PCE S. Peng
Internet-Draft Q. Xiong
Intended status: Standards Track ZTE Corporation
Expires: December 3, 2020 F. Qin
China Mobile
June 1, 2020
PCE TE Constraints for Network Slicing
draft-peng-pce-te-constraints-03
Abstract
This document proposes a set of extensions for PCEP to support the TE
constraints of 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 TE Constraints in Network Slicing . . . . 3
3.1. Source Protocol TLV . . . . . . . . . . . . . . . . . . . 3
3.2. Multi-topology TLV . . . . . . . . . . . . . . . . . . . 4
3.3. The AII TLV . . . . . . . . . . . . . . . . . . . . . . . 5
3.4. Application Specific TLV . . . . . . . . . . . . . . . . 6
3.5. The Color TLV . . . . . . . . . . . . . . . . . . . . . . 7
3.6. The FA-id TLV . . . . . . . . . . . . . . . . . . . . . . 8
4. Security Considerations . . . . . . . . . . . . . . . . . . . 9
5. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 9
6. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 9
7. Normative References . . . . . . . . . . . . . . . . . . . . 9
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 11
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 TE
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 TE Constraints in Network Slicing
As defined in [RFC5440] , the LSPA object is used to specify the LSP
attributes to be taken into account by the PCE during path
computation such as TE constraints. This document proposes several
new TLVs for the LSPA object to carry TE constraints in Network
Slicing.
3.1. Source Protocol TLV
The Source Protocol TLV is optional and is defined to carry the
source protocol constraint.
In a PCReq message, a PCC MAY insert one Source Protocol TLV 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 TLV MUST be interpreted by the PCE as a path
computation request for which no constraints need be applied to any
of the source protocols.
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In a PCRep/PCInit/PCUpd message, the Source Protocol TLV MAY be
carried so as to provide the source protocol information for the
computed path.
The format of the Source Protocol TLV 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type=TBD1 | Length=12 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Protocol-ID | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Identifier |
| (64 bits) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: Source Protocol TLV
The code point for the TLV type is TBD1. The TLV length is 12
octets.
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 TLV
The Multi-topology TLV is optional and is defined to carry the multi-
topology protocol constraint.
In a PCReq message, a PCC MAY insert one Multi-topology TLV 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 TLV 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 TLV MAY be
carried so as to provide the Multi-topology information for the
computed path.
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The Multi-topology TLV MUST be carried after a Source Protocol TLV,
if not it MUST be ignored.
The format of the Multi-topology TLV 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type=TBD2 | Length=4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|R R R R| Multi-Topology ID | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: Multi-topology TLV
The code point for the TLV type is TBD2. The TLV length is 4 octets.
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 TLV
Administrative Instance Identifier (AII) is provided to specify the
TE purpose within a virtual network as per
[I-D.peng-lsr-network-slicing]. The AII TLV is optional and is
defined to carry the AII constraint.
In a PCReq message, a PCC MAY insert one AII TLV to indicate the
global virtual network that MUST be considered by the PCE. The PCE
will perform path computation based on the intra-domain 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 TLV 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 TLV MAY be carried so as to
provide the network slicing information for the computed path.
The format of the AII TLV is shown as Figure 3:
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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=TBD3 | Length=4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| AII |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: AII TLV
The code point for the TLV type is TBD3. The TLV length is 4 octets.
AII (32 bits): indicate the AII information as defined in
[I-D.peng-lsr-network-slicing].
3.4. Application Specific TLV
The Application Specific TLV is optional and is defined to carry the
application specific constraints.
In a PCReq message, a PCC MAY insert one Application Specific TLV to
indicate the application that MUST be considered by the PCE. The PCE
will perform path computation using the specific application
attributes. The absence of the Application Specific TLV 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 TLV MAY be
inserted so as to provide the Application Specific information for
the computed path.
The format of the Application Specific TLV 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type=TBD4 | Length=8 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Standard Application ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| User Defined Application ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4: Application Specific TLV
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The code point for the TLV type is TBD4. The TLV length is 8 octets.
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 TLV
The Color TLV is optional and is defined to carry the color
constraints.
In a PCReq message, a PCC MAY insert one Color TLV to indicate the
traffic engineering purpose that is recognized by 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 existing constraints (i.e, metric, bandwidth,
delay, etc) carried in the message MUST be ignored. The absence of
the Color TLV 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 TLV 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.
The format of the Color TLV 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type=TBD5 | Length=4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Color |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 5: Color TLV
The code point for the TLV type is TBD5. The TLV length is 4 octets.
Color (32 bits): indicate a TE template, 0 is invalid value. It is
consistent with the Color Extended Community defined in
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[I-D.ietf-idr-tunnel-encaps], and color of SR policy defined in
[I-D.ietf-spring-segment-routing-policy].
Note that Color TLV 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 template can be defined to use existing constraints such as
metric, bandwidth, delay, affinity parameters, and the sub-topology
constraints above defined in this document.
3.6. The FA-id TLV
FA-id defined in [I-D.ietf-lsr-flex-algo] is a short mapping of SR
policy color to optimize segment stack depth for the IGP area partial
of the entire SR policy. The overlay service that want to be carried
over a particular 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 dynamicly replacing a long segment list to
short FA segment by headend or controller once the information
contained in the color-template equal to that contained in FAD.
In a PCReq message, a PCC MAY insert one FA-id TLV 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
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
several prefix-SID@FA for inter-domain case.
In a PCRep/PCInit/PCUpd message, the FA-id TLV MAY be inserted so as
to provide the FA plane information for the computed path.
In general, the FA-id TLV 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.
The format of the FA-id TLV is shown as Figure 6:
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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=TBD6 | Length=4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| FA-id | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 6: FA-id TLV
The code point for the TLV type is TBD6. The TLV length is 4 octets.
FA-id (8 bits): indicate an explicit FA-id mapping information.
4. Security Considerations
TBA
5. Acknowledgements
TBA
6. IANA Considerations
IANA is requested to make allocations from the registry, as follows:
+--------+----------------------------+------------------+
| Type | TLV | Reference |
+--------+----------------------------+------------------+
| TBD1 | Source Protocol TLV | [this document] |
| TBD2 | Multi-topology TLV | [this document] |
| TBD3 | AII TLV | [this document] |
| TBD4 | Application Specific TLV | [this document] |
| TBD5 | Color TLV | [this document] |
| TBD6 | FA-id TLV | [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-05 (work in progress), May 2020.
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[I-D.ietf-idr-tunnel-encaps]
Patel, K., Velde, G., and S. Ramachandra, "The BGP Tunnel
Encapsulation Attribute", draft-ietf-idr-tunnel-encaps-15
(work in progress), December 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-13 (work in progress), May 2020.
[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-07 (work in progress), April 2020.
[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-07 (work in progress),
May 2020.
[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>.
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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>.
[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>.
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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