draft-ietf-pce-stateful-sync-optimizations-03.txt   draft-ietf-pce-stateful-sync-optimizations-04.txt 
PCE Working Group E. Crabbe PCE Working Group E. Crabbe
Internet-Draft Internet-Draft
Intended status: Standards Track I. Minei Intended status: Standards Track I. Minei
Expires: April 8, 2016 Google, Inc. Expires: May 4, 2016 Google, Inc.
J. Medved J. Medved
Cisco Systems, Inc. Cisco Systems, Inc.
R. Varga R. Varga
Pantheon Technologies SRO Pantheon Technologies SRO
X. Zhang X. Zhang
D. Dhody D. Dhody
Huawei Technologies Huawei Technologies
October 6, 2015 November 1, 2015
Optimizations of Label Switched Path State Synchronization Procedures Optimizations of Label Switched Path State Synchronization Procedures
for a Stateful PCE for a Stateful PCE
draft-ietf-pce-stateful-sync-optimizations-03 draft-ietf-pce-stateful-sync-optimizations-04
Abstract Abstract
A stateful Path Computation Element (PCE) has access to not only the A stateful Path Computation Element (PCE) has access to not only the
information disseminated by the network's Interior Gateway Protocol information disseminated by the network's Interior Gateway Protocol
(IGP), but also the set of active paths and their reserved resources (IGP), but also the set of active paths and their reserved resources
for its computation. The additional Label Switched Path (LSP) state for its computation. The additional Label Switched Path (LSP) state
information allows the PCE to compute constrained paths while information allows the PCE to compute constrained paths while
considering individual LSPs and their interactions. This requires a considering individual LSPs and their interactions. This requires a
reliable state synchronization mechanism between the PCE and the reliable state synchronization mechanism between the PCE and the
skipping to change at page 1, line 42 skipping to change at page 1, line 42
motivations for optimizations to the base state synchronization motivations for optimizations to the base state synchronization
procedure and specifies the required Path Computation Element procedure and specifies the required Path Computation Element
Communication Protocol (PCEP) extensions. Communication Protocol (PCEP) extensions.
Requirements Language Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119]. document are to be interpreted as described in [RFC2119].
Status of This Memo Status of this Memo
This Internet-Draft is submitted in full conformance with the This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79. provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet- working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/. Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any and may be updated, replaced, or obsoleted by other documents at any
time. It is inappropriate to use Internet-Drafts as reference time. It is inappropriate to use Internet-Drafts as reference
material or to cite them other than as "work in progress." material or to cite them other than as "work in progress."
This Internet-Draft will expire on April 8, 2016. This Internet-Draft will expire on May 4, 2016.
Copyright Notice Copyright Notice
Copyright (c) 2015 IETF Trust and the persons identified as the Copyright (c) 2015 IETF Trust and the persons identified as the
document authors. All rights reserved. document authors. All rights reserved.
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Table of Contents Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4 2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. State Synchronization Avoidance . . . . . . . . . . . . . . . 4 3. State Synchronization Avoidance . . . . . . . . . . . . . . . 5
3.1. Motivation . . . . . . . . . . . . . . . . . . . . . . . 4 3.1. Motivation . . . . . . . . . . . . . . . . . . . . . . . . 5
3.2. State Synchronization Avoidance Procedure . . . . . . . . 4 3.2. State Synchronization Avoidance Procedure . . . . . . . . 5
3.3. PCEP Extensions . . . . . . . . . . . . . . . . . . . . . 9 3.3. PCEP Extensions . . . . . . . . . . . . . . . . . . . . . 9
3.3.1. LSP State Database Version Number TLV . . . . . . . . 9 3.3.1. LSP State Database Version Number TLV . . . . . . . . 9
3.3.2. Speaker Entity Identifier TLV . . . . . . . . . . . . 10 3.3.2. Speaker Entity Identifier TLV . . . . . . . . . . . . 10
4. Incremental State Synchronization . . . . . . . . . . . . . . 11 4. Incremental State Synchronization . . . . . . . . . . . . . . 11
4.1. Motivation . . . . . . . . . . . . . . . . . . . . . . . 11 4.1. Motivation . . . . . . . . . . . . . . . . . . . . . . . . 12
4.2. Incremental Synchronization Procedure . . . . . . . . . . 12 4.2. Incremental Synchronization Procedure . . . . . . . . . . 13
5. PCE-triggered Initial Synchronization . . . . . . . . . . . . 15 5. PCE-triggered Initial Synchronization . . . . . . . . . . . . 15
5.1. Motivation . . . . . . . . . . . . . . . . . . . . . . . 15 5.1. Motivation . . . . . . . . . . . . . . . . . . . . . . . . 15
