PCE Working Group S. Litkowski
Internet-Draft Orange
Intended status: Standards Track S. Sivabalan
Expires: August 31, 2018 Cisco Systems, Inc.
C. Barth
Juniper Networks
D. Dhody
Huawei
February 27, 2018
Path Computation Element communication Protocol extension for signaling
LSP diversity constraint
draft-ietf-pce-association-diversity-03
Abstract
This document introduces a simple mechanism to associate a group of
Label Switched Paths (LSPs) via an extension to the Path Computation
Element Communication Protocol (PCEP) with the purpose of computing
diverse paths for those LSPs. The proposed extension allows a PCC to
advertise to a PCE the belonging of a particular LSP to a disjoint-
group, thus the PCE knows that LSPs in the same group must be
disjoint from each other.
Status of This Memo
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Copyright Notice
Copyright (c) 2018 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
1.1. Requirements Language . . . . . . . . . . . . . . . . . . 3
2. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 3
3. Motivation . . . . . . . . . . . . . . . . . . . . . . . . . 4
4. Protocol extension . . . . . . . . . . . . . . . . . . . . . 7
4.1. Association group . . . . . . . . . . . . . . . . . . . . 7
4.2. Mandatory TLV . . . . . . . . . . . . . . . . . . . . . . 8
4.3. Optional TLVs . . . . . . . . . . . . . . . . . . . . . . 10
4.4. Disjointness objective functions . . . . . . . . . . . . 10
4.5. P-flag considerations . . . . . . . . . . . . . . . . . . 11
4.6. Disjointness computation issues . . . . . . . . . . . . . 14
5. Security Considerations . . . . . . . . . . . . . . . . . . . 15
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15
6.1. Association object Type Indicators . . . . . . . . . . . 15
6.2. PCEP TLVs . . . . . . . . . . . . . . . . . . . . . . . . 15
6.3. Objective Functions . . . . . . . . . . . . . . . . . . . 16
6.4. NO-PATH-VECTOR bit Flags . . . . . . . . . . . . . . . . 16
6.5. PCEP-ERROR codes . . . . . . . . . . . . . . . . . . . . 16
7. Manageability Considerations . . . . . . . . . . . . . . . . 16
7.1. Control of Function and Policy . . . . . . . . . . . . . 16
7.2. Information and Data Models . . . . . . . . . . . . . . . 17
7.3. Liveness Detection and Monitoring . . . . . . . . . . . . 17
7.4. Verify Correct Operations . . . . . . . . . . . . . . . . 17
7.5. Requirements On Other Protocols . . . . . . . . . . . . . 17
7.6. Impact On Network Operations . . . . . . . . . . . . . . 17
8. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 17
9. References . . . . . . . . . . . . . . . . . . . . . . . . . 17
9.1. Normative References . . . . . . . . . . . . . . . . . . 17
9.2. Informative References . . . . . . . . . . . . . . . . . 18
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 18
1. Introduction
[RFC5440] describes the Path Computation Element communication
Protocol (PCEP) which enables the communication between a Path
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Computation Client (PCC) and a Path Control Element (PCE), or between
two PCEs based on the PCE architecture [RFC4655].
PCEP Extensions for Stateful PCE Model [RFC8231] describes a set of
extensions to PCEP to enable active control of MPLS-TE and GMPLS
tunnels. [RFC8281] describes the setup and teardown of PCE-initiated
LSPs under the active stateful PCE model, without the need for local
configuration on the PCC, thus allowing for a dynamic network.
[I-D.ietf-pce-association-group] introduces a generic mechanism to
create a grouping of LSPs which can then be used to define
associations between a set of LSPs and a set of attributes (such as
configuration parameters or behaviours) and is equally applicable to
the active and passive modes of a stateful PCE [RFC8231] or a
stateless PCE [RFC5440].
