Internet Engineering Task Force (IETF) A. Wang
Request for Comments: 9757 China Telecom
Category: Experimental B. Khasanov
ISSN: 2070-1721 MTS Web Services (MWS)
S. Fang
R. Tan
Huawei Technologies
C. Zhu
ZTE Corporation
March 2025
Path Computation Element Communication Protocol (PCEP) Extensions for
Native IP Networks
Abstract
This document introduces extensions to the Path Computation Element
Communication Protocol (PCEP) to support path computation in Native
IP networks through a PCE-based central control mechanism known as
Centralized Control Dynamic Routing (CCDR). These extensions empower
a PCE to calculate and manage paths specifically for Native IP
networks, thereby expanding PCEP's capabilities beyond its
traditional past use
in MPLS and GMPLS networks. By implementing these extensions, IP
network resources can be utilized more efficiently, facilitating the
deployment of traffic engineering in Native IP environments.
Status of This Memo
This document is not an Internet Standards Track specification; it is
published for examination, experimental implementation, and
evaluation.
This document defines an Experimental Protocol for the Internet
community. This document is a product of the Internet Engineering
Task Force (IETF). It represents the consensus of the IETF
community. It has received public review and has been approved for
publication by the Internet Engineering Steering Group (IESG). Not
all documents approved by the IESG are candidates for any level of
Internet Standard; see Section 2 of RFC 7841.
Information about the current status of this document, any errata,
and how to provide feedback on it may be obtained at
https://www.rfc-editor.org/info/rfc9757.
Copyright Notice
Copyright (c) 2025 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
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include Revised BSD License text as described in Section 4.e of the
Trust Legal Provisions and are provided without warranty as described
in the Revised BSD License.
Table of Contents
1. Introduction
2. Conventions Used in This Document
2.1. Use of RBNF
2.2. Experimental Status Consideration
3. Terminology
4. Capability Advertisement
4.1. Open Message
5. PCEP Messages
5.1. The PCInitiate Message
5.2. The PCRpt Message
6. PCECC Native IP TE Procedures
6.1. BGP Session Establishment Procedures
6.2. Explicit Route Establishment Procedures
6.3. BGP Prefix Advertisement Procedures
6.4. Selection of the Raw Mode and Tunnel Mode Forwarding
Strategy
6.5. Cleanup
6.6. Other Procedures
7. New PCEP Objects
7.1. CCI Object
7.2. BGP Peer Info Object
7.3. Explicit Peer Route Object
7.4. Peer Prefix Advertisement Object
8. New Error-Type and Error-Values Defined
9. BGP Considerations
10. Deployment Considerations
11. Manageability Considerations
11.1. Control of Function and Policy
11.2. Information and Data Models
11.3. Liveness Detection and Monitoring
11.4. Verify Correct Operations
11.5. Requirements on Other Protocols
11.6. Impact on Network Operations
12. Security Considerations
13. IANA Considerations
13.1. PCEP Path Setup Types
13.2. PCECC-CAPABILITY Sub-TLV Flag Field
13.3. PCEP Objects
13.4. PCEP-Error Objects
13.5. CCI Object Flag Field
13.6. BPI Object Status Codes
13.7. BPI Object Error Codes
13.8. BPI Object Flag Field
14. References
14.1. Normative References
14.2. Informative References
Acknowledgements
Contributors
Authors' Addresses
1. Introduction
Generally, Multiprotocol Label Switching Traffic Engineering (MPLS-
TE) requires the corresponding network devices to support the
Resource ReSerVation Protocol (RSVP) [RFC3209] and the Label
Distribution Protocol (LDP) [RFC5036] to ensure End-to-End (E2E)
traffic performance. But in Native IP network scenarios described in
[RFC8735], there will be no such signaling protocol to synchronize
the actions among different network devices. It is feasible to use
the central control mode described in [RFC8283] to correlate the
forwarding behavior among different network devices. [RFC8821]
describes the architecture and solution philosophy for the E2E
traffic assurance in the Native IP network via a solution based on
multiple Border Gateway Protocol (BGP) sessions. It requires only
the PCE to send the instructions to the Path Computation Clients
(PCCs) to build multiple BGP sessions, distribute different prefixes
on the established BGP sessions, and assign the different paths to
the BGP next hops.
This document describes the corresponding Path Computation Element
Communication Protocol (PCEP) extensions to transfer the key
information about the BGP peer, peer prefix advertisement, and
explicit peer route on on-path routers.
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.
2.1. Use of RBNF
The message formats in this document are illustrated using Routing
Backus-Naur Form (RBNF) encoding, as specified in [RFC5511]. The use
of RBNF is illustrative only and may elide certain important details;
the normative specification of messages is found in the prose
description. If there is any divergence between the RBNF and the
prose, the prose is considered authoritative.
2.2. Experimental Status Consideration
The procedures outlined in this document are experimental. The
experiment aims to explore the use of PCE (and PCEP) for E2E traffic
assurance in Native IP networks through multiple BGP sessions.
Additional implementation is necessary to gain a deeper understanding
of the operational impact, scalability, and stability of the
mechanism described. Feedback from deployments will be crucial in
determining whether this specification should advance from
Experimental to the IETF Standards Track.
3. Terminology
This document uses the following terms defined in [RFC5440]: PCC,
PCE, and PCEP.
Additionally, the following terminology is used in this document:
BPI: BGP Peer Info
CCDR: Centralized Control Dynamic Routing
CCI: Central Controller Instructions (defined in [RFC9050])
E2E: End-to-End
EPR: Explicit Peer Route
Native IP network: Network that forwards traffic based solely on the
IP address, instead of another indicator, for example, MPLS, etc.
PCECC: PCE as a Central Controller (defined in [RFC8283])
PPA: Peer Prefix Advertisement
PST: Path Setup Type (defined in [RFC8408])
SRP: Stateful PCE Request Parameter (defined in [RFC8231])
RR: Route Reflector
4. Capability Advertisement
4.1. Open Message
During the PCEP Initialization Phase, PCEP speakers (PCE or PCC)
advertise their support of Native IP extensions.
This document defines a new Path Setup Type (PST) [RFC8408] for
Native IP, as follows:
* PST = 4: Path is a Native IP TE path as per [RFC8821].
A PCEP speaker MUST indicate its support of the function described in
this document by sending a PATH-SETUP-TYPE-CAPABILITY TLV in the OPEN
object with this new PST included in the PST list.
[RFC9050] defined the PCECC-CAPABILITY sub-TLV to exchange
information about their the PCEP speakers' PCECC capability. A new flag is
defined in the PCECC-CAPABILITY sub-TLV for Native IP:
N (NATIVE-IP-TE-CAPABILITY - 1 bit - 30): When set to 1 by a PCEP
speaker, this flag indicates that the PCEP speaker is capable of TE
in a Native IP network, as specified in this document. Both the PCC
and PCE MUST set this flag to support this extension.
If a PCEP speaker receives the PATH-SETUP-TYPE-CAPABILITY TLV with
the newly defined PST, but without the N bit set in PCECC-CAPABILITY
sub-TLV, it MUST:
* send a PCErr message with Error-Type=10 (Reception of an invalid
object) and Error-value=39 (PCECC NATIVE-IP-TE-CAPABILITY bit is
not set) and
* terminate the PCEP session.