5.2. PCE-triggered Initial State Synchronization Procedure . . 15 5.2. PCE-triggered Initial State Synchronization Procedure . . 15
6. PCE-triggered Re-synchronization . . . . . . . . . . . . . . 16 6. PCE-triggered Re-synchronization . . . . . . . . . . . . . . . 16
6.1. Motivation . . . . . . . . . . . . . . . . . . . . . . . 16 6.1. Motivation . . . . . . . . . . . . . . . . . . . . . . . . 16
6.2. PCE-triggered State Re-synchronization Procedure . . . . 16 6.2. PCE-triggered State Re-synchronization Procedure . . . . . 16
7. Advertising Support of Synchronization Optimizations . . . . 17 7. Advertising Support of Synchronization Optimizations . . . . . 17
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 18 8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 18
8.1. PCEP-Error Object . . . . . . . . . . . . . . . . . . . . 18 8.1. PCEP-Error Object . . . . . . . . . . . . . . . . . . . . 18
8.2. PCEP TLV Type Indicators . . . . . . . . . . . . . . . . 19 8.2. PCEP TLV Type Indicators . . . . . . . . . . . . . . . . . 19
8.3. STATEFUL-PCE-CAPABILITY TLV . . . . . . . . . . . . . . . 19 8.3. STATEFUL-PCE-CAPABILITY TLV . . . . . . . . . . . . . . . 19
9. Manageability Considerations . . . . . . . . . . . . . . . . 20 9. Manageability Considerations . . . . . . . . . . . . . . . . . 20
9.1. Control of Function and Policy . . . . . . . . . . . . . 20 9.1. Control of Function and Policy . . . . . . . . . . . . . . 20
9.2. Information and Data Models . . . . . . . . . . . . . . . 20 9.2. Information and Data Models . . . . . . . . . . . . . . . 20
9.3. Liveness Detection and Monitoring . . . . . . . . . . . . 20 9.3. Liveness Detection and Monitoring . . . . . . . . . . . . 20
9.4. Verify Correct Operations . . . . . . . . . . . . . . . . 20 9.4. Verify Correct Operations . . . . . . . . . . . . . . . . 20
9.5. Requirements On Other Protocols . . . . . . . . . . . . . 20 9.5. Requirements On Other Protocols . . . . . . . . . . . . . 20
9.6. Impact On Network Operations . . . . . . . . . . . . . . 20 9.6. Impact On Network Operations . . . . . . . . . . . . . . . 21
10. Security Considerations . . . . . . . . . . . . . . . . . . . 20 10. Security Considerations . . . . . . . . . . . . . . . . . . . 21
11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 21 11. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 21
12. Contributors . . . . . . . . . . . . . . . . . . . . . . . . 21 12. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 21
13. References . . . . . . . . . . . . . . . . . . . . . . . . . 21 13. References . . . . . . . . . . . . . . . . . . . . . . . . . . 21
13.1. Normative References . . . . . . . . . . . . . . . . . . 21 13.1. Normative References . . . . . . . . . . . . . . . . . . . 21
13.2. Informative References . . . . . . . . . . . . . . . . . 21 13.2. Informative References . . . . . . . . . . . . . . . . . . 22
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 22 Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 22
1. Introduction 1. Introduction
The Path Computation Element Communication Protocol (PCEP) provides The Path Computation Element Communication Protocol (PCEP) provides
mechanisms for Path Computation Elements (PCEs) to perform path mechanisms for Path Computation Elements (PCEs) to perform path
computations in response to Path Computation Clients (PCCs) requests. computations in response to Path Computation Clients (PCCs) requests.
[I-D.ietf-pce-stateful-pce] describes a set of extensions to PCEP to [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 provide stateful control. A stateful PCE has access to not only the
information carried by the network's Interior Gateway Protocol (IGP), information carried by the network's Interior Gateway Protocol (IGP),
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o PCE-triggered Re-synchronization: To let PCE re-synchronize the o PCE-triggered Re-synchronization: To let PCE re-synchronize the
state for sanity check. (See Section 6.) state for sanity check. (See Section 6.)
2. Terminology 2. Terminology
This document uses the following terms defined in [RFC5440]: PCC, This document uses the following terms defined in [RFC5440]: PCC,
PCE, PCEP Peer. PCE, PCEP Peer.
This document uses the following terms defined in This document uses the following terms defined in
[I-D.ietf-pce-stateful-pce] : Delegation, Redelegation Timeout [I-D.ietf-pce-stateful-pce]: Delegation, Redelegation Timeout
Interval, LSP State Report, LSP Update Request, LSP State Database. Interval, LSP State Report, LSP Update Request, LSP State Database.
Within this document, when describing PCE-PCE communications, the Within this document, when describing PCE-PCE communications, the
requesting PCE fills the role of a PCC. This provides a saving in requesting PCE fills the role of a PCC. This provides a saving in
documentation without loss of function. documentation without loss of function.
