and BCP 79.

   Internet-Drafts are working documents of the Internet Engineering
   Task Force (IETF).  Note that other groups may also distribute
   working documents as Internet-Drafts.  The list of current Internet-
   Drafts is at http://datatracker.ietf.org/drafts/current/.

   Internet-Drafts are draft documents valid for a maximum of six months
   and may be updated, replaced, or obsoleted by other documents at any
   time.  It is inappropriate to use Internet-Drafts as reference
   material or to cite them other than as "work in progress."

   This Internet-Draft will expire on March 15, 2018.

Copyright Notice

   Copyright (c) 2017 IETF Trust and the persons identified as the
   document authors.  All rights reserved.

   This document is subject to BCP 78 and the IETF Trust's Legal
   Provisions Relating to IETF Documents
   (http://trustee.ietf.org/license-info) in effect on the date of
   publication of this document.  Please review these documents



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   carefully, as they describe your rights and restrictions with respect
   to this document.  Code Components extracted from this document must
   include Simplified BSD License text as described in Section 4.e of
   the Trust Legal Provisions and are provided without warranty as
   described in the Simplified BSD License.

Table of Contents

   1.  Introduction . . . . . . . . . . . . . . . . . . . . . . . . .  3
   2.  Terminology  . . . . . . . . . . . . . . . . . . . . . . . . .  3
   3.  Conventions Used in This Document  . . . . . . . . . . . . . .  3
   4.  Connections and Accesses . . . . . . . . . . . . . . . . . . .  4
     4.1.  Information on Inter-domain Link . . . . . . . . . . . . .  4
     4.2.  Information on ABR . . . . . . . . . . . . . . . . . . . .  5
     4.3.  Information on Access Point  . . . . . . . . . . . . . . .  5
   5.  Extensions to PCEP . . . . . . . . . . . . . . . . . . . . . .  6
     5.1.  Messages for Abstract Information  . . . . . . . . . . . .  6
     5.2.  Procedures . . . . . . . . . . . . . . . . . . . . . . . .  7
       5.2.1.  Child Procedures . . . . . . . . . . . . . . . . . . .  7
       5.2.2.  Parent Procedures  . . . . . . . . . . . . . . . . . .  9
   6.  Security Considerations  . . . . . . . . . . . . . . . . . . . 10
   7.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 10
   8.  Acknowledgement  . . . . . . . . . . . . . . . . . . . . . . . 11
   9.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 11
     9.1.  Normative References . . . . . . . . . . . . . . . . . . . 11
     9.2.  Informative References . . . . . . . . . . . . . . . . . . 11
   Appendix A.  Message Encoding  . . . . . . . . . . . . . . . . . . 12
     A.1.  Extension to Existing Message  . . . . . . . . . . . . . . 12
       A.1.1.  TLVs . . . . . . . . . . . . . . . . . . . . . . . . . 12
       A.1.2.  Sub-TLVs . . . . . . . . . . . . . . . . . . . . . . . 13
     A.2.  New Message  . . . . . . . . . . . . . . . . . . . . . . . 14
       A.2.1.  CONNECTION and ACCESS Object . . . . . . . . . . . . . 15



















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1.  Introduction

   A hierarchical PCE architecture is described in RFC 6805, in which a
   parent PCE maintains an abstract domain topology, which contains its
   child domains (seen as vertices in the topology) and the connections
   among them.

   For a domain for which a child PCE is responsible, connections
   attached to the domain may comprise inter-domain links and Area
   Border Routers (ABRs).  For a parent PCE to have the abstract domain
   topology, each of its child PCEs needs to advertise its connections
   to the parent PCE.

   In addition to the connections attached to the domain, there may be
   some access points in the domain, which are the addresses in the
   domain to be accessible outside of the domain.  For example, an
   address of a server in the domain that provides a number of services
   to users outside of the domain is an access point.

   This document presents extensions to the Path Computation Element
   Communication Protocol (PCEP) for a child PCE to advertise the
   information about its connections and access points to its parent PCE
   and for the parent PCE to build and maintain the abstract domain
   topology based on the information.  The extensions may reduce
   configurations, thus simplify operations on a PCE system.

   A child PCE is simply called a child and a parent PCE is called a
   parent in the following sections.

2.  Terminology

   ABR:  Area Border Router.  Router used to connect two IGP areas
      (Areas in OSPF or levels in IS-IS).

   ASBR:  Autonomous System (AS) Border Router.  Router used to connect
      together ASes via inter-AS links.

