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PCE Working Group                                                H. Chen
Internet-Draft                                       Huawei Technologies
Intended status: Standards Track                                  M. Toy
Expires: May 4, 2017
                                                                  L. Liu
                                                                 Fujitsu
                                                                   Z. Li
                                                            China Mobile
                                                        October 31, 2016


             Connections and Accesses for Hierarchical PCE
                   draft-chen-pce-h-connect-access-01

Abstract

   This document presents extensions to the Path Computation Element
   Communication Protocol (PCEP) to distribute information about
   connections and access points 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 May 4, 2017.

Copyright Notice

   Copyright (c) 2016 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
   carefully, as they describe your rights and restrictions with respect



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   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.  Extension to Existing Message  . . . . . . . . . . . . . .  6
       5.1.1.  TLVs . . . . . . . . . . . . . . . . . . . . . . . . .  6
       5.1.2.  Sub-TLVs . . . . . . . . . . . . . . . . . . . . . . .  8
     5.2.  Procedures . . . . . . . . . . . . . . . . . . . . . . . .  9
       5.2.1.  Child Procedures . . . . . . . . . . . . . . . . . . .  9
       5.2.2.  Parent Procedures  . . . . . . . . . . . . . . . . . . 12
   6.  Security Considerations  . . . . . . . . . . . . . . . . . . . 12
   7.  IANA Considerations  . . . . . . . . . . . . . . . . . . . . . 12
   8.  Acknowledgement  . . . . . . . . . . . . . . . . . . . . . . . 12
   9.  References . . . . . . . . . . . . . . . . . . . . . . . . . . 12
     9.1.  Normative References . . . . . . . . . . . . . . . . . . . 12
     9.2.  Informative References . . . . . . . . . . . . . . . . . . 13
   Appendix A.  New Message . . . . . . . . . . . . . . . . . . . . . 13
     A.1.  CONNECTION and ACCESS Object . . . . . . . . . . . . . . . 14
     A.2.  TLVs in CONNECTION and ACCESS Object . . . . . . . . . . . 16





















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1.  Introduction

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

   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 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 and for a parent
   PCE to build and maintain the domain topology as well as access
   points.  The extensions may reduce configurations, thus simplify
   operations on a PCE system.

2.  Terminology

   The following terminology is used in this document.

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

   ASBR:  Autonomous System Border Router.  Router used to connect
      together ASes of the same or different service providers via one
      or more 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 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: Point-to-point
     2)  Local IP address of the link
     3)  Remote IP address of the link
     4)  Traffic engineering metric of the link
     5)  Maximum bandwidth of the link
     6)  Maximum reservable bandwidth of the link
     7)  Unreserved bandwidth of the link
     8)  Administrative group of the link


   Note that 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), 5), 6), 7) and 8), but does not include
   any remote IP address or link ID.  Note that no link ID (i.e., the
   interface address of the designated router for the link) may be
   obtained since no IGP selects it.



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   A parent PCE constructs an AS domain topology after receiving the
   information about each of the inter-domain links described above from
   its child PCEs plus the local node ID such as A's ID.

   A PCE such as a child PCE can constructs a TED for the domain for
   which the PCE is responsible after receiving the information
   described above about each of the links attached to the nodes in the
   domain from the PCCs running on the nodes without running IGP.

   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 PCE the information
   about the ABR, which indicates the identifier (ID) of the ABR.

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

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 PCE
   the information about the address, which indicates the address.




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   The parent PCE has all the access points (i.e., IP addresses) to be
   accessible outside of all its child PCEs' domains after receiving the
   information on the access points from each of its child PCEs.

5.  Extensions to PCEP

   This section describes the extensions to PCEP to distribute the
   information about inter-domain links, ABRs and access points.  The
   information is sent from a child PCE to its parent PCE.  A child PCE
   is simply called a child and a parent PCE is called a parent in the
   following sections.

5.1.  Extension to Existing Message

   An existing Notification message may be extended to advertise the
   information about connections and access points.  Alternatively, a
   new message can be used (refer to Appendix A).

   The following new Notification-type (NT) and Notification-value (NV)
   of a NOTIFICATION object in a Notification message are defined:

   o  NT=8 (TBD): Connections and Accesses

      *  NV=1: Updates on 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 NOTIFICATION object.  The format and
         contents of the TLVs are described below.

      *  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 the TLVs in the object.

