



BESS Working Group                                               H. Jeng
Internet-Draft                                                      AT&T
Intended status: Standards Track                                L. Jalil
Expires: September 7, 2015                                       Verizon
                                                               R. Bonica
                                                        Juniper Networks
                                                                K. Patel
                                                           Cisco Systems
                                                                 L. Yong
                                                     Huawei Technologies
                                                           March 6, 2015


           Covering Prefixes Outbound Route Filter for BGP-4
                draft-ietf-bess-orf-covering-prefixes-06

Abstract

   This document defines a new Outbound Route Filter (ORF) type, called
   the "Covering Prefixes ORF (CP-ORF)".  CP-ORF is applicable in
   Virtual Hub-and-Spoke VPNs.  It also is applicable in BGP/MPLS
   Ethernet VPN (EVPN) networks.

Requirements Language

   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 RFC 2119 [RFC2119].

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 September 7, 2015.






Jeng, et al.            Expires September 7, 2015               [Page 1]

Internet-Draft            Covering Prefixes ORF               March 2015


Copyright Notice

   Copyright (c) 2015 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
   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  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Terminology . . . . . . . . . . . . . . . . . . . . . . .   3
   2.  CP-ORF Encoding . . . . . . . . . . . . . . . . . . . . . . .   3
   3.  Processing Rules  . . . . . . . . . . . . . . . . . . . . . .   6
   4.  Applicability In Virtual Hub-and-Spoke VPNs . . . . . . . . .   9
     4.1.  Multicast Considerations  . . . . . . . . . . . . . . . .  12
   5.  Applicability In BGP/MPLS Ethernet VPN (EVPN) . . . . . . . .  12
   6.  Clean-up  . . . . . . . . . . . . . . . . . . . . . . . . . .  16
   7.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .  16
   8.  Security Considerations . . . . . . . . . . . . . . . . . . .  17
   9.  Contributors  . . . . . . . . . . . . . . . . . . . . . . . .  17
   10. Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .  17
   11. References  . . . . . . . . . . . . . . . . . . . . . . . . .  17
     11.1.  Normative References . . . . . . . . . . . . . . . . . .  17
     11.2.  Informative References . . . . . . . . . . . . . . . . .  18
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .  19

1.  Introduction

   A BGP [RFC4271] speaker can send Outbound Route Filters (ORF)
   [RFC5291] to a peer.  The peer uses ORFs to filter routing updates
   that it sends to the BGP speaker.  Using ORF, a BGP speaker can
   realize a "route pull" paradigm, in which the BGP speaker, on demand,
   pulls certain routes from the peer.

   This document defines a new ORF-type, called the "Covering Prefixes
   ORF (CP-ORF)".  A BGP speaker sends a CP-ORF to a peer in order to
   pull routes that cover a specified host address.  A prefix covers a
   host address if it can be used to forward traffic towards that host
   address.  Section 3 provides a more complete description of covering
   prefix selection criteria.



Jeng, et al.            Expires September 7, 2015               [Page 2]

Internet-Draft            Covering Prefixes ORF               March 2015


   CP-ORF is applicable in Virtual Hub-and-Spoke VPNs [RFC7024]
   [RFC4364].  It also is applicable BGP/MPLS Ethernet VPN (EVPN)
   [RFC7432] networks.

1.1.  Terminology

   This document uses the following terms:

   o  Address Family Identifier (AFI) - defined in [RFC4760]

   o  Subsequent Address Family Identifier (SAFI) - defined in [RFC4760]

   o  VPN IP Default Route - defined in [RFC7024].

   o  V-Hub - defined in [RFC7024].

   o  V-Spoke - defined in [RFC7024].

   o  BGP/MPLS Ethernet VPN (EVPN) - defined in [RFC7432]

   o  EVPN Instance (EVI) - defined in [RFC7432]

   o  Unknown MAC Route (UMR) - A regular EVPN MAC/IP Advertisement
      route where the MAC Address Length is set to 48 and the MAC
      address to 00:00:00:00:00:00

   o  Default MAC Gateway (DMG) - An EVPN PE that advertises a UMR

2.  CP-ORF Encoding

   RFC 5291 augments the BGP ROUTE-REFRESH message so that it can carry
   ORF entries.  When the ROUTE-REFRESH message carries ORF entries, it
   includes the following fields:

   o  AFI [IANA.AFI]

   o  SAFI [IANA.SAFI]

   o  When-to-refresh (IMMEDIATE or DEFERRED)

   o  ORF Type

   o  Length (of ORF entries)

   The ROUTE-REFRESH message also contains a list of ORF entries.  Each
   ORF entry contains the following fields:

   o  Action (ADD, REMOVE, or REMOVE-ALL)



Jeng, et al.            Expires September 7, 2015               [Page 3]

Internet-Draft            Covering Prefixes ORF               March 2015


   o  Match (PERMIT or DENY)

   The ORF entry may also contain Type-specific information.  Type-
   specific information is present only when the Action is equal to ADD
   or REMOVE.  It is not present when the Action is equal to REMOVE-ALL.