3. State Synchronization Avoidance 3. State Synchronization Avoidance
3.1. Motivation 3.1. Motivation
skipping to change at page 5, line 9 skipping to change at page 5, line 45
around. Values 0 and 0xFFFFFFFFFFFFFFFF are reserved. If either of around. Values 0 and 0xFFFFFFFFFFFFFFFF are reserved. If either of
the two values are used during LSP state (re)-synchronization, the the two values are used during LSP state (re)-synchronization, the
PCE speaker receiving this node should send back a PCErr with Error- PCE speaker receiving this node should send back a PCErr with Error-
type 20 Error-value TBD (suggested value - 6) 'Received an invalid type 20 Error-value TBD (suggested value - 6) 'Received an invalid
LSP DB Version Number', and close the PCEP session. Operations that LSP DB Version Number', and close the PCEP session. Operations that
trigger a change to the local LSP state database include a change in 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 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 an LSP or change in any of the LSP attributes that would trigger a
report to the PCE. report to the PCE.
If state synchronization avoidance is enabled, a PCC MUST increment
its LSP State Database Version Number when the 'Redelegation Timeout
Interval' timer expires (see [I-D.ietf-pce-stateful-pce]) for the use
of the Redelegation Timeout Interval).
State synchronization avoidance is advertised on a PCEP session State synchronization avoidance is advertised on a PCEP session
during session startup using the INCLUDE-DB-VERSION (S) 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, capabilities TLV (see Section 7). The peer may move in the network,
either physically or logically, which may cause its connectivity either physically or logically, which may cause its connectivity
details and transport-level identity (such as IP address) to change. details and transport-level identity (such as IP address) to change.
To ensure that a PCEP peer can recognize a previously connected peer To ensure that a PCEP peer can recognize a previously connected peer
even in face of such mobility, each PCEP peer includes the SPEAKER- 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. ENTITY-ID TLV described in Section 3.3.2 in the OPEN message.
If both PCEP speakers set the S 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 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 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 is missing in a PCRpt message, the PCE will generate an error with
Error-Type 6 (mandatory object missing) and Error-Value TBD Error-Type 6 (mandatory object missing) and Error-Value TBD
(suggested value - 12) 'LSP-DB-VERSION TLV missing' and close the (suggested value - 12) 'LSP-DB-VERSION TLV missing' and close the
session. If state synchronization avoidance has not been enabled on session. If state synchronization avoidance has not been enabled on
a PCEP session, the PCC SHOULD NOT include the LSP-DB-VERSION TLV in 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. the LSP Object and the PCE SHOULD ignore it were it to receive one.
If a PCE's LSP state database survived the restart of a PCEP session, 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 PCE will include the LSP-DB-VERSION TLV in its OPEN object, and
the TLV will contain the last LSP State Database Version Number the TLV will contain the last LSP State Database Version Number
received on an LSP State Report from the PCC in the previous PCEP 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 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 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 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 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- restart of a PCEP session, the PCEP speaker MUST NOT include the LSP-
DB-VERSION TLV in the OPEN object. DB-VERSION TLV in the OPEN object.
If both PCEP speakers include the LSP-DB-VERSION TLV in the OPEN If both PCEP speakers include the LSP-DB-VERSION TLV in the OPEN
Object and the TLV values match, the PCC MAY skip state Object and the TLV values match, the PCC MAY skip state
synchronization. Otherwise, the PCC MUST perform full state synchronization. Otherwise, the PCC MUST perform full state
synchronization (see [I-D.ietf-pce-stateful-pce]) or incremental synchronization (see [I-D.ietf-pce-stateful-pce]) or incremental
state synchronization (see Section 4) to the stateful PCE. If the state synchronization (see Section 4) to the stateful PCE. If the
PCC attempts to skip state synchronization (i.e., the SYNC Flag = 0 PCC attempts to skip state synchronization, by setting the SYNC Flag
on the first LSP State Report from the PCC as per to 0 and PLSP-ID to a non-zero value on the first LSP State Report
[I-D.ietf-pce-stateful-pce]), the PCE MUST send back a PCErr with from the PCC as per [I-D.ietf-pce-stateful-pce], the PCE MUST send
Error-Type 20 Error-Value TBD (suggested value - 2) 'LSP Database back a PCErr with Error-Type 20 Error-Value TBD (suggested value - 2)
version mismatch', and close the PCEP session. 'LSP Database version mismatch', and close the PCEP session.
If state synchronization is required, then prior to completing the If state synchronization is required, then prior to completing the
initialization phase, the PCE MUST mark any LSPs in the LSP database initialization phase, the PCE MUST mark any LSPs in the LSP database
that were previously reported by the PCC as stale. When the PCC that were previously reported by the PCC as stale. When the PCC
reports an LSP during state synchronization, if the LSP already reports an LSP during state synchronization, if the LSP already
exists in the LSP database, the PCE MUST update the LSP database and 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 clear the stale marker from the LSP. When it has finished state
synchronization, the PCC MUST immediately send an end of synchronization, the PCC MUST immediately send an end of
synchronization marker. The end of synchronization marker is a Path synchronization marker. The end of synchronization marker is a Path
Computation State Report (PCRpt) message with an LSP object Computation State Report (PCRpt) message with an LSP object
skipping to change at page 6, line 25 skipping to change at page 7, line 17
as stale. as stale.