5.1.1.  TLVs

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

   The format of the Inter-Domain link TLV is illustrated below.  The
   Type=tTBD1 indicates an Inter-Domain link TLV Type.  The Length
   indicates the size of the Inter-Domain Link Sub-TLVs.









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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 (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 4.1, 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.  The Type=tTBD2
   indicates a Router-ID TLV Type.  The Length indicates the size of the
   ID and flags field.

      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)


   Undefined flags MUST 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.

   The format of the Access IPv4 Prefix TLV is shown as follows.  The
   Type=tTBD3 indicates an Access IPv4 Address Prefix TLV Type.  The
   Length indicates the size of the IPv4 prefix and Prefix Length.  The
   Prefix Length indicates the length of the IPv4 prefix.  The IPv4
   Prefix indicates an access IPv4 address prefix.






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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 (tTBD3)          |             Length            |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     | Prefix Length | IPv4 Prefix (variable)                        ~
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   The format of the Access IPv6 Prefix TLV is illustrated below.  The
   Type=tTBD4 indicates an Access IPv6 Address Prefix TLV Type.  The
   Length indicates the size of the IPv6 prefix and Prefix Length.  The
   Prefix Length indicates the length of the IPv6 prefix.  The IPv6
   Prefix indicates an access 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 (tTBD4)          |             Length            |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     | Prefix Length | IPv6 Prefix (variable)                        ~
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


5.1.2.  Sub-TLVs

   The format of the Sub-TLV for a local IPv4 address with mask length
   is shown as follows.  The Type=stTBD1 indicates a local IPv4 Address
   with mask length.  The Length indicates the size of the IPv4 address
   and Mask Length.  The IPv4 Address indicates the local IPv4 address
   of a link.  The Mask Length indicates the length of the IPv4 address
   mask.

      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)         |             Length            |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                          IPv4 Address                         |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |  Mask Length  |
     +-+-+-+-+-+-+-+-+


   The format of the Sub-TLV for a local IPv6 address with mask length
   is illustrated below.  The Type=stTBD2 indicates a local IPv6 Address
   with mask length.  The Length indicates the size of the IPv6 address
   and Mask Length.  The IPv6 Address indicates the local IPv6 address



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   of a link.  The Mask Length indicates the length of the IPv6 address
   mask.

      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 (stTBD2)         |             Length            |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                        IPv6 Address (16 bytes)                |
     ~                                                               ~
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |  Mask Length  |
     +-+-+-+-+-+-+-+-+


5.2.  Procedures

5.2.1.  Child Procedures

   1.  New or Changed Connections and Accesses

   After a child discovers its parent, it sends the parent messages that
   contain 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.

   When there are changes on the connections and the accesses of the
   domain, the child sends its parent messages for the changed
   connections and accesses.

   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 messages containing the information about these links, ABRs
   and access points with indication of Updates on Connections and
   Accesses.

   For example, for a new inter-domain point-to-point link from ASBR A
   in a child's domain to ASBR B in another domain, the child may send
   its parent a Notification message having a NOTIFICATION object with
   NT=8 and NV=1 (indicating Updates on Connections and Accesses), which
   contains a Router-ID TLV, followed by an Inter-domain link TLV.  The
   Router-ID TLV comprises the ID of ASBR A and flag E and I set to 1.
   The Inter-domain link TLV comprises the Sub-TLVs for the information
   on 1) to 8) described in section 4.1.

   For multiple new or changed inter-domain links from ASBR A, the child
   may send its parent a Notification message having a NOTIFICATION
   object with NT=8 and NV=1, which contains a Router-ID TLV for the ID



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   of ASBR A, followed by multiple Inter-domain link TLVs for the links
   from ASBR A. If A is also an ABR, in addition to setting flag E and I
   to 1, the child sets flag B to 1 in the Router-ID TLV.  Thus this one
   message contains the information about multiple inter-domains links
   and an ABR.

   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 in a
   child's domain, the child may send its parent a Notification message
   having a NOTIFICATION object with NT=8 and NV=1, which contains a
   Router-ID TLV for the ID of ASBR X, followed by an Inter-domain link
   TLV for the link attached to ASBR X, another Router-ID TLV for the ID
   of ABR Y with flag B set to 1, and an Access IPv4 Prefix TLV with
   10.10.10.1 and Prefix Length = 32.  The Inter-domain link TLV
   comprises the Sub-TLVs for the information on a), b), 4), 5), 6), 7)
   and 8) described in section 4.1.

   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.

   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 messages
   containing the information about these links, ABRs and access points
   with indication of Withdraw Connections and Accesses.

