PCE S. Peng
Internet-Draft Q. Xiong
Intended status: Standards Track ZTE Corporation
Expires: June 1, 2020 F. Qin
China Mobile
November 29, 2019
PCE TE Constraints for Network Slicing
draft-peng-pce-te-constraints-02
Abstract
This document proposes a set of extensions for PCEP to support the
constraints for network slicing during path computation, e.g, IGP
instance, virtual network, specific application, color template and
FA-id etc.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 2
2. Conventions used in this document . . . . . . . . . . . . . . 3
2.1. Terminology . . . . . . . . . . . . . . . . . . . . . . . 3
2.2. Requirements Language . . . . . . . . . . . . . . . . . . 3
3. PCEP Extensions for Constraints . . . . . . . . . . . . . . . 3
3.1. Source Protocol Object . . . . . . . . . . . . . . . . . 3
3.2. Multi-topology Object . . . . . . . . . . . . . . . . . . 4
3.3. The AII Object . . . . . . . . . . . . . . . . . . . . . 5
3.4. Application Specific Object . . . . . . . . . . . . . . . 6
3.5. The Color Object . . . . . . . . . . . . . . . . . . . . 7
3.6. The FA-id Object . . . . . . . . . . . . . . . . . . . . 8
4. Security Considerations . . . . . . . . . . . . . . . . . . . 9
5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 9
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 10
7. Normative References . . . . . . . . . . . . . . . . . . . . 10
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 12
1. Introduction
[RFC5440] describes the Path Computation Element Protocol (PCEP)
which is used between a Path Computation Element (PCE) and a Path
Computation Client (PCC) (or other PCE) to enable computation of
Multi-protocol Label Switching (MPLS) for Traffic Engineering Label
Switched Path (TE LSP). PCEP Extensions for the Stateful PCE Model
[RFC8231] describes a set of extensions to PCEP to enable active
control of MPLS-TE and Generalized MPLS (GMPLS) tunnels. As depicted
in [RFC4655], a PCE MUST be able to compute the path of a TE LSP by
operating on the TED and considering bandwidth and other constraints
applicable to the TE LSP service request. The constraint parameters
are provided such as metric, bandwidth, delay, affinity, etc.
However these parameters can't meet the network slicing requirements.
According to 5G context, network slicing is the collection of a set
of technologies to support network service differentiation and
meeting the diversified requirements from vertical industries. The
slices may be seen as virtual networks and partition the network
resources into sub-topologies in transport network. Multiple
existing identifiers could be used to identify the virtual network
resource and viewed as constraints of network slicing when PCE is
deployed.
A PCE always perform path computation based on the network topology
information collected through BGP-LS [RFC7752]. BGP-LS can get
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multiple link-state data from multiple IGP instance, or multiple
virtual topologies from a single IGP instance. It is necessary to
restrict the PCE to a small topology scope during path computation
for some special purpose. BGP-LS can also get application specific
TE attributes for a link, it is also necessary to restrict PCE to use
TE attributes of specific application The PCE MUST take the
identifier of slicing into consideration during path computation.
This document proposes a set of extensions for PCEP to support the
constraints for network slicing during path computation, e.g, IGP
instance, virtual network, specific application, color template and
FA-id etc.
2. Conventions used in this document
2.1. Terminology
The terminology is defined as [RFC5440] and [RFC7752].
2.2. Requirements Language
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.
3. PCEP Extensions for Constraints
3.1. Source Protocol Object
The Source Protocol object is optional and can be used for several
purposes.
In a PCReq message, a PCC MAY insert one Source Protocol object to
indicate the source protocol that MUST be considered by the PCE. The
PCE will perform path computation based on the sub-topology
identified by the specific source protocol. The absence of the
Source Protocol object MUST be interpreted by the PCE as a path
computation request for which no constraints need be applied to any
of the source protocols.
In a PCRep/PCInit/PCUpd message, the Source Protocol object MAY be
inserted so as to provide the source protocol information for the
computed path.
