--- 1/draft-ietf-pce-stateful-sync-optimizations-01.txt 2015-01-13 19:14:37.180299091 -0800 +++ 2/draft-ietf-pce-stateful-sync-optimizations-02.txt 2015-01-13 19:14:37.228300264 -0800 @@ -1,26 +1,27 @@ PCE Working Group E. Crabbe -Internet-Draft I. Minei -Intended status: Standards Track Google, Inc. -Expires: December 29, 2014 J. Medved +Internet-Draft +Intended status: Standards Track I. Minei +Expires: July 16, 2015 Google, Inc. + J. Medved Cisco Systems, Inc. R. Varga Pantheon Technologies SRO X. Zhang D. Dhody Huawei Technologies - June 27, 2014 + January 12, 2015 Optimizations of Label Switched Path State Synchronization Procedures for a Stateful PCE - draft-ietf-pce-stateful-sync-optimizations-01 + draft-ietf-pce-stateful-sync-optimizations-02 Abstract A stateful Path Computation Element (PCE) has access to not only the information disseminated by the network's Interior Gateway Protocol (IGP), but also the set of active paths and their reserved resources for its computation. The additional Label Switched Path (LSP) state information allows the PCE to compute constrained paths while considering individual LSPs and their interactions. This requires a reliable state synchronization mechanism between the PCE and the @@ -45,87 +46,107 @@ 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 December 29, 2014. + This Internet-Draft will expire on July 16, 2015. Copyright Notice - Copyright (c) 2014 IETF Trust and the persons identified as the + 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. Table of Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 - 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3 - 3. State Synchronization Avoidance . . . . . . . . . . . . . . . 3 - 3.1. Motivation . . . . . . . . . . . . . . . . . . . . . . . 3 + 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 + 3. State Synchronization Avoidance . . . . . . . . . . . . . . . 4 + 3.1. Motivation . . . . . . . . . . . . . . . . . . . . . . . 4 3.2. State Synchronization Avoidance Procedure . . . . . . . . 4 - 3.3. PCEP Extensions . . . . . . . . . . . . . . . . . . . . . 8 - 3.3.1. LSP State Database Version Number TLV . . . . . . . . 8 - 3.3.2. Speaker Entity Identifier TLV . . . . . . . . . . . . 9 - 4. Incremental State Synchronization . . . . . . . . . . . . . . 10 - 4.1. Motivation . . . . . . . . . . . . . . . . . . . . . . . 10 - 4.2. Incremental Synchronization Procedure . . . . . . . . . . 11 - 5. PCE-triggered Initial Synchronization . . . . . . . . . . . . 13 - 5.1. Motivation . . . . . . . . . . . . . . . . . . . . . . . 13 - 5.2. PCE-triggered Initial State Synchronization Procedure . . 13 - 6. PCE-triggered Re-synchronization . . . . . . . . . . . . . . 14 - 6.1. Motivation . . . . . . . . . . . . . . . . . . . . . . . 14 - 6.2. PCE-triggered State Re-synchronization Procedure . . . . 14 - 7. Advertising Support of Synchronization Optimizations . . . . 15 - 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 16 - 8.1. PCEP-Error Object . . . . . . . . . . . . . . . . . . . . 16 - 8.2. PCEP TLV Type Indicators . . . . . . . . . . . . . . . . 16 - 8.3. STATEFUL-PCE-CAPABILITY TLV . . . . . . . . . . . . . . . 17 - 9. Security Considerations . . . . . . . . . . . . . . . . . . . 17 - 10. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 17 - 11. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 17 - 12. References . . . . . . . . . . . . . . . . . . . . . . . . . 17 - 12.1. Normative References . . . . . . . . . . . . . . . . . . 17 - 12.2. Informative References . . . . . . . . . . . . . . . . . 18 - Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 18 + 3.3. PCEP Extensions . . . . . . . . . . . . . . . . . . . . . 9 + 3.3.1. LSP State Database Version Number TLV . . . . . . . . 9 + 3.3.2. Speaker Entity Identifier TLV . . . . . . . . . . . . 10 + 4. Incremental State Synchronization . . . . . . . . . . . . . . 11 + 4.1. Motivation . . . . . . . . . . . . . . . . . . . . . . . 11 + 4.2. Incremental Synchronization Procedure . . . . . . . . . . 12 + 5. PCE-triggered Initial Synchronization . . . . . . . . . . . . 15 + 5.1. Motivation . . . . . . . . . . . . . . . . . . . . . . . 15 + 5.2. PCE-triggered Initial State Synchronization Procedure . . 15 + 6. PCE-triggered Re-synchronization . . . . . . . . . . . . . . 16 + 6.1. Motivation . . . . . . . . . . . . . . . . . . . . . . . 16 + 6.2. PCE-triggered State Re-synchronization Procedure . . . . 16 + 7. Advertising Support of Synchronization Optimizations . . . . 