Internet DRAFT - draft-tanaka-pce-stateful-pce-mbb
draft-tanaka-pce-stateful-pce-mbb
PCE Working Group Y. Tanaka
Internet-Draft Y. Kamite
Intended status: Standards Track NTT Communications
Expires: September 8, 2019 R. Palleti
C. Li
H. Zheng
Huawei Technologies
March 7, 2019
Make-Before-Break (MBB) MPLS-TE LSP restoration and reoptimization
procedure using Stateful Path Computation Element (PCE).
draft-tanaka-pce-stateful-pce-mbb-08
Abstract
Stateful Path Computation Element (PCE) and its corresponding
protocol extensions provide a mechanism that enables PCE to do
stateful control of Multiprotocol Label Switching (MPLS) Traffic
Engineering Label Switched Paths (TE LSP). Stateful PCE supports
manipulating of the existing LSP's state and attributes (e.g.,
bandwidth and path) via delegation and also instantiation of new LSPs
in the network via PCE Initiation procedures.
In the current MPLS TE network using Resource ReSerVation Protocol
(RSVP-TE), LSPs are often controlled by Make-before-break (M-B-B)
signaling by the headend for the purpose of LSP restoration and
reoptimization. In most cases, it is an essential operation to
reroute LSP traffic without any data disruption.
This document specifies the procedure of applying stateful PCE's
control to make-before-break RSVP-TE signaling. In this document,
two types of restoration/reoptimization procedures are defined,
implicit mode and explicit mode. This document also specifies the
usage and handling of stateful PCEP (PCE Communication Protocol)
messages, expected behavior of PCC as RSVP-TE headend and necessary
extensions of additional PCEP objects.
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 https://datatracker.ietf.org/drafts/current/.
Tanaka, et al. Expires September 8, 2019 [Page 1]
Internet-Draft MBB using Stateful PCE March 2019
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 September 8, 2019.
Copyright Notice
Copyright (c) 2019 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
(https://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. Conventions used in this document . . . . . . . . . . . . . . 3
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 4
4. Motivation . . . . . . . . . . . . . . . . . . . . . . . . . 4
5. Make-Before-Break LSP procedures . . . . . . . . . . . . . . 5
5.1. Implicit Make-Before-Break Mode . . . . . . . . . . . . . 6
5.2. Explicit Make-Before-Break Mode . . . . . . . . . . . . . 8
5.2.1. Initiate Association Group for old LSP . . . . . . . 8
5.2.2. Establish new Trial LSP . . . . . . . . . . . . . . . 9
5.2.3. Switchover Data Traffic triggered by a PCUpd message 11
6. Protocol extension . . . . . . . . . . . . . . . . . . . . . 13
6.1. Association group . . . . . . . . . . . . . . . . . . . . 14
6.2. Trial LSP TLV in ASSOCIATION Objects . . . . . . . . . . 14
6.3. Optional TLVs . . . . . . . . . . . . . . . . . . . . . . 15
6.4. Error Handling . . . . . . . . . . . . . . . . . . . . . 15
7. Security Considerations . . . . . . . . . . . . . . . . . . . 15
8. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15
8.1. PCEP TLV Indicators . . . . . . . . . . . . . . . . . . . 16
8.2. Association Object Type Indicator . . . . . . . . . . . . 16
9. Operational Considerations . . . . . . . . . . . . . . . . . 16
9.1. Operation in multiple PCEs . . . . . . . . . . . . . . . 16
10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 16
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 17
11.1. Normative References . . . . . . . . . . . . . . . . . . 17
Tanaka, et al. Expires September 8, 2019 [Page 2]
Internet-Draft MBB using Stateful PCE March 2019
11.2. Informative References . . . . . . . . . . . . . . . . . 17
Appendix A. Contributors . . . . . . . . . . . . . . . . . . . . 18
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 18
1. Introduction
[RFC5440] describes the Path Computation Element Protocol PCEP. PCEP
enables the communication between a Path Computation Client (PCC) and
a Path Control Element (PCE), or between PCE and PCE, for the purpose
of computation of Multiprotocol Label Switching (MPLS) as well as
Generalzied MPLS (GMPLS) for Traffic Engineering Label Switched Path
(TE LSP) characteristics.