This document specifies a PCEP extension to signal that a particular
group of LSPs should use diverse paths including the requested type
of diversity. A PCC can use this extension to signal to a PCE the
belonging of a particular LSP to a disjoint-group. When a PCE
receives LSP states belonging to the same disjoint-group from some
PCCs, the PCE should ensure that the LSPs within the group are
disjoint from each other.
1.1. 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].
2. Terminology
The following terminology is used in this document.
LSR: Label Switch Router.
MPLS: Multiprotocol Label Switching.
PCC: Path Computation Client. Any client application requesting a
path computation to be performed by a Path Computation Element.
PCE: Path Computation Element. An entity (component, application,
or network node) that is capable of computing a network path or
route based on a network graph and applying computational
constraints.
PCEP: Path Computation Element Communication Protocol.
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SRLG: Shared Risk Link Group.
3. Motivation
Path diversity is a very common use case today in IP/MPLS networks
especially for layer 2 transport over MPLS. A customer may request
that the operator provide two end-to-end disjoint paths across the
IP/MPLS core. The customer may use those paths as primary/backup or
active/active.
Different level of disjointness may be offered:
o Link disjointness: the paths of the associated LSPs should transit
different links (but may use common nodes or different links that
may have some shared fate).
o Node disjointness: the paths of the associated LSPs should transit
different nodes (but may use different links that may have some
shared fate).
o SRLG disjointness: the paths of the associated LSPs should transit
different links that do not share fate (but may use common transit
nodes).
o Node+SRLG disjointness: the paths of the associated LSPs should
transit different links that do not have any common shared fate
and should transit different nodes.
The associated LSPs may originate from the same or from different
head-end(s) and may terminate at the same or different tail-end(s).
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_________________________________________
/ \
/ +------+ \
| | PCE | |
| +------+ |
| |
| ***********************> |
| +------+ 10 +------+ |
CE1 ****| PE 1 | ----- R1 ---- R2 ------- | PE 2 |**** CE2
| +------+ | | +------+ |
| | | |
| | | |
| +------+ | | +------+ |
CE3 ****| PE 3 | ----- R3 ---- R4 ------- | PE 4 |**** CE4
| +------+ ***********************> +------+ |
| |
\ /
\_________________________________________/
Figure 1 - Disjoint paths with different head-ends and tail-ends
In the figure above, the customer wants to have two disjoint paths
between CE1/CE2 and CE3/CE4. From an IP/MPLS network point view, in
this example, the CEs are connected to different PEs to maximize
their disjointness. When LSPs originate from different head-ends,
distributed computation of diverse paths can be difficult. Whereas,
computation via a centralized PCE ensures path disjointness
correctness and simplicity.
[RFC5440] defines a mechanism for the synchronization of a set of
path computation requests by using the SVEC (Synchronization VECtor)
object, that specifies the list of synchronized requests that can
either be dependent or independent. The SVEC object identify the
relationship between the set of path computation requests, identified
by 'Request-ID-number' in RP (Request Parameters) object. [RFC6007]
further clarifies the use of the SVEC list for synchronized path
computations when computing dependent requests as well as describes a
number of usage scenarios for SVEC lists within single-domain and
multi-domain environments.
The SVEC object includes a Flags field that indicates the potential
dependency between the set of path computation request in a similar
way as the Flags field in the TLVs defined in this document. The
path computation request (PCReq) message MAY use both SVEC object to
identify the related path computation request as well as to identify
the diversity association group. The PCE MUST try to find a path
that meets both the constraints. It is possible that the diversity
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set in the association group is different from the one in SVEC
object, this might be true for the same LSP as well. The PCE would
consider both the objects as per the processing rules and aim to find
a path that meets both these constraints. In case no such path is
possible (or the constraints are incompatible), the PCE MUST send a
path computation reply (PCRep) with NO-PATH object indicating path
computation failure as per [RFC5440].