17 + 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 18 + 8.1. PCEP-Error Object . . . . . . . . . . . . . . . . . . . . 18 + 8.2. PCEP TLV Type Indicators . . . . . . . . . . . . . . . . 19 + 8.3. STATEFUL-PCE-CAPABILITY TLV . . . . . . . . . . . . . . . 19 + 9. Manageability Considerations . . . . . . . . . . . . . . . . 20 + 9.1. Control of Function and Policy . . . . . . . . . . . . . 20 + 9.2. Information and Data Models . . . . . . . . . . . . . . . 20 + 9.3. Liveness Detection and Monitoring . . . . . . . . . . . . 20 + 9.4. Verify Correct Operations . . . . . . . . . . . . . . . . 20 + 9.5. Requirements On Other Protocols . . . . . . . . . . . . . 20 + 9.6. Impact On Network Operations . . . . . . . . . . . . . . 20 + 10. Security Considerations . . . . . . . . . . . . . . . . . . . 20 + 11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 21 + 12. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 21 + 13. References . . . . . . . . . . . . . . . . . . . . . . . . . 21 + 13.1. Normative References . . . . . . . . . . . . . . . . . . 21 + 13.2. Informative References . . . . . . . . . . . . . . . . . 21 + Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 22 1. Introduction 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. [I-D.ietf-pce-stateful-pce] describes a set of extensions to PCEP to provide stateful control. A stateful PCE has access to not only the information carried by the network's Interior Gateway Protocol (IGP), but also the set of active paths and their reserved resources for its computations. The additional state allows the PCE to compute constrained paths while considering individual LSPs and their interactions. This requires a reliable state synchronization mechanism between the PCE and the network, PCE and PCC, and between cooperating PCEs. [I-D.ietf-pce-stateful-pce] describes the basic - mechanism for state synchronization. This draft specifies + mechanism for state synchronization. This draft specifies following optimizations for state synchronization and the corresponding PCEP - extensions. + procedures and extensions: + + o State Synchronization Avoidance: To skip state synchronization if + the state has survived and not changed during session restart. + (See Section 3.) + + o Incremental State Synchronization: To do incremental (delta) state + synchronization when possible. (See Section 4.) + + o PCE-triggered Initial Synchronization: To let PCE control the + timing of the initial state synchronization. (See Section 5.) + + o PCE-triggered Re-synchronization: To let PCE re-synchronize the + state for sanity check. (See Section 6.) 2. Terminology This document uses the following terms defined in [RFC5440]: PCC, PCE, PCEP Peer. This document uses the following terms defined in [I-D.ietf-pce-stateful-pce] : Delegation, Redelegation Timeout Interval, LSP State Report, LSP Update Request, LSP State Database. @@ -159,63 +180,66 @@ of the changes to the LSP state database, using a version tracking field called the LSP State Database Version Number. The LSP State Database Version Number, carried in LSP-DB-VERSION TLV (see Section 3.3.1), is owned by a PCC and it MUST be incremented by 1 for each successive change in the PCC's LSP state database. The LSP State Database Version Number MUST start at 1 and may wrap around. Values 0 and 0xFFFFFFFFFFFFFFFF are reserved. If either of the two values are used during LSP state (re)-synchronization, the PCE speaker receiving this node should send back a PCErr with Error- - type 20 Error-value 6 'Received an invalid LSP DB Version Number', - and close the PCEP session. Operations that trigger a change to the - local LSP state database include a change in the LSP operational - state, delegation of an LSP, removal or setup of an LSP or change in - any of the LSP attributes that would trigger a report to the PCE. + type 20 Error-value TBD (suggested value - 6) 'Received an invalid + LSP DB Version Number', and close the PCEP session. Operations that + trigger a change to the local LSP state database include a change in + the LSP operational state, delegation of an LSP, removal or setup of + an LSP or change in any of the LSP attributes that would trigger a + report to the PCE. State synchronization avoidance is advertised on a PCEP session - during session startup using the INCLUDE-DB-VERSION (IDB) bit in the + during session startup using the INCLUDE-DB-VERSION (S) bit in the capabilities TLV (see Section 7). The peer may move in the network, either physically or logically, which may cause its connectivity details and