   When the BGP ROUTE-REFRESH message carries CP-ORF entries, the
   following conditions MUST be true:

   o  ORF Type MUST be equal to CP-ORF (65).

   o  The AFI MUST be equal to IPv4, IPv6 or L2VPN

   o  If the AFI is equal to IPv4 or IPv6, SAFI MUST be equal to MPLS-
      labeled VPN address

   o  If the AFI is equal to L2VPN, the SAFI MUST be equal to BGP EVPN

   o  Match field MUST be equal to PERMIT

   Figure 1 depicts the encoding of the CP-ORF type-specific
   information.

                             +--------------------------------+
                             |  Sequence (32 bits)            |
                             +--------------------------------+
                             |  Minlen   (8 bits)             |
                             +--------------------------------+
                             |  Maxlen   (8 bits)             |
                             +--------------------------------+
                             |  VPN Route Target (64 bits)    |
                             +--------------------------------+
                             |  Import Route Target (64 bits) |
                             +--------------------------------+
                             |  Route Type (8 bits)           |
                             +--------------------------------+
                             |  Host Address                  |
                             |    (0, 32, 48 or 128 bits)     |
                             |           ....
                             +--------------------------------+

                  Figure 1: CP-ORF Type-specific Encoding

   The CP-ORF recipient uses the following fields to select routes
   matching the CP-ORF:

   o  Sequence: Relative position of CP-ORF entry among other CP-ORF
      entries



Jeng, et al.            Expires September 7, 2015               [Page 4]

Internet-Draft            Covering Prefixes ORF               March 2015


   o  Minlen: Minimum length of selected route (measured in bits)

   o  Maxlen: Maximum length of selected route (measured in bits)

   o  VPN Route Target : VPN Route Target carried by selected route

   o  Route Type: Type of selected route

   o  Host Address: Address covered by selected route

   See Section 3 for details.

   The CP-ORF recipient marks routes that match CP-ORF with the Import
   Route Target before advertising those routes to the CP-ORF
   originator.  See Section 3 for details.

   If the ROUTE-REFRESH AFI is equal to IPv4:

   o  The value of Minlen MUST be less than or equal to 32

   o  The value of Maxlen MUST be less than or equal to 32

   o  The value of Minlen MUST be less than or equal to the value of
      Maxlen

   o  The value of Route Type MUST be 0 (i.e., RESERVED)

   o  The Host Address MUST contain exactly 32 bits

   If the ROUTE-REFRESH AFI is equal to IPv6:

   o  The value of Minlen MUST be less than or equal to 128

   o  The value of Maxlen MUST be less than or equal to 128

   o  The value of Minlen MUST be less than or equal to the value of
      Maxlen

   o  The value of Route Type MUST be 0 (i.e., RESERVED)

   o  The Host Address MUST contain exactly 128 bits

   If the ROUTE-REFRESH AFI is equal to L2VPN, the value of Route Type
   MUST be one of the following values, taken from IANA EVPN Registry
   [IANA.EVPN]:

   o  1 - Ethernet Autodiscovery Route




Jeng, et al.            Expires September 7, 2015               [Page 5]

Internet-Draft            Covering Prefixes ORF               March 2015


   o  2 - MAC/IP Advertisement Route

   o  3 - Inclusive Multicast Route

   o  4 - Ethernet Segment Route

   If the ROUTE-REFRESH AFI is equal to L2VPN and the value of Route
   Type is equal to Ethernet Autodiscovery Route, Inclusive Multicast
   Route, or Ethernet Segment Route:

   o  The value of Minlen MUST be equal to 0

   o  The value of Maxlen MUST be equal to 0

   o  The Host Address MUST be absent (i.e., contain 0 bits)

   If the ROUTE-REFRESH AFI is equal to L2VPN and the value of Route
   Type is equal to MAC/IP Advertisement Route:

   o  The value of Minlen MUST be less than or equal to 48

   o  The value of Maxlen MUST be less than or equal to 48

   o  The value of Minlen MUST be less than or equal to the value of
      Maxlen

   o  The Host Address MUST contain exactly 48 bits.