If a PCEP speaker receives the PATH-SETUP-TYPE-CAPABILITY TLV with
the newly defined PST, but without the PCECC-CAPABILITY sub-TLV, it
MUST:
* send a PCErr message with Error-Type=10 (Reception of an invalid
object) and Error-value=33 (Missing PCECC Capability sub-TLV) and
* terminate the PCEP session.
If one or both speakers (PCE and PCC) have not indicated the support
for Native IP, the PCEP extensions for the Native IP MUST NOT be
used. If a Native IP operation is attempted when both speakers have
not agreed on the OPEN messages, the receiver of the message MUST:
* send a PCErr message with Error-Type=19 (Invalid Operation) and
Error-value=29 (Attempted Native IP operations when the capability
was not advertised) and
* terminate the PCEP session.
5. PCEP Messages
The PCECC Native IP TE solution uses the existing PCE Label Switched
Path (LSP) Initiate Request message (PCInitiate) [RFC8281] and PCE
Report message (PCRpt) [RFC8231] to establish multiple BGP sessions,
deploy the E2E Native IP TE path, and advertise route prefixes among
different BGP sessions. A new PST for Native IP is used to indicate
the path setup based on TE in Native IP networks.
The extended PCInitiate message described in [RFC9050] is used to
download or remove the Central Controller Instructions (CCI).
[RFC9050] specifies an object called CCI for the encoding of the
central controller's instructions. This document specifies a new CCI
Object-Type for Native IP. The PCEP messages are extended in this
document to handle the PCECC operations for Native IP. Three new
PCEP objects (BGP Peer Info (BPI), Explicit Peer Route (EPR), and
Peer Prefix Advertisement (PPA)) are defined in this document. Refer
to Section 7 for detailed object definitions. All PCEP procedures
specified in [RFC9050] continue to apply unless specified otherwise.
5.1. The PCInitiate Message
The PCInitiate message defined in [RFC8281] and extended in [RFC9050]
is further extended to support Native IP CCI.
The format of the extended PCInitiate message is as follows:
<PCInitiate Message> ::= <Common Header>
<PCE-initiated-lsp-list>
Where:
<Common Header> is defined in RFC 5440
<PCE-initiated-lsp-list> ::= <PCE-initiated-lsp-request>
[<PCE-initiated-lsp-list>]
<PCE-initiated-lsp-request> ::=
(<PCE-initiated-lsp-instantiation>|
<PCE-initiated-lsp-deletion>|
<PCE-initiated-lsp-central-control>)
<PCE-initiated-lsp-central-control> ::= <SRP>
<LSP>
<cci-list>
<cci-list> ::= <CCI>
[<BPI>|<EPR>|<PPA>]
[<cci-list>]
Where:
* <PCE-initiated-lsp-instantiation> and <PCE-initiated-lsp-deletion>
are as per [RFC8281].
* The LSP and SRP objects are defined in [RFC8231].
When the PCInitiate message is used for Native IP instructions, i.e.,
when the CCI Object-Type is 2, the SRP, LSP, and CCI objects MUST be
present. Error handling for missing SRP, LSP, or CCI objects MUST be
performed as specified in [RFC9050]. Additionally, exactly one
object among the BPI, EPR, or PPA objects MUST be present. The PCEP-
specific LSP identifier (PLSP-ID) and Symbolic Path Name TLVs are set
as per the existing rules in [RFC8231], [RFC8281], and [RFC9050].
The Symbolic Path Name is used by the PCE/PCC to uniquely identify
the E2E Native IP TE path. The related Native IP instructions with
BPI, EPR, or PPA objects are identified by the same Symbolic Path
Name.
If none of the BPI, EPR, or PPA objects are present, the receiving
PCC MUST send a PCErr message with Error-Type=6 (Mandatory Object
missing) and Error-value=19 (Native IP object missing). If there is
more than one BPI, EPR, or PPA object present, the receiving PCC MUST
send a PCErr message with Error-Type=19 (Invalid Operation) and
Error-value=22 (Only one BPI, EPR, or PPA object can be included in
this message).
When the PCInitiate message is not used for Native IP instructions,
i.e., when the CCI Object-Type is not equal to 2, the BPI, EPR, and
PPA objects SHOULD NOT be present. If present, they MUST be ignored
by the receiver.
To clean up the existing Native IP instructions, the SRP object MUST
set the R (remove) bit.
5.2. The PCRpt Message
The PCRpt message is used to acknowledge the Native IP instructions
received from the central controller (PCE) as well as during the
State Synchronization phase.
The format of the PCRpt message is as follows:
<PCRpt Message> ::= <Common Header>
<state-report-list>
Where:
<state-report-list> ::= <state-report>[<state-report-list>]
<state-report> ::= (<lsp-state-report>|
<central-control-report>)
<lsp-state-report> ::= [<SRP>]
<LSP>
<path>
<central-control-report> ::= [<SRP>]
<LSP>
<cci-list>
<cci-list> ::= <CCI>
[<BPI>|<EPR>|<PPA>]
[<cci-list>]
Where:
* <path> is as per [RFC8231].
* The LSP and SRP objects are also defined in [RFC8231].
The error handling for missing CCI objects is as per [RFC9050].
Furthermore, one and only one BPI, EPR, or PPA object MUST be
present.
If none of the BPI, EPR, or PPA objects are present, the receiving
PCE MUST send a PCErr message with Error-Type=6 (Mandatory Object
missing) and Error-value=19 (Native IP object missing). If there is
more than one BPI, EPR, or PPA object present, the receiving PCE MUST
send a PCErr message with Error-Type=19 (Invalid Operation) and
Error-value=22 (Only one BPI, EPR, or PPA object can be included in
this message).
When the PCInitiate message is not used for Native IP instructions,
i.e., when the CCI Object-Type is not equal to 2, the BPI, EPR, and
PPA objects SHOULD NOT be present. If present, they MUST be ignored
by the receiver.
6. PCECC Native IP TE Procedures
The detailed procedures for the TE in the Native IP environment are
described in the following sections.
6.1. BGP Session Establishment Procedures
The PCInitiate and PCRpt message pair is used to exchange the
configuration parameters for a BGP peer session. This pair of PCEP
messages are exchanged between a PCE and each BGP peer (acting as the
PCC), which needs to establish a BGP session. After the BGP peer
session has been initiated via this pair of PCEP messages, the BGP
session establishes and operates in a normal fashion. The BGP peers
can be used for External BGP (EBGP) peers or Internal BGP (IBGP)
peers. For IBGP connection topologies, the Route Reflector (RR) is
required.
The PCInitiate message is sent to the BGP router and/or RR (which are
acting as the PCC).
The RR topology for a single Autonomous System (AS) is shown in
Figure 1. The BGP routers R1, R3, and R7 are within a single AS. R1
and R7 are BGP RR clients, and R3 is an RR. The PCInitiate message
is sent to the BGP routers R1, R3, and R7, which need to establish a
BGP session.
PCInitiate message creates an autoconfiguration function for these
BGP peers by providing the indicated Peer AS and the Local/Peer IP
Address.
When the PCC receives the BPI and CCI objects (with the R bit set to
0 in the SRP object) in the PCInitiate message, the PCC SHOULD try to
establish the BGP session with the indicated Peer as per the AS and
Local/Peer IP Address.
During the establishment procedure, the PCC MUST report the status of
the BGP session to the PCE via the PCRpt message, with the status
field in the BPI object set to the appropriate value and the
corresponding SRP and CCI objects included.
