Network Working Group L. Jin Internet-Draft ZTE Corporation Intended status: Standards Track F. Jounay Expires: March 7, 2013 France Telecom I. Wijnands Cisco Systems, Inc N. Leymann Deutsche Telekom AG Sep 3, 2012 LDP Extensions for Hub & Spoke Multipoint Label Switched Path draft-jjwl-mpls-mldp-hsmp-01.txt Abstract This draft introduces a hub & spoke multipoint LSP (short for HSMP LSP), which allows traffic both from root to leaf through P2MP LSP and also leaf to root along the co-routed reverse path. That means traffic entering the HSMP LSP from application/customer at the root node travels downstream, exactly as if it was traveling downstream along a P2MP LSP to each leaf node, and traffic entering the HSMP LSP at any leaf node travels upstream along the tree to the root as if it is unicast to the root, except that it follows the path of the tree rather than ordinary unicast to the root. 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 RFC2119 [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 March 7, 2013. Jin, et al. Expires March 7, 2013 [Page 1] Internet-Draft draft-jin-jounay-mpls-mldp-hsmp Sep 2012 Copyright Notice Copyright (c) 2012 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 . . . . . . . . . . . . . . . . . . . . . . . . . 3 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 3. Applications . . . . . . . . . . . . . . . . . . . . . . . . . 3 3.1. Time synchronization scenario . . . . . . . . . . . . . . 4 3.2. VPMS scenario . . . . . . . . . . . . . . . . . . . . . . 4 3.3. IPTV scenario . . . . . . . . . . . . . . . . . . . . . . 4 4. Setting up HSMP LSP with LDP . . . . . . . . . . . . . . . . . 5 4.1. Support for HSMP LSP setup with LDP . . . . . . . . . . . 5 4.2. HSMP FEC Elements . . . . . . . . . . . . . . . . . . . . 6 4.3. Using the HSMP FEC Elements . . . . . . . . . . . . . . . 6 4.3.1. HSMP LSP Label Map . . . . . . . . . . . . . . . . . . 6 4.3.2. HSMP LSP Label Withdraw . . . . . . . . . . . . . . . 8 4.3.3. HSMP LSP upstream LSR change . . . . . . . . . . . . . 9 5. HSMP LSP on a LAN . . . . . . . . . . . . . . . . . . . . . . 9 6. Redundancy considerations . . . . . . . . . . . . . . . . . . 9 7. Co-routed path exceptions . . . . . . . . . . . . . . . . . . 9 8. Security Considerations . . . . . . . . . . . . . . . . . . . 10 9. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10 10. Acknowledgement . . . . . . . . . . . . . . . . . . . . . . . 10 11. References . . . . . . . . . . . . . . . . . . . . . . . . . . 10 11.1. Normative references . . . . . . . . . . . . . . . . . . . 10 11.2. Informative References . . . . . . . . . . . . . . . . . . 11 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 11 Jin, et al. Expires March 7, 2013 [Page 2] Internet-Draft draft-jin-jounay-mpls-mldp-hsmp Sep 2012 1. Introduction The point-to-multipoint LSP defined in [RFC6388] allows traffic to transmit from root to several leaf nodes, and multipoint-to- multipoint LSP allows traffic from every node to transmit to every other node. This draft introduces a hub & spoke multipoint LSP (short for HSMP LSP), which allows traffic both from root to leaf through P2MP LSP and also leaf to root along the co-routed reverse path. That means traffic entering the HSMP LSP at the root node travels downstream, exactly as if it was traveling downstream along a P2MP LSP, and traffic entering the HSMP LSP at any other node travels upstream along the tree to the root. A packet traveling upstream should be thought of as being unicast to the root, except that it follows the path of the tree rather than ordinary unicast to the root. 2. Terminology 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]. This document uses some terms and acronyms as follows: mLDP: Multipoint extensions for LDP P2MP LSP: An LSP that has one Ingress LSR and one or more Egress LSRs. MP2MP LSP: An LSP that connects a set of nodes, such that traffic sent by any node in the LSP is delivered to all others. HSMP LSP: hub & spoke multipoint LSP. An LSP allows traffic both from root to leaf through P2MP LSP and also leaf to root along the co-routed reverse path. PTP: The timing and synchronization protocol used by IEEE1588 3. Applications In some cases, the P2MP LSP may not have a reply path for the OAM message (e.g, LSP Ping). If P2MP LSP is provided by HSMP LSP, then the upstream path could be exactly used as the OAM message reply path. This is especially useful in the case of P2MP LSP fault detection, performance measurement, root node redundancy and etc. There are several other applications that could take advantage of Jin, et al. Expires March 7, 2013 [Page 3] Internet-Draft draft-jin-jounay-mpls-mldp-hsmp Sep 2012 such kind of LDP based HSMP LSP as described below. 