Networking Working Group Ran. Chen Internet-Draft Shaofu. Peng Intended status: Standards Track ZTE Corporation Expires: November 10, 2017 May 09, 2017 LDP Extensions for FEC elements sharing label draft-chenpeng-mpls-ldp-ext-01 Abstract Label Distribution Protocol (LDP) is defined in [RFC5036] for distribution of labels inside one MPLS domain. It defined how to associate a Forwarding Equivalence Class (FEC) with each label it distributes. A FEC is a list of one or more FEC elements, but it does not describe operations how to achieve one or more FEC element share the same label. Currently Label resources are getting more and more nervous, and it is necessary to save the label resources. This document defines extensions to the LDP protocol to achieve one or more FEC element share the same label. 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 10, 2017. Copyright Notice Copyright (c) 2017 IETF Trust and the persons identified as the document authors. All rights reserved. This document is subject to BCP 78 and the IETF Trust's Legal Provisions Relating to IETF Documents (http://trustee.ietf.org/license-info) in effect on the date of Chen & Peng Expires November 10, 2017 [Page 1] Internet-DraftLDP Extensions for FEC elements sharing label May 2017 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 2. Conventions used in this document . . . . . . . . . . . . . . 2 3. LDP Extension . . . . . . . . . . . . . . . . . . . . . . . . 2 3.1. Host-parasitism FEC Relationship TLV . . . . . . . . . . 3 3.2. Label Borrowing Message . . . . . . . . . . . . . . . . . 4 4. Operations . . . . . . . . . . . . . . . . . . . . . . . . . 4 4.1. Egress Operation . . . . . . . . . . . . . . . . . . . . 4 4.2. Ingress/Transit Operation . . . . . . . . . . . . . . . . 5 5. Security Considerations . . . . . . . . . . . . . . . . . . . 6 6. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 6 7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 6 8. Normative references . . . . . . . . . . . . . . . . . . . . 6 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 7 1. Introduction Label Distribution Protocol (LDP) is defined in [RFC5036] for distribution of labels inside one MPLS domain. It defined how to associate a Forwarding Equivalence Class (FEC) with each label it distributes. A FEC is a list of one or more FEC elements, but it does not describe operations how to achieve one or more FEC element share the same label. Currently Label resources are getting more and more nervous, and it is necessary to save the label resources. This document defines extensions to the LDP protocol to achieve one or more FEC element share the same label. 2. 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. 3. LDP Extension Chen & Peng Expires November 10, 2017 [Page 2] Internet-DraftLDP Extensions for FEC elements sharing label May 2017 3.1. Host-parasitism FEC Relationship TLV The following section describes the protocol extensions required to support one or more FEC element share the same label. Labels are bound to Forwarding Equivalence Classes (FECs). A Host- parasitism FEC Relationship is a list of one or more FEC elements. The FEC Relationship TLV encodes FEC items. 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |1|1| H-P Relationship(TBD) | Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Sequence Number | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Prefix(2) | Host Address Family | PreLen | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Host Prefix | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Prefix(2) | Parasitic Address Family | PreLen | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Parasitic Prefix 1 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | | ... ... | | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Prefix(2) | Parasitic Address Family | PreLen | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Parasitic Prefix n | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 1 The FEC Relationship TLV contains a Host-FEC element, and 0 or many Parasitic-FEC elements. Both Host-FEC element and the Parasitic-FEC element are use the same format as defined in [RFC5036]. The type of the FEC Elements is 0x02(prefix).The Host-FEC indicates Label Lender, and the Parasitic-FEC indicates Label borrowing. Sequence Number Specifies a 4 octet unsigned sequence number that identifies the sequence number of the Host-parasitism FEC Relationship. The greater the Sequence Number, the more new the Host-parasitism FEC Relationship. if the difference between the larger one and the smaller one is more than half of the value of a 4 Chen & Peng Expires November 10, 2017 [Page 3] Internet-DraftLDP Extensions for FEC elements sharing label May 2017 octet unsigned integer, it indicates that there is a turnover, and the smaller value of the Sequence Number , the more new the Host- parasitism FEC Relationship. 