[RFC8231] describes the stateful Path Computation Elements (PCE) and
defines the extensions to PCEP to enable stateful control of LSPs
within and across PCEP sessions, further it also describes mechanisms
to effect LSP state synchronization between PCCs and PCEs, and PCE
control of timing and sequence of path computations within and across
PCEP sessions.
Today, however, there is no detailed procedure specified for
restoration and reoptimization of MPLS-TE LSP using stateful PCE. In
today's MPLS RSVP-TE mechanism, make-before-break (M-B-B) is a widely
common scheme supported by headend Label Edge Router (LER) in order
to assure no traffic disruption during restoration and
reoptimization. Hence it is naturally desirable for stateful PCE to
control M-B-B based signaling and forwarding process.
This document specifies the definite procedures of applying stateful
PCE's control of the M-B-B procedures. In this document, two types
of restoration/reoptimization procedures are defined, Implicit mode
and Explicit mode. This document also specifies the usage and
handling of stateful PCEP (PCE Communication Protocol) messages,
expected behavior of PCC as RSVP-TE headend and several extensions of
additional objects.
2. Conventions used in this document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and
"OPTIONAL" in this document are to be interpreted as described in BCP
14 [RFC2119] [RFC8174] when, and only when, they appear in all
capitals, as shown here.
Tanaka, et al. Expires September 8, 2019 [Page 3]
Internet-Draft MBB using Stateful PCE March 2019
3. Terminology
This document uses the following terms defined in [RFC5440]: PCC,
PCE, PCEP Peer.
This document uses the following terms defined in [RFC3209]: make-
before-break (M-B-B), Path State Block (PSB).
This document uses the following terms defined in [RFC4426] and
[RFC4427]: recovery, protection, restoration.
According to their definition the term "recovery" is generically used
to denote both protection and restoration; the specific terms
"protection" and "restoration" are used only when differentiation is
required. The subtle distinction between protection and restoration
is made based on the resource allocation done during the recovery
period. Hence the protection allocates LSP resource in advance of a
failure, while the restoration allocates LSP resource after a failure
occur.
4. Motivation
As for current MPLS mechanism, make-before-break(M-B-B) concept is
outlined in [RFC3209], which allows adaptive and smooth RSVP-TE LSP
rerouting that does not disrupt traffic or adversely impact network
operations while rerouting is in progress. M-B-B is applicable for
reoptimizing LSP's route and resources for several use cases, for
example, to adopt better path for reversion after failure, to change
traversing node/links for planned maintenance, to change bandwidth of
LSPs etc. M-B-B is also used for global restoration scenario in case
of failure, which is effective if operators do not want to reserve
both working and standby LSP's bandwidth in advance. Once failure
occur, LSP becomes down, however PSB (Path State Block) of a headend
node remains and keep resources intact. Using M-B-B, the headend
node is able to resignals working LSP while the PSB remains until new
restoration LSP is successfully established. In real deployment, it
can also be operated with local protection scheme FRR (Fast ReRoute).
Since M-B-B operational scheme is universally common in MPLS network
today, it is naturally much desirable to utilize it under the
architecture of stateful PCE.
The basic procedure of the Make-Before-Break method is outlined as
follows:
1. Establish a new LSP
Tanaka, et al. Expires September 8, 2019 [Page 4]
Internet-Draft MBB using Stateful PCE March 2019
2. Transfer data traffic from old LSP onto the new LSP
3. Tear down the old LSP (Release old PSB)
In M-B-B, it is an important behavior that headend node handles the
sequence of data traffic switchover. The headend is able to Make one
or more new LSPs for a particular Tunnel (i.e., it is allowed to
signal multiple LSPs with different LSP-IDs that share a common
Tunnel IDs), and the headend will switch the traffic to only one (or
some) of those LSPs. In some use cases about stateful PCE, it is
expected that controller/operators can watch and control when the
data is switched over and which LSPs are used. Therefore, this
document covers such a procedure and related message extensions.
