PCE Working Group E. Crabbe
Internet-Draft Google, Inc.
Intended status: Standards Track J. Medved
Expires: April 11, 2014 Cisco Systems, Inc.
I. Minei
Juniper Networks, Inc.
R. Varga
Pantheon Technologies SRO
X. Zhang
D. Dhody
Huawei Technologies
October 8, 2013
Optimizations of State Synchronization Procedures for Stateful PCE
draft-minei-pce-stateful-sync-optimizations-00
Abstract
A stateful Path Computation Element (PCE) has access to not only the
information carried by the network's IGP, but also to 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
reliable state synchronization mechanisms between the PCE and the
network, PCE and path computation clients (PCCs), and between
cooperating PCEs. The basic mechanism for state synchronization is
part of the Stateful PCE specification. This draft specifies
optimizations related to state synchronization procedures.
Requirements Language
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in [RFC2119].
Status of this Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at http://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
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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 April 11, 2014.
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.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . 4
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
3. State synchronization avoidance . . . . . . . . . . . . . . . 4
3.1. Motivation . . . . . . . . . . . . . . . . . . . . . . . . 4
3.2. State Synchronization Avoidance procedures . . . . . . . . 5
3.3. LSP State Database Version Number TLV . . . . . . . . . . 9
3.3.1. Use of the LSP-DB-VERSION TLV in the OPEN object . . . 10
3.3.2. Use of the LSP-DB-VERSION TLV in the LSP object . . . 10
3.4. Speaker Entity Identifier TLV . . . . . . . . . . . . . . 10
4. PCE-triggered State Synchronization . . . . . . . . . . . . . 11
4.1. Motivation . . . . . . . . . . . . . . . . . . . . . . . . 11
4.2. PCE-triggered State Synchronization Procedures . . . . . . 11
5. Incremental State Synchronization . . . . . . . . . . . . . . 12
5.1. Motivation . . . . . . . . . . . . . . . . . . . . . . . . 12
5.2. Incremental synchronization procedures . . . . . . . . . . 14
6. Advertising support of the synchronization optimizations . . . 16
7. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 17
7.1. PCEP-Error Object . . . . . . . . . . . . . . . . . . . . 17
7.2. PCEP TLV Type Indicators . . . . . . . . . . . . . . . . . 17
7.3. STATEFUL-PCE-CAPABILITY TLV . . . . . . . . . . . . . . . 17
8. Security Considerations . . . . . . . . . . . . . . . . . . . 18
9. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . . 18
10. Contributors . . . . . . . . . . . . . . . . . . . . . . . . . 18
11. Normative References . . . . . . . . . . . . . . . . . . . . . 18
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . . 19
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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 IGP, but also to 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
reliable state synchronization mechanisms 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 optimizations for state
synchronization.
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] : Passive Stateful PCE, Active Stateful
PCE, Delegation, Delegation Timeout Interval, LSP State Report, LSP
Update Request, LSP Priority, LSP State Database, Revocation.
Within this document, when describing PCE-PCE communications, the
requesting PCE fills the role of a PCC. This provides a saving in
documentation without loss of function.
The message formats in this document are specified using Routing
Backus-Naur Format (RBNF) encoding as specified in [RFC5511].
3. State synchronization avoidance
3.1. Motivation
The purpose of State Synchronization is to provide a checkpoint-in-
time state replica of a PCC's LSP state in a PCE. State
Synchronization is performed immediately after the Initialization
phase ([RFC5440]). [I-D.ietf-pce-stateful-pce] describes the basic
mechanism for state synchronization.
State synchronization is not always necessary following a PCEP
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session restart. If the state of both PCEP peers did not change, the
synchronization phase may be skipped. This can result in significant
savings in both control-plane data exchanged and the time it takes
for the session to become fully operational.