3.  Processing Rules

   According to [RFC4271], every BGP speaker maintains a single Loc-RIB.
   For each of its peers, the BGP speaker also maintains an Outbound
   Filter and an Adj-RIB-Out. The Outbound Filter defines policy that
   determines which Loc-RIB entries are processed into the corresponding
   Adj-RIB-Out. Mechanisms such as RT-Contstrain [RFC4684] and ORF
   [RFC5291] enable a router's peer to influence the Outbound Filter.
   Therefore, the Outbound Filter for a given peer is constructed using
   a combination of the locally configured policy and the information
   received via RT-Constrain and ORF from the peer.

   Using this model we can describe the operations of CP-ORF as follows:

   When a BGP speaker receives a ROUTE-REFRESH message that contains a
   CP-ORF, and that ROUTE-REFRESH message violates any of the encoding
   rules specified in Section 2, the BGP speaker MUST ignore the entire
   ROUTE-REFRESH message.  It SHOULD also log the event.  However, an
   implementation MAY apply logging thresholds to avoid excessive
   messaging or log file overflow.



Jeng, et al.            Expires September 7, 2015               [Page 6]

Internet-Draft            Covering Prefixes ORF               March 2015


   Otherwise, the BGP speaker processes each CP-ORF entry as indicated
   by the Action field.  If the Action is equal to ADD, the BGP speaker
   adds the CP-ORF entry to the Outbound Filter associated with the peer
   in the position specified by the Sequence field.  If the Action is
   equal to REMOVE, the BGP speaker removes the CP-ORF entry from the
   Outbound Filter.  If the Action is equal to REMOVE-ALL, the BGP
   speaker removes all CP-ORF entries from the Outbound Filter.

   Whenever the BGP speaker applies an Outbound Filter to a route
   contained in its Loc-RIB, it evaluates the route in terms of the CP-
   ORF entries first.  It then evaluates the route in terms of the
   remaining, non-CP-ORF entries.  The rules for the former are
   described below.  The rules for the latter are outside the scope of
   this document.

   The following route types can match a CP-ORF:

   o  IPv4-VPN

   o  IPv6-VPN

   o  L2VPN

   In order for an IPv4-VPN route or IPv6-VPN route to match a CP-ORF,
   all of the following conditions MUST be true:

   o  the route carries an RT whose value is the same as the CP-ORF VPN
      Route Target

   o  the route prefix length is greater than or equal to the CP-ORF
      Minlen plus 64 (i.e., the length of a VPN Route Distinguisher)

   o  the route prefix length is less than or equal to the CP-ORF Maxlen
      plus 64 (i.e., the length of a VPN Route Distinguisher)

   o  ignoring the Route Distinguisher, the leading bits of the route
      prefix are identical to the leading bits of the CP-ORF Host
      Address.  CP-ORF Minlen defines the number of bits that must be
      identical.

   o  Loc-RIB does not contain a more specific route that also satisfies
      all of the above listed conditions.

   The BGP speaker ignores Route Distinguishers when determining whether
   a prefix matches a host address.  For example, assume that a CP-ORF
   carries the following information:

   o  Minlen equal to 1



Jeng, et al.            Expires September 7, 2015               [Page 7]

Internet-Draft            Covering Prefixes ORF               March 2015


   o  Maxlen equal to 32

   o  Host Address equal to 192.0.2.1

   Assume also that Loc-RIB contains routes for the following IPv4-VPN
   prefixes, and that all of these routes carry an RT whose value is the
   same as the CP-ORF VPN Route Target:

   o  1:0.0.0.0/64.

   o  2:192.0.2.0/88

   o  3:192.0.2.0/89

   Only the prefix 3:192.0.2.0/89 matches the CP-ORF.  The prefix
   1:0.0.0.0/64 does not match, because its length (64) is less than the
   CP-ORF Minlen (1) plus the length of an L3VPN Route Distinguisher
   (64).  If Loc-RIB did not contain the prefix 3:192.0.2.0/89,
   2:192.0.2.0/88 would match the CP-ORF.  However, because Loc-RIB also
   contains a more specific covering route (3:192.0.2.0/89),
   2:192.0.2.0/88 does not match.  Only 3:192.0.2.0/89 satisfies all of
   the above listed match criteria.  Note that the matching algorithm
   ignored Route Distinguishers.