5. Make-Before-Break LSP procedures
There are possibly two modes introduced for Make-Before-Break
procedure under stateful PCE. The first one is "implicit M-B-B
mode", where the operation is triggered by a Update Request(PCUpd)
message from a PCE, and a PCC handles whole Make-Before-Break steps
(signaling, transferring data traffic and teardown) by itself. This
mode utilizes the existing messages and procedures as defined in
[RFC8231] .
The second one is "explicit M-B-B mode", where the operation is
triggered by a PCUpd message with a new TRIAL LSP TLV (defined in
Section 6.2). A PCE also controls timing and sequence of the M-B-B
steps that a PCC takes. This procedure uses ASSOCIATION Object that
is defined in [I-D.ietf-pce-association-group].
Both types of procedure require at least two LSPs residing in a
single MPLS-TE tunnel, working LSP and trial LSPs. An ingress node
is currently transporting data traffic on the working LSP, and then
it establishes one or more trial LSPs. As per [RFC3209] Section 2.5.
"LSP ID" of a restoration LSP, which is newly signaled, differs from
that of a working LSP in RSVP-TE. Note that it is also used for LSP-
ID in LSP Identifiers TLVs in PCEP messages, and it differs from
PLSP-ID ([RFC8231]). In this document, LSP ID of a working LSP
describes "old" and that of a trial LSP describes "new" as a simple
example.
Implicit mode has high affinity with most existing MPLS edge node
implementations which perform entire steps of M-B-B automatically at
once. This mode is particularly applicable for migration scenario
for the existing deployment where service providers want their
recovery/reoptimization operation be delegated to a centralized PCE.
Tanaka, et al. Expires September 8, 2019 [Page 5]
Internet-Draft MBB using Stateful PCE March 2019
Explicit mode is much more flexible than Implicit mode since it
allows PCEs to manage each step of the M-B-B. Explicit mode is
applicable to several new use cases that require split control of
signaling and data switchover. For example, if end-to-end data path
is created by connecting multiple individual LSPs across different
segments (e.g., LSP stitching), in reoptimization scenario, data
flowing cannot be started unless signaling of all LSPs is completed.
Similarly, there is a case under Software Defined Networking (SDN)
applications, where MPLS domain is connected to other non-MPLS
domains, and the end-to-end data switchover timing should be
carefully coordinated with various different methods of path/flow
setup in each domain.
PCC and PCE can distinguish which mode, implicit mode or explicit
mode, is to be performed by checking the presence of ASSOCIATION and
certain TLV in the PCEP messages. The implementation MAY support
both modes, but for each restoration/reoptimization operation, either
one of them SHOULD be exclusively applied.
5.1. Implicit Make-Before-Break Mode
This specifies the detailed procedure of M-B-B LSP restoration and
reoptimization using existing messages which are defined in [RFC8231]
. This procedure is based on the existing messages/TLVs and no
extensions are required. Once a PCC receives PCUpd message from a
PCE, the PCC automatically executes the implicit M-B-B procedure as
described in [RFC8231] Section 6.2.
First, A PCUpd message is sent from a PCE to trigger M-B-B
procedure. Once receiving the PCUpd message, the PCC starts
signaling a new restoration/reoptimization LSP and it replies back
to the PCE a PCRpt message with LSP-IDENTIFIERS TLV (with new LSP-
ID) in the LSP Object to notify the result of signaling. If the
new LSP failed to setup, the PCC sends to the PCE the detail of
the result in a PCErr or PCRpt message with the same SRP (Stateful
PCE Request Parameters) object as that of the PCUpd message and it
MAY wait for a next instruction from the PCE.
Second, once a new LSP is successfully established, a PCC
transfers data traffic from working LSP to new LSP automatically.
Finally, when a PCC successfully transferred data traffic to the
new LSP, the PCC tears down the (previous) working LSP by RSVP-TE
signaling, then the PCC sends another PCRpt message. That PCRpt
message carries a LSP Object with LSP-IDENTIFIERS TLV (with old
LSP-ID) which indicates the value of RSVP-TE signaling the PCC has
just torn down. As per [RFC8231], the message has to have SRP-ID
set to 0x00000000.