transport-level identity (such as IP address) to change. To ensure that a PCEP peer can recognize a previously connected peer even in face of such mobility, each PCEP peer includes the SPEAKER- ENTITY-ID TLV described in Section 3.3.2 in the OPEN message. - If both PCEP speakers set the IDB flag in the OPEN object's STATEFUL- + If both PCEP speakers set the S flag in the OPEN object's STATEFUL- PCE-CAPABILITY TLV to 1, the PCC MUST include the LSP-DB-VERSION TLV in each LSP object of the PCRpt message. If the LSP-DB-VERSION TLV is missing in a PCRpt message, the PCE will generate an error with - error-type 6 (mandatory object missing) and Error Value 12 (LSP-DB- - VERSION TLV missing) and close the session. If state synchronization - avoidance has not been enabled on a PCEP session, the PCC SHOULD NOT - include the LSP-DB-VERSION TLV in the LSP Object and the PCE SHOULD - ignore it were to receive one. + Error-Type 6 (mandatory object missing) and Error-Value TBD + (suggested value - 12) 'LSP-DB-VERSION TLV missing' and close the + session. If state synchronization avoidance has not been enabled on + a PCEP session, the PCC SHOULD NOT include the LSP-DB-VERSION TLV in + the LSP Object and the PCE SHOULD ignore it were to receive one. If a PCE's LSP state database survived the restart of a PCEP session, the PCE will include the LSP-DB-VERSION TLV in its OPEN object, and the TLV will contain the last LSP State Database Version Number received on an LSP State Report from the PCC in the previous PCEP session. If a PCC's LSP State Database survived the restart of a PCEP session, the PCC will include the LSP-DB-VERSION TLV in its OPEN object and the TLV will contain the latest LSP State Database Version Number. If a PCEP speaker's LSP state database did not survive the restart of a PCEP session, the PCEP speaker MUST NOT include the LSP- DB-VERSION TLV in the OPEN object. 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 to the stateful PCE. If the PCC attempts to skip - state synchronization (i.e., the SYNC Flag = 0 on the first LSP State - Report from the PCC as per [I-D.ietf-pce-stateful-pce]), the PCE MUST - send back a PCErr with Error-type 20 Error-value 2 'LSP Database + synchronization. Otherwise, the PCC MUST perform full state + synchronization (see [I-D.ietf-pce-stateful-pce]) or incremental + state synchronization (see Section 4) to the stateful PCE. If the + PCC attempts to skip state synchronization (i.e., the SYNC Flag = 0 + on the first LSP State Report from the PCC as per + [I-D.ietf-pce-stateful-pce]), the PCE MUST send back a PCErr with + Error-Type 20 Error-Value TBD (suggested value - 2) 'LSP Database version mismatch', and close the PCEP session. If state synchronization is required, then prior to completing the initialization phase, the PCE MUST mark any LSPs in the LSP database that were previously reported by the PCC as stale. When the PCC reports an LSP during state synchronization, if the LSP already exists in the LSP database, the PCE MUST update the LSP database and clear the stale marker from the LSP. When it has finished state synchronization, the PCC MUST immediately send an end of synchronization marker. The end of synchronization marker is a Path @@ -241,22 +265,22 @@ Figure 1 shows an example sequence where the state synchronization is skipped. +-+-+ +-+-+ |PCC| |PCE| +-+-+ +-+-+ | | |--Open--, | | DBv=42 \ ,---Open--| - | IDB=1 \ / DBv=42 | - | \/ IDB=1 | + | S=1 \ / DBv=42 | + | \/ S=1 | | /\ | | / `-------->| (OK to skip sync) (Skip sync) |<--------` | | . | | . | | . | | | |--PCRpt,DBv=43,SYNC=0-->| (Regular | | LSP State Report) |--PCRpt,DBv=44,SYNC=0-->| (Regular @@ -271,22 +295,22 @@ session setup. Note that the same state synchronization sequence would happen if either the PCC or the PCE would not include the LSP- DB-VERSION TLV in their respective Open messages. +-+-+ +-+-+ |PCC| |PCE| +-+-+ +-+-+ | | |--Open--, | | DBv=46 \ ,---Open--| - | IDB=1 \ / DBv=42 | - | \/ IDB=1 | + | S=1 \ / DBv=42 | + | \/ S=1 | | /\ | | / `-------->| (Expect sync) (Do sync) |<--------` | | | |--PCRpt,DBv=46,SYNC=1-->| (Sync start) | . | | . | | . | |--PCRpt,DBv=46,SYNC=0-->| (Sync done) | . |(Purge LSP State @@ -295,53 +319,56 @@ |--PCRpt,DBv=47,SYNC=0-->| (Regular | | LSP State Report) |--PCRpt,DBv=48,SYNC=0-->| (Regular | | LSP State Report) |--PCRpt,DBv=49,SYNC=0-->| | | Figure 2: State Synchronization Performed Figure 3 shows an example sequence where the state synchronization is - skipped, but because one or both PCEP speakers set the IDB Flag to 