When the PCC receives this message with the R bit set to 1 in the SRP
object in the PCInitiate message, the PCC MUST clear the BGP
configuration and tear down the BGP session that is indicated by the
BPI object.
When the PCC successfully clears the specified BGP session
configuration, it MUST report the result via the PCRpt message, with
the BPI object and the corresponding SRP and CCI objects included.
+------------------+
+-----------> PCE <----------+
| +--------^---------+ |
| | |
| PCInitiate/PCRpt |
| | |
| +----v--+ |
+---------------+ R3(RR)+-----------------+
| +-------+ |
PCInitiate/PCRpt PCInitiate/PCRpt
| |
+v-+ +--+ +--+ +-v+
|R1+----------+R5+----------+R6+---------+R7|
++-+ +-++ +--+ +-++
| | |
| +--+ +--+ |
+------------+R2+----------+R4+-----------+
+--+ +--+
Figure 1: BGP Session Establishment Procedures (R3 acts as the RR)
The message peers, message types, message key parameters, and
procedures in the above figure are shown below:
+-------+ +-------+
|PCC | | PCE |
|R1 | +-------+
+------| | |
| PCC +-------+ |
| R3 | | (For R1/R3 BGP Session on R1) |
+------| | |<-PCInitiate,CC-ID=X,Symbolic Path Name=Class A-|
| | | |BPI Object(Peer AS, Local_IP=R1_A, Peer_IP=R3_A)|
|PCC +--------+ | |
|R7 | | |----PCRpt,CC-ID=X(Symbolic Path Name=Class A)-->|
| | | |BPI Object(Peer AS, Local_IP=R1_A, Peer_IP=R3_A)|
+--------+ | |
| | (For R1/R3 BGP Session on R3) |
| |<--PCInitiate,CC-ID=Y1,Symbolic Path Name=Class A-----|
| | BPI Object(Peer AS, Local_IP=R3_A, Peer_IP=R1_A)|
| |---PCRpt,CC-ID=Y1,Symbolic Path Name=Class A--------->|
| | BPI Object(Peer AS, Local_IP=R3_A, Peer_IP=R1_A)|
| | |
| | (For R3/R7 BGP Session on R3) |
| |<--PCInitiate,CC-ID=Y2,Symbolic Path Name=Class A-----|
| | BPI Object(Peer AS, Local_IP=R3_A, Peer_IP=R7_A) |
| |----PCRpt,CC-ID=Y2,Symbolic Path Name=Class A-------->|
| | BPI Object(Peer AS, Local_IP=R3_A, Peer_IP=R7_A) |
| |
| (For R3/R7 BGP Session on R7) |
|<--PCInitiate,CC-ID=Z,Symbolic Path Name=Class A--------------|
| BPI Object(Peer AS, Local_IP=R7_A, Peer_IP=R3_A) |
|---PCRpt,CC-ID=Z,Symbolic Path Name=Class A------------------>|
| BPI Object(Peer AS, Local_IP=R7_A, Peer_IP=R3_A) |
Figure 2: Message Information and Procedures
The Local/Peer IP Address MUST be dedicated to the usage of the
Native IP TE solution and MUST NOT be used by other BGP sessions that
are established manually or in other ways. If the Local IP Address
or Peer IP Address within the BPI object is used in other existing
BGP sessions, the PCC MUST report such an error situation via a PCErr
message with:
* Error-Type=33 (Native IP TE failure) and Error-value=1 (Local IP
is in use) or
* Error-Type=33 (Native IP TE failure) and Error-value=2 (Remote IP
is in use).
The detailed Error-Types and Error-values are defined in Section 8.
If the established BGP session is broken, the PCC MUST report such
information via a PCRpt message with the status field set to "BGP
session down" in the associated BPI object. The error code field
within the BPI object SHOULD indicate the reason that leads to the
BGP session being down. In the future, when the BGP session is up
again, the PCC MUST report that as well via the PCRpt message with
the status field set to "BGP Session Established".
6.2. Explicit Route Establishment Procedures
The explicit route establishment procedures can be used by a PCE to
install a route on the PCC, using the PCInitiate and PCRpt message
pair. Such explicit routes operate the same as static routes
installed by network management protocols (e.g., Network
Configuration Protocol (NETCONF) / YANG). The procedures of such
explicit route addition and removal MUST be controlled by the PCE in
a specific order so that the pathways are established without loops.
For the purpose of explicit route addition, the PCInitiate message
ought to be sent to every router on the explicit path. In the
example, for the explicit route from R1 to R7, the PCInitiate message
is sent to R1, R2, and R4, as shown in Figure 3. For the explicit
route from R7 to R1, the PCInitiate message is sent to R7, R4, and
R2, as shown in Figure 5.
When the PCC receives the EPR and the CCI object (with the R bit set
to 0 in the SRP object) in the PCInitiate message, the PCC SHOULD
install the explicit route to the peer in the RIB/FIB.
When the PCC successfully installs the explicit route to the peer, it
MUST report the result via the PCRpt message, with the EPR object and
the corresponding SRP and CCI objects included.
When the PCC receives the EPR and the CCI object with the R bit set
to 1 in the SRP object in the PCInitiate message, the PCC MUST remove
the explicit route to the peer that is indicated by the EPR object.
When the PCC has removed the explicit route that is indicated by this
object, it MUST report the result via the PCRpt message, with the EPR
object and the corresponding SRP and CCI objects included.