   In order for an EVPN route to match a CP-ORF, all of the following
   conditions MUST be true:

   o  the EVPN route type is equal to the CP-ORF Route Type

   o  the route carries an RT whose value is equal to the CP-ORF VPN
      Route Target

   In addition, if the CP-ORF Route Type is equal to MAC/IP
   Advertisement Route, the following conditions also MUST be true:

   o  the EVPN Route MAC Address Length is greater than or equal to the
      CP-ORF Minlen plus 64 (i.e., the length of a VPN Route
      Distinguisher)

   o  the EVPN Route MAC Address Length is less than or equal to the CP-
      ORF Maxlen plus 64 (i.e., the length of a VPN Route Distinguisher)

   o  ignoring the Route Distinguisher, the leading bits of the EVPN
      Route MAC Address are identical to the leading bits of the CP-ORF
      Host Address.  CP-ORF Minlen defines the number of bits that must
      be identical.





Jeng, et al.            Expires September 7, 2015               [Page 8]

Internet-Draft            Covering Prefixes ORF               March 2015


   If a route matches the selection criteria of a CP-ORF entry, and it
   does not violate any subsequent rule specified by the Outbound Filter
   (e.g., rules that reflect local policy, or rules that are due to RT-
   Constrains), the BGP speaker places the route into the Adj-RIB-Out.
   In Adj-RIB-Out, the BGP speaker adds the CP-ORF Import Route Target
   to the list of Route Targets that the route already carries.  The BGP
   speaker also adds a Transitive Opaque Extended Community [RFC4360]
   with subtype equal to CP-ORF (0x03).  As a result of being placed in
   Adj-RIB-Out, the route is advertised to the peer associated with the
   Adj-RIB-Out.

   Receiving CP-ORF entries with REMOVE or REMOVE-ALL Actions may cause
   a route that has previously been installed in a particular Adj-RIB-
   Out be excluded from that Adj-RIB-Out. In this case, as specified in
   [RFC4271], "the previously advertised route in that Adj-RIB-Out MUST
   be withdrawn from service by means of an UPDATE message".

   RFC 5291 states that a BGP speaker should respond to a ROUTE REFRESH
   message as follows:

   "If the When-to-refresh indicates IMMEDIATE, then after processing
   all the ORF entries carried in the message the speaker re-advertises
   to the peer routes from the Adj-RIB-Out associated with the peer that
   have the same AFI/SAFI as what is carried in the message, and taking
   into account all the ORF entries for that AFI/SAFI received from the
   peer.  The speaker MUST re-advertise all the routes that have been
   affected by the ORF entries carried in the message, but MAY also re-
   advertise the routes that have not been affected by the ORF entries
   carried in the message."

   When the ROUTE-REFRESH message includes only CP-ORF entries, the BGP
   speaker MUST re-advertise routes that have been affected by these CP-
   ORF entries.  It is RECOMMENDED not to re-advertise the routes that
   have not been affected by the CP-ORF entries.

   The behavior when the ROUTE-REFRESH message includes one or more CP-
   ORF entries and one or more ORF entries of a different type remains
   unchanged from that described in RFC 5291.

4.  Applicability In Virtual Hub-and-Spoke VPNs

   In a Virtual Hub-and-Spoke environment, VPN sites are attached to
   Provider Edge (PE) routers.  For a given VPN, a PE router acts in
   exactly one of the following roles:

   o  As neither a V-hub nor a V-Spoke

   o  As a V-hub



Jeng, et al.            Expires September 7, 2015               [Page 9]

Internet-Draft            Covering Prefixes ORF               March 2015


   o  As a V-spoke

   To illustrate CP-ORF operation in conjunction with Virtual Hub-and-
   Spoke assume the following:

   o  One of the sites in a particular VPN, RED-VPN, is connected to a
      PE that acts as neither a V-hub nor a V-Spoke for RED-VPN.  We
      refer to this PE as PE1.

   o  Another site in RED-VPN is connected to another PE, and that PE
      acts as a V-hub for RED-VPN.  We refer to this PE as V-hub1.

   o  Yet another site in RED-VPN is connected to another PE, and that
      PE acts as a V-spoke for RED-VPN.  We refer to this PE as
      V-spoke1.

   All of these PEs advertise RED-VPN routes to a route reflector (RR).
   They mark these routes with a route target, which we will call RT-
   RED.  In particular, PE1 advertises a RED-VPN route to a prefix that
   we will call P.  P covers a host address, that we will call H.

   For the purpose of illustration also assume that the PEs and the RRs
   use Route Target Constraint [RFC4684].

   V-hub1 serves the RED-VPN.  Therefore, V-hub1 advertises a VPN IP
   default route for the RED-VPN to the RR, carrying the route target
   RT-RED-FROM-HUB1.

