[Docs] [txt|pdf] [Tracker] [Email] [Diff1] [Diff2] [Nits]

Versions: (draft-keyupate-l2vpn-fat-pw-bgp) 00 draft-ietf-bess-fat-pw-bgp

Bess                                                            K. Patel
Internet-Draft                                                S. Boutros
Intended status: Standards Track                                J. Liste
Expires: October 31, 2015                                  Cisco Systems
                                                                  B. Wen
                                                                 Comcast
                                                              J. Rabadan
                                                          Alcatel-Lucent
                                                          April 29, 2015


 Extensions to BGP Signaled Pseudowires to support Flow-Aware Transport
                                 Labels
                 draft-keyupate-bess-fat-pw-bgp-00.txt

Abstract

   [RFC6391] describes a mechanism that uses an additional label (Flow
   Label) in the MPLS label stack that allows Label Switch Routers to
   balance flows within Pseudowires at a finer granularity than the
   individual Pseudowires across the Equal Cost Multiple Paths (ECMPs)
   that exists within the Packet Switched Network (PSN).

   Furthermore,[RFC6391] defines the LDP protocol extensions required to
   synchronize the flow label states between the ingress and egress PEs
   when using the signaling procedures defined in the [RFC4447].

   This draft defines protocol extensions required to synchronize flow
   label states among PEs when using the BGP-based signaling procedures
   defined in [RFC4761].  These protocol extensions are equally
   applicable to point-to-point L2VPNs defined in [RFC6624].

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 October 31, 2015.



Patel, et al.           Expires October 31, 2015                [Page 1]


Internet-DraftExtensions to BGP Signaled PWs for FAT Labels   April 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.

   This document may contain material from IETF Documents or IETF
   Contributions published or made publicly available before November
   10, 2008.  The person(s) controlling the copyright in some of this
   material may not have granted the IETF Trust the right to allow
   modifications of such material outside the IETF Standards Process.
   Without obtaining an adequate license from the person(s) controlling
   the copyright in such materials, this document may not be modified
   outside the IETF Standards Process, and derivative works of it may
   not be created outside the IETF Standards Process, except to format
   it for publication as an RFC or to translate it into languages other
   than English.

Table of Contents

   1.  Introduction  . . . . . . . . . . . . . . . . . . . . . . . .   2
     1.1.  Requirements Language . . . . . . . . . . . . . . . . . .   3
   2.  Modifications to Layer 2 Info Extended Community  . . . . . .   3
   3.  Signaling the Presence of the Flow Label  . . . . . . . . . .   5
   4.  Acknowledgements  . . . . . . . . . . . . . . . . . . . . . .   6
   5.  Contributors  . . . . . . . . . . . . . . . . . . . . . . . .   6
   6.  IANA Considerations . . . . . . . . . . . . . . . . . . . . .   6
   7.  Security Considerations . . . . . . . . . . . . . . . . . . .   6
   8.  References  . . . . . . . . . . . . . . . . . . . . . . . . .   6
     8.1.  Normative References  . . . . . . . . . . . . . . . . . .   6
     8.2.  Informative References  . . . . . . . . . . . . . . . . .   7
   Authors' Addresses  . . . . . . . . . . . . . . . . . . . . . . .   7

1.  Introduction

   A pseudowire (PW)[RFC3985] is normally transported over one single
   network path, even if multiple Equal Cost Multiple Paths (ECMPs)
   exist between the ingress and egress PW provider edge (PE) equipment.
   This is required to preserve the characteristics of the emulated



Patel, et al.           Expires October 31, 2015                [Page 2]


Internet-DraftExtensions to BGP Signaled PWs for FAT Labels   April 2015


   service.  The use of a single path to preserve the packet delivery
   order remains the default mode of operation of a PW and is described
   in [RFC4385], [RFC4928].

   Using the principles defined in [RFC6391], this draft augments the
   BGP-signaling procedures of [RFC4761] and [RFC6624] to allow an
   OPTIONAL mode that may be employed when the use of ECMPs is known to
   be beneficial to the operation of the PW.

   High bandwidth Ethernet-based services are a prime example that
   benefits from the ability to load-balance flows in a PW over multiple
   PSN paths.  In general, load-balancing is applicable when the PW
   attachment circuit bandwidth and PSN core link bandwidth are of same
   order of magnitude.

   To achieve the load-balancing goal,[RFC6391] introduces the notion of
   an additional Label Stack Entry (LSE) (Flow label) located at the
   bottom of the stack (right after PW LSE).  Label Switching Routers
   (LSRs) commonly generate a hash of the label stack in order to
   discriminate and distribute flows over available ECMPs.  The presence
   of the Flow label (closely associated to a flow determined by the
   ingress PE) will normally provide the greatest entropy.