+------------------+
+----------> PCE +
| +----^-----------^-+
| | |
| | |
| | +------+ |
+---------------|-+R3(RR)+--|-------------+
PCInitiate/PCRpt | +------+ | |
| | | |
+v-+ +--+ | | +--+ +--+
|R1+------+R5+---+-----------|---+R6+----+R7|
++-+ +--+ | | +--+ +-++
| PCInitiate/PCRpt PCInitiate/PCRpt |
| | | |
| +--v--+ +--v-+ |
+------------+- R2 +-----+ R4 +-----------+
+--+--+ +--+-+
Figure 3: Explicit Route Establish Procedures (from R1 to R7)
The message peers, message types, message key parameters, and
procedures in the above figure are shown below:
+-------+ +-------+
|PCC | | PCE |
|R4 | +-------+
+------| | |
| PCC +-------+ |
| R2 | | (EPR route on R4) |
+------| | |<-PCInitiate,CC-ID=Z,Symbolic Path Name=Class A|
| | | | EPR Object(Peer Address=R7_A, Next Hop=R7_A)|
|PCC +--------+ | |
|R1 | | |----PCRpt,CC-ID=Z,Symbolic Path Name=Class A-->|
| | | | EPR Object(Peer Address=R7_A, Next Hop=R7_A)|
+--------+ | |
| | (EPR route on R2) |
| |<--PCInitiate,CC-ID=Y,Symbolic Path Name=Class A-----|
| | EPR Object(Peer Address=R7_A, Next Hop=R4_A) |
| |----PCRpt,CC-ID=Y,Symbolic Path Name=Class A-------->|
| | EPR Object(Peer Address=R7_A, Next Hop=R4_A) |
| | |
| |
| (EPR route on R1) |
|<--PCInitiate,CC-ID=X,Symbolic Path Name=Class A-------------|
| EPR Object(Peer Address=R7_A, Next Hop=R2_A) |
|---PCRpt,CC-ID=X1(Symbolic Path Name=Class A)--------------->|
| EPR Object(Peer Address=R7_A, Next Hop=R2_A) |
Figure 4: Message Information and Procedures
+------------------+
+ PCE <-----------+
+----^-----------^-+ |
| | |
| | |
| +------+ | |
+-----------------+R3(RR)+--|-------------+
| | +------+ | PCInitiate/PCRpt
| | | |
+--+ +--+ | | +--+ +-v+
|R1+------+R5+---+-----------|---+R6+----+R7|
++-+ +--+ | | +--+ +-++
| PCInitiate/PCRpt PCInitiate/PCRpt |
| | | |
| +--v--+ +--v-+ |
+------------+- R2 +-----+ R4 +-----------+
+--+--+ +--+-+
Figure 5: Explicit Route Establish Procedures (from R7 to R1)
The message peers, message types, message key parameters, and
procedures in the above figure are shown below:
+-------+ +-------+
|PCC | | PCE |
|R2 | +-------+
+------| | |
| PCC +-------+ |
| R4 | | (EPR route on R2) |
+------| | |<-PCInitiate,CC-ID=X,Symbolic Path Name=Class A|
| | | | EPR Object(Peer Address=R1_A, Next Hop=R1_A) |
|PCC +--------+ | |
|R7 | | |----PCRpt,CC-ID=X,Symbolic Path Name=Class A-->|
| | | | EPR Object(Peer Address=R1_A, Next Hop=R1_A) |
+--------+ | |
| | (EPR route on R4) |
| |<--PCInitiate,CC-ID=Y,Symbolic Path Name=Class A-----|
| | EPR Object(Peer Address=R1_A, Next Hop=R2_A) |
| |----PCRpt,CC-ID=Y,Symbolic Path Name=Class A-------->|
| | EPR Object(Peer Address=R1_A, Next Hop=R2_A) |
| | |
| |
| (EPR route on R7) |
|<--PCInitiate,CC-ID=Z,Symbolic Path Name=Class A-------------|
| EPR Object(Peer Address=R1_A, Next Hop=R4_A) |
|---PCRpt,CC-ID=Z,Symbolic Path Name=Class A----------------->|
| EPR Object(Peer Address=R1_A, Next Hop=R4_A) |
Figure 6: Explicit Route Establish Procedures (from R7 to R1)
To avoid the transient loop while deploying the explicit peer route,
the EPR object MUST be sent to the PCCs in the reverse order of the
E2E path. To remove the explicit peer route, the EPR object MUST be
sent to the PCCs in the same order as the E2E path.
To accomplish ECMP effects, the PCE can send multiple EPR/CCI objects
to the same node, with the same route priority and peer address value
but a different next-hop address.
The PCC MUST verify that the next-hop address is reachable. In case
of failure, the PCC MUST send the corresponding error via a PCErr
message, with the error information: Error-Type=33 (Native IP TE
failure) and Error-value=3 (Explicit Peer Route Error).
When the peer info is not the same as the peer info that is indicated
in the BPI object in the PCC for the same path that is identified by
Symbolic Path Name TLV, a PCErr message MUST be reported, with the
error information Error-Type=33 (Native IP TE failure) and Error-
value=4 (EPR/BPI Peer Info mismatch). Note that the same error can
be used in case no BPI is received at the PCC.
If the PCE needs to update the path, it MUST first instruct the new
CCI with the updated EPR corresponding to the new next hop to use and
then instruct the removal of the older CCI.
6.3. BGP Prefix Advertisement Procedures
The detailed procedures for BGP prefix advertisement are shown below,
using the PCInitiate and PCRpt message pair.
The PCInitiate message SHOULD be sent to the PCC that acts as a BGP
peer edge router only. In the example, it is sent to R1 and R7,
respectively.
When the PCC receives the PPA and the CCI object (with the R bit set
to 0 in the SRP object) in the PCInitiate message, the PCC SHOULD
send the prefixes indicated in this object to the identified BGP peer
via the corresponding BGP session [RFC4271].
When the PCC has successfully sent the prefixes to the appointed BGP
peer, it MUST report the result via the PCRpt messages, with the PPA
object and the corresponding SRP and CCI objects included.
When the PCC receives the PPA and the CCI object with the R bit set
to 1 in the SRP object in the PCInitiate message, the PCC MUST
withdraw the prefix advertisement to the peer indicated by this
object.
When the PCC successfully withdraws the prefixes that are indicated
by this object, it MUST report the result via the PCRpt message, with
the PPA object and the corresponding SRP and CCI objects included.
+------------------+
+----------> PCE <-----------+
| +------------------+ |
| +--+ |
+------------------+R3+-------------------+
PCInitiate/PCRpt +--+ PCInitiate/PCRpt
| |
+v-+ +--+ +--+ +-v+
|R1+----------+R5+----------+R6+---------+R7|
++-+ +--+ +--+ +-++
(BGP Router) (BGP Router)
| |
| |
| +--+ +--+ |
+------------+R2+----------+R4+-----------+
+--+ +--+
Figure 7: BGP Prefix Advertisement Procedures
The message peers, message types, message key parameters, and
procedures in the above figure are shown below:
+-------+ +-------+
|PCC | | PCE |
|R1 | +-------+
+------| | |
| PCC +-------+ |
| R7 | | (Instruct R1 to advertise Prefix 1_A to R7) |
| | |<-PCInitiate,CC-ID=X,Symbolic Path Name=Class A|
| | | PPA Object(Peer IP=R7_A, Prefix=1_A) |
+--------+ | |
| |----PCRpt,CC-ID=X,Symbolic Path Name=Class A-->|
| | PPA Object(Peer IP=R7_A, Prefix=1_A) |
| |
| (Instruct R7 to advertise Prefix 7_A to R1 ) |
|<--PCInitiate,CC-ID=Z,Symbolic Path Name=Class A-----|
| PPA Object(Peer IP=R1_A, Prefix=7_A) |
|----PCRpt,CC-ID=Z,Symbolic Path Name=Class A-------->|
| PPA Object(Peer IP=R1_A, Prefix=7_A) |
| |
Figure 8: Message Information and Procedures
The AFI/SAFI for the corresponding BGP session SHOULD match the Peer
Prefix Advertisement Object-Type, i.e., AFI/SAFI SHOULD be 1/1 for
the IPv4 prefix and 2/1 for the IPv6 prefix. In case of mismatch, an
error, i.e., Error-Type=33 (Native IP TE failure) and Error-value=5
(BPI/PPA Address Family mismatch), MUST be reported via the PCErr
message.
When the peer info is not the same as the peer info that is indicated
in the BPI object in the PCC for the same path that is identified by
Symbolic Path Name TLV, an error, i.e., Error-Type=33 (Native IP TE
failure) and Error-value=6 (PPA/BPI Peer Info mismatch), MUST be
reported via the PCErr message. Note that the same error can be used
in case no BPI is received at the PCC.
6.4. Selection of the Raw Mode and Tunnel Mode Forwarding Strategy
Normally, when the above procedures are finished, the user traffic
will be forwarded via the appointed path, but the forwarding will be
based solely on the destination of user traffic. If traffic is
coming into the network from different attached points but to the
same destination, they could share the priority path, which may not
be the initial desire. For example, as illustrated in Figure 1, the
initial aim is to ensure that traffic enters the network via R1 and
exits the network at R7 via R5-R6-R7. If some traffic enters the
network via the R2 router, passes through R5, and exits at R7, they
may share the priority path among R5-R6-R7, which may not be the
desired effect.