Tanaka, et al. Expires September 8, 2019 [Page 6]
Internet-Draft MBB using Stateful PCE March 2019
Following Figure 1 illustrates the example of implicit M-B-B
procedure, in following conditions. Tunnel ID and LSP ID are
included in an LSP Identifiers TLV in a LSP Object.
working LSP : ERO=a-b, Tunnel ID=T1, LSP ID=old, PLSP-ID=X
restoration LSP : ERO=a-c-b, Tunnel ID=T1, LSP ID=new, PLSP-ID=X
__c__
/ \
PCE PCC(Ingress)--a-------b---Egress
| | |
| Data on old LSP =>)))))))))))))))))))))))|
| | : |
|--PCUpd(PLSP-ID=X,->| : |
| SRP-ID=Y, | |
| ERO=a-c-b) |---Path(ERO=a-c-b-, --> |
| | LSP ID new) |
| | |
| | <-----Resv-------------|
| <- PCRpt(PLSP-ID=X,| |
| O=Up, | |
| SRP-ID=Y, | |
| Tunnel ID=T1, | |
| LSP ID=new) | |
| | |
| | |
| Transfer data |))))))))))))))))))))))))|
| from old to new =>}}}}}}}}}}}}}}}}}}}}}}}}|
| | : |
| | : |
| |---PathTear(ERO=a-b, -> |
| | LSP ID old) |
| <- PCRpt(PLSP-ID=X,| |
| O=Dn,R=1, | |
| SRP-ID=0, | |
| Tunnel ID=T1, | |
| LSP ID=old) | |
O flag = Operational flag in LSP object.
R flag = Remove flag in LSP object.
Figure 1: Implicit Make-Before-Break Procedure
Tanaka, et al. Expires September 8, 2019 [Page 7]
Internet-Draft MBB using Stateful PCE March 2019
5.2. Explicit Make-Before-Break Mode
Comparing to the implicit M-B-B mode, explicit M-B-B mode allows a
PCE to control timing and sequence of subsequent make-before-break
steps.
As per [I-D.ietf-pce-association-group], LSPs are associated with
other LSPs with which they interact by adding them to a common
association group. In this draft, this grouping is used to define
associations between a set of LSPs. This document define one new
association type called "Explicit MBB Association Type" of value
TBD1.
Prior to start of explicit M-B-B mode, PCE makes an association
group for the working LSP by including the Association Object
(defined in [I-D.ietf-pce-association-group]) with "Explicit MBB
Association Type". This allows the PCEs to identify the LSP
belong to a Make-Before-Break association group. PCE may include
the TRIAL-LSP TLV that is defined in this document with D(Data
Switchover) and T(Trial LSP) flags set to 0 in Association Object.
This is a pre-requisite for the explicit M-B-B.
First step of the explicit M-B-B, the PCE triggers signaling of a
new LSP at the PCC by sending a PCUpd/PCInitiate message with T
flag in TRIAL-LSP TLV set to 1, in the ASSOCIATION Object. The
PCC sends a PCRpt message back to the PCE to notify the result of
the signaling of the new LSP.
Second, the PCE instructs the PCC to transfer data traffic from
old LSP to new LSP by sending a PCUpd message with D flag in
TRIAL-LSP TLV set to 1, in the ASSOCIATION Object. The PCC
automatically tears down the (previous) working LSP once the
traffic switchover successfully is executed. Then it sends back
to the PCE a PCRpt message to notify the result of the switchover.
[Editor's Note - The operator may want to separate the second step
into traffic switchover and tearing down old LSP. It is further
study about the separate operation of third step.]
The following subsections specify each Explicit Make-Before-Break
step in detail.
5.2.1. Initiate Association Group for old LSP
As a pre-requisite before starting explicit M-B-B, PCE makes an
association group for working LSP by sending PCUpd message that
contains ASSOCIATION object with TRIAL-LSP TLV with both D and T
flags set to zero. TRIAL-LSP TLV is optional in the ASSOCIATION
object at this step.
Tanaka, et al. Expires September 8, 2019 [Page 8]
Internet-Draft MBB using Stateful PCE March 2019
Figure 2 illustrates an example of working LSP (PLSP-ID P1, Tunnel ID
T1, LSP-ID old, Association Group ID G1 and ERO Ingress-a-b-Egress).