   V-spoke1 establishes a BGP session with the RR, negotiating the CP-
   ORF capability, as well as the Multiprotocol Extensions Capability
   [RFC4760].  Upon establishment of the BGP session, the RR does not
   advertise any routes to V-spoke1.  The RR will not advertise any
   routes until it receives either a ROUTE-REFRESH message or a BGP
   UPDATE message containing a Route Target Membership NLRI [RFC4684].

   Immediately after the BGP session is established, V-spoke1 sends the
   RR a BGP UPDATE message containing a Route Target Membership NLRI.
   The Route Target Membership NLRI specifies RT-RED-FROM-HUB1 as its
   route target.  In response to the BGP-UPDATE message, the RR
   advertises the VPN IP default route for the RED-VPN to V-spoke1.
   This route carries the route target RT-RED-FROM-HUB1.  V-spoke1
   subjects this route to its import policy and accepts it because it
   carries the route target RT-RED-FROM-HUB1.

   Now, V-spoke1 begins normal operation, sending all of its RED-VPN
   traffic through V-hub1.  At some point, V-spoke1 determines that it
   might benefit from a more direct route to H.  (Criteria by which




Jeng, et al.            Expires September 7, 2015              [Page 10]

Internet-Draft            Covering Prefixes ORF               March 2015


   V-spoke1 determines that it needs a more direct route to H are beyond
   the scope of this document.)

   In order to discover a more direct route, V-spoke1 assigns a unique
   numeric identifier to H.  V-spoke1 then sends a ROUTE-REFRESH message
   to the RR, containing the following information:

   o  AFI is equal to IPv4 or IPv6, as appropriate

   o  SAFI is equal to "MPLS-labeled VPN address"

   o  When-to-refresh is equal IMMEDIATE

   o  Action is equal to ADD

   o  Match is equal to PERMIT

   o  ORF Type is equal to CP-ORF

   o  CP-ORF Sequence is equal to the identifier associated with H

   o  CP-ORF Minlen is equal to 1

   o  CP-ORF Maxlen is equal to 32 or 128, as appropriate

   o  CP-ORF VPN Route Target is equal to RT-RED

   o  CP-ORF Import Route Target is equal to RT-RED-FROM-HUB1

   o  CP-ORF Route Type is equal to 0 (i.e., undefined)

   o  CP-ORF Host Address is equal H

   Upon receipt of the ROUTE-REFRESH message, the RR MUST ensure that it
   carries all routes belonging to the RED-VPN.  In at least one special
   case, where all of the RR clients are V-spokes and none of the RR
   clients are V-hubs, the RR will lack some or all of the required RED-
   VPN routes.  So, the RR sends a BGP UPDATE message containing a Route
   Target Membership NLRI for VPN-RED to all of its peers.  This causes
   the peers to advertise VPN-RED routes to the RR, if they have not
   done so already.

   Next, the RR adds the received CP-ORF to the Outbound Filter
   associated with V-spoke1.  Using the procedures in Section 3, the RR
   determines whether any of the routes in its Loc-RIB satisfy the
   selection criteria of the newly updated Outbound Filter.  If any
   routes satisfy the match criteria, they are added to the Adj-RIB-Out
   associated with V-spoke1.  In Adj-RIB-Out, the RR adds RT-RED-FROM-



Jeng, et al.            Expires September 7, 2015              [Page 11]

Internet-Draft            Covering Prefixes ORF               March 2015


   HUB1 to the list of Route Targets that the route already carries.
   The RR also adds a Transitive Opaque Extended Community [RFC4360]
   with subtype equal to CP-ORF.  Finally, RR advertises the newly added
   routes to V-spoke1.  In this example, the RR advertises P to V-Spoke1
   with a next-hop of PE1.

   V-spoke1 subjects the advertised routes to its import policy and
   accepts them because they carry the route target RT-RED-FROM-HUB1.

   V-spoke1 may repeat this process whenever it discovers another flow
   that might benefit from a more direct route to its destination.

4.1.  Multicast Considerations

   When applying Multicast VPN [RFC6513][RFC6514] procedures, routes
   bearing a Transitive Opaque Extended Community [RFC4360] with subtype
   equal to CP-ORF MUST NOT be used to determine Eligible Upstream
   Multicast Hops (UMH).