The PCEP extension for stateful PCE [RFC8231] defined new PCEP
messages - PCRpt, PCUpd and PCInitiate. These messages uses PLSP-ID
in the LSP object for identification. Moreover to allow diversity
between LSPs originating from different PCCs, the generic mechanism
to create a grouping of LSPs as described in
[I-D.ietf-pce-association-group] equally applicable to the active and
passive modes of a stateful PCE is better suited.
Using PCEP, the PCC MUST indicate that disjoint path computation is
required, such indication SHOULD include disjointness parameters such
as the type of disjointness, the disjoint group-id, and any
customization parameters according to the configured local policy.
As mentioned previously, the extension described in
[I-D.ietf-pce-association-group] is well suited to associated a set
of LSPs with a particular disjoint-group.
The management of the disjoint group-ids will be a key point for the
operator as the Association ID field is limited to 65535. The local
configuration of IPv4/IPv6 association source, or Global Association
Source/Extended Association ID should allow to overcome this
limitation. For example, when a PCC or PCE initiates all the LSPs in
a particular disjoint-group, it can set the IPv4/IPv6 association
source can be set to one of its IP address. When disjoint LSPs are
initiated from different head-ends, a unique association identifier
SHOULD be used for those LSPs: this can be achieved by setting the
IPv4/IPv6 source address to a common value (zero value can be used)
as well as the Association ID.
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Initiate & Monitor LSP
|
| PCReq/PCRpt
V {Disjoint-group Y}
+-----+ ----------------> +-----+
_ _ _ _ _ _| PCE | | | PCE |
| +-----+ | ----------> +-----+
| PCInitiate | | PCReq/PCRpt
|{Disjoint-group X} | | {Disjoint-group Y}
| | |
| .-----. | | .-----.
| ( ) | +----+ ( )
| .--( )--. | |PE 1|--.--( )--.
V ( ) | +----+ ( )
+---+ ( ) | ( )
|PCC|----( (G)MPLS network ) +----+ ( (G)MPLS network )
+---+ ( ) |PE 3|------( )
Disjoint-group X ) +----+ ( )
{Monitor LSP} '--( )--' '--( )--'
( ) ( )
'-----' '-----'
Case 1: Disjointness initiated by Case 2: Disjointness initiated by
PCE and enforced by PCC PCC and enforced by PCE
Figure 2 - Sample use-cases for carrying disjoint-group over PCEP
session
Using the disjoint-group within a PCUpd or PCInitiate may have two
purposes:
o Information: in case the PCE is performing the path computation,
it may communicate to the PCC the locally used parameters in the
attribute-list of the LSP.
o Configuration: in case the PCE is updating the diversity
parameters.
4. Protocol extension
4.1. 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
disjoint group a set of LSPs belongs to. This document defines a new
Association type, based on the generic Association object -
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o Association type = TBD1 ("Disjointness Association Type").
The association type is considered to be both dynamic and operator-
configured.
A disjoint group can have two or more LSPs. But a PCE may be limited
in how many LSPs it can take into account when computing
disjointness. If a PCE receives more LSPs in the group than it can
handle in its computation algorithm, it SHOULD apply disjointness
computation to only a subset of LSPs in the group. The subset of
disjoint LSPs will be decided by the implementation.
Local polices on the PCC or PCE MAY define the computational behavior
for the other LSPs in the group. For example, the PCE may provide no
path, a shortest path, or a constrained path based on relaxing
disjointness, etc.
Associating a particular LSP to multiple disjoint groups is
authorized from a protocol perspective, however there is no insurance
that the PCE will be able to compute properly the multi-disjointness
constraint.
4.2. Mandatory TLV
The disjoint group MUST carry the following TLV:
o DISJOINTNESS-CONFIGURATION-TLV: Used to communicate some
disjointness configuration parameters.
In addition, the disjoint group MAY carry the following TLV in a
PCUpd or PCRep message:
o DISJOINTNESS-STATUS-TLV: Used to communicate the status of the
computed disjointness.
The DISJOINTNESS-CONFIGURATION-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 = [TBD2] | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags |T|P|S|N|L|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Flags:
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* L (Link diverse) bit: when set, this indicates that the
computed paths within the disjoint group MUST NOT have any link
in common.