3.1. Time synchronization scenario [IEEE1588] over MPLS is defined in [I-D.ietf-tictoc-1588overmpls]. It is required that the LSP used to transport PTP event message between a Master Clock and a Slave Clock, and the LSP between the same Slave Clock and Master Clock must be co-routed. By using point- to-multipoint technology to transmit PTP event messages from Master Clock at root side to Slave Clock at leaf side will greatly improve the bandwidth usage. Unfortunately current point-to-multipoint LSP only provides unidirectional path from root to leaf, which cannot provide a co-routed reverse path for the PTP event messages. LDP based HSMP LSP described in this draft provides unidirectional point- to-multipoint LSP from root to leaf and co-routed reverse path from leaf to root. 3.2. VPMS scenario Point to multipoint PW described in [I-D.ietf-pwe3-p2mp-pw] requires to setup reverse path from leaf node (referred as egress PE) to root node (referred as ingress PE), if HSMP LSP is used to multiplex P2MP PW, the reverse path can also be multiplexed to HSMP upstream path to avoid setup independent reverse path. In that case, the operational cost will be reduced for maintaining only one HSMP LSP, instead of P2MP LSP and n (number of leaf nodes) P2P reverse LSPs. The VPMS defined in [I-D.ietf-l2vpn-vpms-frmwk-requirements] requires reverse path from leaf to root node. The P2MP PW multiplexed to HSMP LSP can provide VPMS with reverse path, without introducing independent reverse path from each leaf to root. 3.3. IPTV scenario The mLDP based HSMP LSP can also be applied in a typical IPTV scenario. There is usually only one location with senders but there are many receiver locations. If IGMP is used for signaling between senders as IGMP querier and receivers, the IGMP messages from the receivers are travelling only from the leaves to the root (and from root towards leaves) but not from leaf to leaf. In addition traffic from the root is only replicated towards the leaves. Then leaf node receiving IGMP message (for SSM case) will join HSMP LSP, and then send IGMP message upstream to root along HSMP LSP. Note that in above case, there is no node redundancy for IGMP querier. And the node redundancy for IGMP querier could be provided by two independent VPMS instances with HSMP applied. Jin, et al. Expires March 7, 2013 [Page 4] Internet-Draft draft-jin-jounay-mpls-mldp-hsmp Sep 2012 4. Setting up HSMP LSP with LDP HSMP LSP is similar with MP2MP LSP described in [RFC6388], with the difference that the leaf LSRs can only send traffic to root node along the same path of traffic from root node to leaf node. HSMP LSP consists of a downstream path and upstream path. The downstream path is same as MP2MP LSP, while the upstream path is only from leaf to root node, without communication between leaf and leaf nodes. The transmission of packets from the root node of a HSMP LSP to the receivers is identical to that of a P2MP LSP. Traffic from a leaf node follows the upstream path toward the root node, along the identical path of downstream path. For setting up the upstream path of a HSMP LSP, ordered mode MUST be used which is same as MP2MP. Ordered mode can guarantee a leaf to start sending packets to root immediately after the upstream path is installed, without being dropped due to an incomplete LSP. Due to much of same behavior between HSMP LSP and MP2MP LSP, the following sections only describe the difference between the two entities. 4.1. Support for HSMP LSP setup with LDP HSMP LSP also needs the LDP capabilities [RFC5561] to indicate the supporting for the setup of HSMP LSPs. An implementation supporting the HSMP LSP procedures specified in this document MUST implement the procedures for Capability Parameters in Initialization Messages. Advertisement of the HSMP LSP Capability indicates support of the procedures for HSMP LSP setup. A new Capability Parameter TLV is defined, the HSMP LSP Capability. Following is the format of the HSMP LSP Capability Parameter. 