Note that a PCE/PCC MAY force state synchronization by not including Note that a PCE/PCC MAY force state synchronization by not including
the LSP-DB-VERSION TLV in its OPEN object. the LSP-DB-VERSION TLV in its OPEN object.
Since a PCE does not make changes to the LSP State Database Version Since a PCE does not make changes to the LSP State Database Version
Number, a PCC should never encounter this TLV in a message from the Number, a PCC should never encounter this TLV in a message from the
PCE (other than the OPEN message). A PCC SHOULD ignore the LSP-DB- PCE (other than the OPEN message). A PCC SHOULD ignore the LSP-DB-
VERSION TLV, were it to receive one from a PCE. VERSION TLV, were it to receive one from a PCE.
If state synchronization avoidance is enabled, a PCC MUST increment
its LSP State Database Version Number when the 'Redelegation Timeout
Interval' timer expires (see [I-D.ietf-pce-stateful-pce]) for the use
of the Redelegation Timeout Interval).
Figure 1 shows an example sequence where the state synchronization is Figure 1 shows an example sequence where the state synchronization is
skipped. skipped.
+-+-+ +-+-+ +-+-+ +-+-+
|PCC| |PCE| |PCC| |PCE|
+-+-+ +-+-+ +-+-+ +-+-+
| | | |
|--Open--, | |--Open--, |
| DBv=42 \ ,---Open--| | DBv=42 \ ,---Open--|
| S=1 \ / DBv=42 | | S=1 \ / DBv=42 |
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mechanism between PCCs and stateful PCEs. During the state mechanism between PCCs and stateful PCEs. During the state
synchronization, a PCC sends the information of all its LSPs (i.e., 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 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 synchronization overhead when there is a small number of LSP state
change in the network between PCEP session restart, this section change in the network between PCEP session restart, this section
defines a mechanism for incremental (Delta) LSP Database (LSP-DB) defines a mechanism for incremental (Delta) LSP Database (LSP-DB)
synchronization. synchronization.
4.1. Motivation 4.1. Motivation
According to [I-D.ietf-pce-stateful-pce] , if a PCE restarts and its According to [I-D.ietf-pce-stateful-pce], if a PCE restarts and its
LSP-DB survived, PCCs with mismatched LSP State Database Version LSP-DB survived, PCCs with mismatched LSP State Database Version
Number will send all their LSPs information (full LSP-DB) to the Number will send all their LSPs information (full LSP-DB) to the
stateful PCE, even if only a small number of LSPs underwent state stateful PCE, even if only a small number of LSPs underwent state
change. It can take a long time and consume large communication change. It can take a long time and consume large communication
channel bandwidth. channel bandwidth.
Figure 6 shows an example of LSP state synchronization. Figure 6 shows an example of LSP state synchronization.
+-----+ +-----+
| PCE | | PCE |
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Figure 6: Topology Example Figure 6: Topology Example
Assuming there are 320 LSPs in the network, with each PCC having 80 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 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 PCC (i.e., 80 LSPs in total), are changed. Hence when PCEP session
restarts, the stateful PCE needs to synchronize 320 LSPs with all restarts, the stateful PCE needs to synchronize 320 LSPs with all
PCCs. But actually, 240 LSPs stay the same. If performing full LSP PCCs. But actually, 240 LSPs stay the same. If performing full LSP
state synchronization, it can take a long time to carry out the state synchronization, it can take a long time to carry out the
synchronization of all LSPs. It is especially true when only a low synchronization of all LSPs. It is especially true when only a low
bandwidth communication channel is available and there is a bandwidth communication channel is available (e.g., in-band control
substantial number of LSPs in the network. Another disadvantage of channel for optical transport networks) and there is a substantial
full LSP synchronization is that it is a waste of communication number of LSPs in the network. Another disadvantage of full LSP
bandwidth to perform full LSP synchronization given the fact that the synchronization is that it is a waste of communication bandwidth to
number of LSP changes can be small during the time when PCEP session perform full LSP synchronization given the fact that the number of
is down. LSP changes can be small during the time when PCEP session is down.
An incremental (Delta) LSP Database (LSP-DB) state synchronization is An incremental (Delta) LSP Database (LSP-DB) state synchronization is
described in this section, where only the LSPs underwent state change described in this section, where only the LSPs underwent state change
are synchronized between the session restart. This may include are synchronized between the session restart. This may include new/
new/modified/deleted LSPs. modified/deleted LSPs.
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.
4.2. Incremental Synchronization Procedure 4.2. Incremental Synchronization Procedure
[I-D.ietf-pce-stateful-pce] describes state synchronization and [I-D.ietf-pce-stateful-pce] describes state synchronization and
Section 3 describes state synchronization avoidance by using LSP-DB- Section 3 describes state synchronization avoidance by using LSP-DB-
VERSION TLV in its OPEN object. This section extends this idea to VERSION TLV in its OPEN object. This section extends this idea to
only synchronize the delta (changes) in case of version mismatch. only synchronize the delta (changes) in case of version mismatch.
