Network Working Group Xian Zhang Internet-Draft Gang Xie Intended status: Standard Track Dhruv Dhody Huawei Expires: January 04, 2014 July 05, 2013 LSP Synchronization for Stateful Path Computation Element (PCE) draft-zhx-pce-stateful-lsp-sync-00.txt Abstract The Path Computation Element Communication Protocol (PCEP) provides mechanisms for Path Computation Elements (PCEs) to perform path computations in response to Path Computation Clients (PCCs) requests. [Stateful-pcep] specifies a set of extensions to PCEP to enable stateful control of MPLS-TE and GMPLS Label Switched Paths (LSPs) via PCEP and maintaining of these LSPs at the stateful PCE. This document describes the mechanisms for incremental LSP Database (LSP- DB) synchronization as well as PCE control of the LSP-DB synchronization process. Status of this Memo This Internet-Draft is submitted to IETF in full conformance with the provisions of BCP 78 and BCP 79. Internet-Drafts are working documents of the Internet Engineering Task Force (IETF), its areas, and its working groups. Note that other groups may also distribute working documents as Internet- Drafts. 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." The list of current Internet-Drafts can be accessed at http://www.ietf.org/ietf/1id-abstracts.txt. The list of Internet-Draft Shadow Directories can be accessed at http://www.ietf.org/shadow.html. This Internet-Draft will expire on January 04, 2014. Zhang et al Expires December 2014 [Page 1] draft-zhx-pce-stateful-lsp-sync-00.txt July 2013 Copyright Notice Copyright (c) 2013 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. Motivation ............................................. 3 1.2. Conventions used in this document .......................4 2. PCEP Requirements and Objective ..............................4 3. LSP Synchronization Procedure................................ 4 3.1. New PCEP extensions .....................................4 3.2. Procedure .............................................. 4 4. IANA Considerations ......................................... 6 5. Manageability Considerations .................................6 6. Security Considerations ......................................6 7. Contributors ................................................ 6 8. References .................................................. 7 8.1. Normative References.................................... 7 Authors' Addresses ............................................. 7 1. Introduction [Stateful-pcep] describes a Label Switched Path (LSP) state synchronization mechanism between Path Computation Clients (PCCs) and PCEs for a stateful PCE. It includes mechanisms for LSP state synchronization and avoidance between a PCC and a PCE when the PCEP session restarts. After PCEP session set up, PCC compares the LSP State Database version with the PCE. If the database version is mismatched, state synchronization will be performed. During state synchronization, a PCC sends the information of all its LSPs (full LSP-DB) to the stateful PCE. This document proposes a mechanism for incremental (Delta) LSP Database (LSP-DB) synchronization as well as allowing PCE to control the timing of the LSP-DB synchronization process. Zhang et al Expires January 2014 [Page 2] draft-zhx-pce-stateful-lsp-sync-00.txt July 2013 1.1. Motivation If a PCE restarts and its LSP-DB survived, all PCCs with mismatched LSP State Database version will send all their LSPs information (full LSP-DB) to the stateful PCE, even if only a small number of LSPs underwent state change. It can take a long time and consume large communication channel bandwidth. Moreover, the stateful PCE can get overloaded with all the PCC performing full synchronization with it at the same time. Figure 1 shows an example of LSP state synchronization. +-----+ | PCE | +-----+ / / / / +------+ +------+ | PCC1 |------------| PCC2 | +------+ +------+ | | | | +------+ +------+ | PCC3 |------------| PCC4 | +------+ +------+ Assuming there are 320 LSPs in the network, with each PCC having 80 LSPs. During the time when the PCEP session is down, 20 LSPs of each PCC (i.e., 80 LSPs in total), are changed. Hence when PCEP session restarts, the stateful PCE needs to synchronize 320 LSPs with all PCCs. But actually, 240 LSPs stay the same. If performing full LSP state synchronization, it can take a long time to carry out the synchronization of all LSPs. It is especially true when only a low bandwidth communication channel is available and there is a substantial number of LSPs in the network. Another disadvantage of full LSP synchronization is that it is a waste of communication bandwidth to perform full LSP synchronization given the fact that the number of LSP changes can be small during the time when PCEP session is down. An incremental (Delta) LSP Database (LSP-DB) state synchronization is described in this document, where only the LSPs underwent state change are synchronized between the session restart. This may include new/modify/deleted LSPs. Furthermore, to avoid overloading the PCE, the proposed method enable a stateful PCE to control the LSP synchronization timing. Zhang et al Expires January 2014 [Page 3] draft-zhx-pce-stateful-lsp-sync-00.txt July 2013 1.2. 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 RFC-2119 [RFC2119]. 