PCE Working Group S. Sivabalan
Internet-Draft Ciena Corporation
Intended status: Standards Track C. Filsfils
Expires: October 16, 2021 Cisco Systems, Inc.
J. Tantsura
Juniper Networks
S. Previdi
C. Li
Huawei Technologies
April 14, 2021
Carrying Binding Label/Segment Identifier in PCE-based Networks.
draft-ietf-pce-binding-label-sid-08
Abstract
In order to provide greater scalability, network opacity, and service
independence, Segment Routing (SR) utilizes a Binding Segment
Identifier (BSID). It is possible to associate a BSID to an RSVP-TE
signaled Traffic Engineering Label Switching Path or an SR Traffic
Engineering path. The BSID can be used by an upstream node for
steering traffic into the appropriate TE path to enforce SR policies.
This document specifies the binding value as an MPLS label or Segment
Identifier. It further specify an approach for reporting binding
label/SID by a Path Computation Client (PCC) to the Path Computation
Element (PCE) to support PCE-based Traffic Engineering policies.
Status of This Memo
This Internet-Draft is submitted in full conformance with the
provisions of BCP 78 and BCP 79.
Internet-Drafts are working documents of the Internet Engineering
Task Force (IETF). Note that other groups may also distribute
working documents as Internet-Drafts. The list of current Internet-
Drafts is at https://datatracker.ietf.org/drafts/current/.
Internet-Drafts are draft documents valid for a maximum of six months
and may be updated, replaced, or obsoleted by other documents at any
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material or to cite them other than as "work in progress."
This Internet-Draft will expire on October 16, 2021.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Requirements Language . . . . . . . . . . . . . . . . . . . . 5
3. Terminology . . . . . . . . . . . . . . . . . . . . . . . . . 5
4. Path Binding TLV . . . . . . . . . . . . . . . . . . . . . . 6
4.1. SRv6 Endpoint Behavior and SID Structure . . . . . . . . 7
5. Operation . . . . . . . . . . . . . . . . . . . . . . . . . . 8
6. Binding SID in SR-ERO . . . . . . . . . . . . . . . . . . . . 10
7. Binding SID in SRv6-ERO . . . . . . . . . . . . . . . . . . . 11
8. PCE Allocation of Binding label/SID . . . . . . . . . . . . . 11
9. Implementation Status . . . . . . . . . . . . . . . . . . . . 13
9.1. Huawei . . . . . . . . . . . . . . . . . . . . . . . . . 13
9.2. Cisco . . . . . . . . . . . . . . . . . . . . . . . . . . 13
10. Security Considerations . . . . . . . . . . . . . . . . . . . 14
11. Manageability Considerations . . . . . . . . . . . . . . . . 14
11.1. Control of Function and Policy . . . . . . . . . . . . . 14
11.2. Information and Data Models . . . . . . . . . . . . . . 14
11.3. Liveness Detection and Monitoring . . . . . . . . . . . 14
11.4. Verify Correct Operations . . . . . . . . . . . . . . . 15
11.5. Requirements On Other Protocols . . . . . . . . . . . . 15
11.6. Impact On Network Operations . . . . . . . . . . . . . . 15
12. IANA Considerations . . . . . . . . . . . . . . . . . . . . . 15
12.1. PCEP TLV Type Indicators . . . . . . . . . . . . . . . . 15
12.1.1. TE-PATH-BINDING TLV . . . . . . . . . . . . . . . . 15
12.2. LSP Object . . . . . . . . . . . . . . . . . . . . . . . 16
12.3. PCEP Error Type and Value . . . . . . . . . . . . . . . 16
13. Acknowledgements . . . . . . . . . . . . . . . . . . . . . . 17
14. References . . . . . . . . . . . . . . . . . . . . . . . . . 17
14.1. Normative References . . . . . . . . . . . . . . . . . . 17
14.2. Informative References . . . . . . . . . . . . . . . . . 19
Appendix A. Contributor Addresses . . . . . . . . . . . . . . . 20
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 20
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1. Introduction
A Path Computation Element (PCE) can compute Traffic Engineering
paths (TE paths) through a network where those paths are subject to
various constraints. Currently, TE paths are either set up using the
RSVP-TE signaling protocol or Segment Routing (SR). We refer to such
paths as RSVP-TE paths and SR-TE paths respectively in this document.
As per [RFC8402] SR allows a headend node to steer a packet flow
along any path. The headend node is said to steer a flow into an
Segment Routing Policy (SR Policy). Further, as per
[I-D.ietf-spring-segment-routing-policy], an SR Policy is a framework
that enables instantiation of an ordered list of segments on a node
for implementing a source routing policy with a specific intent for
traffic steering from that node.