0, + skipped, but because one or both PCEP speakers set the S Flag to 0, the PCC does not send LSP-DB-VERSION TLVs in subsequent PCRpt messages to the PCE. If the current PCEP session restarts, the PCEP speakers will have to perform state synchronization, since the PCE does not know the PCC's latest LSP State Database Version Number information. +-+-+ +-+-+ |PCC| |PCE| +-+-+ +-+-+ | | |--Open--, | | DBv=42 \ ,---Open--| - | IDB=0 \ / DBv=42 | - | \/ IDB=0 | + | S=0 \ / DBv=42 | + | \/ S=0 | | /\ | | / `-------->| (OK to skip sync) (Skip sync) |<--------` | | . | | . | | . | |------PCRpt,SYNC=0----->| (Regular | | LSP State Report) |------PCRpt,SYNC=0----->| (Regular | | LSP State Report) |------PCRpt,SYNC=0----->| | | Figure 3: State Synchronization Skipped, no LSP-DB-VERSION TLVs sent from PCC 3.3. PCEP Extensions + A new INCLUDE-DB-VERSION (S) bit is added in the stateful + capabilities TLV (see Section 7 for details). + 3.3.1. LSP State Database Version Number TLV The LSP State Database Version Number (LSP-DB-VERSION) TLV is an optional TLV that MAY be included in the OPEN object and the LSP object. The format of the LSP-DB-VERSION TLV is shown in the following figure: 0 1 2 3 @@ -387,27 +414,27 @@ +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type=[TBD] | Length (variable) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | // Speaker Entity Identifier // | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 5: SPEAKER-ENTITY-ID TLV format - The type of the TLV is [TBD] and it has a a variable length, which - MUST be greater than 0 and padded to 4-octet alignment (, and padding - is not included in the Length field). The value contains the entity - identifier of the speaker transmitting this TLV. This identifier is - required to be unique within its scope of visibility, which is - usually limited to a single domain. It MAY be configured by the - operator. Alternatively, it can be derived automatically from a + The type of the TLV is [TBD] and it has a variable length, which MUST + be greater than 0. The Value is padded to 4-octet alignment. The + padding is not included in the Length field. The value contains the + entity identifier of the speaker transmitting this TLV. This + identifier is required to be unique within its scope of visibility, + which is usually limited to a single domain. It MAY be configured by + the operator. Alternatively, it can be derived automatically from a suitably-stable unique identifier, such as a MAC address, serial number, Traffic Engineering Router ID, or similar. In the case of inter-domain connections, the speaker SHOULD prefix its usual identifier with the domain identifier of its residence, such as Autonomous System number, IGP area identifier, or similar. The relationship between this identifier and entities in the Traffic Engineering database is intentionally left undefined. From a manageability point of view, a PCE or PCC implementation @@ -415,21 +442,21 @@ Identifier. 4. Incremental State Synchronization [I-D.ietf-pce-stateful-pce] describes the LSP state synchronization mechanism between PCCs and stateful PCEs. During the state synchronization, a PCC sends the information of all its LSPs (i.e., the full LSP-DB) to the stateful PCE. In order to reduce the state synchronization overhead when there is a small number of LSP state change in the network between PCEP session restart, this section - proposes a mechanism for incremental (Delta) LSP Database (LSP-DB) + defines a mechanism for incremental (Delta) LSP Database (LSP-DB) synchronization. 4.1. Motivation According to [I-D.ietf-pce-stateful-pce] , if a PCE restarts and its LSP-DB survived, PCCs with mismatched LSP State Database Version Number 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. @@ -481,42 +508,44 @@ 4.2. Incremental Synchronization Procedure [I-D.ietf-pce-stateful-pce] describes state synchronization and Section 3 describes state synchronization avoidance by using LSP-DB- VERSION TLV in its OPEN object. This section extends this idea to only synchronize the delta (changes) in case of version mismatch. If both PCEP speakers include the LSP-DB-VERSION TLV in the OPEN object and the LSP-DB-VERSION TLV values match, the PCC MAY skip state synchronization. Otherwise, the PCC MUST perform state - synchronization. Instead of dumping full LSP-DB to the stateful PCE - again, the PCC synchronizes the delta (changes) as described in - Figure 7 when DELTA-LSP-SYNC-CAPABILITY (D flag) is set to 1 by both - PCC and PCE (see Section 7). Other combinations