* N (Node diverse) bit: when set, this indicates that the
computed paths within the disjoint group MUST NOT have any node
in common.
* S (SRLG diverse) bit: when set, this indicates that the
computed paths within the disjoint group MUST NOT share any
SRLG (Shared Risk Link Group).
* P (Shortest path) bit: when set, this indicates that the
computed path of the LSP SHOULD satisfies all constraints and
objective functions first without considering the diversity
constraint. This means that an LSP with P flag set should be
placed as if the disjointness constraint has not been
configured, while the other LSP in the association with P flag
unset should be placed by taking into account the disjointness
constraint. Setting P flag changes the relationship between
LSPs to a unidirectional relationship (LSP 1 with P=0 depends
of LSP 2 with P=1, but LSP 2 with P=1 does not depend of LSP 1
with P=0).
* T (Strict disjointness) bit: when set, if disjoint paths cannot
be found, PCE should return no path for LSPs that could not be
be disjoint. When unset, PCE is allowed to relax disjointness
by using either applying a requested objective function or any
other behavior if no objective function is requested (e.g.:
using a lower disjoint type (link instead of node) or relaxing
disjointness constraint at all).
If a PCEP speaker receives a disjoint-group without DISJOINTNESS-
CONFIGURATION-TLV, it SHOULD reply with a PCErr Error-type=6
(Mandatory Object missing) and Error-value=TBD7.
The DISJOINTNESS-STATUS-TLV uses the same format as the DISJOINTNESS-
CONFIGURATION-TLV with a different type:
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 = [TBD3] | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags |T|P|S|N|L|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
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Any new flag defined for the DISJOINTNESS-CONFIGURATION-TLV MUST be
automatically added to the DISJOINTNESS-STATUS-TLV.
4.3. Optional TLVs
The disjoint 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 [RFC7150].
4.4. Disjointness objective functions
An objective function MAY be applied to the disjointness computation
to drive the PCE computation behavior. In this case, the OF-List TLV
(defined in ([RFC5541]) is used as an optional TLV in the Association
Group Object. The PCEP OF-List TLV allow multiple OF-Codes inside
the TLV, a sender SHOULD include a single OF-Code in the OF-List TLV
when included in the Association Group, and the receiver MUST
consider the first OF-code only and ignore others if included.
To minimize the common shared resources (Node, Link or SRLG) between
a set of paths during path computation three new OF codes are
proposed:
MSL
* Name: Minimize the number of shared (common) Links.
* Objective Function Code: TBD4
* Description: Find a set of paths such that it passes through the
least number of shared (common) links.
MSS
* Name: Minimize the number of shared (common) SRLGs.
* Objective Function Code: TBD5
* Description: Find a set of paths such that it passes through the
least number of shared (common) SRLGs.
MSN
* Name: Minimize the number of shared (common) Nodes.
* Objective Function Code: TBD6
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* Description: Find a set of paths such that it passes through the
least number of shared (common) nodes.
[RFC5440] uses SVEC diversity flag for node, link or SRLG to describe
the potential disjointness between the set of path computation
requests used in PCEP protocol.
This document defines three new OF codes to maximize diversity as
much as possible, in other words, minimize the common shared
resources (Node,Link or SRLG) between a set of paths.
It may be interesting to note that the diversity flags in the SVEC
object and OF for diversity can be used together. Some example of
usage are listed below -
o SVEC object with node-diverse bit=1 - ensure full node-diversity.
o SVEC object with node-diverse bit=1 and OF=MSS - full node diverse
with as much as SRLG-diversity as possible.
o SVEC object with domain-diverse bit=1;link diverse bit=1 and
OF=MSS - full domain and node diverse path with as much as SRLG-
diversity as possible.
o SVEC object with node-diverse bit=1 and OF=MSN - ensure full node-
diversity.