5.  Applicability In BGP/MPLS Ethernet VPN (EVPN)

   In a EVPN environment, CE devices are attached to Provider Edge (PE)
   routers.  A CE can be a host, a router or a switch.  For a given EVPN
   Instance (EVI), a PE router acts in exactly one of the following
   roles:

   o  As neither a Default MAC Gateway (DMG) nor a Spoke

   o  As a DMG

   o  As a Spoke

   To illustrate CP-ORF operation in the EVPN environment assume the
   following:

   o  A CE device in a particular EVI, RED-EVI, is connected to a PE
      that acts as neither a DMG nor a Spoke for RED-EVI.  We refer to
      this PE as PE1.

   o  Another CE device in RED-EVI is connected to another PE, and that
      PE acts as a DMG for RED-EVI.  We refer to this PE as DMG1.

   o  Yet another CE device in RED-EVI is connected to another PE, and
      that PE acts as a Spoke for RED-EVI.  We refer to this PE as
      Spoke1.

   All of these PEs advertise RED-EVI routes to a RR.  They mark these
   routes with a route target, which we will call RT-RED.  In



Jeng, et al.            Expires September 7, 2015              [Page 12]

Internet-Draft            Covering Prefixes ORF               March 2015


   particular, PE1 advertises a RED-EVI route to a MAC Address that we
   will call M.

   The RED-EVI VRFs on all of these PEs are provisioned to import EVPN
   routes that carry RT-RED.

   Since DMG1 acts as a DMG for RED-EVI, DMG1 advertises a Unknown MAC
   Route (UMR) for the RED-EVI to the RR, carrying the route target RT-
   RED.  The UMR is characterized as follows:

   o  EVPN Route Type is equal to MAC/IP Advertisement Route

   o  MAC address length is equal to 0

   o  IP address length is equal to 0

   Spoke1 establishes a BGP session with the RR, negotiating the CP-ORF
   capability, as well as the Multiprotocol Extensions Capability
   [RFC4760].  Upon establishment of the BGP session, the RR does not
   advertise any routes to Spoke1.  The RR will not advertise any routes
   until it receives a ROUTE-REFRESH message.

   Immediately after the BGP session is established, Spoke1 sends the RR
   a ROUTE REFRESH message containing the following information:

   o  AFI is equal to L2VPN

   o  SAFI is equal to BGP EVPN

   o  When-to-refresh is equal IMMEDIATE

   o  Action is equal to ADD

   o  Match is equal to PERMIT

   The ROUTE REFRESH message also contains four ORF entries.  The first
   ORF entry contains the following information:

   o  ORF Type is equal to CP-ORF

   o  CP-ORF Sequence is equal 1

   o  CP-ORF Minlen is equal to 0

   o  CP-ORF Maxlen is equal to 0

   o  CP-ORF VPN Route Target is equal to RT-RED




Jeng, et al.            Expires September 7, 2015              [Page 13]

Internet-Draft            Covering Prefixes ORF               March 2015


   o  CP-ORF Import Route Target is equal to RT-RED

   o  CP-ORF Route Type is equal to 1 (Ethernet Autodiscovery Route)

   The second ORF entry contains the following information:

   o  ORF Type is equal to CP-ORF

   o  CP-ORF Sequence is equal 2

   o  CP-ORF Minlen is equal to 0

   o  CP-ORF Maxlen is equal to 0

   o  CP-ORF VPN Route Target is equal to RT-RED

   o  CP-ORF Import Route Target is equal to RT-RED

   o  CP-ORF Route Type is equal to 2 (MAC/IP Advertisement Route)

   The third ORF entry contains the following information:

   o  ORF Type is equal to CP-ORF

   o  CP-ORF Sequence is equal 3

   o  CP-ORF Minlen is equal to 0

   o  CP-ORF Maxlen is equal to 0

   o  CP-ORF VPN Route Target is equal to RT-RED

   o  CP-ORF Import Route Target is equal to RT-RED

   o  CP-ORF Route Type is equal to 3 (Inclusive Multicast Route)

   The fourth ORF entry contains the following information:

   o  ORF Type is equal to CP-ORF

   o  CP-ORF Sequence is equal 4

   o  CP-ORF Minlen is equal to 0

   o  CP-ORF Maxlen is equal to 0

   o  CP-ORF VPN Route Target is equal to RT-RED




Jeng, et al.            Expires September 7, 2015              [Page 14]

Internet-Draft            Covering Prefixes ORF               March 2015


   o  CP-ORF Import Route Target is equal to RT-RED

   o  CP-ORF Route Type is equal to 4 (Ethernet Segment Route)

   In response to the ROUTE REFRESH message, the RR advertises the
   following to V-spoke1:

   o  All Ethernet Autodiscovery Routes belonging to RED-EVI

   o  A UMR advertised by DMG1 and belonging to RED-EVI

   o  All Inclusive Multicast Routes belonging to RED-EVI

   o  All Ethernet Segment Routes belonging to RED-EVI

   All of these routes carries the route target RT-RED.  Spoke1 subjects
   these routes to its import policy and accepts them because they carry
   the route target RT-RED.