of D flag setting by - PCC and PCE result in full LSP-DB synchronization procedure as - described in [I-D.ietf-pce-stateful-pce]. If a PCC has to force full - LSP DB synchronization due to reasons including but not limited: (1) - local policy configured at the PCC; (2) no sufficient LSP state - caches for incremental update, the PCC can set the D flag to 0. Note - a PCC may have to bring down the current session and force a full - LSP-DB synchronization with D flag set to 0 in the subsequent open - message. + synchronization. Incremental State synchronization capability is + advertised on a PCEP session during session startup using the DELTA- + LSP-SYNC-CAPABILITY (D) bit in the capabilities TLV (see Section 7). + Instead of dumping full LSP-DB to the stateful PCE again, the PCC + synchronizes the delta (changes) as described in Figure 7 when D flag + and S flag is set to 1 by both PCC and PCE. Other combinations of D + and S flags setting by PCC and PCE result in full LSP-DB + synchronization procedure as described in + [I-D.ietf-pce-stateful-pce]. If a PCC has to force full LSP DB + synchronization due to reasons including but not limited: (1) local + policy configured at the PCC; (2) no sufficient LSP state caches for + incremental update, the PCC can set the D flag to 0. Note a PCC may + have to bring down the current session and force a full LSP-DB + synchronization with D flag set to 0 in the subsequent open message. +-+-+ +-+-+ |PCC| |PCE| +-+-+ +-+-+ | | |--Open--, | | DBv=46 \ ,---Open--| - | IDB=1 \ / DBv=42 | - | T=1 \/ IDB=1 | - | /\ T=1 | + | S=1 \ / DBv=42 | + | D=1 \/ S=1 | + | /\ D=1 | | / \ | | / `-------->| (Expect Delta sync) (Do sync)|<--------` | (DONOT Purge LSP (Delta) | | State) | | (Delta Sync starts) |--PCRpt,DBv=46,SYNC=1-->| | . | | . | | . | | . | @@ -534,36 +563,40 @@ As per Section 3, the LSP State Database Version Number 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. It is not necessary for a PCC to store a complete history of LSP Database change, but rather remember the LSP state changes (including - LSP modification, setup and deletion) that happend between the PCEP + LSP modification, setup and deletion) that happened between the PCEP session(s) restart in order to carry out incremental state synchronization. After the synchronization procedure finishes, the PCC can dump this history information. In the example shown in - Figure 7, the PCC needs to store the LSP state changes that happend + Figure 7, the PCC needs to store the LSP state changes that happened between DB Version 43 to 46 and synchronizes these changes only when performing incremental LSP state update. So a PCC needs to remember the LSP state changes that happened when an existing PCEP session to a stateful PCE goes down in the hope of doing incremental synchronisation when the session is re-established. If a PCC finds out it does not have sufficient information to complete incremental synchronisation after advertising incremental LSP state synchronization capability, it MUST send a PCErr with - error-type 20 and error-value 5(see Section 8.1) and terminate the - session. + Error-Type 20 and Error-Value 5 'A PCC indicates to a PCE that it can + not complete the state synchronization' (defined in + [I-D.ietf-pce-stateful-pce]) and terminate the session. + + The other procedures and error checks remain unchanged from the full + state synchronization ([I-D.ietf-pce-stateful-pce]). 5. PCE-triggered Initial Synchronization 5.1. Motivation In networks such as optical transport networks, the control channel between network nodes can be realized through in-band overhead thus has limited bandwidth. With a stateful PCE connected to the network via one network node, it is desirable to control the timing of PCC state synchronization so as not to overload the low communication @@ -571,235 +604,303 @@ (be it incremental or full) when the session restarts , when there is comparatively large amount of control information needing to be synchronized between the stateful PCE and the network. The method proposed, i.e., allowing PCE to trigger the state synchronization, is similar to the function proposed in Section 6 but is used in different scenarios and for different purposes. 