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Only one Source Protocol Object could be inserted in the above
messages, otherwise the first one MUST be considered and others MUST
be ignored.
Source Protocol Object-Class is TBA.
Source Protocol Object-Type is 1.
The format of the Source Protocol object is shown as Figure 1:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Protocol-ID | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Identifier |
| (64 bits) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: Source Protocol Object
The Source Protocol object body has a fixed length of 12 bytes.
Protocol-ID (8 bits): defined in [RFC7752] section 3.2.
Reserved (24 bits): This field MUST be set to zero on transmission
and MUST be ignored on receipt.
Identifier (64 bits): defined in [RFC7752] section 3.2.
3.2. Multi-topology Object
The Multi-topology object is optional and can be used for several
purposes.
In a PCReq message, a PCC MAY insert one Multi-topology object to
indicate the sub-topology of an IGP instance that MUST be considered
by the PCE. The PCE will perform path computation based on the sub-
topology identified by the specific Multi-Topology ID within a source
protocol. The absence of the Multi-topology object MUST be
interpreted by the PCE as a path computation request for which no
constraints need be applied to any of the multi-topologies.
In a PCRep/PCInit/PCUpd message, the Multi-topology object MAY be
inserted so as to provide the Multi-topology information for the
computed path.
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Only one Multi-topology Object could be inserted in the above
messages, otherwise the first one MUST be considered and others MUST
be ignored. It MUST be inserted with a Source Protocol Object, if
not it MUST be ignored.
Multi-topology Object-Class is TBA.
Multi-topology Object-Type is 1.
The format of the Multi-topology object is shown as Figure 2:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|R R R R| Multi-Topology ID | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: Multi-topology Object
The Multi-topology object body has a fixed length of 4 bytes.
Multi-Topology ID (12 bits): Semantics of the IS-IS MT-ID are defined
in Section 7.2 of [RFC5120]. Semantics of the OSPF MT-ID are defined
in Section 3.7 of [RFC4915]. If the value is derived from OSPF, then
the upper 9 bits MUST be set to 0. Bits R are reserved and SHOULD be
set to 0 when originated and ignored on receipt.
Reserved (16 bits): This field MUST be set to zero on transmission
and MUST be ignored on receipt.
3.3. The AII Object
The AII object is optional and can be used for several purposes.
In a PCReq message, a PCC MAY insert one AII object to indicate the
global virtual network that MUST be considered by the PCE. The PCE
will perform path computation based on the intra or inter-domain sub-
topology identified by the specific AII, which is independent of
routing protocols such as IGP/BGP. The absence of the AII object
MUST be interpreted by the PCE as a path computation request for
which no constraints need be applied to any of the virtual network,
i.e, a default AII (0) will be applied.
In a PCRep/PCInit/PCUpd message, the AII object MAY be inserted so as
to provide the network slicing information for the computed path.
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Only one AII Object could be inserted in the above messages,
otherwise the first one MUST be considered and others MUST be
ignored.
AII Object-Class is TBA.
AII Object-Type is 1.
The format of the AII object is shown as Figure 3:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| AII |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: AII Object
The AII object body has a fixed length of 4 bytes.
AII (32 bits): Administrative Instance Identifier defined in
[I-D.peng-lsr-network-slicing].
3.4. Application Specific Object
The Application Specific object is optional and can be used for
several purposes.
In a PCReq message, a PCC MAY insert one Application Specific object
to indicate the appliaction that MUST be considered by the PCE. The
PCE will perform path computation using the specific application
attributes. The absence of the Application Specific object MUST be
interpreted by the PCE as a path computation request for which no
constraints need be applied to any of the Application Specific
attributes.
In a PCRep/PCInit/PCUpd message, the Application Specific object MAY
be inserted so as to provide the Application Specific information for
the computed path.