   Now, Spoke1 begins normal operation, sending all of its RED-VPN
   traffic through DMG1.  At some point, Spoke1 determines that it might
   benefit from a more direct route to M.  (Criteria by which Spoke1
   determines that it needs a more direct route to M are beyond the
   scope of this document.)

   In order to discover a more direct route, Spoke1 assigns a unique
   numeric identifier to M.  V-spoke1 then sends a ROUTE-REFRESH message
   to the RR, containing the following information:

   o  AFI is equal to L2VPN

   o  SAFI is equal to BGP EVPN

   o  When-to-refresh is equal IMMEDIATE

   o  Action is equal to ADD

   o  Match is equal to PERMIT

   o  ORF Type is equal to CP-ORF

   o  CP-ORF Sequence is equal to the identifier associated with M

   o  CP-ORF Minlen is equal to 1

   o  CP-ORF Maxlen is equal to 48

   o  CP-ORF VPN Route Target is equal to RT-RED



Jeng, et al.            Expires September 7, 2015              [Page 15]

Internet-Draft            Covering Prefixes ORF               March 2015


   o  CP-ORF Import Route Target is equal to RT-RED

   o  CP-ORF Route Type is equal to 2 (i.e., MAC/IP Advertisement Route)

   o  CP-ORF Host Address is equal M

   Next, the RR adds the received CP-ORF to the Outbound Filter
   associated with Spoke1.  Using the procedures in Section 3, the RR
   determines whether any of the routes in its Loc-RIB satisfy the
   selection criteria of the newly updated Outbound Filter.  If any
   routes satisfy the match criteria, they are added to the Adj-RIB-Out
   associated with Spoke1.  The RR adds a Transitive Opaque Extended
   Community [RFC4360] with subtype equal to CP-ORF.  Note that as these
   routes are added to the Adj-RIB-Out, the RR does not change the list
   of Route Targets that the route already carries.  Finally, RR
   advertises the newly added routes to V-spoke1.  In this example, the
   RR advertises M to V-Spoke1 with a next-hop of PE1.

   Spoke1 subjects the advertised routes to its import policy and
   accepts them because they carry the route target RT-RED.

   Spoke1 may repeat this process whenever it discovers another flow
   that might benefit from a more direct route to its destination.

   Note that in general an EVI may have more than one DMG, in which case
   each spoke would receive a UMR from each of them.  The spoke should
   follow its local route selection procedures to select one of them as
   the "best", and use the selected one.

6.  Clean-up

   Each CP-ORF consumes memory and compute resources on the device that
   supports it.  Therefore, in order to obtain optimal performance, BGP
   speakers periodically evaluate all CP-ORFs that they have originated
   and remove unneeded CP-ORFs.  The criteria by which a BGP speaker
   identifies unneeded CP-ORF entries is a matter of local policy, and
   is beyond the scope of this document.

7.  IANA Considerations

   This memo uses code points from the first-come-first-served range of
   the following registries:









Jeng, et al.            Expires September 7, 2015              [Page 16]

Internet-Draft            Covering Prefixes ORF               March 2015


     +-----------------------------------------------+---------------+
     | Registry                                      | Code Point    |
     +-----------------------------------------------+---------------+
     | BGP Outbound Route Filtering (ORF) Types      | CP-ORF (65)   |
     | Transitive Opaque Extended Community Sub-Type | CP-ORF (0x03) |
     +-----------------------------------------------+---------------+

   IANA is requested to update the above mentioned registry entries so
   that they include a stable reference to this memo.

8.  Security Considerations

   Each CP-ORF consumes memory and compute resources on the device that
   supports it.  Therefore, a device supporting CP-ORF takes the
   following steps to protect itself from oversubscription:

   o  When negotiating the ORF capability, advertise willingness to
      receive the CP-ORF only to known, trusted iBGP peers.  See
      Section 5 of RFC 5291 for negotiation details.

   o  Enforce a per-peer limit on the number of CP-ORFs that can be
      installed at any given time.  Ignore all requests to add CP-ORFs
      beyond that limit

   Security considerations for BGP are presented in RFC4271 while
   further security analysis of BGP is found in [RFC6952].