5.2. PCE-triggered Initial State Synchronization Procedure Support of PCE-triggered state synchronization is advertised during - session startup using the TRIGGERED-SYNC (T) bit in the STATEFUL-PCE- - CAPABILITY TLV (see Section 7). + session startup using the TRIGGERED-INITIAL-SYNC (F) bit in the + STATEFUL-PCE-CAPABILITY TLV (see Section 7). + + If the TRIGGERED-INITIAL-SYNC capability is not advertised and the + PCC receives a PCUpd with the SYNC flag set to 1, it MUST send a + PCErr with the SRP-ID-number of the PCUpd, Error-Type 20 and Error- + Value TBD (suggested value - 4) 'Attempt to trigger synchronization + when the TRIGGERED-SYNC capability has not been advertised' (see + Section 8.1). A stateful PCE MAY choose to control the LSP-DB synchronization process. To allow PCE to do so, PCEP speakers MUST set T bit to 1 to - indicate this (as described in Section 6). If the LSP-DB Version is + indicate this (as described in Section 7). If the LSP-DB Version is mis-matched, it can send a PCUpd message with PLSP-ID = 0 and SYNC = 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 are re-establishing PCEP sessions with it. When the capability of PCE control is enabled, only after a PCC receives - this message, it will start sending information to the PCE. This - PCE-triggering capability can be applied to both full and incremental - state synchronization. If applied to the later, the PCCs only send - information that PCE does not possess, which is inferred from the - LSP-DB version information exchanged in the OPEN message (see - Section 4.2 for detailed procedure). + this message, it will start sending information to the PCE. The PCC + SHOULD NOT send PCRpt messages to the stateful PCE before it triggers + the State Synchronization. This PCE-triggering capability can be + applied to both full and incremental state synchronization. If + applied to the later, the PCCs only send information that PCE does + not possess, which is inferred from the LSP-DB version information + exchanged in the OPEN message (see Section 4.2 for detailed + procedure). + + Once the initial state synchronization is triggered by the PCE, the + procedures and error checks remain unchanged from the full state + synchronization ([I-D.ietf-pce-stateful-pce]). 6. PCE-triggered Re-synchronization 6.1. Motivation The accuracy of the computations performed by the PCE is tied to the accuracy of the view the PCE has on the state of the LSPs. - Therefore, it can be beneficial to be able to resynchronize this + Therefore, it can be beneficial to be able to re-synchronize this state even after the session has been established. The PCE may use this approach to continuously sanity check its state against the network, or to recover from error conditions without having to tear down sessions. 6.2. PCE-triggered State Re-synchronization Procedure Support of PCE-triggered state synchronization is advertised during - session startup using the TRIGGERED-SYNC (T) bit in the STATEFUL-PCE- - CAPABILITY TLV (see Section 7). The PCE can choose to resynchronize - its entire LSP database or a single LSP. + session startup using the TRIGGERED-RESYNC (T) bit in the STATEFUL- + PCE-CAPABILITY TLV (see Section 7). The PCE can choose to re- + synchronize its entire LSP database or a single LSP. - To trigger resynchronization for an LSP, the PCE MUST first mark the + To trigger re-synchronization for an LSP, the PCE MUST first mark the LSP as stale and then send a Path Computation State Update (PCUpd) for it, with the SYNC flag in the LSP object set to 1. The PCE SHOULD NOT include any parameter updates for the LSP, and the PCC SHOULD ignore such updates if the SYNC flag is set. The PCC MUST - respond with a PCRpt message and SHOULD include the SRP-ID-number of - the PCUpd that triggered the resynchronization. + respond with a PCRpt message with the LSP state, SYNC Flag set to 0 + and MUST include the SRP-ID-number of the PCUpd message that + triggered the resynchronization. - The PCE can also trigger resynchronization of the entire LSP + The PCE can also trigger re-synchronization of the entire LSP database. The PCE MUST first mark all LSPs in the LSP database that were previously reported by the PCC as stale and then send a PCUpd with an LSP object containing a PLSP-ID of 0 and with the SYNC flag set to 1. This PCUpd message is the trigger for the PCC to enter the synchronization phase as described in [I-D.ietf-pce-stateful-pce] and start sending PCRpt messages. After the receipt of the end-of- synchronization marker, the PCE will purge LSPs which were not - refreshed. The SRP-ID-number of the PCUpd that triggered the - resynchronization SHOULD be included in each of the PCRpt messages. + refreshed. The SRP-ID-number of the PCUpd that triggered the re- + synchronization SHOULD be included in each of the PCRpt messages. - If the TRIGGERED-SYNC capability is not advertised and the PCC + If the TRIGGERED-RESYNC capability is not advertised and the PCC receives a PCUpd with the SYNC flag set to 1, it MUST send a PCErr - with the SRP-ID-number of the PCUpd, error-type 20 and error-value - 4.