   For example, for the inter-domain point-to-point link from ASBR A to
   ASBR B down, the child may send its parent a Notification message
   having a NOTIFICATION object with NT=8 and NV=2 (indicating Withdraw
   Connections and Accesses), which contains a Router-ID TLV, followed
   by an Inter-domain link TLV.  The Router-ID TLV comprises the ID of
   ASBR A and flag E and I set to 1.  The Inter-domain link TLV
   comprises the Sub-TLVs for the information on 1), 2) and 3) described
   in section 4.1.

   For multiple inter-domain links from ASBR A down, the child may send
   its parent a Notification message having a NOTIFICATION object with
   NT=8 and NV=2, which contains a Router-ID TLV for the ID of ASBR A,
   followed by multiple Inter-domain link TLVs for the links from ASBR



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   A. The TLV for a point-to-point link comprises the Sub-TLVs for the
   information on 1), 2) and 3) described in section 4.1.  The TLV for a
   broadcast link comprises the Sub-TLVs for the information on a) and
   b) described in section 4.1.

   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, the
   parent can compute a path crossing these domains directly and
   efficiently without sending any path computation request to its
   children.

   4.  Child as a Parent

   There are a number of ways in which a child as a parent abstracts or
   summarizes the domain information it has to its parent.

   One way is that the child sends its parent all the domain information
   it has if the child and the parent are in a same organization.  The
   information includes the network topology inside a domain if the
   child responsible for the domain is in the same organization.  The
   information contains 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 the domains that its children
   are responsible as a cloud.  This 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



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   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

   A parent stores the connections and accesses for each of its children
   according to the messages for connections and accesses received.  For
   a message containing updates on connections and accesses, it updates
   the connections and accesses accordingly.  For a message containing
   withdraw connections and accesses, it removes the connections and
   accesses.

   When a child is down, its parent removes the connections and accesses
   of the child's domain.

   After receiving the messages for connections and accesses from its
   children, a parent builds and maintains a 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.

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.

8.  Acknowledgement

   The authors would like to thank Eric Wu and others 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,
              <http://www.rfc-editor.org/info/rfc2119>.



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

Appendix A.  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 points (AC for short) is as
   follows:







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     <AC Message> ::= <Common Header>
                      <NRP>
                      <Connection-List>
                      [<Access-Address-List>]
     where:
       <Connection-List> ::= <Connection>
                             [<Connection-List>]
       <Connection> ::= [<Inter-Domain-Link> | <ABR>]
       <Access-Address-List> ::= <Access-Address>
                                 [<Access-Address-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 points are withdrawn.  When flag W
   is set to one, the parent removes the connections and accesses
   contained in the message after receiving it from its child.  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.

   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.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.







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     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:

        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 Prefix object body is as follows:




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        Object-Class = ocTBD1 (Connection and Access)
        Object-Type = 3 (CA Access IPv4 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 Prefix TLVs             |
     +-+-+-+-+-+-+-+-+                                               +
     ~                                                               ~
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   Each of the Access IPv4 Prefix TLVs describes an access IPv4 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 format of Access IPv6 Prefix object body is shown below:

        Object-Class = ocTBD1 (Connection and Access)
        Object-Type = 4 (CA Access 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 IPv6 Prefix TLVs             |
     +-+-+-+-+-+-+-+-+                                               +
     ~                                                               ~
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


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

A.2.  TLVs in CONNECTION and ACCESS Object

   The format of the Router-ID 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            |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                          32-bit/48-bit ID                     ~
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   The format of the Access IPv4 Prefix TLV 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 (tTBD2)          |             Length            |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     | Prefix Length | IPv4 Prefix (variable)                        ~
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   The format of the Access IPv6 Prefix 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 (tTBD3)          |             Length            |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     | Prefix Length | IPv6 Prefix (variable)                        ~
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   The format of the Inter-Domain link TLV is shown 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 (tTBD4)          |             Length            |
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
     |                 Inter-Domain Link Sub-TLVs                    |
     ~                                                               ~
     +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+


   The inter-domain link sub-TLVs are for the information on a link
   described in section 4.1, which are the sub-TLVs defined in RFC 3630
   or their equivalents except for local IP address with mask length.

Authors' Addresses

   Huaimo Chen
   Huawei Technologies
   Boston, MA,
   USA

   EMail: Huaimo.chen@huawei.com







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   Mehmet Toy
   USA

   EMail: mtoy054@yahoo.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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