   Furthermore, following the procedures for Inter-AS scenarios
   described in [RFC4761] section 3.4, the Flow label should never be
   handled by the ASBRs, only the terminating PEs on each AS will be
   responsible for popping or pushing this label.  This is equally
   applicable to Method B [section 3.4.2] of [RFC4761] where ASBRs are
   responsible for swapping the PW label as traffic traverses from ASBR
   to PE and ASBR to ASBR directions.  Therefore, the Flow label will
   remain untouched across AS boundaries.

1.1.  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].

2.  Modifications to Layer 2 Info Extended Community

   The Layer 2 Info Extended Community is used to signal control
   information about the pseudowires to be setup.  The extended
   community format is described in [RFC4761].  The format of this
   extended community is described as:







Patel, et al.           Expires October 31, 2015                [Page 3]


Internet-DraftExtensions to BGP Signaled PWs for FAT Labels   April 2015


         +------------------------------------+
         | Extended community type (2 octets) |
         +------------------------------------+
         |  Encaps Type (1 octet)             |
         +------------------------------------+
         |  Control Flags (1 octet)           |
         +------------------------------------+
         |  Layer-2 MTU (2 octet)             |
         +------------------------------------+
         |  Reserved (2 octets)               |
         +------------------------------------+

         Layer 2 Info Extended Community

    Control Flags:

            This field contains bit flags relating to the control
            information about pseudowires. This field is augmented with
            a definition of 2 new flags field.

          0 1 2 3 4 5 6 7
         +-+-+-+-+-+-+-+-+
         |Z|Z|Z|T|R|Z|C|S|      (Z = MUST Be Zero)
         +-+-+-+-+-+-+-+-+

         Control Flags Bit Vector

   With Reference to the Control Flags Bit Vector, the following bits in
   the Control Flags are defined; the remaining bits, designated Z, MUST
   be set to zero when sending and MUST be ignored when receiving this
   Extended Community.

         Z   Must be set to Zero.

         T   When the bit value is 1, the PE is requesting the ability
             to send a Pseudowire packet that includes a flow label.
             When the bit value is 0, the PE is indicating that it will
             not send a Pseudowire packet containing a flow label.

         R   When the bit value is 1, the PE is able to receive a
             Pseudowire packet with a flow label present. When the bit
             value is 0, the PE is unable to receive a Pseudowire packet
             with the flow label present.

         C   Defined in [RFC4761].

         S   Defined in [RFC4761].




Patel, et al.           Expires October 31, 2015                [Page 4]


Internet-DraftExtensions to BGP Signaled PWs for FAT Labels   April 2015


3.  Signaling the Presence of the Flow Label

   As part of the Pseudowire signaling procedures described in
   [RFC4761], a Layer 2 Info Extended Community is advertised in the
   VPLS BGP NLRI.  This draft recommends that the Control Flags field of
   this extended community be used to synchronize the flow label states
   amongst PEs for a given L2VPN.

   A PE that wishes to send a flow label in a Pseudowire packet MUST
   include in its VPLS BGP NLRI a Layer 2 Info Extended Community using
   Control Flags field with T = 1.

   A PE that is willing to receive a flow label in a Pseudowire packet
   MUST include in its VPLS BGP NLRI a Layer 2 Info Extended Community
   using Control Flags field with R = 1.

   A PE that receives a VPLS BGP NLRI containing a Layer 2 Info Extended
   Community with R = 0 NUST NOT include a flow label in the Pseudowire
   packet.

   Therefore, a PE sending a Control Flags field with T = 1 and
   receiving a Control Flags field with R = 1 MUST include a flow label
   in the Pseudowire packet.  Under all other combinations, a PE MUST
   NOT include a flow label in the Pseudowire packet.

   A PE MAY support the configuration of the flow label (T and R bits)
   on a per-service (e.g.  VPLS VFI) basis.  Furthermore, it is also
   possible that on a given service, PEs may not share the same flow
   label settings.  The presence of a flow label is therefore determined
   on a per-peer basis and according to the local and remote T and R bit
   values.  For example, a PE part of a VPLS and with a local T = 1,
   must only transmit traffic with a flow label to those peers that
   signaled R = 1.  And if the same PE has local R = 1, it must only
   expect to receive traffic with a flow label from peers with T = 1.
   Any other traffic MUST not have a flow label.