The above normal traffic forwarding behavior is clarified as a Raw
mode forwarding strategy. Such a mode can only achieve the moderate
traffic path control effect. To achieve the strict traffic path
control effect, the entry point MUST tunnel the user traffic from the
entry point of the network to the exit point of the network, which is
also between the BGP peer established via Section 6.1. Such
forwarding behavior is called the Tunnel mode forwarding strategy.
For simplicity, the IP-in-IP tunnel type [RFC2003] is used between
the BGP peers by default.
The selection of Raw mode and Tunnel mode forwarding strategies are
controlled via the T bit in the BPI object, which is defined in
Section 7.2
6.5. Cleanup
To remove the Native IP state from the PCC, the PCE MUST send
explicit CCI cleanup instructions for PPA, EPR, and BPI objects,
respectively, with the R bit set in the SRP object. If the PCC
receives a PCInitiate message but does not recognize the Native IP
information in the CCI, the PCC MUST generate a PCErr message with
Error-Type=19 (Invalid Operation) and Error-value=30 (Unknown Native
IP Info) and MUST include the SRP object to specify the error is for
the corresponding cleanup (via a PCInitiate message).
6.6. Other Procedures
The handling of the State Synchronization, redundant PCEs,
redelegation, and cleanup is the same as other CCIs as specified in
[RFC9050].
7. New PCEP Objects
One new CCI Object-Type and three new PCEP objects are defined in
this document. All new PCEP objects are as per [RFC5440].
7.1. CCI Object
The Central Control Instructions (CCI) Object (defined in [RFC9050])
is used by the PCE to specify the forwarding instructions. This
document defines another Object-Type for Native IP procedures.
The CCI Object-Type is 2 for Native IP, as follows:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| CC-ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | Flags |
+---------------------------------------------------------------+
| |
// Optional TLVs //
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 9: CCI Object for Native IP
The CC-ID field is as described in [RFC9050]. The following fields
are defined for CCI Object-Type 2.
Reserved: 2 bytes. Set to zero while sending and ignored on
receipt.
Flags: 2 bytes. Used to carry any additional information about the
Native IP CCI. Currently, no flag bits are defined. Unassigned
flags are set to zero while sending and ignored on receipt.
Optional TLVs may be included within the CCI object body. The
Symbolic Path Name TLV [RFC8231] MUST be included in the CCI Object-
Type 2 to identify the E2E TE path in the Native IP environment.
7.2. BGP Peer Info Object
The BGP Peer Info (BPI) object is used to specify the information
about the peer with which the PCC wants to establish the BGP session.
This object is included and sent to the source and destination router
of the E2E path in case there is no Route Reflection (RR) involved.
If the RR is used between the source and destination routers, then
such information is sent to the source router, RR, and destination
router, respectively.
By default, the Local/Peer IP Address MUST be a unicast address and
dedicated to the usage of the Native IP TE solution and MUST NOT be
used by other BGP sessions that are established by manual or other
configuration mechanisms.
The BGP Peer Info Object-Class is 46.
The BGP Peer Info Object-Type is 1 for IPv4 and 2 for IPv6.
The format of the BGP Peer Info object body for IPv4 (Object-Type=1)
is as follows:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Peer AS Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ETTL | Status | Error Code | Flag |T|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Local IP Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Peer IP Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// Optional TLVs //
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 10: BGP Peer Info Object Body Format for IPv4
The format of the BGP Peer Info object body for IPv6 (Object-Type=2)
is as follows:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Peer AS Number |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| ETTL | Status | Error Code | Flag |T|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Local IP Address (16 bytes) |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Peer IP Address (16 bytes) |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// Optional TLVs //
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 11: BGP Peer Info Object Body Format for IPv6
Peer AS Number: 4 bytes. Indicates the AS number of the Remote
Peer. Note that if 2-byte AS numbers are in use, the low-order
bits (16 through 31) are used, and the high-order bits (0 through
15) are set to zero.
ETTL: 1 byte. EBGP Time To Live. Indicates the multi-hop count for
the EBGP session. It should be 0 and ignored when Local AS and
Peer AS are the same.
Status: 1 byte. Indicates the BGP session status between the peers.
Its values are defined below:
0: Reserved
1: BGP Session Established
2: BGP Session Establishment In Progress
3: BGP Session Down
4-255: Reserved
Error Code: 1 byte. Indicates the reason that the BGP session can't
be established.
0: Unspecific
1: ASes do not match, BGP Session Failure
2: Peer IP can't be reached, BGP Session Failure
3-255: Reserved
Flag: 1 byte.
Currently, only bit 7 (T bit) is defined. When the T bit is set,
the traffic SHOULD be sent in the IP-in-IP tunnel (the tunnel
source is the Local IP Address, and the tunnel destination is the
Peer IP Address). When the T bit is cleared, the traffic is sent
via its original source and destination address. The Tunnel mode
(i.e., the T bit is set) is used when the operator wants to ensure
only the traffic from the specified (entry, exit) pair, and the
Raw mode (i.e., the T bit is clear) is used when the operator
wants to ensure traffic from any entry to the specified
destination. Unassigned flags are set to zero while sending and
ignored on receipt.
Local IP Address(4/16 bytes): Unicast IP address of the local
router, used to peer with another end router. When the Object-
Type is 1, the length is 4 bytes; when the Object-Type is 2, the
length is 16 bytes.
Peer IP Address(4/16 bytes): Unicast IP address of the peer router,
used to peer with the local router. When the Object-Type is 1,
the length is 4 bytes; when the Object-Type is 2, the length is 16
bytes.
Optional TLVs: TLVs that are associated with this object; can be
used to convey other necessary information for dynamic BGP session
establishment. No TLVs are currently defined.
When the PCC receives a BPI object, with Object-Type=1, it SHOULD try
to establish a BGP session with the peer in AFI/SAFI=1/1.
When the PCC receives a BPI object, with Object-Type=2, it SHOULD try
to establish a BGP session with the peer in AFI/SAFI=2/1.
7.3. Explicit Peer Route Object
The Explicit Peer Route (EPR) object is defined to specify the
explicit peer route to the corresponding peer address on each device
that is on the E2E Native IP TE path. This Object ought to be sent
to all the devices on the path that are calculated by the PCE.
Although the object is named "Explicit Peer Route", it can be seen
that the routes it installs are simply host routes. The use of this
object to install host routes for any purpose other than reaching the
corresponding peer address on each device that is on the E2E Native
IP TE path is outside the scope of this specification.
By default, the path established by this object MUST have higher
priority than the other paths calculated by the dynamic IGP protocol
and MUST have lower priority than the static route configured by
manual, NETCONF, or any other static means.
The Explicit Peer Route Object-Class is 47.
The Explicit Peer Route Object-Type is 1 for IPv4 and 2 for IPv6.
The format of the Explicit Peer Route object body for IPv4 (Object-
Type=1) is as follows:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Route Priority | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Peer IPv4 Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Next Hop IPv4 Address to the Peer |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// Optional TLVs //
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 12: Explicit Peer Route Object Body Format for IPv4
The format of the Explicit Peer Route object body for IPv6 (Object-
Type=2) is as follows:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Route Priority | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Peer IPv6 Address |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Next Hop IPv6 Address to the Peer |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// Optional TLVs //
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 13: Explicit Peer Route Object Body Format for IPv6
Route Priority: 2 bytes. The priority of this explicit route. The
higher priority SHOULD be preferred by the device. This field is
used to indicate the preferred path at each hop.
Reserved: Set to zero while sending and ignored on receipt.