   TED:  Traffic Engineering Database.

   This document uses terminology defined in [RFC5440].

3.  Conventions Used in This Document

   The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
   "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
   document are to be interpreted as described in [RFC2119].





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4.  Connections and Accesses

   A connection is an inter-domain link between two domains in general.
   An ABR is also a connection, which connects two special domains
   called areas in a same Autonomous System (AS).

   An access point in a domain is an address in the domain to be
   accessible to the outside of the domain.  An access point is simply
   called an access.

4.1.  Information on Inter-domain Link

   An inter-domain link connects two domains in two different ASes.
   Since there is no IGP running over an inter-domain link, we may not
   obtain the information about the link generated by an IGP.  We may
   suppose that IP addresses are configured on inter-domain links.

   For a point-to-point (P2P) link connecting two ABSRs A and B in two
   different domains, from A's point of view, the following information
   about the link may be obtained:

     1)  Link Type: P2P
     2)  Local IP address
     3)  Remote IP address
     4)  Traffic engineering metric
     5)  Maximum bandwidth
     6)  Maximum reservable bandwidth
     7)  Unreserved bandwidth
     8)  Administrative group
     9)  SRLG


   We will have a link ID if it is configured; otherwise no link ID
   (i.e., the Router ID of the neighbor) may be obtained since no IGP
   adjacency over the link is formed.

   For a broadcast link connecting multiple ASBRs in a number of
   domains, on each of the ASBRs X, the same information about the link
   as above may be obtained except for the followings:

     a)  Link Type: Multi-access,
     b)  Local IP address with mask length, and
     c)  No Remote IP address.


   In other words, the information about the broadcast link obtained by
   ASBR X comprises a), b), 4) to 9), but does not include any remote IP
   address or link ID.  We will have a link ID if it is configured;



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   otherwise no link ID (i.e., the interface address of the designated
   router for the link) may be obtained since no IGP selects it.

   A parent constructs an abstract AS domain topology after receiving
   the information about each of the inter-domain links described above
   from its children.

   RFC 5392 and RFC 5316 describe the distributions of inter-domain
   links in OSPF and IS-IS respectively.  For each inter-domain link,
   its neighboring AS number and neighboring ASBR Identity (TE Router
   ID) need to be configured in IGP (OSPF or IS-IS).

   In addition, an IGP adjacency between a network node running IGP and
   a PCE running IGP as a component needs to be configured and fully
   established if we want the PCE to obtain the inter-domain link
   information from IGP.

   These configurations and IGP adjacency establishment are not needed
   if the extensions in this draft are used.

   RFC 7752 (BGP-LS) describes the distributions of TE link state
   information including inter-domain link state.  A BGP peer between a
   network node running BGP and a PCE running BGP as a component needs
   to be configured and the peer relation must be established before the
   PCE can obtain the inter-domain link information from BGP.  However,
   some networks may not run BGP.

4.2.  Information on ABR

   For an AS running IGP and containing multiple areas, an ABR connects
   two or more areas.  For each area connected to the ABR, the PCE as a
   child responsible for the area sends its parent the information about
   the ABR, which indicates the identifier (ID) of the ABR.

   A parent has the information about each of its children, which
   includes the domain such as the area for which the child is
   responsible.  The parent knows all the areas to which each ABR
   connects after receiving the information on the ABR from each of its
   children.

4.3.  Information on Access Point

   For an IP address in a domain to be accessible outside of the domain,
   the PCE as a child responsible for the domain sends its parent the
   information about the address.

   The parent has all the access points (i.e., IP addresses) to be
   accessible outside of all its children' domains after receiving the



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   information on the access points from each of its children.

5.  Extensions to PCEP

   This section focuses on procedures for abstracting domain information
   after briefing messages containing the abstract information.

5.1.  Messages for Abstract Information

   A child abstracts its domain to its parent through sending its parent
   a message containing the abstract information on the domain.  After
   the relation between the child and the parent is determined, the
   parent has some information on the child, which includes the child's
   ID and domain.  The message does not need to contain this
   information.  It comprises the followings:

   o  For new or updated Connections and Accesses,

      *  Indication of Update Connections and Accesses

      *  Detail Information about Connections and Accesses

   o  For Connections and Accesses down,

      *  Indication of Withdraw Connections and Accesses

      *  ID Information about Connections and Accesses

   For a P2P link from ASBR A to B and a broadcast link connecting to A,
   the detail information on the links includes A's ID, the information
   on the P2P link and the information on the broadcast link described
   in Section 4.  The ID information on the links includes A's ID, 1) to
   3) for the P2P link and a) to b) for the broadcast link described in
   Section 4.  A link ID for a link is included if it is configured.

