Bess K. Patel Internet-Draft S. Boutros Intended status: Standards Track J. Liste Expires: November 26, 2016 Cisco Systems B. Wen Comcast J. Rabadan Alcatel-Lucent May 25, 2016 Extensions to BGP Signaled Pseudowires to support Flow-Aware Transport Labels draft-ietf-bess-fat-pw-bgp-01.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 November 26, 2016. Patel, et al. Expires November 26, 2016 [Page 1] Internet-DraftExtensions to BGP Signaled PWs for FAT Labels May 2016 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 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 . . . . . . . . . . . . . . . . . . . . . . . 8 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 November 26, 2016 [Page 2] Internet-DraftExtensions to BGP Signaled PWs for FAT Labels May 2016 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 November 26, 2016 [Page 3] Internet-DraftExtensions to BGP Signaled PWs for FAT Labels May 2016 +------------------------------------+ | 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|Z|T|R|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 November 26, 2016 [Page 4] Internet-DraftExtensions to BGP Signaled PWs for FAT Labels May 2016 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 November 26, 2016 [Page 5] Internet-DraftExtensions to BGP Signaled PWs for FAT Labels May 2016 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, DOI 10.17487/RFC2119, March 1997, . Patel, et al. Expires November 26, 2016 [Page 6] Internet-DraftExtensions to BGP Signaled PWs for FAT Labels May 2016 [RFC3985] Bryant, S., Ed. and P. Pate, Ed., "Pseudo Wire Emulation Edge-to-Edge (PWE3) Architecture", RFC 3985, DOI 10.17487/RFC3985, March 2005, . [RFC4271] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A Border Gateway Protocol 4 (BGP-4)", RFC 4271, DOI 10.17487/RFC4271, 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, DOI 10.17487/RFC4385, February 2006, . [RFC4447] Martini, L., Ed., Rosen, E., El-Aawar, N., Smith, T., and G. Heron, "Pseudowire Setup and Maintenance Using the Label Distribution Protocol (LDP)", RFC 4447, DOI 10.17487/RFC4447, April 2006, . [RFC4761] Kompella, K., Ed. and Y. Rekhter, Ed., "Virtual Private LAN Service (VPLS) Using BGP for Auto-Discovery and Signaling", RFC 4761, DOI 10.17487/RFC4761, January 2007, . [RFC4928] Swallow, G., Bryant, S., and L. Andersson, "Avoiding Equal Cost Multipath Treatment in MPLS Networks", BCP 128, RFC 4928, DOI 10.17487/RFC4928, June 2007, . [RFC6391] Bryant, S., Ed., Filsfils, C., Drafz, U., Kompella, V., Regan, J., and S. Amante, "Flow-Aware Transport of Pseudowires over an MPLS Packet Switched Network", RFC 6391, DOI 10.17487/RFC6391, November 2011, . 8.2. Informative References [RFC2842] Chandra, R. and J. Scudder, "Capabilities Advertisement with BGP-4", RFC 2842, DOI 10.17487/RFC2842, May 2000, . [RFC2858] Bates, T., Rekhter, Y., Chandra, R., and D. Katz, "Multiprotocol Extensions for BGP-4", RFC 2858, DOI 10.17487/RFC2858, June 2000, . Patel, et al. Expires November 26, 2016 [Page 7] Internet-DraftExtensions to BGP Signaled PWs for FAT Labels May 2016 [RFC6624] Kompella, K., Kothari, B., and R. Cherukuri, "Layer 2 Virtual Private Networks Using BGP for Auto-Discovery and Signaling", RFC 6624, DOI 10.17487/RFC6624, May 2012, . Authors' Addresses Keyur Patel Cisco Systems 170 W. Tasman Drive San Jose, CA 95134 USA Email: keyupate@cisco.com 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 Patel, et al. Expires November 26, 2016 [Page 8] Internet-DraftExtensions to BGP Signaled PWs for FAT Labels May 2016 Jorge Rabadan Alcatel-Lucent 777 E. Middlefield Road Mountain View, CA 94043 USA Email: jorge.rabadan@alcatel-lucent.com Patel, et al. Expires November 26, 2016 [Page 9]