Peer (IPv4/IPv6) Address: Peer address for the BGP session (4/16
bytes).
Next Hop (IPv4/IPv6) Address to the Peer: Indicates the next-hop
address (4/16 bytes) to the corresponding peer address.
Optional TLVs: TLVs that are associated with this object; can be
used to convey other necessary information for explicit peer path
establishment. No TLVs are currently defined.
7.4. Peer Prefix Advertisement Object
The Peer Prefix Advertisement (PPA) object is defined to specify the
IP prefixes that are advertised to the corresponding peer. This
object only needs to be included and sent to the source/destination
router of the E2E path.
The prefix information included in this object MUST only be
advertised to the indicated peer and SHOULD NOT be advertised to
other BGP peers.
The Peer Prefix Advertisement Object-Class is 48.
The Peer Prefix Advertisement Object-Type is 1 for IPv4 and 2 for
IPv6.
The format of the Peer Prefix Advertisement object body for IPv4 is
as follows:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Peer IPv4 Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| No. of Prefix | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv4 Prefix #1 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Prefix #1 Len | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| : |
| : |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv4 Prefix #n |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Prefix #n Len | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// Optional TLVs //
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 14: Peer Prefix Advertisement Object Body Format for IPv4
The format of the Peer Prefix Advertisement object body for IPv6 is
as follows:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Peer IPv6 Address |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| No. of Prefix | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv6 Prefix #1 |
| |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Prefix #1 Len | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| : |
| : |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv6 Prefix #n |
| |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|Prefix #n Len | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// Optional TLVs //
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 15: Peer Prefix Advertisement Object Body Format for IPv6
Common Fields:
No. of Prefix: 1 byte. Identifies the number of prefixes that
are advertised to the peer in the PPA object.
Reserved: 3 bytes. Ought to be set to zero while sending and
ignored on receipt.
Prefix Len: 1 byte. Identifies the length of the prefix.
Optional TLVs: TLVs that are associated with this object; can be
used to convey other necessary information for prefix
advertisement. No TLVs are currently defined.
For IPv4:
Peer IPv4 Address: 4 bytes. Identifies the Peer IPv4 Address
that the associated prefixes will be sent to.
IPv4 Prefix: 4 bytes. Identifies the prefix that will be sent to
the peer identified by the Peer IPv4 Address.
For IPv6:
Peer IPv6 Address: 16 bytes. Identifies the Peer IPv6 Address
that the associated prefixes will be sent to.
IPv6 Prefix: Identifies the prefix that will be sent to the peer
identified by the Peer IPv6 Address.
If in the future a requirement is identified to advertise IPv4
prefixes towards an IPv6 peering address or IPv6 prefixes towards an
IPv4 peering address, then a new Peer Prefix Advertisement Object-
Type can be defined for these purposes.
8. New Error-Type and Error-Values Defined
A PCEP-ERROR object is used to report a PCEP error and is
characterized by an Error-Type that specifies that type of error and
an Error-value that provides additional information about the error.
An additional Error-Type and several Error-values are defined to
represent the errors related to the newly defined objects that are
related to Native IP TE procedures. See Table 4 for the newly
defined Error-Type and Error-values.
9. BGP Considerations
This document defines procedures and objects to create the BGP
sessions and to advertise the associated prefixes dynamically. Only
the key information, for example, Peer IP Addresses, and Peer AS
numbers are exchanged via the PCEP. Other parameters that are needed
for the BGP session setup SHOULD be derived from their default
values.
When the PCE sends out the PCInitiate message with the BPI object
embedded to establish the BGP session between the PCC peers, the PCC
SHOULD report the BGP session status. For instance, the PCC could
respond with "BGP Session Establishment In Progress" initially and,
on session establishment, send another PCRpt message with the state
updated to "BGP Session Established". If there is any error during
the BGP session establishment, the PCC SHOULD indicate the reason
with the appropriate status value set in the BPI object.
Upon receiving such key information, the BGP module on the PCC SHOULD
try to accomplish the task appointed by the PCEP and report the
successful status to the PCEP modules after the session is set up.
There is no influence on the current implementation of the BGP Finite
State Machine (FSM). PCEP focuses only on the success and failure
status of the BGP session and acts upon such information accordingly.
The error-handling procedures related to incorrect BGP parameters are
specified in Sections 6.1, 6.2, and 6.3.
10. Deployment Considerations
The information transferred in this document is mainly used for the
BGP session setup, explicit route deployment, and prefix
distribution. The planning, allocation, and distribution of the peer
addresses within IGP need to be accomplished in advance, and they are
out of the scope of this document.
The communication of PCE and PCC described in this document MUST
follow the State Synchronization procedures described in [RFC8232],
i.e., treat the three newly defined objects (BPI, EPR, and PPA)
associated with the same Symbolic Path Name as the attribute of the
same path in the LSP Database (LSP-DB).
When the PCE detects that one or some of the PCCs are out of its
control, it MUST recompute and redeploy the traffic engineering path
for Native IP on the currently active PCCs. The PCE MUST ensure the
avoidance of the possible transient loop in such node failure when it
deploys the explicit peer route on the PCCs.
In case of a PCE failure, a new PCE can gain control over the Central
Controller Instructions as described in [RFC9050].
As per the PCEP procedures in [RFC8281], the State Timeout Interval
timer is used to ensure that a PCE failure does not result in
automatic and immediate disruption for the services. Similarly, as
per [RFC9050], the Central Controller Instructions are not removed
immediately upon PCE failure. Instead, they could be redelegated to
the new PCE before the expiration of this timer or be cleaned up on
the expiration of this timer. This allows for network cleanup
without manual intervention. The PCC supports the removal of CCI as
one of the behaviors applied on the expiration of the State Timeout
Interval timer.
11. Manageability Considerations
11.1. Control of Function and Policy
A PCE or PCC implementation SHOULD allow the PCECC Native IP
capability to be enabled/disabled as part of the global
configuration.
11.2. Information and Data Models
[RFC7420] describes the PCEP MIB; this MIB could be extended to get
the PCECC Native IP capability status. The PCEP YANG module
[YANG-PCEP] could be extended to enable/disable the PCECC Native IP
capability.
11.3. Liveness Detection and Monitoring
Mechanisms defined in this document do not imply any new liveness
detection and monitoring requirements beyond those already listed in
[RFC5440]. The operator relies on existing IP liveness detection and
monitoring.
11.4. Verify Correct Operations
Verification of the mechanisms defined in this document can be built
on those already listed in [RFC5440], [RFC8231], and [RFC9050].
Further, the operator needs to be able to verify the status of BGP
sessions and prefix advertisements.
11.5. Requirements on Other Protocols
Mechanisms defined in this document require the interaction with BGP.
Section 9 describes in detail the considerations regarding the BGP.
During the BGP session establishment, the Local/Peer IP Address MUST
be dedicated to the usage of the Native IP TE solution and MUST NOT
be used by other BGP sessions that are established manually or in
other ways.
11.6. Impact on Network Operations
[RFC8821] describes the various deployment considerations in CCDR
architecture and their impact on network operations.