__c__
/ \
PCE PCC(Ingress)--a-------b---Egress
| data traffic on old LSP |
| |))))))))))))))))))))))))|
|--PCUpd ------>| : |
| LSP Object | : |
| PLSP-ID=P1 | : |
| SRP-ID=S1 | : |
| LSP ID=old | |
| ASSOC Object | |
| Assoc-Type=MBB | |
| Assoc-ID=G1 | |
| +TRIAL-LSP TLV | |
| D-Flag=0 | |
| T-Flag=0 | |
| | |
Figure 2: Initiate Associate Group for old LSP
5.2.2. Establish new Trial LSP
As a first step of M-B-B procedure, a PCC establishes a new LSP for
restoration once PCC receives a PCInitiate/PCUpd message with T flag
(in TRIAL-LSP TLV) set to 1, in a ASSOCIATION Object from a PCE. We
call this newly established LSPs for restoration "trial LSP". A
trial LSP is signaled the same RSVP-TE Tunnel ID but different LSP ID
from active working LSP, and both the active working LSP and new
trial LSPs MUST be signaled with Shared Explicit style as describes
in [RFC3209].
When a new trial LSP was signaled successfully, the PCC sends a PCRpt
message toward the PCE to notify the result. The PCRpt message from
the PCC MUST have the LSP object with LSP-IDENTIFIERS TLV that
indicates RSVP-TE Tunnel ID and LSP ID the PCC has just established.
If a new trial LSP failed to be established by some reason of RSVP-TE
signaling, the PCC MUST send to the PCE a PCRpt message carrying LSP-
IDENTIFIERS TLV and RSVP-ERROR-SPEC TLV as defined in [RFC8231]
Section 7.3.4.
Tanaka, et al. Expires September 8, 2019 [Page 9]
Internet-Draft MBB using Stateful PCE March 2019
A PCC SHOULD accept multiple PCInitiate/PCUpd messages with TRIAL-LSP
TLV in a ASSOCIATION Object. And a PCC SHOULD establish as many
trial lsps as the number of PCInitiate/PCUpd messages it receives. A
PCC may also choose to implement a limit on the number of such
PCInitiate/PCUpd message.
Figure 3 illustrates a example, working LSP(PLSP-ID P1, Tunnel ID T1,
LSP-ID old, ERO Ingress-a-b-Egress), trial LSP(PLSP-ID P1, Tunnel ID
T1, LSP-ID new, ERO Ingress-a-c-b-Egress).
Tanaka, et al. Expires September 8, 2019 [Page 10]
Internet-Draft MBB using Stateful PCE March 2019
__c__
/ \
PCE PCC(Ingress)--a-------b---Egress
| data traffic on old LSP |
| | |
| PCInitiate/ |))))))))))))))))))))))))|
|--PCUpd ------>| : |
| LSP Object | : |
| PLSP-ID=P1 | : |
| SRP-ID=S2 | : |
| Tunnel ID=T1 | |
| LSP ID=0 | |
| ASSOC Object | |
| Assoc-Type=MBB | |
| Assoc-ID=G1 | |
| +TRIAL-LSP TLV | |
| D-Flag=0 | |
| T-Flag=1 | |
| ERO Obj=a-c-b | |
| | |
| |---Path(LSP ID=new, --> |
| | ERO=a-c-b) |
| | |
| | <----- Resv------------|
|<--PCRpt ---------| |
| LSP Object | : |
| PLSP-ID=P1 |))))))))))))))))))))))))|
| SRP-ID=S2 | : |
| Tunnel ID=T1 | : |
| LSP ID=new | : |
| ASSOC Object | : |
| Assoc-Type=MBB | : |
| Assoc-ID=G1 | : |
| +TRIAL-LSP TLV | : |
| D-Flag=0 | : |
| T-Flag=1 | : |
| RRO Obj=a-c-b | : |
| | |
Figure 3: Establish new LSP
5.2.3. Switchover Data Traffic triggered by a PCUpd message
As a second step, the PCC(Ingress) transfers data traffic from a
working LSP to a trial LSP. To specify desired LSP for transferring
Tanaka, et al. Expires September 8, 2019 [Page 11]
Internet-Draft MBB using Stateful PCE March 2019
data traffic, a PCUpd message from a PCE MUST have a TRIAL-LSP TLV
set D flag to 1, in a ASSOCIATION Object.