As described in [RFC8402], a Binding Segment Identifier (BSID) is
bound to a Segment Routed (SR) Policy, instantiation of which may
involve a list of SIDs. Any packets received with an active segment
equal to a BSID are steered onto the bound SR Policy. A BSID may be
either a local (SR Local Block (SRLB)) or a global (SR Global Block
(SRGB)) SID. As per Section 6.4 of
[I-D.ietf-spring-segment-routing-policy] a BSID can also be
associated with any type of interfaces or tunnel to enable the use of
a non-SR interface or tunnel as a segment in a SID-list. In this
document, binding label/SID is used to generalize the allocation of
binding value for both SR and non-SR paths.
[RFC5440] describes the Path Computation Element Protocol (PCEP) for
communication between a Path Computation Client (PCC) and a PCE or
between a pair of PCEs as per [RFC4655]. [RFC8231] specifies
extensions to PCEP that allow a PCC to delegate its Label Switched
Paths (LSPs) to a stateful PCE. A stateful PCE can then update the
state of LSPs delegated to it. [RFC8281] specifies a mechanism
allowing a PCE to dynamically instantiate an LSP on a PCC by sending
the path and characteristics.
[RFC8664] provides a mechanism for a network controller (acting as a
PCE) to instantiate SR-TE paths (candidate paths) for an SR Policy
onto a head-end node (acting as a PCC) using PCEP. For more
information on the SR Policy Architecture, see
[I-D.ietf-spring-segment-routing-policy].
A binding label/SID has local significance to the ingress node of the
corresponding TE path. When a stateful PCE is deployed for setting
up TE paths, it may be desirable for PCC to report the binding label/
SID to the stateful PCE for the purpose of enforcing end-to-end TE/SR
policy. A sample Data Center (DC) use-case is illustrated in the
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Figure 1. In the MPLS DC network, an SR LSP (without traffic
engineering) is established using a prefix SID advertised by BGP (see
[RFC8669]). In the IP/MPLS WAN, an SR-TE LSP is set up using the
PCE. The list of SIDs of the SR-TE LSP is {A, B, C, D}. The gateway
node 1 (which is the PCC) allocates a binding SID X and reports it to
the PCE. In order for the access node to steer the traffic over the
SR-TE LSP, the PCE passes the SID stack {Y, X} where Y is the prefix
SID of the gateway node-1 to the access node. In the absence of the
binding SID X, the PCE should pass the SID stack {Y, A, B, C, D} to
the access node. This example also illustrates the additional
benefit of using the binding SID to reduce the number of SIDs imposed
on the access nodes with a limited forwarding capacity.
SID stack
{Y, X} +-----+
_ _ _ _ _ _ _ _ _ _ _ _ _ _| PCE |
| +-----+
| ^
| | Binding
| .-----. | SID (X) .-----.
| ( ) | ( )
V .--( )--. | .--( )--.
+------+ ( ) +-------+ ( ) +-------+
|Access|_( MPLS DC Network )_|Gateway|_( IP/MPLS WAN )_|Gateway|
| Node | ( ==============> ) |Node-1 | ( ================> ) |Node-2 |
+------+ ( SR path ) +-------+ ( SR-TE path ) +-------+
'--( )--' Prefix '--( )--'
( ) SID of ( )
'-----' Node-1 '-----'
is Y SIDs for SR-TE LSP:
{A, B, C, D}
Figure 1: A sample Use-case of Binding SID
A PCC could report the binding label/SID allocated by it to the
stateful PCE via Path Computation State Report (PCRpt) message. It
is also possible for a stateful PCE to request a PCC to allocate a
specific binding label/SID by sending a Path Computation Update
Request (PCUpd) message. If the PCC can successfully allocate the
specified binding value, it reports the binding value to the PCE.
Otherwise, the PCC sends an error message to the PCE indicating the
cause of the failure. A local policy or configuration at the PCC
SHOULD dictate if the binding label/SID needs to be assigned.
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In this document, we introduce a new OPTIONAL TLV that a PCC can use
in order to report the binding label/SID associated with a TE LSP, or
a PCE to request a PCC to allocate a specific binding label/SID
value. This TLV is intended for TE LSPs established using RSVP-TE,
SR, or any other future method. Also, in the case of SR-TE LSPs, the
TLV can carry a binding label (for SR-TE path with MPLS data-plane)
or a binding IPv6 SID (e.g., IPv6 address for SR-TE paths with IPv6
data-plane). Throughout this document, the term "binding value"
means either an MPLS label or SID.