If both PCEP speakers include the LSP-DB-VERSION TLV in the OPEN 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 object and the LSP-DB-VERSION TLV values match, the PCC MAY skip
state synchronization. Otherwise, the PCC MUST perform state state synchronization. Otherwise, the PCC MUST perform state
synchronization. Incremental State synchronization capability is synchronization. Incremental State synchronization capability is
advertised on a PCEP session during session startup using the DELTA- advertised on a PCEP session during session startup using the DELTA-
LSP-SYNC-CAPABILITY (D) bit in the capabilities TLV (see Section 7). 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 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 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 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 and S flags setting by PCC and PCE result in full LSP-DB
synchronization procedure as described in synchronization procedure as described in
[I-D.ietf-pce-stateful-pce]. If a PCC has to force full LSP DB [I-D.ietf-pce-stateful-pce]. The PCC MAY force a full LSP DB
synchronization due to reasons including but not limited: (1) local synchronization by setting the D flag to zero in the OPEN message.
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| |PCC| |PCE|
+-+-+ +-+-+ +-+-+ +-+-+
| | | |
|--Open--, | |--Open--, |
| DBv=46 \ ,---Open--| | DBv=46 \ ,---Open--|
| S=1 \ / DBv=42 | | S=1 \ / DBv=42 |
| D=1 \/ S=1 | | D=1 \/ S=1 |
| /\ D=1 | | /\ D=1 |
skipping to change at page 15, line 4 skipping to change at page 15, line 7
It is not necessary for a PCC to store a complete history of LSP It is not necessary for a PCC to store a complete history of LSP
Database change, but rather remember the LSP state changes (including Database change, but rather remember the LSP state changes (including
LSP modification, setup and deletion) that happened between the PCEP LSP modification, setup and deletion) that happened between the PCEP
session(s) restart in order to carry out incremental state session(s) restart in order to carry out incremental state
synchronization. After the synchronization procedure finishes, the synchronization. After the synchronization procedure finishes, the
PCC can dump this history information. In the example shown in PCC can dump this history information. In the example shown in
Figure 7, the PCC needs to store the LSP state changes that happened 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 between DB Version 43 to 46 and synchronizes these changes only when
performing incremental LSP state update. So a PCC needs to remember performing incremental LSP state update. So a PCC needs to remember
the LSP state changes that happened when an existing PCEP session to at least the LSP state changes that happened after an existing PCEP
a stateful PCE goes down in the hope of doing incremental session with a stateful PCE goes down to have any chance of doing
synchronisation when the session is re-established. incremental synchronisation when the session is re-established.
If a PCC finds out it does not have sufficient information to If a PCC finds out it does not have sufficient information to
complete incremental synchronisation after advertising incremental complete incremental synchronisation after advertising incremental
LSP state synchronization capability, it MUST send a PCErr with LSP state synchronization capability, it MUST send a PCErr with
Error-Type 20 and Error-Value 5 'A PCC indicates to a PCE that it can Error-Type 20 and Error-Value 5 'A PCC indicates to a PCE that it can
not complete the state synchronization' (defined in not complete the state synchronization' (defined in
[I-D.ietf-pce-stateful-pce]) and terminate the session. [I-D.ietf-pce-stateful-pce]) and terminate the session. The PCC
SHOULD re-establish the session with the D bit set to 0 in the OPEN
message.
The other procedures and error checks remain unchanged from the full The other procedures and error checks remain unchanged from the full
state synchronization ([I-D.ietf-pce-stateful-pce]). state synchronization ([I-D.ietf-pce-stateful-pce]).
5. PCE-triggered Initial Synchronization 5. PCE-triggered Initial Synchronization
5.1. Motivation 5.1. Motivation
In networks such as optical transport networks, the control channel In networks such as optical transport networks, the control channel
between network nodes can be realized through in-band overhead thus between network nodes can be realized through in-band overhead thus
skipping to change at page 15, line 37 skipping to change at page 15, line 42
channel available in the network during the initial synchronization channel available in the network during the initial synchronization
(be it incremental or full) when the session restarts , when there is (be it incremental or full) when the session restarts , when there is
comparatively large amount of control information needing to be comparatively large amount of control information needing to be
synchronized between the stateful PCE and the network. The method synchronized between the stateful PCE and the network. The method
proposed, i.e., allowing PCE to trigger the state synchronization, is proposed, i.e., allowing PCE to trigger the state synchronization, is
similar to the function proposed in Section 6 but is used in similar to the function proposed in Section 6 but is used in
different scenarios and for different purposes. different scenarios and for different purposes.