Data switchover happens from old LSP to new trial LSP, once PCC
receives a PCUpd message with D flag in TRIAL-LSP TLV set to 1 in the
ASSOCIATION object from a PCE.
The PCC SHOULD tear down the old working LSP and other trial LSPs
which the data traffic is no longer used immediately once the data
traffic successfully switched over (See Figure 4).
[Editor's Note - Another option would be, a PCC tears down old lsp
separately using mechanism in [RFC8281] for PCE-Initiated LSPs.]
The PCC sends to the PCE a PCRpt message to notify the removal of
both old LSP and other trial LSPs, which SRP-ID is set to 0x00000000.
Tanaka, et al. Expires September 8, 2019 [Page 12]
Internet-Draft MBB using Stateful PCE March 2019
__c__
/ \
PCE PCC(Ingress)--a-------b---Egress
| | |
| |))))))))))))))))))))))))| data on old LSP
|--PCUpd ------> |))))))))))))))))))))))))|
| LSP Object |}}}}}}}}}}}}}}}}}}}}}}}}| data on new LSP
| PLSP ID=P1 |}}}}}}}}}}}}}}}}}}}}}}}}|
| SRP ID=S3 |}}}}}}}}}}}}}}}}}}}}}}}}|
| Tunnel ID=T1 | : |
| LSP ID=new | : |
| ASSOC Object | : |
| Assoc-Type=MBB | |
| Assoc-ID=G1 | |
| +TRIAL-LSP TLV | |
| D-Flag=1 | |
| T-Flag=0 | |
| | |
| <-- PCRpt --------| |
| LSP Object | |
| PLSP ID=P1 | |
| SRP ID=S3 | |
| Tunnel ID=T1 | |
| LSP ID=new | |
| |--PathTear(ERO a-b, -->| Tear down old
| | Tunnel=T1,LSP ID=old) | automatically
| | |
| <-- PCRpt(O=Dn,R=1,| |
| PLSP ID=P1 | |
| SRP ID=0 | |
| Tunnel ID=T1 | |
| LSP-ID=old) | |
| | |
| | |
O flag = Operational flag in LSP object.
R flag = Remove flag in LSP object.
Figure 4: Transfer data traffic from old LSP to new LSP
6. Protocol extension
Tanaka, et al. Expires September 8, 2019 [Page 13]
Internet-Draft MBB using Stateful PCE March 2019
6.1. Association group
As per [I-D.ietf-pce-association-group], LSPs are associated with
other LSPs with which they interact by adding them to a common
association group. The Association ID will be used to identify the
MBB group a set of LSPs belongs to. This document defines a new
Association type, based on the generic Association object -
o Association type = TBD1 ("Explicit MBB Association Type").
[I-D.ietf-pce-association-group] specify the mechanism for the
capability advertisement of the association types supported by a PCEP
speaker by defining a ASSOC-Type-List TLV to be carried within an
OPEN object. This capability exchange for the association type
described in this document (i.e. Explicit MBB Association Type) MUST
be done before using the policy association, i.e., the PCEP speaker
MUST include the Explicit MBB Association Type (TBD1) in the ASSOC-
Type-List TLV before using this association type in the PCEP
messages.
This Association-Type is dynamic in nature and created by the PCC or
PCE for the LSPs belonging to the same TE tunnel (as described in
[RFC3209]) originating at the same head node and terminating at the
same destination. These associations are conveyed via PCEP messages
to the PCEP peer. Operator-configured Association Range MUST NOT be
set for this association-type and MUST be ignored.
6.2. Trial LSP TLV in ASSOCIATION Objects
This document defines a new TLV named TRIAL-LSP TLV which can be
optionally carried in the ASSOCIATION object.