3.2. Label Borrowing Message The document defines a new LDP message: Label Borrowing Message. An LSR sends a Label Borrowing message to an LDP peer to advertise label borrowing relationship to the peer. The Label Borrowing message Must include a Host-parasitism FEC Relationship TLV. The encoding for the Label Borrowing message is: 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |1| Label Borrowing (TBD) | Message Length | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Message ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Action | Reserved | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Host-parasitism FEC Relationship TLV | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 2 U-bit: The value is set to 1, it indicates the unknown TLV MUST be silently ignored and the rest of the message processed as if the unknown TLV did not exist. Message ID: 32-bit value used to identify this message. Action: Set to 1, it indicates Label borrowing. Set to 0, it indicates Label does not borrow. 4. Operations 4.1. Egress Operation The Egress may involve one or more of the following actions: o A Egress node advertises Label Mapping messages for the Host-FEC label to one or more LDP peers, The LDP label distribution procedures is the same as described in [RFC5036]. Chen & Peng Expires November 10, 2017 [Page 4] Internet-DraftLDP Extensions for FEC elements sharing label May 2017 o According to local policy that is configed on Egress node, all or part of the Parasitic-FECs can share the same label with the Host- FEC. The Egress node MUST advertises a Label Borrowing Message included the Host-parasitism FEC Relationship TLV with action set to 1. If the local policy is coarsness-grained that enforced all Parasitic-FECs to share the Host-FEC's label, the Host-parasitism FEC Relationship TLV can only contain the single Host-FEC element, and Parasitic-FECs elements are empty. Otherwise, the Host- parasitism FEC Relationship TLV need contain not only the Host-FEC element, but also specific Parasitic-FECs elements who need to share Host-FEC's label due to a local fine-grained policy. o When the Host-FEC label is available, and if due to a local coarsness or fine-grained policy that all Parasitic-FECs which borrowed label from the Host-FEC didnt borrow again, the Egress node MUST advertises a Label Borrowing Message included the Host- parasitism FEC Relationship TLV with action set to 0, only contain that single Host-FEC element, and Parasitic-FECs elements are empty. Otherwise, if due to a local fine-grained policy, some Parasitic-FECs didnot want to borrow the Host-FEC's label, but there are always any other Parasitic-FECs left to share label, an updated Label Borrowing Message included the Host-parasitism FEC Relationship TLV with action set to 1 need to be advertised, contain the Host-FEC element and the specific Parasitic-FECs elements. 4.2. Ingress/Transit Operation An LSR which received a Label Borrowing Message from an LDP peer may involve one or more of the following actions: o Maintain the up-to-date Host-parasitism FEC Relationship. It will compare the sequence number in the received Label Borrow Message and the existed locally maintained Host-parasitism FEC Relationship data. If the Label Borrow Message is newer than the locally maintained data, it will overwrite the later, otherwise it will be ignored. If the Host-parasitism FEC Relationship only contained a single Host-FEC, the Parasitic-FECs could be determined by checking IGP/BGP prefixes whose original advertised router-id are same as the Host-FEC, and also by local FEC- policy(i.e. which IGP/BGP prefix could be installed as an LDP FEC due to local FEC-policy). o Based on the borrowed label get from the up-to-date Host- parasitism FEC Relationship data, Install ILM entries at the transit node and FTN entries at the ingress node for Parasitic- FECs. The outgoing label of the Parasitic-FEC's FTN entry will be same as the one of the Host-FEC's FTN entry. Both the incoming Chen & Peng Expires November 10, 2017 [Page 5] Internet-DraftLDP Extensions for FEC elements sharing label May 2017 label and outgoing label of the parasitic-FEC's ILM entry will be same as the ones of the Host-FEC's ILM entry. o Transmission of the up-to-date Label Borrowing message to one or more other LDP peers; Note that the traditional process of received Label Mapping/Withdraw Message for an FEC MUST NOT be affected by the process of the Label Borrow Message if the FEC is also a Parasitic-FEC according to the up-to-date Host-parasitism FEC Relationship data. That is, the priority of the traditional process is higher. 5. Security Considerations TBD. 6. Acknowledgements TBD. 7. IANA Considerations TBD. 8. 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, . [RFC3031] Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol Label Switching Architecture", RFC 3031, DOI 10.17487/RFC3031, January 2001, . [RFC5036] Andersson, L., Ed., Minei, I., Ed., and B. Thomas, Ed., "LDP Specification", RFC 5036, DOI 10.17487/RFC5036, October 2007, . [RFC7794] Ginsberg, L., Ed., Decraene, B., Previdi, S., Xu, X., and U. Chunduri, "IS-IS Prefix Attributes for Extended IPv4 and IPv6 Reachability", RFC 7794, DOI 10.17487/RFC7794, March 2016, . Chen & Peng Expires November 10, 2017 [Page 6] Internet-DraftLDP Extensions for FEC elements sharing label May 2017 Authors' Addresses Ran Chen ZTE Corporation No.50 Software Avenue,Yuhuatai District Nanjing, Jiangsu Province 210012 China Phone: +86 025 88014636 Email: chen.ran@zte.com.cn Shaofu Peng ZTE Corporation No.68 Zijinghua Road,Yuhuatai District Nanjing, Jiangsu Province 210012 China Email: peng.shaofu@zte.com.cn Chen & Peng Expires November 10, 2017 [Page 7]