   For an ABR X, the information on X includes X's ID and a flag
   indicating that X is ABR.

   For an Access X (address), the detail information on X includes X and
   a cost associated with it.  The ID information on X is X itself.

   There are a few ways to encode the information above into a message.
   For example, one way is to extend an existing Notification message
   for including the information.  Another way is to use a new message.
   These are put in Appendix A for your reference.






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5.2.  Procedures

5.2.1.  Child Procedures

5.2.1.1.  New or Changed Connections and Accesses

   After a child determines its parent, it sends the parent a message
   containing the information about the connections (i.e., inter-domain
   links and ABRs) from its domain to its adjacent domains and the
   access points in its domain.

   For any new or changed inter-domain links, ABRs and access points in
   the domain for which a child is responsible, the child sends its
   parent a message containing the information about these links, ABRs
   and access points with indication of Update Connections and Accesses.

   For example, for a new inter-domain P2P link from ASBR A in a child's
   domain to ASBR B in another domain, the child sends its parent a
   message containing an indication of Update Connections and Accesses,
   A's ID, and the detail information on the link described in section
   4.1.

   For multiple new or changed inter-domain links from ASBR A, the child
   sends its parent a message having an indication of Update Connections
   and Accesses, and A's ID followed by the detail information about
   each of the links.

   In another example, for a new or changed inter-domain broadcast link
   connected to ASBR X, an ABR Y and an access point 10.10.10.1/32 with
   cost 10 in a child's domain, the child sends its parent a message
   containing an indication of Update Connections and Accesses, and X's
   ID followed by the detail information about the link attached to X
   and the detail information about ABR Y, and the information on access
   10.10.10.1/32 with cost 10.

   For changes on the attributes (such as bandwidth) of an inter-domain
   link, a threshold may be used to control the frequency of updates
   that are sent from a child to its parent.  At one extreme, the
   threshold is set to let a child send its parent a update message for
   any change on the attributes of an inter-domain link.  At another
   extreme, the threshold is set to make a child not to send its parent
   any update message for any change on the attributes of an inter-
   domain link.  Typically, the threshold is set to allow a child to
   send its parent a update message for a significant change on the
   attributes of an inter-domain link.






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5.2.1.2.  Connections and Accesses Down

   For any inter-domain links, ABRs and access points down in the domain
   for which a child is responsible, the child sends its parent a
   message containing the information about these links, ABRs and access
   points with indication of Withdraw Connections and Accesses.

   For example, for the inter-domain P2P link from ASBR A down, the
   child sends its parent a message containing an indication of Withdraw
   Connections and Accesses, and A's ID, which is followed by the ID
   information about the link.

   For multiple inter-domain links from ASBR A down, the child sends its
   parent a message having an indication of Withdraw Connections and
   Accesses, and A's ID, which is followed by the ID information about
   each of the links.

5.2.1.3.  Child and Parent in Same Organization

   If a child and its parent are in a same organization, the child may
   send its parent the information inside its domain.  For a parent,
   after all its children in its organization send their parent the
   information in their domains, connections and access points, it has
   in its TED the detail information inside each of its children's
   domains and the connections among these domains.  The parent can
   compute a path crossing these domains directly and efficiently
   without sending any path computation request to its children.

5.2.1.4.  Child as a Parent

   There are a few ways in which a child as a parent abstracts its
   domain information to its parent.

   One way is that the child sends its parent all its domain information
   if the child and the parent are in a same organization.  The
   information includes the detail network topology inside each of the
   child's domains, the inter-domain links connecting the domains that
   the child's children are responsible and the inter-domain links
   connecting these domains to other adjacent domains.

   In another way, the child abstracts each of the domains that its
   children are responsible as a cloud (or say abstract node) and these
   clouds are connected by the inter-domain links attached to the
   domains.  The child sends its parent all the inter-domain links
   attached to any of the domains.

   In a third way, the child abstracts all its domains including the
   domains for which its children are responsible as a cloud.  This



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   abstraction is described below in details.

   If a parent P1 is also a child of another parent P2, P1 as a child
   sends its parent P2 a message containing the information about the
   connections and access points.  P1 as a parent has the connections
   among its children's domains.  But these connections are hidden from
   its parent P2.  P1 may have connections from its children's domains
   to other domains.  P1 as a child sends its parent P2 these
   connections.