5.2. PCE-triggered Initial State Synchronization Procedure 5.2. PCE-triggered Initial State Synchronization Procedure
Support of PCE-triggered state synchronization is advertised during Support of PCE-triggered initial state synchronization is advertised
session startup using the TRIGGERED-INITIAL-SYNC (F) bit in the during session startup using the TRIGGERED-INITIAL-SYNC (F) bit in
STATEFUL-PCE-CAPABILITY TLV (see Section 7). 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 In order to allow a stateful PCE to control the LSP-DB
process. To allow PCE to do so, PCEP speakers MUST set T bit to 1 to synchronization after establishing a PCEP session, both PCEP speakers
indicate this (as described in Section 7). If the LSP-DB Version is MUST set F bit to 1 in the OPEN message. If the TRIGGERED-INITIAL-
mis-matched, it can send a PCUpd message with PLSP-ID = 0 and SYNC = SYNC capability is not advertised by a PCE and the PCC receives a
1 in order to trigger the LSP-DB synchronization process. In this PCUpd with the SYNC flag set to 1, it MUST send a PCErr with the SRP-
way, the PCE can control the sequence of LSP synchronization among ID-number of the PCUpd, Error-Type 20 and Error-Value TBD (suggested
all the PCCs that are re-establishing PCEP sessions with it. When value - 4) 'Attempt to trigger synchronization when the TRIGGERED-
the capability of PCE control is enabled, only after a PCC receives SYNC capability has not been advertised' (see Section 8.1). If the
this message, it will start sending information to the PCE. The PCC LSP-DB Version is mis-matched, it can send a PCUpd message with
SHOULD NOT send PCRpt messages to the stateful PCE before it triggers PLSP-ID = 0 and SYNC = 1 in order to trigger the LSP-DB
the State Synchronization. This PCE-triggering capability can be synchronization process. In this way, the PCE can control the
applied to both full and incremental state synchronization. If sequence of LSP synchronization among all the PCCs that are re-
applied to the later, the PCCs only send information that PCE does establishing PCEP sessions with it. When the capability of PCE
not possess, which is inferred from the LSP-DB version information control is enabled, only after a PCC receives this message, it will
exchanged in the OPEN message (see Section 4.2 for detailed start sending information to the PCE. The PCC SHOULD NOT send PCRpt
procedure). 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 Once the initial state synchronization is triggered by the PCE, the
procedures and error checks remain unchanged from the full state procedures and error checks remain unchanged from the full state
synchronization ([I-D.ietf-pce-stateful-pce]). synchronization ([I-D.ietf-pce-stateful-pce]).
6. PCE-triggered Re-synchronization 6. PCE-triggered Re-synchronization
6.1. Motivation 6.1. Motivation
The accuracy of the computations performed by the PCE is tied to the 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. accuracy of the view the PCE has on the state of the LSPs.
Therefore, it can be beneficial to be able to re-synchronize 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 state even after the session has been established. The PCE may use
this approach to continuously sanity check its state against the this approach to continuously sanity check its state against the
network, or to recover from error conditions without having to tear network, or to recover from error conditions without having to tear
down sessions. down sessions.
6.2. PCE-triggered State Re-synchronization Procedure 6.2. PCE-triggered State Re-synchronization Procedure
Support of PCE-triggered state synchronization is advertised during Support of PCE-triggered state synchronization is advertised by both
session startup using the TRIGGERED-RESYNC (T) bit in the STATEFUL- PCEP speakers during session startup using the TRIGGERED-RESYNC (T)
PCE-CAPABILITY TLV (see Section 7). The PCE can choose to re- bit in the STATEFUL-PCE-CAPABILITY TLV (see Section 7). The PCE can
synchronize its entire LSP database or a single LSP. choose to re-synchronize its entire LSP database or a single LSP.
To trigger re-synchronization 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) 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 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 NOT include any parameter updates for the LSP, and the PCC
SHOULD ignore such updates if the SYNC flag is set. The PCC MUST SHOULD ignore such updates if the SYNC flag is set. The PCC MUST
respond with a PCRpt message with the LSP state, SYNC Flag set to 0 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 and MUST include the SRP-ID-number of the PCUpd message that
triggered the resynchronization. triggered the resynchronization.
skipping to change at page 17, line 12 skipping to change at page 17, line 17
database. The PCE MUST first mark all LSPs in the LSP database that 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 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 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 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 synchronization phase as described in [I-D.ietf-pce-stateful-pce] and
start sending PCRpt messages. After the receipt of the end-of- start sending PCRpt messages. After the receipt of the end-of-
synchronization marker, the PCE will purge LSPs which were not synchronization marker, the PCE will purge LSPs which were not
refreshed. The SRP-ID-number of the PCUpd that triggered the re- refreshed. The SRP-ID-number of the PCUpd that triggered the re-
synchronization SHOULD be included in each of the PCRpt messages. synchronization SHOULD be included in each of the PCRpt messages.