3.2. State Synchronization Avoidance procedures
State Synchronization MAY be skipped following a PCEP session restart
if the state of both PCEP peers did not change during the period
prior to session re-initialization. To be able to make this
determination, state must be exchanged and maintained by both PCE and
PCC during normal operation. This is accomplished by keeping track
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 is an unsigned 64-bit value
that MUST be incremented by 1 for each successive change in the LSP
state database. The LSP State Database Version Number MUST start at
1 and may wrap around. Values 0 and 0xFFFFFFFFFFFFFFFF are reserved.
The PCC is the owner of the LSP State Database Version Number, which
is incremented each time a change is made to the PCC's local LSP
State Database. 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 addition of an LSP or change in any
of the LSP attributes that would trigger a report to the PCE. When
State Synchronization avoidance is enabled on a PCEP session, a PCC
includes the LSP-DB-VERSION TLV in the LSP Object on each LSP State
Report. The LSP-DB-VERSION TLV contains a PCC's LSP State Database
version.
State Synchronization Avoidance is advertised on a PCEP session
during session startup using the INCLUDE-DB-VERSION bit in the
capabilities TLV (see Section 6). 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 3.4 in the OPEN message.
If both PCEP speakers set the INCLUDE-DB-VERSION Flag in the OPEN
object's STATEFUL-PCE-CAPABILITY TLV to 1, the PCC will include the
LSP-DB-VERSION TLV in each LSP Object. The TLV will contain the
PCC's latest LSP State Database Version Number.
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 a previous PCEP
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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 sent on an LSP State Report from the PCC in the previous PCEP
session. 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. If the PCC attempts to skip State Synchronization
(i.e. the SYNC Flag = 0 on the first LSP State Report from the PCC),
the PCE MUST send back a PCError with Error-type 20 Error-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 PCRpt
message with an LSP object containing a PLSP-ID of 0 and with the
SYNC flag set to 0 ([I-D.ietf-pce-stateful-pce]). The LSP-DB-VERSION
TLV MUST be included and contain the PCC's latest LSP State Database
Version Number. On receiving this state report, the PCE MUST purge
any LSPs from the LSP database that are still marked as stale.
Note that a PCE/PCC MAY force State Synchronization by not including
the LSP-DB-VERSION TLV in its OPEN object.
Figure 1 shows an example sequence where State Synchronization is
skipped. In the figure, IDB stands for INCLUDE-DB-VERSION.
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+-+-+ +-+-+
|PCC| |PCE|
+-+-+ +-+-+
| |
|--Open--, |
| DBv=42 \ ,---Open--|
| IDB=1 \ / DBv=42 |
| \/ IDB=1 |
| /\ |
| / `-------->| (OK to skip sync)
(Skip sync) |<--------` |
| . |
| . |
| . |
| |
|--PCRpt,DBv=43,SYNC=0-->| (Regular
| | LSP State Report)
|--PCRpt,DBv=44,SYNC=0-->| (Regular
| | LSP State Report)
|--PCRpt,DBv=45,SYNC=0-->|
| |
Figure 1: State Synchronization skipped
Figure 2 shows an example sequence where State Synchronization is
performed due to LSP State Database version mismatch during the PCEP
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. In the figure, IDB
stands for INCLUDE-DB-VERSION.
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+-+-+ +-+-+
|PCC| |PCE|
+-+-+ +-+-+
| |
|--Open--, |
| DBv=46 \ ,---Open--|
| IDB=1 \ / DBv=42 |
| \/ IDB=1 |
| /\ |
| / `-------->| (Expect sync)
(Do sync) |<--------` |
| |
|--PCRpt,DBv=46,SYNC=1-->| (Sync start)
| . |
| . |
| . |
|--PCRpt,DBv=46,SYNC=1-->| (Sync done)
| . |(Purge LSP State)
| . |
| . |
|--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 State Synchronization is
skipped, but because one or both PCEP Speakers set the INCLUDE-DB-
VERSION Flag to 0, the PCC does not send LSP-DB-VERSION TLVs to the
PCE. If the current PCEP session restarts, the PCEP Speakers will
have to perform State Synchronization, since the PCE will not know
the PCC's latest LSP State Database Version Number. In the figure
IDB stands for INCLUDE-DB-VERSION.