   P1 as a parent has the access points in its children's domains to be
   accessible outside of the domains.  P1 as child may not send all of
   these to its parent P2.  It sends its parent some of these access
   points according to some local policies.

   From P2's point of view, its child P1 is responsible for one domain,
   which has some connections to its adjacent domains and some access
   points to be accessible.

5.2.2.  Parent Procedures

5.2.2.1.  Process Connections and Accesses

   A parent stores into its TED the connections and accesses for each of
   its children according to the messages containing connections and
   accesses received.  For a message containing Update Connections and
   Accesses, it updates the connections and accesses in the TED
   accordingly.  For a message containing Withdraw Connections and
   Accesses, it removes the connections and accesses from the TED.

   After receiving the messages for connections and accesses from its
   children, the parent builds and maintains the TED for the topology of
   its children's domains, in which each of the domains is seen as a
   cloud or an abstract node.  The information inside each of the
   domains is hidden from the parent.  There are connections among the
   domains and the access points in the domains to be accessible in the
   topology.

   For a new P2P link from node A to B with no link ID configured, when
   receiving a message containing the link from a child, the parent
   stores the link from A into its TED, where A is attached to the
   child's domain as a cloud.  It finds the link's remote end B using
   the remote IP address of the link.  After finding B, it associates
   the link attached to A with B and the link attached to B with A. This
   creates a bidirectional connection between A and B.

   For a new P2P link from node A to B with link ID configured, when
   receiving a message containing the link, the parent stores the link



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   from A into its TED.  It finds the link's remote end B using the link
   ID (i.e., B's ID).

   For a new broadcast link connecting multiple nodes with no link ID
   configured, when the parent receives a message containing the link
   attached to node X, it stores the link from X into its TED.  It finds
   the link's remote end P using the link's local IP address with
   network mask.  P is a Pseudo node identified by the local IP address
   of the designated node selected from the nodes connected to the link.
   After finding P, it associates the link attached to X with P and the
   link connected to P with X. If P is not found, a new Pseudo node P is
   created.  The parent associates the link attached to X with P and the
   link attached to P with X. This creates a bidirectional connection
   between X and P.

   The first node and second node from which the parent receives a
   message containing the link is selected as the designed node and
   backup designed node respectively.  After the designed node is down,
   the backup designed node becomes the designed node and the node other
   than the designed node with the largest local IP address connecting
   to the link is selected as the backup designed node.

   When the old designed node is down and the backup designed node
   becomes the new designed node, the parent updates its TED through
   removing the link between each of nodes X and old P (the Pseudo node
   corresponding to the old designed node) and adding a link between
   each of nodes X (still connecting to the broadcast link) and new P
   (the Pseudo node corresponding to the new designed node).

5.2.2.2.  Detail Topology in a Domain

   If a parent is in a same organization as its child, it stores into
   its TED the detail information inside the child's domain when
   receiving a message containing the information from the child;
   otherwise, it discards the information and issues a warning
   indicating that the information is sent to a wrong place.

6.  Security Considerations

   The mechanism described in this document does not raise any new
   security issues for the PCEP protocols.

7.  IANA Considerations

   This section specifies requests for IANA allocation.






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8.  Acknowledgement

   The authors would like to thank Jescia Chen, Adrian Farrel, and Eric
   Wu for their valuable comments on this draft.

9.  References

9.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/
              RFC2119, March 1997,
              <https://www.rfc-editor.org/info/rfc2119>.

   [RFC6805]  King, D., Ed. and A. Farrel, Ed., "The Application of the
              Path Computation Element Architecture to the Determination
              of a Sequence of Domains in MPLS and GMPLS", RFC 6805,
              DOI 10.17487/RFC6805, November 2012,
              <https://www.rfc-editor.org/info/rfc6805>.

   [RFC5440]  Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation
              Element (PCE) Communication Protocol (PCEP)", RFC 5440,
              DOI 10.17487/RFC5440, March 2009,
              <https://www.rfc-editor.org/info/rfc5440>.

   [RFC3630]  Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering
              (TE) Extensions to OSPF Version 2", RFC 3630,
              DOI 10.17487/RFC3630, September 2003,
              <https://www.rfc-editor.org/info/rfc3630>.