If the TRIGGERED-RESYNC capability is not advertised and the PCC If the TRIGGERED-RESYNC capability is not advertised by a PCE and the
receives a PCUpd with the SYNC flag set to 1, it MUST send a PCErr PCC receives a PCUpd with the SYNC flag set to 1, it MUST send a
with the SRP-ID-number of the PCUpd, Error-Type 20 and Error-Value PCErr with the SRP-ID-number of the PCUpd, Error-Type 20 and Error-
TBD (suggested value - 4) 'Attempt to trigger synchronization when Value TBD (suggested value - 4) 'Attempt to trigger synchronization
the TRIGGERED-SYNC capability has not been advertised' (see when the TRIGGERED-SYNC capability has not been advertised' (see
Section 8.1). Section 8.1).
Once the state re-synchronization is triggered by the PCE, the Once the state re-synchronization is triggered by the PCE, the
procedures and error checks remain unchanged from the full state procedures and error checks remain unchanged from the full state
synchronization ([I-D.ietf-pce-stateful-pce]). This would also synchronization ([I-D.ietf-pce-stateful-pce]). This would also
include PCE triggering multiple state re-synchronization requests include PCE triggering multiple state re-synchronization requests
while synchronization is in progress. while synchronization is in progress.
7. Advertising Support of Synchronization Optimizations 7. Advertising Support of Synchronization Optimizations
skipping to change at page 18, line 9 skipping to change at page 18, line 15
The value comprises a single field - Flags (32 bits): The value comprises a single field - Flags (32 bits):
U (LSP-UPDATE-CAPABILITY - 1 bit): defined in U (LSP-UPDATE-CAPABILITY - 1 bit): defined in
[I-D.ietf-pce-stateful-pce]. [I-D.ietf-pce-stateful-pce].
S (INCLUDE-DB-VERSION - 1 bit): if set to 1 by both PCEP Speakers, 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. the PCC will include the LSP-DB-VERSION TLV in each LSP Object.
See Section 3.2 for details. See Section 3.2 for details.
I (LSP-INSTANTIATION-CAPABILITY - 1 bit): defined in [I-D.ietf-pce-p I (LSP-INSTANTIATION-CAPABILITY - 1 bit): defined in
ce-initiated-lsp]. [I-D.ietf-pce-pce-initiated-lsp].
T (TRIGGERED-RESYNC - 1 bit): if set to 1 by both PCEP Speakers, the 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 PCE can trigger re-synchronization of LSPs at any point in the
life of the session. See Section 6.2 for details. life of the session. See Section 6.2 for details.
D (DELTA-LSP-SYNC-CAPABILITY - 1 bit): if set to 1 by a PCEP D (DELTA-LSP-SYNC-CAPABILITY - 1 bit): if set to 1 by a PCEP
speaker, it indicates that the PCEP speaker allows incremental speaker, it indicates that the PCEP speaker allows incremental
(delta) state synchronization. See Section 4.2 for details. (delta) state synchronization. See Section 4.2 for details.
F (TRIGGERED-INITIAL-SYNC - 1 bit): if set to 1 by both PCEP F (TRIGGERED-INITIAL-SYNC - 1 bit): if set to 1 by both PCEP
skipping to change at page 19, line 37 skipping to change at page 19, line 37
value 6): No sufficient LSP value 6): No sufficient LSP
change information for change information for
incremental LSP state incremental LSP state
synchronization. synchronization.
Error-Value=TBD(suggested This document Error-Value=TBD(suggested This document
value 7): Received an invalid value 7): Received an invalid
LSP DB Version Number LSP DB Version Number
8.2. PCEP TLV Type Indicators 8.2. PCEP TLV Type Indicators
This document defines the following new PCEP TLVs: IANA is requested to make the following allocation in the "PCEP TLV
Type Indicators" registry.
Value Meaning Reference Value Meaning Reference
TBD(suggested value 23) LSP-DB-VERSION This document TBD(suggested value 23) LSP-DB-VERSION This document
TBD(suggested value 24) SPEAKER-ENTITY-ID This document TBD(suggested value 24) SPEAKER-ENTITY-ID This document
8.3. STATEFUL-PCE-CAPABILITY TLV 8.3. STATEFUL-PCE-CAPABILITY TLV
The following values are defined in this document for the Flags field The STATEFUL-PCE-CAPABILITY TLV is defined in
in the STATEFUL-PCE-CAPABILITY-TLV in the OPEN object: [I-D.ietf-pce-stateful-pce] and a registry is requested to be created
to manage the flags in the TLV. IANA is requested to make the
following allocation in the aforementioned registry.