4.5. P-flag considerations
As mentioned in Section 4.2, the P-flag (when set) indicates that the
computed path of the LSP SHOULD satisfies all constraints and
objective functions first without considering the diversity
constraint. This could be required in some primary/backup scenarios
where the primary path should use the more optimal path available
(taking into account the other constraints). When disjointness is
computed, it is important for the algorithm to know that it should
try to optimize the path of one or more LSPs in the disjoint group
(for instance the primary path) while other paths are allowed to be
longer (compared to a similar path without the disjointness
constraint). Without such a hint, the disjointness algorithm may set
a path for all LSPs that may not completely fulfil the customer
requirement.
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_________________________________________
/ \
/ +------+ \
| | PCE | |
| +------+ |
| |
| |
| +------+ 10 +------+ |
CE1 ****| PE 1 | ----- R1 ---- R2 ------- | PE 2 |**** CE2
| +------+ | | +------+ |
| | | |
| | | |
| +------+ | | +------+ |
CE3 ****| PE 3 | ----- R3 ---- R4 ------- | PE 4 |**** CE4
| +------+ \ | / +------+ |
| \ | 10 / |
\ +-- R5 --------- R6 /
\_________________________________________/
Figure 3
In the figure above, a customer has two dual homed sites (CE1/CE3 and
CE2/CE4). This customer wants two disjoint paths between the two
sites. Due to physical meshings, the customer wants to use CE1 and
CE2 as primary (for instance CE3 and CE4 are hosted in a remote site
for redundancy purpose compared the customer hosts).
Without any hint (constraint) provided, the PCE may compute the two
disjoint LSPs as a batch leading to PE1->PE2 using a path
PE1->R1->R2->PE2 and PE3->PE4 using PE3->R3->R4->PE4. In this case,
even if the disjointness constraint is fulfilled, the path from PE1
to PE2 does not use the best optimal path available in the network
(RTD may be higher): the customer requirement is thus not completely
fulfilled.
The usage of the P-Flag allows the PCE to know that a particular LSP
should be tied to the best path as if the disjointness constraint was
not requested.
In our example, if the P-Flag is set to the LSP PE1->PE2, the PCE
should use the path PE1->R1->R3->R4->R2->PE2 for this LSP, while the
other LSP should be disjoint from this path. The second LSP will be
placed on PE3->R5->R6->PE4 as it is allowed to be longer.
Driving the PCE disjointness computation may be done in other ways by
for instance setting a metric boundary reflecting an RTD boundary.
Other constraints may also be used.
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The P-Flag allows a simple expression that the disjointness
constraint should not make the LSP worst.
Any constraint added to a path disjointness computation may reduce
the chance to find suitable paths. The usage of the P-flag, as any
other constraint, may prevent to find a disjoint path. In the
example above, if we consider that the router R5 is down, if PE1->PE2
has the P-flag set, there is no room available to place PE3->PE4 (the
disjointness constraint cannot be fulfilled). If PE->PE2 has the
P-flag unset, the algorithm may be able to place PE1->PE2 on R1->R2
link leaving a room for PE3->PE4 using the R3->R4 link. When using
P-flag or any additional constraint on top of the disjointness
constraint, the user should be aware that there is less chance to
fulfill the disjointness constraint.
Multiple LSPs in the same disjoint group may have the P-flag set. In
such a case, those LSPs may not be disjoint from each other but will
be disjoint from others LSPs in the group that have the P-flag unset.
_________________________________________
/ \
/ +------+ \
| | PCE | |
| +------+ |
| |
| |
| +------+ 10 +------+ |
CE1 ****| PE 1 | ----- R1 ---- R2 ------- | PE 2 |**** CE2
| +------+ | \ | +------+ |
| | \2 | |
| | \ | |
| +------+ | \ | +------+ |
CE3 ****| PE 3 | ----- R3 ---- R4 ------- | PE 4 |**** CE4
| +------+ +------+ |
| |
\ /
\_________________________________________/
Figure 4
In the figure above, we still consider the same previous
requirements, so PE1->PE2 LSP should be optimized (P-flag set) while
PE3->PE4 should be disjoint and may use a longer path.