(see Section 8.1) + with the SRP-ID-number of the PCUpd, Error-Type 20 and Error-Value + TBD (suggested value - 4) 'Attempt to trigger synchronization when + the TRIGGERED-SYNC capability has not been advertised' (see + Section 8.1). + + Once the state re-synchronization is triggered by the PCE, the + procedures and error checks remain unchanged from the full state + synchronization ([I-D.ietf-pce-stateful-pce]). This would also + include PCE triggering multiple state re-synchronization requests + while synchronization is in progress. 7. Advertising Support of Synchronization Optimizations Support for each of the optimizations described in this document requires advertising the corresponding capabilities during session establishment time. New flags are defined for the STATEFUL-PCE-CAPABILITY TLV defined in [I-D.ietf-pce-stateful-pce]. Its format is shown in the following figure: 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type | Length=4 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ - | Flags |D|T|I|S|U| + | Flags |F|D|T|I|S|U| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 8: STATEFUL-PCE-CAPABILITY TLV Format The value comprises a single field - Flags (32 bits): U (LSP-UPDATE-CAPABILITY - 1 bit): defined in [I-D.ietf-pce-stateful-pce]. S (INCLUDE-DB-VERSION - 1 bit): if set to 1 by both PCEP Speakers, the PCC will include the LSP-DB-VERSION TLV in each LSP Object. + See Section 3.2 for details. I (LSP-INSTANTIATION-CAPABILITY - 1 bit): defined in [I-D.ietf-pce-p ce-initiated-lsp]. - T (TRIGGERED-SYNC - 1 bit): if set to 1 by both PCEP Speakers, the - PCE can trigger (re)-synchronization of LSPs at any point in the - life of the session. + T (TRIGGERED-RESYNC - 1 bit): if set to 1 by both PCEP Speakers, the + PCE can trigger re-synchronization of LSPs at any point in the + life of the session. See Section 6.2 for details. D (DELTA-LSP-SYNC-CAPABILITY - 1 bit): if set to 1 by a PCEP speaker, it indicates that the PCEP speaker allows incremental - state synchronization. + (delta) state synchronization. See Section 4.2 for details. + + F (TRIGGERED-INITIAL-SYNC - 1 bit): if set to 1 by both PCEP + Speakers, the PCE SHOULD trigger initial (first) state + synchronization. See Section 5.2 for details. 8. IANA Considerations This document requests IANA actions to allocate code points for the protocol elements defined in this document. 8.1. PCEP-Error Object IANA is requested to make the following allocation in the "PCEP-ERROR Object Error Types and Values" registry. Error-Type Meaning Reference 6 Mandatory Object missing [RFC5440] - Error-value= TBD(suggested This document + Error-Value= TBD(suggested This document value 12): LSP-DB-VERSION TLV missing 20 LSP State synchronization [I-D.ietf-pce-stateful-pce] error - Error-value= TBD(suggested This document + Error-Value= TBD(suggested This document value 2): LSP Database version mismatch. - Error-value=TBD(suggested This document + Error-Value=TBD(suggested This document value 3): The LSP-DB-VERSION TLV Missing when state synchronization avoidance is enabled. - Error-value=TBD(suggested This document + Error-Value=TBD(suggested This document value 4): Attempt to trigger a synchronization when the - TRIGGERED-SYNC capability has - not been advertised. - Error-value=TBD(suggested This document + PCE triggered synchronization + capability has not been + advertised. + Error-Value=TBD(suggested This document value 6): No sufficient LSP change information for incremental LSP state synchronization. - Error-value=TBD(suggested This document + Error-Value=TBD(suggested This document value 7): Received an invalid LSP DB Version Number 8.2. PCEP TLV Type Indicators This document defines the following new PCEP TLVs: Value Meaning Reference - TBD(suggested value LSP-DB-VERSION This document - 23) - TBD(suggested value SPEAKER-ENTITY-ID This document - 24) + TBD(suggested value 23) LSP-DB-VERSION This document + TBD(suggested value 24) SPEAKER-ENTITY-ID This document 8.3. STATEFUL-PCE-CAPABILITY TLV The following values are defined in this document for the Flags field in the STATEFUL-PCE-CAPABILITY-TLV in the OPEN object: Bit Description Reference + TBD(suggested value 26) TRIGGERED-INITIAL-SYNC This document + TBD(suggested value 