Only one Application Specific Object could be inserted in the above
messages, otherwise the first one MUST be considered and others MUST
be ignored.
Application Specific Object-Class is TBA.
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Application Specific Object-Type is 1.
The format of the Application Specific object is shown as Figure 4:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Standard Application ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| User Defined Application ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4: Application Specific Object
The Application Specific object body has a fixed length of 8 bytes.
Standard Application ID: Represents a bit-position value for a single
STANDARD application that is defined in the IANA "IGP Parameters"
registries under the "Link Attribute Applications" registry
[I-D.ietf-isis-te-app].
User Defined Application ID: Represents a single user defined
application which is a specific implementation.
3.5. The Color Object
The Color object is optional and can be used for several purposes.
In a PCReq message, a PCC MAY insert one Color object to indicate the
traffic engineering purpose that is recognized by the both PCE and
PCC with no conflict meaning. The PCE will perform path computation
based on the color template. The same color template may be also
defined at PCC and the exsiting constraints (i.e, metric, bandwidth,
dealy, etc) carried in the message MUST be ignored. The absence of
the Color object MUST be interpreted by the PCE as a path computation
request for which traditional constraints that are contained in
message need be applied.
In a PCRep/PCInit/PCUpd message, the Color object MAY be inserted so
as to provide the TE purpose information for the computed path, the
PCC recognize the color value that match a local color-template.
Only one Color Object could be inserted in the above messages,
otherwise the first one MUST be considered and others MUST be
ignored.
Color Object-Class is TBA.
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Color Object-Type is 1.
The format of the Color object is shown as Figure 5:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Color |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 5: Color Object
The Color object body has a fixed length of 4 bytes.
Color (32 bits): indicate a TE template, 0 is invalid value. It is
consistent with the Color Extended Community defined in
[I-D.ietf-idr-tunnel-encaps], and color of SR policy defined in
[I-D.ietf-spring-segment-routing-policy].
Note that Color Object defined in this document is used to represent
a TE template, it can be suitable for any TE instance such as RSVP-
TE, SR-TE, SR-policy. [I-D.barth-pce-segment-routing-policy-cp] has
proposed the SR policy KEY (that also includes a color information)
as an association group KEY to associate many candidate paths,
however it is only for association purpose but not constraint purpose
for path computation.
A color tempate can be defined to use exsiting constraints such as
metric, bandwidth, dealy, affinity parameters, and the sub-topology
constraints above defined in this document.
3.6. The FA-id Object
FA-id defined in [I-D.ietf-lsr-flex-algo] is a short mapping of SR
policy color to optimaze segment stack depth for the IGP area partial
of the entire SR policy. The overlay service that want to be carried
over a particual SR-FA path must firstly let the SR policy supplier
know that requirement. There are two possible ways to map a color to
an FA-id. One is explicit mapping configuration within color
template, the other is dynamic to replace a long segment list to
short FA segment by headend or controller once the creterias
contained in the color-template equal to that contained in FAD.
In a PCReq message, a PCC MAY insert one FA-id object to indicate the
above explicit FA-id mapping. The PCE will perform path computation
based on the FA-id. In detailed, The PCE will check if there are
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connectivity within the corresponding Flex-algo plane to the
destination. If yes, the path computation result will be represented
as segment list with a single prefix-SID@FA for intra-domain case, or
serveral prefix-SID@FA for inter-domain case.
In a PCRep/PCInit/PCUpd message, the FA-id object MAY be inserted so
as to provide the FA plane information for the computed path.
In general, the FA-id object is only meaningful for the domain that
headend node belongs to. For inter-domain case, operator MUST ensure
the FA-id configuration of different domain are same for an E2E
slice, when he want to explicitly indicate FA-id in PCEP message.
Only one FA-id Object could be inserted in the above messages,
otherwise the first one MUST be considered and others MUST be
ignored.
FA-id Object-Class is TBA.
FA-id Object-Type is 1.