9.2.  Informative References

   [RFC5305]  Li, T. and H. Smit, "IS-IS Extensions for Traffic
              Engineering", RFC 5305, DOI 10.17487/RFC5305,
              October 2008, <https://www.rfc-editor.org/info/rfc5305>.

   [RFC5392]  Chen, M., Zhang, R., and X. Duan, "OSPF Extensions in
              Support of Inter-Autonomous System (AS) MPLS and GMPLS
              Traffic Engineering", RFC 5392, DOI 10.17487/RFC5392,
              January 2009, <https://www.rfc-editor.org/info/rfc5392>.

   [RFC5316]  Chen, M., Zhang, R., and X. Duan, "ISIS Extensions in
              Support of Inter-Autonomous System (AS) MPLS and GMPLS
              Traffic Engineering", RFC 5316, DOI 10.17487/RFC5316,
              December 2008, <https://www.rfc-editor.org/info/rfc5316>.

   [RFC7752]  Gredler, H., Ed., Medved, J., Previdi, S., Farrel, A., and
              S. Ray, "North-Bound Distribution of Link-State and



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              Traffic Engineering (TE) Information Using BGP", RFC 7752,
              DOI 10.17487/RFC7752, March 2016,
              <https://www.rfc-editor.org/info/rfc7752>.

Appendix A.  Message Encoding

A.1.  Extension to Existing Message

   An existing Notification message may be extended to advertise the
   information about connections and access points.  The following new
   Notification-type (NT) and Notification-value (NV) of a NOTIFICATION
   object in the message are defined:

   o  NT=8 (TBD): Connections and Accesses

      *  NV=1: Update Connections and Accesses.  A NT=8 and NV=1
         indicates that the child sends its parent updates on the
         information about Connections and Accesses, and TLVs containing
         the information are in the object.

      *  NV=2: Withdraw Connections and Accesses.  A NT=8 and NV=2
         indicates that the child asks its parent to remove Connections
         and Accesses indicated by TLVs in the object.

A.1.1.  TLVs

   Four TLVs are defined for connections and accesses.  They are Inter-
   Domain link TLV, Router-ID TLV, Access IPv4/IPv6 Prefix TLV.

   The format of the Inter-Domain link TLV is illustrated below.

      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |         Type (tTBD1)          |             Length            |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                 Inter-Domain Link Sub-TLVs                    |
     ~                                                               ~
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   An Inter-Domain link TLV describes a single inter-domain link.  It
   comprises a number of inter-domain link sub-TLVs for the information
   described in section 4, which are the sub-TLVs defined in RFC 3630 or
   their equivalents except for the local IP address with mask length
   defined below.

   The format of the Router-ID TLV is shown below.  Undefined flags MUST



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   be set to zero.  The ID indicates the ID of a router.  For a router
   running OSPF, the ID may be the 32-bit OSPF router ID of the router.
   For a router running IS-IS, the ID may be the 48-bit IS-IS router ID
   of the router.  For a router not running OSPF or IS-IS, the ID may be
   the 32-bit ID of the router configured.

      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |         Type (tTBD2)          |             Length            |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |B|E|I|      Flags              |                               |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+                               +
     |                          32-bit/48-bit ID                     ~
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     Flag B:     Set to 1 indicating ABR (B is for Border)
     Flag E:     Set to 1 indicating ASBR (E is for External)
     Flag I:     Set to 1 indicating ID of local router (I is for ID)


   The format of the Access IPv4/IPv6 Prefix TLV is shown as follows.
   The cost is the metric to the prefix.  The Prefix Length indicates
   the length of the prefix.  The IPv4/IPv6 Prefix indicates an access
   IPv4/IPv6 address prefix.

      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |       Type (tTBD3/tTDB4)      |             Length            |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                              cost                             |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     | Prefix Length | IPv4/IPv6 Prefix (variable)                   ~
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


A.1.2.  Sub-TLVs

   The format of the Sub-TLV for a local IPv4/IPv6 address with mask
   length is shown as follows.











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      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |      Type (stTBD1/stTBD2)     |             Length            |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                       IPv4/IPv6 Address                       ~
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |  Mask Length  |
     +-+-+-+-+-+-+-+-+


   The IPv4/IPv6 Address indicates the local IPv4/IPv6 address of a
   link.  The Mask Length indicates the length of the IPv4/IPv6 address
   mask.