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+-+-+ +-+-+
|PCC| |PCE|
+-+-+ +-+-+
| |
|--Open--, |
| DBv=42 \ ,---Open--|
| IDB=0 \ / DBv=42 |
| \/ IDB=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. 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
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=[TBD] | Length=8 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LSP State DB Version Number |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4: LSP-DB-VERSION TLV format
The type of the TLV is [TBD] and it has a fixed length of 8 octets.
The value contains a 64-bit unsigned integer.
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3.3.1. Use of the LSP-DB-VERSION TLV in the OPEN object
The LSP-DB-VERSION_TLV is included as an optional TLV in the OPEN
object when a PCEP Speaker wishes to determine if State
Synchronization can be skipped when a PCEP session is restarted. If
sent from a PCE, the TLV contains the local LSP State Database
Version Number from the last valid LSP State Report received from a
PCC. If sent from a PCC, the TLV contains the PCC's local LSP State
Database Version Number, which is incremented each time the LSP State
Database is updated.
3.3.2. Use of the LSP-DB-VERSION TLV in the LSP object
The LSP-DB-VERSION TLV can be included as an optional TLV in the LSP
object.
If State Synchronization Avoidance has been enabled on a PCEP session
(as described in Section 3.2), a PCC MUST include the LSP-DB-VERSION
TLV in each LSP Object sent out on the session. If the TLV is
missing, 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 it to
receive one.
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
PCE (other than the OPEN message). A PCC SHOULD ignore the LSP-DB-
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).
3.4. Speaker Entity Identifier TLV
SPEAKER-ENTITY-ID is an optional TLV that MAY be included in the OPEN
Object when a PCEP Speaker wishes to determine if State
Synchronization can be skipped when a PCEP session is restarted. It
contains a unique identifier for the node that does not change during
the life time of the PCEP Speaker. It identifies the PCEP Speaker to
its peers if the Speaker's IP address changed.
The format of the SPEAKER-ENTITY-ID TLV is shown in the following
figure:
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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=[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. 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
SHOULD allow the operator to configure a SPEAKER-ENTITY-ID.
4. PCE-triggered State Synchronization
4.1. 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
state even after the session has 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.
4.2. PCE-triggered State Synchronization Procedures
Support of PCE-triggered state synchronization is advertised on a
PCEP session during session startup using the TRIGGERED-SYNC (T) bit
in the capabilities TLV. The PCE can choose to resynchronize its
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entire LSP database, or a single LSP.
To trigger resynchronization for an LSP, the PCE MUST first mark the
LSP as stale and then send a PCUpd for it, with the SYNC flag 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 reply with a PCRpt and SHOULD include the SRP-ID-number of the
PCUpd that triggered the report.
The PCE can also trigger resynchronization of the entire LSP
database. The PCE MUST first mark any LSPs in the LSP database that
were previously reported by the PCC as stale and then send a PCUpd
for 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 report
SHOULD be included in each of the PCRpt messages.
If the TRIGGERED-SYNC capability was 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 7.1)
5. Incremental State Synchronization
[I-D.ietf-pce-stateful-pce] describes LSP state synchronization
mechanism between PCCs and PCEs for a stateful PCE. After PCEP
session set up, PCC compares the LSP State Database version with the
PCE as described in Section 3. 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 section 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 during incremental syncronization.
5.1. 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 6 shows an example of LSP state
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synchronization.
+-----+
| PCE |
+-----+
/
/
/
/
+------+ +------+
| PCC1 |------------| PCC2 |
+------+ +------+
| |
| |
+------+ +------+
| PCC3 |------------| PCC4 |
+------+ +------+
Figure 6: Topology Example
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 section, 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 trigger the LSP
synchronization (similar to Section 4).
PCEP extensions for stateful PCEs to perform LSP synchronization
SHOULD allow:
o 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.
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o A stateful PCE to control the timing of PCC synchronizing its LSP
state with the PCE during incremental synchronisation.
5.2. Incremental synchronization procedures
[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 as
well as to allow a stateful PCE to control the timing of this
process.