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|0| HSMP LSP Cap(TBD IANA) | Length (= 1) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ |1| Reserved | +-+-+-+-+-+-+-+-+ Figure 1. HSMP LSP Capability Parameter encoding The HSMP LSP capability type is to be assigned by IANA. Jin, et al. Expires March 7, 2013 [Page 5] Internet-Draft draft-jin-jounay-mpls-mldp-hsmp Sep 2012 4.2. HSMP FEC Elements Similar as MP2MP LSP, we define two new protocol entities, the HSMP downstream FEC and upstream FEC Element. If a FEC TLV contains an HSMP FEC Element, the HSMP FEC Element MUST be the only FEC Element in the FEC TLV. The structure, encoding and error handling for the HSMP downstream and upstream FEC Elements are the same as for the MP2MP FEC Element described in [RFC6388] Section 4.2. The difference is that two additional new FEC types are used: HSMP downstream type (TBD, IANA) and HSMP upstream type (TBD, IANA). 4.3. Using the HSMP FEC Elements In order to describe the message processing clearly, following defines the processing of the HSMP FEC Elements, which is inherited from [RFC6388] section 4.3. 1. HSMP downstream LSP (or simply downstream ): a HSMP LSP downstream path with root node address X and opaque value Y. 2. HSMP upstream LSP (or simply upstream ): a HSMP LSP upstream path for root node address X and opaque value Y which will be used by any of downstream node to send traffic upstream to root node. 3. HSMP downstream FEC Element : a FEC Element with root node address X and opaque value Y used for a downstream HSMP LSP. 4. HSMP upstream FEC Element : a FEC Element with root node address X and opaque value Y used for an upstream HSMP LSP. 5. HSMP-D Label Map : A Label Map message with a single HSMP downstream FEC Element and label TLV with label L. Label L MUST be allocated from the per-platform label space of the LSR sending the Label Map Message. 6. HSMP-U Label Map : A Label Map message with a single HSMP upstream FEC Element and label TLV with label Lu. Label Lu MUST be allocated from the per-platform label space of the LSR sending the Label Map Message. 4.3.1. HSMP LSP Label Map This section specifies the procedures for originating HSMP Label Map messages and processing received HSMP label map messages for a particular HSMP LSP. The procedure of downstream HSMP LSP is same as that of downstream MP2MP LSP described in [RFC6388]. Under the operation of ordered mode, the upstream LSP will be setup by sending Jin, et al. Expires March 7, 2013 [Page 6] Internet-Draft draft-jin-jounay-mpls-mldp-hsmp Sep 2012 HSMP LSP mapping message with label which is allocated by upstream LSR to its downstream LSR one by one from root to leaf node, installing the upstream forwarding table by every node along the LSP. Detail procedure of upstream HSMP LSP is different with that of upstream MP2MP LSP, and is specified in below section. All labels discussed here are downstream-assigned [RFC5332] except those which are assigned using the procedures described in section 5. Determining the upstream LSR for a HSMP LSP follows the procedure for a MP2MP LSP described in [RFC6388] Section 4.3.1.1. Determining one's downstream HSMP LSR procedure is much same as defined in [RFC6388] section 4.3.1.2. A LDP peer U which receives a HSMP-D Label Map from a LDP peer D will treat D as downstream HSMP LSR. Determining the forwarding interface to an LSR has same procedure as defined in [RFC6388] section 2.4.1.2. 