A.2.  New Message

   A new message may be defined to advertise the connections and
   accesses from a child to its parent.  The format of the message
   containing Connections and Access (AC for short) is as follows:

     <AC Message> ::= <Common Header> <NRP>
                      <Connection-List> [<Access-List>]
     where:
       <Connection-List> ::= <Connection> [<Connection-List>]
       <Connection> ::= [<Inter-Domain-Link> | <ABR>]
       <Access-List> ::= <Access-Address> [<Access-List>]


   Where the value of the Message-Type in the Common Header indicates
   the new message type.  The exact value is to be assigned by IANA.  A
   new RP (NRP) object will be defined, which follows the Common Header.

   A new flag W (Withdraw) in the NRP object is defined to indicate
   whether the connections and access are withdrawn.  When flag W is set
   to one, the parent removes the connections and accesses contained in
   the message after receiving it.  When flag W is set to zero, the
   parent adds/updates the connections and accesses in the message after
   receiving it.

   An alternative to flag W in the NRP object is a similar flag in each
   CONNECTION and ACCESS object such as using one bit in Res flags for
   flag W. For example, when the flag is set to one in the object, the
   parent removes the connections and accesses in the object after
   receiving it.  When the flag is set to zero in the object, the parent
   adds/updates the connections and accesses in the object after
   receiving it.




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   In another option, one byte in a CONNECTION and ACCESS Object is
   defined as flags field and one bit is used as flag W. The other
   undefined bits in the flags field MUST be set to zero.

   The objects in the new message are defined below.

A.2.1.  CONNECTION and ACCESS Object

   A new object, called CONNECTION and ACCESS Object (CA for short), is
   defined.  It has Object-Class ocTBD1.  Four Object-Types are defined
   under CA object:

     o  CA Inter-Domain Link: CA Object-Type is 1.

     o  CA ABR: CA Object-Type is 2.

     o  CA Access IPv4 Prefix: CA Object-Type is 3.

     o  CA Access IPv6 Prefix: CA Object-Type is 4.

   Each of these objects are described below.

   The format of Inter-Domain Link object body is as follows:

        Object-Class = ocTBD1 (Connection and Access)
        Object-Type = 1 (CA Inter-Domain Link)
      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |W|    Flags    |             Router-ID TLV                     |
     +-+-+-+-+-+-+-+-+                                               +
     ~                                                               ~
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                      Inter-Domain Link TLVs                   |
     ~                                                               ~
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   The Router-ID TLV indicates an ASBR in the domain, which is a local
   end of inter-domain links.  Each of the Inter-Domain Link TLVs
   describes an inter-domain link and comprises a number of inter-domain
   link Sub-TLVs.  Flag W=1 indicates withdraw the links.  W=0 indicates
   new or changed links.

   The format of ABR object body is illustrated below:






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        Object-Class = ocTBD1 (Connection and Access)
        Object-Type = 2 (CA ABR)
      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |W|    Flags    |             Router-ID TLVs                    |
     +-+-+-+-+-+-+-+-+                                               +
     ~                                                               ~
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   Each of the Router-ID TLVs indicates an ABR in the domain.  Flag W=1
   indicates withdraw the ABRs.  W=0 indicates new ABRs.

   The format of Access IPv4/IPv6 Prefix object body is as follows:

        Object-Class = ocTBD1 (Connection and Access)
        Object-Type = 3/4 (CA Access IPv4/IPv6 Prefix)
      0                   1                   2                   3
      0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |W|    Flags    |           Access IPv4/IPv6 Prefix TLVs        |
     +-+-+-+-+-+-+-+-+                                               +
     ~                                                               ~
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   Each of the Access IPv4/IPv6 Prefix TLVs describes an access IPv4/
   IPv6 address prefix in the domain, which is accessible to outside of
   the domain.  Flag W=1 indicates withdraw the address prefixes.  W=0
   indicates new address prefixes.

   The TLVs in the objects are the same as those described above.

Authors' Addresses

   Huaimo Chen
   Huawei Technologies
   Boston, MA,
   USA

   EMail: Huaimo.chen@huawei.com









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   Mehmet Toy
   Verizon
   USA

   EMail: mehmet.toy@verizon.com


   Xufeng Liu
   Jabil
   McLean, VA
   USA

   EMail: Xufeng_Liu@jabil.com


   Lei Liu
   Fujitsu
   USA

   EMail: lliu@us.fujitsu.com


   Zhenqiang Li
   China Mobile
   No.32 Xuanwumenxi Ave., Xicheng District
   Beijing  100032
   P.R. China

   EMail: li_zhenqiang@hotmail.com






















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