12. Security Considerations
In this setup, the BGP sessions, prefix advertisement, and explicit
peer route establishment are all controlled by the PCE. See
[RFC4271] for classical BGP implementation security considerations
and [RFC4272] for classical BGP vulnerabilities analysis. Security
considerations in [RFC5440] for the basic PCEP, [RFC8231] for PCEP
extension for stateful PCE, and [RFC8281] for PCE-initiated LSP setup
SHOULD be considered. To prevent a bogus PCE from sending harmful
messages to the network nodes, the network devices SHOULD
authenticate the PCE and ensure a secure communication channel
between them. Thus, the mechanisms described in [RFC8253] for the
usage of TLS for PCEP and [RFC9050] for protection against malicious
PCEs SHOULD be used.
If the default values discussed in Section 9 aren't enough and
securing the BGP transport is required (for example, by using TCP
Authentication Option (TCP-AO) [RFC5925]), a suitable value can be
provided through the addition of optional TLVs to the BGP Peer Info
object that conveys the necessary additional information (for
example, a key chain [RFC8177] name).
13. IANA Considerations
13.1. PCEP Path Setup Types
[RFC8408] created the "PCEP Path Setup Types" registry within the
"Path Computation Element Protocol (PCEP) Numbers" registry group.
IANA has allocated a new codepoint within this registry, as follows:
+=======+===================+===========+
| Value | Description | Reference |
+=======+===================+===========+
| 4 | Native IP TE Path | RFC 9757 |
+-------+-------------------+-----------+
Table 1: PCEP Path Setup Types Registry
13.2. PCECC-CAPABILITY Sub-TLV Flag Field
[RFC9050] created the "PCECC-CAPABILITY sub-TLV" registry within the
"Path Computation Element Protocol (PCEP) Numbers" registry group to
manage the value of the PCECC-CAPABILITY sub-TLV's 32-bit Flag field.
IANA has allocated a new bit position within this registry, as
follows:
+=====+===========+===========+
| Bit | Name | Reference |
+=====+===========+===========+
| 30 | Native IP | RFC 9757 |
+-----+-----------+-----------+
Table 2: PCECC-CAPABILITY
Sub-TLV Registry
13.3. PCEP Objects
IANA has allocated new codepoints in the "PCEP Objects" registry, as
follows:
+==============+===================+=============+===========+
| Object-Class | Name | Object-Type | Reference |
| Value | | | |
+==============+===================+=============+===========+
| 44 | CCI Object-Type | 2: Native | RFC 9757 |
| | | IP | |
+--------------+-------------------+-------------+-----------+
| 46 | BGP Peer Info | 0: Reserved | RFC 9757 |
| | Object-Type | | |
| | +-------------+-----------+
| | | 1: IPv4 | RFC 9757 |
| | | address | |
| | +-------------+-----------+
| | | 2: IPv6 | RFC 9757 |
| | | address | |
+--------------+-------------------+-------------+-----------+
| 47 | Explicit Peer | 0: Reserved | RFC 9757 |
| | Route Object-Type | | |
| | +-------------+-----------+
| | | 1: IPv4 | RFC 9757 |
| | | address | |
| | +-------------+-----------+
| | | 2: IPv6 | RFC 9757 |
| | | address | |
+--------------+-------------------+-------------+-----------+
| 48 | Peer Prefix | 0: Reserved | RFC 9757 |
| | Advertisement | | |
| | Object-Type | | |
| | +-------------+-----------+
| | | 1: IPv4 | RFC 9757 |
| | | address | |
| | +-------------+-----------+
| | | 2: IPv6 | RFC 9757 |
| | | address | |
+--------------+-------------------+-------------+-----------+
Table 3: PCEP Objects Registry
13.4. PCEP-Error Objects
IANA has allocated a new Error-Type and several Error-values in the
"PCEP-ERROR Object Error Types and Values" registry within the "Path
Computation Element Protocol (PCEP) Numbers" registry group, as
follows:
+============+=================+===============================+
+============+==============+==========================+===========+
| Error-Type | Meaning | Error-value |
+============+=================+===============================+ Reference |
+============+==============+==========================+===========+
| 6 | Mandatory | 19: Native IP object missing | RFC 9757 |
| | Object | missing | |
+------------+-----------------+-------------------------------+
| | missing | | |
+------------+--------------+--------------------------+-----------+
| 10 | Reception of an | 39: PCECC NATIVE-IP-TE- | RFC 9757 |
| | an invalid object | CAPABILITY bit is not | |
| | object | set |
+------------+-----------------+-------------------------------+ |
+------------+--------------+--------------------------+-----------+
| 19 | Invalid | 22: Only one BPI, EPR, or PPA | RFC 9757 |
| | Operation | or PPA object can be included in | |
| | | included in this message | |
| +-------------------------------+ | +--------------------------+-----------+
| | | 29: Attempted Native IP | RFC 9757 |
| | | operations when the | |
| | | capability was not | |
| | | advertised | |
| +-------------------------------+ | +--------------------------+-----------+
| | | 30: Unknown Native IP | RFC 9757 |
| | | Info |
+------------+-----------------+-------------------------------+ |
+------------+--------------+--------------------------+-----------+
| 33 | Native IP TE | 0: Unassigned | RFC 9757 |
| | failure | | |
| +-------------------------------+ | +--------------------------+-----------+
| | | 1: Local IP is in use | RFC9757 |
| | +-------------------------------+ +--------------------------+-----------+
| | | 2: Remote IP is in use | RFC 9757 |
| | +-------------------------------+ +--------------------------+-----------+
| | | 3: Explicit Peer Route | RFC 9757 |
| | | Error | |
| +-------------------------------+ | +--------------------------+-----------+
| | | 4: EPR/BPI Peer Info | RFC 9757 |
| | | mismatch | |
| +-------------------------------+ | +--------------------------+-----------+
| | | 5: BPI/PPA Address Family | RFC 9757 |
| | | Family mismatch | |
| +-------------------------------+ | +--------------------------+-----------+
| | | 6: PPA/BPI Peer Info | RFC 9757 |
| | | mismatch |
+------------+-----------------+-------------------------------+ |
+------------+--------------+--------------------------+-----------+
Table 4: PCEP-ERROR Object Error Types and Values Registry
The reference for each new Error-Type/Error-value should be set to
this document.
13.5. CCI Object Flag Field
IANA has created the "CCI Object Flag Field for Native IP" registry
to manage the 16-bit Flag field of the new CCI object. New values
are to be assigned by IETF Review [RFC8126]. Each bit should be
tracked with the following qualities:
* bit number (counting from bit 0 as the most significant bit and
bit 15 as the least significant bit)
* capability description
* defining RFC
Currently, no flags are assigned.
13.6. BPI Object Status Codes
IANA has created the "BPI Object Status Code Field" registry within
the "Path Computation Element Protocol (PCEP) Numbers" registry
group. New values are assigned by IETF Review [RFC8126]. Each value
should be tracked with the following qualities: value, meaning, and
defining RFC. The following values are defined in this document:
+=======+=======================================+===========+
| Value | Meaning | Reference |
+=======+=======================================+===========+
| 0 | Reserved | RFC 9757 |
+-------+---------------------------------------+-----------+
| 1 | BGP Session Established | RFC 9757 |
+-------+---------------------------------------+-----------+
| 2 | BGP Session Establishment In Progress | RFC 9757 |
+-------+---------------------------------------+-----------+
| 3 | BGP Session Down | RFC 9757 |
+-------+---------------------------------------+-----------+
| 4-255 | Unassigned | RFC 9757 |
+-------+---------------------------------------+-----------+
Table 5: BPI Object Status Code Field Registry
13.7. BPI Object Error Codes
IANA has created the "BPI Object Error Code Field" registry within
the "Path Computation Element Protocol (PCEP) Numbers" registry
group. New values are assigned by IETF Review [RFC8126]. Each value
should be tracked with the following qualities: value, meaning, and
defining RFC. The following values are defined in this document:
+=======+=========================================+===========+
| Value | Meaning | Reference |
+=======+=========================================+===========+
| 0 | Reserved | RFC 9757 |
+-------+-----------------------------------------+-----------+
| 1 | ASes do not match - BGP Session Failure | RFC 9757 |
+-------+-----------------------------------------+-----------+
| 2 | Peer IP can't be reached - BGP Session | RFC 9757 |
| | Failure | |
+-------+-----------------------------------------+-----------+
| 3-255 | Unassigned | RFC 9757 |
+-------+-----------------------------------------+-----------+
Table 6: BPI Object Error Code Field Registry
13.8. BPI Object Flag Field
IANA has created the "BPI Object Flag Field" registry within the
"Path Computation Element Protocol (PCEP) Numbers" registry group.