Regarding PE1->PE2, there are two paths that are satisfying the
constraints (ECMP): PE1->R1->R4->R2->PE2 (path 1) and
PE1->R1->R3->R4->R2->PE2 (path 2). An implementation may choose one
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of the paths or even use boths (using both may happen in case Segment
Routing TE is used, allowing ECMP).
If the implementation elects only one path, there is a chance that
picking up one path may prevent disjointness. In our example, if
path 2 is used for PE1->PE2, there is no room left for PE3->PE4 while
if path 1 is used, PE3->PE4 can be placed on R3->R4 link.
When P-flag is set for an LSP and when ECMPs are available, an
implementation MAY select a path that allows disjointness.
4.6. Disjointness computation issues
There may be some cases where the PCE is not able to provide a set of
disjoint paths for one or more LSPs in the association.
When the T-bit is set (Strict disjointness requested), if
disjointness cannot be ensured for one or more LSPs, the PCE SHOULD
reply with a PCUpd message containing an empty ERO. In addition to
the empty ERO Object, the PCE MAY add the NO-PATH-VECTOR TLV
([RFC5440]) in the LSP Object.
This document adds new bits in the NO-PATH-VECTOR TLV:
bit "TBD7": when set, the PCE indicates that it could not find a
disjoint path for this LSP.
bit "TBD8": when set, the PCE indicates that it does not support
the requested disjointness computation.
When the T-bit is unset, the PCE is allowed to reduce the required
level of disjointness. The actual level of disjointness computed by
the PCE can be reported through the DISJOINTNESS-STATUS-TLV by
setting the appropriate flags in the TLV. While the DISJOINTNESS-
CONFIGURATION-TLV defines the expected level of disjointness required
by configuration, the DISJOINTNESS-STATUS-TLV defines the actual
level of disjointness computed.
There are some cases where the PCE may need to completely relax the
disjointness constraint in order to provide a path to all the LSPs
that are part of the association. A mechanism that allows the PCE to
fully relax a constraint is considered by the authors as more global
to PCEP rather than linked to the disjointness use case. As a
consequence, it is considered as out of scope of the document.
All LSPs in a particular disjoint group MUST use the same combination
of T,S,N,L flags in the DISJOINTNESS-CONFIGURATION-TLV. If a PCE
receives PCRpt messages for LSPs belonging to the same disjoint group
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but having an inconsistent combination of T,S,N,L flags, the PCE
SHOULD NOT try to compute disjointness path and SHOULD reply a PCErr
with Error-type 5 (Policy Violation) and Error-Value TBD6
(Inconsistent parameters in DISJOINTNESS-CONFIGURATION TLV) to all
PCCs involved in the disjoint group.
5. 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.
6. IANA Considerations
6.1. Association object Type Indicators
This document defines the following new association type originally
defined in [I-D.ietf-pce-association-group].
Value Name Reference
TBD1 Disjoint-group
Association Type [This I.D.]
6.2. PCEP TLVs
This document defines the following new PCEP TLVs:
Value Name Reference
TBD2 DISJOINTNESS-CONFIGURATION-TLV [This I.D.]
TBD3 DISJOINTNESS-STATUS-TLV [This I.D.]
IANA is requested to manage the space of flags carried in the
DISJOINTNESS-CONFIGURATION-TLV defined in this document, numbering
them from 0 as the least significant bit.
New bit numbers may be allocated in future.
IANA is requested to allocate the following bit numbers in the
DISJOINTNESS-CONFIGURATION-TLV flag space:
Bit Number Name Reference
0 Link disjointness [This I.D.]
1 Node disjointness [This I.D.]
2 SRLG disjointness [This I.D.]
3 Shortest-path [This I.D.]
4 Strict disjointness [This I.D.]
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6.3. Objective Functions
three new Objective Functions have been defined. IANA has made the
following allocations from the PCEP "Objective Function" sub-
registry:
Value Description Reference
TBD4 MSL [This I.D.]