27) DELTA-LSP-SYNC-CAPABILITY This document + TBD(suggested value 28) TRIGGERED-RESYNC This document + TBD(suggested value 30) INCLUDE-DB-VERSION This document - TBD(suggested value DELTA-LSP-SYNC-CAPABILITY This document - 28) - TBD(suggested value TRIGGERED-SYNC This document - 29) - TBD(suggested value INCLUDE-DB-VERSION This document - 30) +9. Manageability Considerations -9. Security Considerations + All manageability requirements and considerations listed in [RFC5440] + and [I-D.ietf-pce-stateful-pce] apply to PCEP protocol extensions + defined in this document. In addition, requirements and + considerations listed in this section apply. + +9.1. Control of Function and Policy + + A PCE or PCC implementation MUST allow configuring the state + synchronization optimization capabilities as described in this + document. The implementation SHOULD also allow the operator to + configure the Speaker Entity Identifier (Section 3.3.2). + +9.2. Information and Data Models + + The PCEP MIB module SHOULD be extended to include advertised stateful + capabilities, and synchronization status. + +9.3. Liveness Detection and Monitoring + + Mechanisms defined in this document do not imply any new liveness + detection and monitoring requirements in addition to those already + listed in [RFC5440]. + +9.4. Verify Correct Operations + + Mechanisms defined in this document do not imply any new operation + verification requirements in addition to those already listed in + [RFC5440] and [I-D.ietf-pce-stateful-pce]. + +9.5. Requirements On Other Protocols + + Mechanisms defined in this document do not imply any new requirements + on other protocols. + +9.6. Impact On Network Operations + + Mechanisms defined in this document do not have any impact on network + operations in addition to those already listed in [RFC5440] and + [I-D.ietf-pce-stateful-pce]. + +10. Security Considerations The security considerations listed in [I-D.ietf-pce-stateful-pce] - apply to this document as well. + apply to this document as well. However, because the protocol + modifications outlined in this document allow the PCE to control + state (re)-synchronization timing and sequence, it also introduces a + new attack vector: an attacker may flood the PCC with triggered re- + synchronization request at a rate which exceeds the PCC's ability to + process them, either by spoofing messages or by compromising the PCE + itself. The PCC is free to drop any trigger re-synchronization + request without additional processing. -10. Acknowledgements +11. Acknowledgements - We would like to thank Young Lee and Jonathan Hardwick for their - comments and discussions. + We would like to thank Young Lee, Jonathan Hardwick, Sergio Belotti + and Cyril Margaria for their comments and discussions. -11. Contributors +12. Contributors Gang Xie Huawei Technologies F3-5-B R&D Center, Huawei Industrial Base, Bantian, Longgang District Shenzhen, Guangdong, 518129 P.R. China Email: xiegang09@huawei.com -12. References +13. References -12.1. Normative References +13.1. Normative References [I-D.ietf-pce-stateful-pce] Crabbe, E., Minei, I., Medved, J., and R. Varga, "PCEP Extensions for Stateful PCE", draft-ietf-pce-stateful- - pce-09 (work in progress), June 2014. + pce-10 (work in progress), October 2014. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC5440] Vasseur, JP. and JL. Le Roux, "Path Computation Element (PCE) Communication Protocol (PCEP)", RFC 5440, March 2009. -12.2. Informative References +13.2. Informative References [I-D.ietf-pce-pce-initiated-lsp] Crabbe, E., Minei, I., Sivabalan, S., and R. Varga, "PCEP Extensions for PCE-initiated LSP Setup in a Stateful PCE - Model", draft-ietf-pce-pce-initiated-lsp-01 (work in - progress), June 2014. + Model", draft-ietf-pce-pce-initiated-lsp-02 (work in + progress), October 2014. Authors' Addresses Edward Crabbe - Google, Inc. - 1600 Amphitheatre Parkway - Mountain View, CA 94043 - US - Email: edc@google.com + Email: edward.crabbe@gmail.com Ina Minei Google, Inc. 1600 Amphitheatre Parkway Mountain View, CA 94043 US Email: inaminei@google.com Jan Medved @@ -810,25 +911,25 @@ Email: jmedved@cisco.com Robert Varga Pantheon Technologies SRO Mlynske Nivy 56 Bratislava 821 05 Slovakia Email: robert.varga@pantheon.sk + Xian Zhang Huawei Technologies F3-5-B R&D Center, Huawei Industrial Base, Bantian, Longgang District Shenzhen, Guangdong 518129 P.R.China Email: zhang.xian@huawei.com - Dhruv Dhody Huawei Technologies Leela Palace Bangalore, Karnataka 560008 - INDIA + India Email: dhruv.ietf@gmail.com