New values are to be assigned by IETF Review [RFC8126]. Each bit
should be tracked with the following qualities:
* bit number (counting from bit 0 as the most significant bit)
* capability description
* defining RFC
The following values are defined in this document:
+=====+==================+===========+
| Bit | Meaning | Reference |
+=====+==================+===========+
| 0-6 | Unassigned |
+-----+------------------+-----------+
| 7 | T (IP-in-IP) bit | RFC 9757 |
+-----+------------------+-----------+
Table 7: BPI Object Flag Field
Registry
14. References
14.1. Normative References
[RFC2003] Perkins, C., "IP Encapsulation within IP", RFC 2003,
DOI 10.17487/RFC2003, October 1996,
<https://www.rfc-editor.org/info/rfc2003>.
[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>.
[RFC4271] Rekhter, Y., Ed., Li, T., Ed., and S. Hares, Ed., "A
Border Gateway Protocol 4 (BGP-4)", RFC 4271,
DOI 10.17487/RFC4271, January 2006,
<https://www.rfc-editor.org/info/rfc4271>.
[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>.
[RFC5511] Farrel, A., "Routing Backus-Naur Form (RBNF): A Syntax
Used to Form Encoding Rules in Various Routing Protocol
Specifications", RFC 5511, DOI 10.17487/RFC5511, April
2009, <https://www.rfc-editor.org/info/rfc5511>.
[RFC5925] Touch, J., Mankin, A., and R. Bonica, "The TCP
Authentication Option", RFC 5925, DOI 10.17487/RFC5925,
June 2010, <https://www.rfc-editor.org/info/rfc5925>.
[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>.
[RFC8126] Cotton, M., Leiba, B., and T. Narten, "Guidelines for
Writing an IANA Considerations Section in RFCs", BCP 26,
RFC 8126, DOI 10.17487/RFC8126, June 2017,
<https://www.rfc-editor.org/info/rfc8126>.
[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>.
[RFC8232] Crabbe, E., Minei, I., Medved, J., Varga, R., Zhang, X.,
and D. Dhody, "Optimizations of Label Switched Path State
Synchronization Procedures for a Stateful PCE", RFC 8232,
DOI 10.17487/RFC8232, September 2017,
<https://www.rfc-editor.org/info/rfc8232>.
[RFC8253] Lopez, D., Gonzalez de Dios, O., Wu, Q., and D. Dhody,
"PCEPS: Usage of TLS to Provide a Secure Transport for the
Path Computation Element Communication Protocol (PCEP)",
RFC 8253, DOI 10.17487/RFC8253, October 2017,
<https://www.rfc-editor.org/info/rfc8253>.
[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>.
[RFC8408] Sivabalan, S., Tantsura, J., Minei, I., Varga, R., and J.
Hardwick, "Conveying Path Setup Type in PCE Communication
Protocol (PCEP) Messages", RFC 8408, DOI 10.17487/RFC8408,
July 2018, <https://www.rfc-editor.org/info/rfc8408>.
[RFC9050] Li, Z., Peng, S., Negi, M., Zhao, Q., and C. Zhou, "Path
Computation Element Communication Protocol (PCEP)
Procedures and Extensions for Using the PCE as a Central
Controller (PCECC) of LSPs", RFC 9050,
DOI 10.17487/RFC9050, July 2021,
<https://www.rfc-editor.org/info/rfc9050>.
14.2. 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>.
[RFC4272] Murphy, S., "BGP Security Vulnerabilities Analysis",
RFC 4272, DOI 10.17487/RFC4272, January 2006,
<https://www.rfc-editor.org/info/rfc4272>.
[RFC5036] Andersson, L., Ed., Minei, I., Ed., and B. Thomas, Ed.,
"LDP Specification", RFC 5036, DOI 10.17487/RFC5036,
October 2007, <https://www.rfc-editor.org/info/rfc5036>.
[RFC8177] Lindem, A., Ed., Qu, Y., Yeung, D., Chen, I., and J.
Zhang, "YANG Data Model for Key Chains", RFC 8177,
DOI 10.17487/RFC8177, June 2017,
<https://www.rfc-editor.org/info/rfc8177>.
[RFC8283] Farrel, A., Ed., Zhao, Q., Ed., Li, Z., and C. Zhou, "An
Architecture for Use of PCE and the PCE Communication
Protocol (PCEP) in a Network with Central Control",
RFC 8283, DOI 10.17487/RFC8283, December 2017,
<https://www.rfc-editor.org/info/rfc8283>.
[RFC8735] Wang, A., Huang, X., Kou, C., Li, Z., and P. Mi,
"Scenarios and Simulation Results of PCE in a Native IP
Network", RFC 8735, DOI 10.17487/RFC8735, February 2020,
<https://www.rfc-editor.org/info/rfc8735>.
[RFC8821] Wang, A., Khasanov, B., Zhao, Q., and H. Chen, "PCE-Based
Traffic Engineering (TE) in Native IP Networks", RFC 8821,
DOI 10.17487/RFC8821, April 2021,
<https://www.rfc-editor.org/info/rfc8821>.
[YANG-PCEP]
Dhody, D., Beeram, V. P., Hardwick, J., and J. Tantsura,
"A YANG Data Model for Path Computation Element
Communications Protocol (PCEP)", Work in Progress,
Internet-Draft, draft-ietf-pce-pcep-yang-30, 26 January
2025, <https://datatracker.ietf.org/doc/html/draft-ietf-
pce-pcep-yang-30>.
Acknowledgements
Thanks to Mike Koldychev, Susan Hares, Siva Sivabalan, and Adam
Simpson for their valuable suggestions and comments.
Contributors
Dhruv Dhody has contributed to this document.
Authors' Addresses
Aijun Wang
China Telecom
Beiqijia Town, Changping District
Beijing
102209
China
Email: wangaijun@tsinghua.org.cn
Boris Khasanov
MTS Web Services (MWS)
Andropova av., 18/9
Moscow
115432
Russian Federation
Email: bhassanov@yahoo.com
Sheng Fang
Huawei Technologies
Huawei Bld., No.156 Beiqing Rd.
Beijing
China
Email: fsheng@huawei.com
Ren Tan
Huawei Technologies
Huawei Bld., No.156 Beiqing Rd.
Beijing
China
Email: tanren@huawei.com
Chun Zhu
ZTE Corporation
50 Software Avenue, Yuhua District
Nanjing
Jiangsu, 210012
China
Email: zhu.chun1@zte.com.cn