The format of the FA-id object is shown as Figure 6:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| FA-id | Unused |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 6: FA-id Object
The FA-id object body has a fixed length of 4 bytes.
FA-id (8 bits): indicate an explicit FA-id mapping.
4. Security Considerations
TBA
5. Acknowledgements
TBA
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6. IANA Considerations
IANA is requested to make allocations from the registry, as follows:
+---------+-------------------------------+------------------+
| Value | Object | Reference |
+---------+-------------------------------+------------------+
| TBA1 | Source Protocol Object | [this document] |
| TBA2 | Multi-topology Object | [this document] |
| TBA3 | AII Object | [this document] |
| TBA4 | Application Specific Object | [this document] |
| TBA5 | Color Object | [this document] |
| TBA6 | FA-id Object | [this document] |
+---------+-------------------------------+------------------+
Table 1
7. Normative References
[I-D.barth-pce-segment-routing-policy-cp]
Koldychev, M., Sivabalan, S., Barth, C., Li, C., and H.
Bidgoli, "PCEP extension to support Segment Routing Policy
Candidate Paths", draft-barth-pce-segment-routing-policy-
cp-04 (work in progress), October 2019.
[I-D.ietf-idr-tunnel-encaps]
Patel, K., Velde, G., and S. Ramachandra, "The BGP Tunnel
Encapsulation Attribute", draft-ietf-idr-tunnel-encaps-14
(work in progress), September 2019.
[I-D.ietf-isis-te-app]
Ginsberg, L., Psenak, P., Previdi, S., Henderickx, W., and
J. Drake, "IS-IS TE Attributes per application", draft-
ietf-isis-te-app-09 (work in progress), October 2019.
[I-D.ietf-lsr-flex-algo]
Psenak, P., Hegde, S., Filsfils, C., Talaulikar, K., and
A. Gulko, "IGP Flexible Algorithm", draft-ietf-lsr-flex-
algo-05 (work in progress), November 2019.
[I-D.ietf-spring-segment-routing-policy]
Filsfils, C., Sivabalan, S., Voyer, D., Bogdanov, A., and
P. Mattes, "Segment Routing Policy Architecture", draft-
ietf-spring-segment-routing-policy-03 (work in progress),
May 2019.
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[I-D.peng-lsr-network-slicing]
Peng, S., Chen, R., and G. Mirsky, "Packet Network Slicing
using Segment Routing", draft-peng-lsr-network-slicing-00
(work in progress), February 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>.
[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>.
[RFC4915] Psenak, P., Mirtorabi, S., Roy, A., Nguyen, L., and P.
Pillay-Esnault, "Multi-Topology (MT) Routing in OSPF",
RFC 4915, DOI 10.17487/RFC4915, June 2007,
<https://www.rfc-editor.org/info/rfc4915>.
[RFC5120] Przygienda, T., Shen, N., and N. Sheth, "M-ISIS: Multi
Topology (MT) Routing in Intermediate System to
Intermediate Systems (IS-ISs)", RFC 5120,
DOI 10.17487/RFC5120, February 2008,
<https://www.rfc-editor.org/info/rfc5120>.
[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>.
[RFC7752] Gredler, H., Ed., Medved, J., Previdi, S., Farrel, A., and
S. Ray, "North-Bound Distribution of Link-State and
Traffic Engineering (TE) Information Using BGP", RFC 7752,
DOI 10.17487/RFC7752, March 2016,
<https://www.rfc-editor.org/info/rfc7752>.
[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>.
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Authors' Addresses
Shaofu Peng
ZTE Corporation
No.50 Software Avenue
Nanjing, Jiangsu 210012
China
Email: peng.shaofu@zte.com.cn
Quan Xiong
ZTE Corporation
No.6 Huashi Park Rd
Wuhan, Hubei 430223
China
Email: xiong.quan@zte.com.cn
Fengwei Qin
China Mobile
Beijing
China
Email: qinfengwei@chinamobile.com
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