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 7 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 [I-D.ietf-pce-stateful-pce].
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+-+-+ +-+-+
|PCC| |PCE|
+-+-+ +-+-+
| |
|--Open--, |
| DBv=46 \ ,---Open--|
| IDB=1 \ / DBv=42 |
| D=1 \/ IDB=1 |
| T=1 /\ T=1 |
| / \ D=1 |
| / `-------->| (Expect Delta sync)
(Do sync)|<--------` | (Do not Purge LSP
(Delta) | | State)
(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-->|
| |
Figure 7: Incremental synchronization procedures
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 4. 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 inferred from the LSP DB Version information
exchange in the OPEN message. Note that the PCE should not mark the
existing LSPs as stale for incremental state synchronisation
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procedure.
As per Section 3, 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 7, 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.
6. Advertising support of the synchronization optimizations
Support for each of the optimizations described in this document
requires advertising support of the capability at 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|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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.
I (LSP-INSTANTIATION-CAPABILITY - 1 bit): defined in
[I-D.crabbe-pce-pce-initiated-lsp]
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T (TRIGGERED-SYNC - 1 bit): if set to 1 by both PCEP Speakers, the
PCE can trigger synchronization of LSPs at any point in the life
of the session. The flag must be advertised by both PCC and PCE
for PCUpd messages with the SYNC flag set to be allowed on a PCEP
session.
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.
7. IANA Considerations
This document requests IANA actions to allocate code points for the
protocol elements defined in this document. Values shown here are
suggested for use by IANA.
7.1. PCEP-Error Object
This document defines new Error-Value values for the LSP State
synchronization error defined in [I-D.ietf-pce-stateful-pce].
Error-Type Meaning
6 Mandatory Object missing
Error-value=12: LSP-DB-VERSION TLV missing
20 LSP State synchronization error.
Error-value=2: LSP Database version mismatch.
Error-value=3: The LSP-DB-VERSION TLV Missing when
State Synchronization Avoidance
enabled.
Error-value=4: Attempt to trigger a synchronization
when the TRIGGERED-SYNC capability has
not been advertised.
7.2. PCEP TLV Type Indicators
This document defines the following new PCEP TLVs:
Value Meaning Reference
23 LSP-DB-VERSION This document
24 SPEAKER-ENTITY-ID This document
7.3. 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:
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Bit Description Reference
28 DELTA-LSP-SYNC-CAPABILITY This document
29 TRIGGERED-SYNC This document
30 INCLUDE-DB-VERSION This document
8. Security Considerations
The security considerations listed in [I-D.ietf-pce-stateful-pce]
apply to this document as well.
9. Acknowledgements
We would like to thank Young Lee for his contributions.
10. 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
11. Normative References
[I-D.crabbe-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-crabbe-pce-pce-initiated-lsp-02 (work in
progress), July 2013.
[I-D.ietf-pce-stateful-pce]
Crabbe, E., Medved, J., Minei, I., and R. Varga, "PCEP
Extensions for Stateful PCE",
draft-ietf-pce-stateful-pce-06 (work in progress),
August 2013.
[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.
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[RFC5511] Farrel, A., "Routing Backus-Naur Form (RBNF): A Syntax
Used to Form Encoding Rules in Various Routing Protocol
Specifications", RFC 5511, April 2009.
Authors' Addresses
Edward Crabbe
Google, Inc.
1600 Amphitheatre Parkway
Mountain View, CA 94043
US
Email: edc@google.com
Jan Medved
Cisco Systems, Inc.
170 West Tasman Dr.
San Jose, CA 95134
US
Email: jmedved@cisco.com
Ina Minei
Juniper Networks, Inc.
1194 N. Mathilda Ave.
Sunnyvale, CA 94089
US
Email: ina@juniper.net
Robert Varga
Pantheon Technologies SRO
Mlynske Nivy 56
Bratislava 821 05
Slovakia
Email: robert.varga@pantheon.sk
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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
Email: dhruv.ietf@gmail.com
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