4.3.1.1. HSMP LSP leaf node operation The leaf node operation is same as the operation of MP2MP LSP defined in [RFC6388] section 4.3.1.4, only with different FEC element processing and specified below. A leaf node Z will send a HSMP-D Label Map to U, instead of MP2MP-D Label Map . and expects a HSMP-U Label Map from node U and checks whether it already has forwarding state for upstream . The created forwarding state on leaf node Z is same as the leaf node of MP2MP LSP. Z will push label Lu onto the traffic that Z wants to forward over the HSMP LSP. 4.3.1.2. HSMP LSP transit node operation Suppose node Z receives a HSMP-D Label Map from LSR D, the procedure is same as processing MP2MP-D Label Mapping message defined in [RFC6388] section 4.3.1.5, and the processing protocol entity is HSMP-D label mapping message. The different procedure is specified below. Node Z checks if upstream LSR U already assigned a label Lu to upstream . If not, transit node Z waits until it receives a HSMP-U Label Map from LSR U. Once the HSMP-U Label Map is received from LSR U, node Z checks whether it already has forwarding state upstream with incoming label Lu' and outgoing label Lu. If it does, Z sends a HSMP-U Label Map to downstream node. If it does not, it allocates a label Lu' and creates a new Jin, et al. Expires March 7, 2013 [Page 7] Internet-Draft draft-jin-jounay-mpls-mldp-hsmp Sep 2012 label swap for Lu' with Label Lu over interface Iu. Interface Iu is determined via the procedures in Section 4.3.1. Node Z determines the downstream HSMP LSR as per Section 4.3.1, and sends a HSMP-U Label Map to node D. Since a packet from any downstream node is forwarded only to the upstream node, the same label (representing the upstream path) can be distributed to all downstream nodes. This differs from the procedures for MPMP LSPs [RFC6388], where a distinct label must be distributed to each downstream node. The forwarding state upstream on node Z will be like this {, }. Iu means the upstream interface over which Z receives HSMP-U Label Map from LSR U. Packets from any downstream interface over which Z send HSMP-U Label Map with label Lu' will be forwarded to Iu with label Lu' swap to Lu. 4.3.1.3. HSMP LSP root node operation Suppose root node Z receives a HSMP-D Label Map from node D, the procedure is much same as processing MP2MP-D Label Mapping message defined in [RFC6388] section 4.3.1.6, and the processing protocol entity is HSMP-D label mapping message. The different procedure is specified below. Node Z checks if it has forwarding state for upstream . If not, Z creates a forwarding state for incoming label Lu' that indicates that Z is the LSP egress. E.g., the forwarding state might specify that the label stack is popped and the packet passed to some specific application. Node Z determines the downstream HSMP LSR as per section 4.3.1, and sends a HSMP-U Label Map to node D. Since Z is the root of the tree, Z will not send a HSMP-D Label Map and will not receive a HSMP-U Label Map. 4.3.2. HSMP LSP Label Withdraw The HSMP Label Withdraw procedure is much same as MP2MP leaf operation defined in [RFC6388] section 4.3.2, and the processing protocol entities are HSMP FECs. The only difference is process of HSMP-U label release message, which is specified below. When a transit node Z receives a HSMP-U label release message from downstream node D, Z should check if there are any incoming interface in forwarding state upstream . If all downstream nodes are released and there is no incoming interface, Z should delete the forwarding state upstream and send HSMP-U label release message to its upstream node. Jin, et al. Expires March 7, 2013 [Page 8] Internet-Draft draft-jin-jounay-mpls-mldp-hsmp Sep 2012 4.3.3. HSMP LSP upstream LSR change The procedure for changing the upstream LSR is the same as defined in [RFC6388] section 4.3.3, except it is applied to HSMP FECs. 5. HSMP LSP on a LAN The procedure to process P2MP LSP on a LAN has been described in [RFC6388]. When the LSR forwards a packet downstream on one of those LSPs, the packet's top label must be the "upstream LSR label", and the packet's second label is "LSP label". When establishing the downstream path of a HSMP LSP, as defined in [RFC6389], a label request for a LSP label is send to the upstream LSR. The upstream LSR should send label mapping that contains the LSP label for the downstream HSMP FEC and the upstream LSR context label. At the same time, it must also send label mapping for upstream HSMP FEC to downstream node. Packets sent by the upstream router can be forwarded downstream using this forwarding state based on a two label lookup. Packets traveling upstream need to be forwarded in the direction of the root by using the label allocated by upstream LSR. 6. Redundancy considerations In some scenario, it is necessary to provide two root nodes for redundancy purpose. One way to implement this is to use two independent HSMP LSPs acting as active/standby. At one time, only one HSMP LSP will be active, and the other will be standby. After detecting the failure of active HSMP LSP, the root and leaf nodes will switch the traffic to the new active HSMP LSP which is switched from former standby LSP. The detail of redundancy mechanism will be for future study. 