2. PCEP Requirements and Objective PCEP extensions for stateful PCEs to perform LSP synchronization SHOULD allow: - Incremental LSP state synchronization between session restarts. Note this does not exclude the need for a stateful PCE to request a full LSP DB synchronization. - A stateful PCE to control the timing of PCC synchronizing its LSP state with the PCE. 3. LSP Synchronization Procedure [Stateful-pcep] describes state synchronization as well as state synchronization avoidance by using LSP-DB-VERSION TLV in its OPEN object. This document extends this idea to only synchronize the delta (changes) in case of version mismatch as well as to allow a stateful PCE to control the timing of this process. 3.1. New PCEP extensions Two new bits are added in the STATEFUL-PCE-CAPABILITY TLV defined in [Stateful-pcep] for incremental (delta) LSP synchronization and PCE control: D (DELTA-LSP-SYNC-CAPABILITY - 1 bit): if set to 1 by a PCEP speaker, the D Flag indicates that the PCEP speaker allows delta or incremental state synchronization. C (PCE-CONTROL-SYNC - 1 bit): if set to 1 by a stateful PCE, the C Flag indicates that the PCE will control the triggering of LSP state synchronization. This bit is not used by a PCC and MUST be set to 0 and ignored by the PCE upon receipt. 3.2. Procedure If both PCEP speakers include the LSP-DB-VERSION TLV in the OPEN Object and the TLV values match, the PCC MAY skip state synchronization. Otherwise, the PCC MUST perform state synchronization. Instead of dumping full LSP-DB to PCE again, the PCC synchronizes the delta (changes) as described in figure 1 when D flag is set to 1 by both PCC and PCE. Other combinations of D flag setting by PCC and PCE result in full LSP-DB synchronization procedure as described in [Stateful-pcep]. Zhang et al Expires January 2014 [Page 4] draft-zhx-pce-stateful-lsp-sync-00.txt July 2013 +-+-+ +-+-+ |PCC| |PCE| +-+-+ +-+-+ | | |--Open--, | | DBv=46 \ ,---Open--| | IDB=1 \ / DBv=42 | | D=1 \/ IDB=1 | | /\ C=1 | | / \ D=1 | | / `-------->| (Expect Delta sync) (Do sync) |<--------` | (Do not Purge LSP State) (Delta) | | (Wait for PCE to | | trigger LSP state | | sync) | | |<-----PCUpd, S=1--------| (ask for LSP Sync, PLSP-ID =0) | | (Delta Sync starts) |--PCRpt,DBv=43,SYNC=1-->| | . | | . | | . | | . | |--PCRpt,DBv=46,SYNC=0-->| (Sync done, PLSP-ID=0) | | | | |--PCRpt,DBv=47,SYNC=0-->| (Regular | | LSP State Report) |--PCRpt,DBv=48,SYNC=0-->| (Regular | | LSP State Report) |--PCRpt,DBv=49,SYNC=0-->| | | A stateful PCE MAY choose to control the LSP-DB synchronization process. To allow PCE to do so, it MUST set C bit to 1 to indicate this. If the LSP DB version is mis-matched, it can send a PCUpd message with PLSP-ID = 0 and S =1 in order to trigger the LSP-DB synchronization process. In this way, the PCE can control the sequence of LSP synchronization among all the PCCs that re- establishing PCEP sessions with it. When the capability of PCE control is enable, only after a PCC receives this message, it will then start sending information that PCE does not possess, which is Zhang et al Expires January 2014 [Page 5] draft-zhx-pce-stateful-lsp-sync-00.txt July 2013 inferred from the LSP DB Version information exchange in the OPEN message. As per [Stateful-pcep], the LSP State Database version is incremented each time a change is made to the PCC's local LSP State Database. Each LSP is associated with the DB version at the time of its state change. This is needed to determine which LSP and what information needs to be synchronized in incremental state synchronization. In the example shown in Figure 1, PCC synchronizes all LSPs that are updated between DB Version 43 to 46. A PCC SHOULD remember the deleted LSP as well, so that PCRpt message with deleted status can be sent to the stateful PCE. 4. IANA Considerations 4.1. STATEFUL-PCE-CAPABILITY TLV As discussed in Section 3.1, two new STATEFUL-PCE-CAPABILITY TLV Flag Field has been defined. IANA has made the following allocation from the PCEP "STATEFUL-PCE-CAPABILITY TLV Flag Field" sub-registry: Bit Description Reference TBD DELTA-LSP-SYNC-CAPABILITY [This I.D.] TBD PCE-CONTROL-SYNC-CAPABILITY [This I.D.] 5. Manageability Considerations The procedure defined in this document does not incur new manageability issues and the issues described in [Stateful-pcep] should be followed. 6. Security Considerations NONE 7. Contributors Young Lee Huawei Technologies 5360 Legacy Dr. Building 3 Plano, TX 75024 USA Phone: (469) 277-5838 Email: leeyoung@huawei.com Zhang et al Expires January 2014 [Page 6] draft-zhx-pce-stateful-lsp-sync-00.txt July 2013 8. References 8.1. Normative References [Stateful-pcep] Crabbe, E., Medved, J., Varga, R., Minei, I., "PCEP Extensions for Stateful PCE", draft-ietf-pce-stateful-pce, work in progress. Authors' Addresses Xian Zhang Huawei Technologies Research Area F3-1B, Huawei Industrial Base, Shenzhen, 518129, China Phone: +86-755-28972645 Email: zhang.xian@huawei.com Gang Xie Huawei Technologies Research Area F3 Huawei Industrial Base, Shenzhen, 518129, China Email xiegang09@huawei.com Dhruv Dhody Huawei Technologies Leela Palace Bangalore, Karnataka 560008 INDIA Email: dhruv.dhody@huawei.com Zhang et al Expires January 2014 [Page 7]