TBD5 MSN [This I.D.]
TBD6 MSS [This I.D.]
6.4. NO-PATH-VECTOR bit Flags
This documents defines new bits for the NO-PATH-VECTOR TLV in the
"NO-PATH-VECTOR TLV Flag Field" sub-registry of the "Path Computation
Element Protocol (PCEP) Numbers" registry:
Bit Number Name Reference
TBD7 Disjoint path not found [This I.D.]
TBD8 Requested disjointness [This I.D.]
computation not supported
6.5. PCEP-ERROR codes
IANA is requested to allocate new Error Types and Error Values within
the " PCEP-ERROR Object Error Types and Values" sub-registry of the
PCEP Numbers registry, as follows:
Error-Type Meaning
5 Policy violation
Error-value=TBD6: Inconsistent parameters
in DISJOINTNESS-CONFIGURATION TLV
6 Mandatory Object missing
Error-value=TBD7: DISJOINTNESS-CONFIGURATION TLV missing
7. Manageability Considerations
7.1. Control of Function and Policy
An operator MUST be allowed to configure the disjointness
associations and parameters at PCEP peers and associate it with the
LSPs.
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7.2. Information and Data Models
[RFC7420] describes the PCEP MIB, there are no new MIB Objects for
this document.
7.3. Liveness Detection and Monitoring
Mechanisms defined in this document do not imply any new liveness
detection and monitoring requirements in addition to those already
listed in [RFC5440].
7.4. Verify Correct Operations
Mechanisms defined in this document do not imply any new operation
verification requirements in addition to those already listed in
[RFC5440].
7.5. Requirements On Other Protocols
Mechanisms defined in this document do not imply any new requirements
on other protocols.
7.6. Impact On Network Operations
Mechanisms defined in this document do not have any impact on network
operations in addition to those already listed in [RFC5440].
8. Acknowledgments
A special thanks to author of [I-D.ietf-pce-association-group], this
document borrow some of the text from it. Authors would also like to
thank Adrian Farrel for his useful comments.
9. References
9.1. Normative References
[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>.
[RFC4655] Farrel, A., Vasseur, J., and J. Ash, "A Path Computation
Element (PCE)-Based Architecture", RFC 4655,
DOI 10.17487/RFC4655, August 2006,
<https://www.rfc-editor.org/info/rfc4655>.
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[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>.
[RFC5541] Le Roux, JL., Vasseur, JP., and Y. Lee, "Encoding of
Objective Functions in the Path Computation Element
Communication Protocol (PCEP)", RFC 5541,
DOI 10.17487/RFC5541, June 2009,
<https://www.rfc-editor.org/info/rfc5541>.
[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-04 (work in progress), August
2017.
[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>.
9.2. Informative References
[RFC7150] Zhang, F. and A. Farrel, "Conveying Vendor-Specific
Constraints in the Path Computation Element Communication
Protocol", RFC 7150, DOI 10.17487/RFC7150, March 2014,
<https://www.rfc-editor.org/info/rfc7150>.
[RFC7420] Koushik, A., Stephan, E., Zhao, Q., King, D., and J.
Hardwick, "Path Computation Element Communication Protocol
(PCEP) Management Information Base (MIB) Module",
RFC 7420, DOI 10.17487/RFC7420, December 2014,
<https://www.rfc-editor.org/info/rfc7420>.
[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>.
Authors' Addresses
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Stephane Litkowski
Orange
EMail: stephane.litkowski@orange.com
Siva Sivabalan
Cisco Systems, Inc.
2000 Innovation Drive
Kanata, Ontario K2K 3E8
Canada
EMail: msiva@cisco.com
Colby Barth
Juniper Networks
EMail: cbarth@juniper.net
Dhruv Dhody
Huawei
EMail: dhruv.dhody@huawei.com
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