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=TBD2 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags |D|T|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 5: TRIAL-LSP TLV format
TRIAL-LSP TLV is an optional TLV of the ASSOCIATION Object and is
used in a PCInitiate/PCUpd message especially to perform explicit
mode M-B-B. A PCC signals a trial LSP once it receives a PCUpd in
which ASSOCIATION object has a TRIAL-LSP TLV.
Tanaka, et al. Expires September 8, 2019 [Page 14]
Internet-Draft MBB using Stateful PCE March 2019
T(Trial LSP - 1 bit): This field MUST be set to 1 in a PCInitiate/
PCUpd message when a PCE requests a PCC to signal new trial LSP.
It MUST be zero for a working LSP.
D(Data switchover - 1 bit): This field MUST be set to 1 in a PCUpd
message when a PCE requests a PCC to switchover data traffic for
new trial LSP. It MUST be zero otherwise.
Flags: None defined. MUST be set to zero. Ignored on receipt.
6.3. Optional TLVs
The MBB association group MAY carry some optional TLVs including but
not limited to:
o VENDOR-INFORMATION-TLV: Used to communicate arbitrary vendor
specific behavioral information,, described in [RFC7470].
6.4. Error Handling
As per the processing rules specified in section 5.4 of
[I-D.ietf-pce-association-group], if a PCEP speaker does not support
this association-type, it would return a PCErr message with Error-
Type 26 (Early allocation by IANA) "Association Error" and Error-
Value 1 "Association-type is not supported".
All LSPs (new or old) within this association MUST belong to the same
TE Tunnel (as described in [RFC3209]) and have the same source and
destination. If a PCEP speaker attempts to add an LSP to this
association and the Tunnel ID (as carried in LSP-IDENTIFIERS TLV
[RFC8231], with description as per [RFC3209]) or source or
destination of the LSP is different from the LSP(s) in the PPAG, the
PCC MUST send PCErr with Error-Type= 29 (Early allocation by IANA)
(Association Error) [I-D.ietf-pce-association-group] and Error-Value
= TBD (Tunnel ID or End points mismatch).
All processing as per section 5.4 of [I-D.ietf-pce-association-group]
continue to apply.
7. Security Considerations
This document defines one new type for association, which do not add
any new security concerns beyond those discussed in [RFC5440],
[RFC8231] and [I-D.ietf-pce-association-group] in itself.
8. IANA Considerations
Tanaka, et al. Expires September 8, 2019 [Page 15]
Internet-Draft MBB using Stateful PCE March 2019
8.1. PCEP TLV Indicators
This document defines the following new PCEP TLVs:
Value Meaning Reference
TBD2 TRIAL-LSP TLV This document
8.2. Association Object Type Indicator
This document defines the following new association type originally
defined in [I-D.ietf-pce-association-group].
Value Name Reference
TBD1 MBB Association Type This document
9. Operational Considerations
9.1. Operation in multiple PCEs
In addition to basic operations under multiple PCEs as described in
[RFC8231], a PCC supports both types of M-B-B operations.
Implicit mode M-B-B requires only one PCUpd message to trigger M-B-B
process, therefore a PCC accepts a message from a primary PCE whom
the PCC delegates the LSPs to. An attempt to update parameters of a
non-delegated LSP results in the PCC sending a PCErr message as
defined in [RFC8231].
Explicit mode M-B-B requires at least three PCUpd messages(1. for new
Association-Group creation, 2. for trial-LSP signaling, 3. for
traffic switchover) to trigger each subsequent step. All steps MUST
be taken by one primary PCE because state synchronization of trial-
LSPs between the primary and backup PCE may be complex. If the PCC
revokes LSP delegations after a Redelegation Timeout Interval, the
PCC MUST tear down all trial-LSPs and redelegate a working LSP to
alternate PCE. An attempt to trigger either step of explicit mode
M-B-B of a non-delegated LSP results in the PCC sending the same
PCErr as implicit mode M-B-B.
10. Acknowledgments
Many thanks to Ina Minei, Adrian Farrel, Yimin Shen, and Xian Zhang
for their ideas and feedback in documentation.