7. Co-routed path exceptions There are some exceptional cases that mLDP based HSMP LSP could not achieve co-routed path. One possible case is using static routing between LDP neighbors; another possible case is IGP cost asymmetric generated by physical link cost asymmetric, or TE-Tunnels used between LDP neighbors. The LSR/LER in HSMP LSP could detect if the path is co-routed or not, if not co-routed, an indication could be generated to the management system. Jin, et al. Expires March 7, 2013 [Page 9] Internet-Draft draft-jin-jounay-mpls-mldp-hsmp Sep 2012 8. Security Considerations The same security considerations apply as for the MP2MP LSP described in [RFC6388]. 9. IANA Considerations This document requires allocation of two new LDP FEC Element types from the "Label Distribution Protocol (LDP) Parameters registry" the "Forwarding Equivalence Class (FEC) Type Name Space": 1. the HSMP-upstream FEC type - requested value TBD 2. the HSMP-downstream FEC type - requested value TBD This document requires allocation of one new code points for the HSMP LSP capability TLV from "Label Distribution Protocol (LDP) Parameters registry" the "TLV Type Name Space": HSMP LSP Capability Parameter - requested value TBD 10. Acknowledgement The author would like to thank Eric Rosen, Sebastien Jobert, Fei Su, Edward, Mach Chen, Thomas Morin for their valuable comments. 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. [RFC5332] Eckert, T., Rosen, E., Aggarwal, R., and Y. Rekhter, "MPLS Multicast Encapsulations", RFC 5332, August 2008. [RFC5561] Thomas, B., Raza, K., Aggarwal, S., Aggarwal, R., and JL. Le Roux, "LDP Capabilities", RFC 5561, July 2009. [RFC6388] Wijnands, IJ., Minei, I., Kompella, K., and B. Thomas, "Label Distribution Protocol Extensions for Point-to- Multipoint and Multipoint-to-Multipoint Label Switched Paths", RFC 6388, November 2011. [RFC6389] Aggarwal, R. and JL. Le Roux, "MPLS Upstream Label Jin, et al. Expires March 7, 2013 [Page 10] Internet-Draft draft-jin-jounay-mpls-mldp-hsmp Sep 2012 Assignment for LDP", RFC 6389, November 2011. 11.2. Informative References [I-D.ietf-l2vpn-vpms-frmwk-requirements] Kamite, Y., JOUNAY, F., Niven-Jenkins, B., Brungard, D., and L. Jin, "Framework and Requirements for Virtual Private Multicast Service (VPMS)", draft-ietf-l2vpn-vpms-frmwk-requirements-04 (work in progress), July 2011. [I-D.ietf-pwe3-p2mp-pw] Sivabalan, S., Boutros, S., and L. Martini, "Signaling Root-Initiated Point-to-Multipoint Pseudowire using LDP", draft-ietf-pwe3-p2mp-pw-04 (work in progress), March 2012. [I-D.ietf-tictoc-1588overmpls] Davari, S., Oren, A., Bhatia, M., Roberts, P., and L. Montini, "Transporting PTP messages (1588) over MPLS Networks", draft-ietf-tictoc-1588overmpls-02 (work in progress), October 2011. [IEEE1588] "IEEE standard for a precision clock synchronization protocol for networked measurement and control systems", IEEE1588v2 , March 2008. [RFC4762] Lasserre, M. and V. Kompella, "Virtual Private LAN Service (VPLS) Using Label Distribution Protocol (LDP) Signaling", RFC 4762, January 2007. [RFC6374] Frost, D. and S. Bryant, "Packet Loss and Delay Measurement for MPLS Networks", RFC 6374, September 2011. Authors' Addresses Lizhong Jin ZTE Corporation 889, Bibo Road Shanghai, 201203, China Email: lizhong.jin@zte.com.cn Jin, et al. Expires March 7, 2013 [Page 11] Internet-Draft draft-jin-jounay-mpls-mldp-hsmp Sep 2012 Frederic Jounay France Telecom 2, avenue Pierre-Marzin 22307 Lannion Cedex, FRANCE Email: frederic.jounay@orange.ch IJsbrand Wijnands Cisco Systems, Inc De kleetlaan 6a Diegem 1831, Belgium Email: ice@cisco.com Nicolai Leymann Deutsche Telekom AG Winterfeldtstrasse 21 Berlin 10781 Email: N.Leymann@telekom.de Jin, et al. Expires March 7, 2013 [Page 12]