9.  Contributors

   The following individuals contributed to the development of this
   document:

   o  Yakov Rekhter

   o  Xiaohu Xu

10.  Acknowledgements

   The authors wish to acknowledge Han Nguyen, James Uttaro and Alvaro
   Retana for their comments and contributions.

11.  References

11.1.  Normative References

   [RFC2119]  Bradner, S., "Key words for use in RFCs to Indicate
              Requirement Levels", BCP 14, RFC 2119, March 1997.




Jeng, et al.            Expires September 7, 2015              [Page 17]

Internet-Draft            Covering Prefixes ORF               March 2015


   [RFC4271]  Rekhter, Y., Li, T., and S. Hares, "A Border Gateway
              Protocol 4 (BGP-4)", RFC 4271, January 2006.

   [RFC4360]  Sangli, S., Tappan, D., and Y. Rekhter, "BGP Extended
              Communities Attribute", RFC 4360, February 2006.

   [RFC4684]  Marques, P., Bonica, R., Fang, L., Martini, L., Raszuk,
              R., Patel, K., and J. Guichard, "Constrained Route
              Distribution for Border Gateway Protocol/MultiProtocol
              Label Switching (BGP/MPLS) Internet Protocol (IP) Virtual
              Private Networks (VPNs)", RFC 4684, November 2006.

   [RFC4760]  Bates, T., Chandra, R., Katz, D., and Y. Rekhter,
              "Multiprotocol Extensions for BGP-4", RFC 4760, January
              2007.

   [RFC5291]  Chen, E. and Y. Rekhter, "Outbound Route Filtering
              Capability for BGP-4", RFC 5291, August 2008.

   [RFC6513]  Rosen, E. and R. Aggarwal, "Multicast in MPLS/BGP IP
              VPNs", RFC 6513, February 2012.

   [RFC6514]  Aggarwal, R., Rosen, E., Morin, T., and Y. Rekhter, "BGP
              Encodings and Procedures for Multicast in MPLS/BGP IP
              VPNs", RFC 6514, February 2012.

   [RFC7024]  Jeng, H., Uttaro, J., Jalil, L., Decraene, B., Rekhter,
              Y., and R. Aggarwal, "Virtual Hub-and-Spoke in BGP/MPLS
              VPNs", RFC 7024, October 2013.

   [RFC7432]  Sajassi, A., Aggarwal, R., Bitar, N., Isaac, A., Uttaro,
              J., Drake, J., and W. Henderickx, "BGP MPLS-Based Ethernet
              VPN", RFC 7432, February 2015.

11.2.  Informative References

   [IANA.AFI]
              IANA, "Address Family Numbers",
              <http://www.iana.org/assignments/address-family-numbers/
              address-family-numbers.xhtml>.

   [IANA.EVPN]
              IANA, "Ethernet VPN (EVPN)",
              <http://www.iana.org/assignments/evpn/evpn.xhtml>.







Jeng, et al.            Expires September 7, 2015              [Page 18]

Internet-Draft            Covering Prefixes ORF               March 2015


   [IANA.SAFI]
              IANA, "Subsequent Address Family Identifiers (SAFI)
              Parameters", <http://www.iana.org/assignments/safi-
              namespace/safi-namespace.xhtml#safi-namespace-2>.

   [RFC4364]  Rosen, E. and Y. Rekhter, "BGP/MPLS IP Virtual Private
              Networks (VPNs)", RFC 4364, February 2006.

   [RFC6952]  Jethanandani, M., Patel, K., and L. Zheng, "Analysis of
              BGP, LDP, PCEP, and MSDP Issues According to the Keying
              and Authentication for Routing Protocols (KARP) Design
              Guide", RFC 6952, May 2013.

Authors' Addresses

   Huajin Jeng
   AT&T

   Email: hj2387@att.com


   Luay Jalil
   Verizon

   Email: luay.jalil@verizon.com


   Ron Bonica
   Juniper Networks
   2251 Corporate Park Drive
   Herndon, Virginia  20170
   USA

   Email: rbonica@juniper.net


   Keyur Patel
   Cisco Systems
   170 W. Tasman Drive
   San Jose, California  95134
   USA

   Email: keyupate@cisco.com








Jeng, et al.            Expires September 7, 2015              [Page 19]

Internet-Draft            Covering Prefixes ORF               March 2015


   Lucy Yong
   Huawei Technologies
   Austin, Texas
   USA

   Email: lucy.yong@huawei.com













































Jeng, et al.            Expires September 7, 2015              [Page 20]