   Modification of flow label settings may impact traffic over a PW as
   these could trigger changes in the PEs data-plane programming (i.e.
   imposition / disposition of flow label).  This is an implementation
   specific behavior and outside the scope of this draft

   The signaling procedures in [RFC4761] state that the unspecified bits
   in the Control Flags field (bits 0-5) MUST be set to zero when
   sending and MUST be ignored when receiving.  The signaling procedure
   described here is therefore backwards compatible with existing
   implementations.  A PE not supporting the extensions described in
   this draft will always advertise a value of ZERO in the position
   assigned by this draft to the R bit and therefore a flow label will



Patel, et al.           Expires October 31, 2015                [Page 5]


Internet-DraftExtensions to BGP Signaled PWs for FAT Labels   April 2015


   never be included in a packet sent to it by one of its peers.
   Similarly, it will always advertise a value of ZERO in the position
   assigned by this draft to the T bit and therefore a peer will know
   that a flow label will never be included in a packet sent by it.

   Note that what is signaled is the desire to include the flow LSE in
   the label stack.  The value of the flow label is a local matter for
   the ingress PE, and the label value itself is not signaled.

4.  Acknowledgements

   The authors would like to thank Bertrand Duvivier and John Drake for
   their review and comments.

5.  Contributors

   In addition to the authors listed above, the following individuals
   also contributed to this document:

   Eric Lent

   John Brzozowski

   Steven Cotter

6.  IANA Considerations

7.  Security Considerations

   This extension to BGP does not change the underlying security issues
   inherent in the existing [RFC4271].

8.  References

8.1.  Normative References

   [I-D.ietf-l2vpn-vpls-multihoming]
              Kothari, B., Kompella, K., Henderickx, W., Balus, F.,
              Uttaro, J., Palislamovic, S., and W. Lin, "BGP based
              Multi-homing in Virtual Private LAN Service", draft-ietf-
              l2vpn-vpls-multihoming-06 (work in progress), July 2013.

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

   [RFC3985]  Bryant, S. and P. Pate, "Pseudo Wire Emulation Edge-to-
              Edge (PWE3) Architecture", RFC 3985, March 2005.




Patel, et al.           Expires October 31, 2015                [Page 6]


Internet-DraftExtensions to BGP Signaled PWs for FAT Labels   April 2015


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

   [RFC4385]  Bryant, S., Swallow, G., Martini, L., and D. McPherson,
              "Pseudowire Emulation Edge-to-Edge (PWE3) Control Word for
              Use over an MPLS PSN", RFC 4385, February 2006.

   [RFC4447]  Martini, L., Rosen, E., El-Aawar, N., Smith, T., and G.
              Heron, "Pseudowire Setup and Maintenance Using the Label
              Distribution Protocol (LDP)", RFC 4447, April 2006.

   [RFC4761]  Kompella, K. and Y. Rekhter, "Virtual Private LAN Service
              (VPLS) Using BGP for Auto-Discovery and Signaling", RFC
              4761, January 2007.

   [RFC4928]  Swallow, G., Bryant, S., and L. Andersson, "Avoiding Equal
              Cost Multipath Treatment in MPLS Networks", BCP 128, RFC
              4928, June 2007.

   [RFC6391]  Bryant, S., Filsfils, C., Drafz, U., Kompella, V., Regan,
              J., and S. Amante, "Flow-Aware Transport of Pseudowires
              over an MPLS Packet Switched Network", RFC 6391, November
              2011.

8.2.  Informative References

   [RFC2842]  Chandra, R. and J. Scudder, "Capabilities Advertisement
              with BGP-4", RFC 2842, May 2000.

   [RFC2858]  Bates, T., Rekhter, Y., Chandra, R., and D. Katz,
              "Multiprotocol Extensions for BGP-4", RFC 2858, June 2000.

   [RFC6624]  Kompella, K., Kothari, B., and R. Cherukuri, "Layer 2
              Virtual Private Networks Using BGP for Auto-Discovery and
              Signaling", RFC 6624, May 2012.

Authors' Addresses

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

   Email: keyupate@cisco.com






Patel, et al.           Expires October 31, 2015                [Page 7]


Internet-DraftExtensions to BGP Signaled PWs for FAT Labels   April 2015


   Sami Boutros
   Cisco Systems
   170 W. Tasman Drive
   San Jose, CA  95134
   USA

   Email: sboutros@cisco.com


   Jose Liste
   Cisco Systems
   170 W. Tasman Drive
   San Jose, CA  95134
   USA

   Email: jliste@cisco.com


   Bin Wen
   Comcast
   1701 John F Kennedy Blvd
   Philadelphia, PA  19103
   USA

   Email: bin_wen@cable.comcast.com


   Jorge Rabadan
   Alcatel-Lucent
   777 E. Middlefield Road
   Mountain View, CA  94043
   USA

   Email: jorge.rabadan@alcatel-lucent.com

















Patel, et al.           Expires October 31, 2015                [Page 8]


Html markup produced by rfcmarkup 1.126, available from https://tools.ietf.org/tools/rfcmarkup/