Tanaka, et al. Expires September 8, 2019 [Page 16]
Internet-Draft MBB using Stateful PCE March 2019
11. References
11.1. Normative References
[I-D.ietf-pce-association-group]
Minei, I., Crabbe, E., Sivabalan, S., Ananthakrishnan, H.,
Dhody, D., and Y. Tanaka, "PCEP Extensions for
Establishing Relationships Between Sets of LSPs", draft-
ietf-pce-association-group-08 (work in progress), March
2019.
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC5440] Vasseur, JP., Ed. and JL. Le Roux, Ed., "Path Computation
Element (PCE) Communication Protocol (PCEP)", RFC 5440,
DOI 10.17487/RFC5440, March 2009,
<https://www.rfc-editor.org/info/rfc5440>.
[RFC8174] Leiba, B., "Ambiguity of Uppercase vs Lowercase in RFC
2119 Key Words", BCP 14, RFC 8174, DOI 10.17487/RFC8174,
May 2017, <https://www.rfc-editor.org/info/rfc8174>.
[RFC8231] Crabbe, E., Minei, I., Medved, J., and R. Varga, "Path
Computation Element Communication Protocol (PCEP)
Extensions for Stateful PCE", RFC 8231,
DOI 10.17487/RFC8231, September 2017,
<https://www.rfc-editor.org/info/rfc8231>.
[RFC8281] Crabbe, E., Minei, I., Sivabalan, S., and R. Varga, "Path
Computation Element Communication Protocol (PCEP)
Extensions for PCE-Initiated LSP Setup in a Stateful PCE
Model", RFC 8281, DOI 10.17487/RFC8281, December 2017,
<https://www.rfc-editor.org/info/rfc8281>.
11.2. Informative References
[RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V.,
and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP
Tunnels", RFC 3209, DOI 10.17487/RFC3209, December 2001,
<https://www.rfc-editor.org/info/rfc3209>.
Tanaka, et al. Expires September 8, 2019 [Page 17]
Internet-Draft MBB using Stateful PCE March 2019
[RFC4426] Lang, J., Ed., Rajagopalan, B., Ed., and D. Papadimitriou,
Ed., "Generalized Multi-Protocol Label Switching (GMPLS)
Recovery Functional Specification", RFC 4426,
DOI 10.17487/RFC4426, March 2006,
<https://www.rfc-editor.org/info/rfc4426>.
[RFC4427] Mannie, E., Ed. and D. Papadimitriou, Ed., "Recovery
(Protection and Restoration) Terminology for Generalized
Multi-Protocol Label Switching (GMPLS)", RFC 4427,
DOI 10.17487/RFC4427, March 2006,
<https://www.rfc-editor.org/info/rfc4427>.
[RFC7470] Zhang, F. and A. Farrel, "Conveying Vendor-Specific
Constraints in the Path Computation Element Communication
Protocol", RFC 7470, DOI 10.17487/RFC7470, March 2015,
<https://www.rfc-editor.org/info/rfc7470>.
Appendix A. Contributors
Dhruv Dhody
Huawei Technologies
Divyashree Techno Park, Whitefield
Bangalore, Karnataka 560066
India
Email: dhruv.ietf@gmail.com
Authors' Addresses
Yosuke Tanaka
NTT Communications Corporation
Granpark Tower
3-4-1 Shibaura, Minato-ku
Tokyo 108-8118
Japan
Email: yosuke.tanaka@ntt.com
Yuji Kamite
NTT Communications Corporation
Granpark Tower
3-4-1 Shibaura, Minato-ku
Tokyo 108-8118
Japan
Email: y.kamite@ntt.com
Tanaka, et al. Expires September 8, 2019 [Page 18]
Internet-Draft MBB using Stateful PCE March 2019
Ramanjaneya Reddy Palleti
Huawei Technologies
Divyashree Techno Park, Whitefield
Bangalore, Karnataka 560066
India
Email: ramanjaneya.palleti@huawei.com
Cheng Li
Huawei Technologies
Huawei Campus, No. 156 Beiqing Rd.
Beijing 100095
China
Email: chengli13@huawei.com
Haomian Zheng
Huawei Technologies
H1-1-A043S Huawei Industrial Base, Songshanhu
Dongguan, Guangdong 523808
China
Email: zhenghaomian@huawei.com
Tanaka, et al. Expires September 8, 2019 [Page 19]