Bit Description Reference Bit Description Reference
TBD(suggested value 26) TRIGGERED-INITIAL-SYNC This document TBD(suggested value 26) TRIGGERED-INITIAL-SYNC This document
TBD(suggested value 27) DELTA-LSP-SYNC-CAPABILITY This document TBD(suggested value 27) DELTA-LSP-SYNC-CAPABILITY This document
TBD(suggested value 28) TRIGGERED-RESYNC This document TBD(suggested value 28) TRIGGERED-RESYNC This document
TBD(suggested value 30) INCLUDE-DB-VERSION This document TBD(suggested value 30) INCLUDE-DB-VERSION This document
9. Manageability Considerations 9. Manageability Considerations
All manageability requirements and considerations listed in [RFC5440] All manageability requirements and considerations listed in [RFC5440]
and [I-D.ietf-pce-stateful-pce] apply to PCEP protocol extensions and [I-D.ietf-pce-stateful-pce] apply to PCEP protocol extensions
defined in this document. In addition, requirements and defined in this document. In addition, requirements and
considerations listed in this section apply. considerations listed in this section apply.
9.1. Control of Function and Policy 9.1. Control of Function and Policy
A PCE or PCC implementation MUST allow configuring the state A PCE or PCC implementation MUST allow configuring the state
synchronization optimization capabilities as described in this synchronization optimization capabilities as described in this
document. The implementation SHOULD also allow the operator to document. The implementation SHOULD also allow the operator to
configure the Speaker Entity Identifier (Section 3.3.2). configure the Speaker Entity Identifier ( Section 3.3.2).
9.2. Information and Data Models 9.2. Information and Data Models
The PCEP MIB module SHOULD be extended to include advertised stateful An implementation SHOULD allow the operator to view the stateful
capabilities, and synchronization status. capabilities advertised by each peer, and the current synchronization
status with each peer. To serve this purpose, the PCEP MIB module
can be extended to include advertised stateful capabilities, and
synchronization status.
9.3. Liveness Detection and Monitoring 9.3. Liveness Detection and Monitoring
Mechanisms defined in this document do not imply any new liveness Mechanisms defined in this document do not imply any new liveness
detection and monitoring requirements in addition to those already detection and monitoring requirements in addition to those already
listed in [RFC5440]. listed in [RFC5440].
9.4. Verify Correct Operations 9.4. Verify Correct Operations
Mechanisms defined in this document do not imply any new operation Mechanisms defined in this document do not imply any new operation
skipping to change at page 21, line 21 skipping to change at page 21, line 34
We would like to thank Young Lee, Jonathan Hardwick, Sergio Belotti We would like to thank Young Lee, Jonathan Hardwick, Sergio Belotti
and Cyril Margaria for their comments and discussions. and Cyril Margaria for their comments and discussions.
12. Contributors 12. Contributors
Gang Xie Gang Xie
Huawei Technologies Huawei Technologies
F3-5-B R&D Center, Huawei Industrial Base, Bantian, Longgang District F3-5-B R&D Center, Huawei Industrial Base, Bantian, Longgang District
Shenzhen, Guangdong, 518129 Shenzhen, Guangdong, 518129
P.R. China P.R. China
Email: xiegang09@huawei.com Email: xiegang09@huawei.com
13. References 13. References
13.1. Normative References 13.1. Normative References
[I-D.ietf-pce-stateful-pce] [I-D.ietf-pce-stateful-pce]
Crabbe, E., Minei, I., Medved, J., and R. Varga, "PCEP Crabbe, E., Minei, I., Medved, J., and R. Varga, "PCEP
Extensions for Stateful PCE", draft-ietf-pce-stateful- Extensions for Stateful PCE",
pce-11 (work in progress), April 2015. draft-ietf-pce-stateful-pce-12 (work in progress),
October 2015.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119, Requirement Levels", BCP 14, RFC 2119, DOI 10.17487/
DOI 10.17487/RFC2119, March 1997, RFC2119, March 1997,
<http://www.rfc-editor.org/info/rfc2119>. <http://www.rfc-editor.org/info/rfc2119>.
[RFC5440] Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation [RFC5440] Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation
Element (PCE) Communication Protocol (PCEP)", RFC 5440, Element (PCE) Communication Protocol (PCEP)", RFC 5440,
DOI 10.17487/RFC5440, March 2009, DOI 10.17487/RFC5440, March 2009,
<http://www.rfc-editor.org/info/rfc5440>. <http://www.rfc-editor.org/info/rfc5440>.
13.2. Informative References 13.2. Informative References
[I-D.ietf-pce-pce-initiated-lsp] [I-D.ietf-pce-pce-initiated-lsp]
Crabbe, E., Minei, I., Sivabalan, S., and R. Varga, "PCEP Crabbe, E., Minei, I., Sivabalan, S., and R. Varga, "PCEP
Extensions for PCE-initiated LSP Setup in a Stateful PCE Extensions for PCE-initiated LSP Setup in a Stateful PCE
Model", draft-ietf-pce-pce-initiated-lsp-04 (work in Model", draft-ietf-pce-pce-initiated-lsp-05 (work in
progress), April 2015. progress), October 2015.
Authors' Addresses Authors' Addresses
Edward Crabbe Edward Crabbe
Email: edward.crabbe@gmail.com Email: edward.crabbe@gmail.com
Ina Minei Ina Minei
Google, Inc. Google, Inc.
1600 Amphitheatre Parkway 1600 Amphitheatre Parkway
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