Additionally, to support the PCE based central controller [RFC8283]
operation where the PCE would take responsibility for managing some
part of the MPLS label space for each of the routers that it
controls, the PCE could directly make the binding label/SID
allocation and inform the PCC. See Section 8 for details.
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. Terminology
The following terminologies are used in this document:
BSID: Binding Segment Identifier.
LSP: Label Switched Path.
PCC: Path Computation Client.
PCE: Path Computation Element
PCEP: Path Computation Element Protocol.
RSVP-TE: Resource ReserVation Protocol-Traffic Engineering.
SID: Segment Identifier.
SR: Segment Routing.
TLV: Type, Length, and Value.
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4. Path Binding TLV
The new optional TLV is called "TE-PATH-BINDING TLV" (whose format is
shown in the Figure 2) is defined to carry the binding label/SID for
a TE path. This TLV is associated with the LSP object specified in
[RFC8231]. This TLV can also be carried in the PCEP-ERROR object
[RFC5440] in case of error. Multiple instance of TE-PATH-BINDING
TLVs MAY be present in the LSP and PCEP-ERROR object. The type of
this TLV is 55 (early allocated by IANA). The length is variable.
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 | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| BT | Flags | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ Binding Value (variable length) ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: TE-PATH-BINDING TLV
TE-PATH-BINDING TLV is a generic TLV such that it is able to carry
binding label/SID (i.e. MPLS label or SRv6 SID). It is formatted
according to the rules specified in [RFC5440]. The value portion of
the TLV comprise of:
Binding Type (BT): A one-octet field identifies the type of binding
included in the TLV. This document specifies the following BT
values:
o BT = 0: The binding value is a 20-bit MPLS label value. The TLV
is padded to 4-bytes alignment. The Length MUST be set to 7 and
first 20 bits are used to encode the MPLS label value.
o BT = 1: The binding value is a 32-bit MPLS label stack entry as
per [RFC3032] with Label, TC [RFC5462], S, and TTL values encoded.
Note that the receiver MAY choose to override TC, S, and TTL
values according to its local policy. The Length MUST be set to
8.
o BT = 2: The binding value is an SRv6 SID with a format of a 16
octet IPv6 address, representing the binding SID for SRv6. The
Length MUST be set to 20.
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o BT = 3: The binding value is a 24 octet field, defined in
Section 4.1, that contains the SRv6 SID as well as its Behavior
and Structure. The Length MUST be set to 28.
Section 12.1.1 defines the IANA registry used to maintain all these
binding types as well as any future ones. Note that, multiple TE-
PATH-BINDING TLVs with different Binding Types MAY be present for the
same LSP.
Flags: 1 octet of flags. Following flag is defined in the new
registry "TE-PATH-BINDING TLV Flag field" as described in
Section 12.1.1:
0 1 2 3 4 5 6 7
+-+-+-+-+-+-+-+-+
|R| |
+-+-+-+-+-+-+-+-+
Figure 3: Flags
where:
o R (Removal - 1 bit): When set, the requesting PCEP peer requires
the removal of the binding value for the LSP. When unset, the
PCEP peer indicates that the binding value is added or retained
for the LSP. This flag is used in the PCRpt and PCUpd messages.
It is ignored in other PCEP messages.
o The unassigned flags MUST be set to 0 while sending and ignored on
receipt.
Reserved: MUST be set to 0 while sending and ignored on receipt.
Binding Value: A variable-length field, padded with trailing zeros to
a 4-octet boundary. For the BT as 0, the 20 bits represent the MPLS
label. For the BT as 1, the 32-bits represent the MPLS label stack
entry as per [RFC3032]. For the BT as 2, the 128-bits represent the
SRv6 SID. For the BT as 3, the Binding Value also contains the SRv6
Endpoint Behavior and SID Structure, defined in Section 4.1.
4.1. SRv6 Endpoint Behavior and SID Structure
This section specify the format of the Binding Value in the TE-PATH-
BINDING TLV when the BT is set to 3 for the SRv6 Binding SIDs
[RFC8986], as shown in Figure 4.
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SRv6 Binding SID (16 octets) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Reserved | Endpoint Behavior |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| LB Length | LN Length | Fun. Length | Arg. Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 4: SRv6 Endpoint Behavior and SID Structure
The Binding Value consist of:
o SRv6 Binding SID: 16 octets. The 128-bits IPv6 address,
representing the binding SID for SRv6.
o Reserved: 2 octets. It MUST be set to 0 on transmit and ignored
on receipt.
o Endpoint Behavior: 2 octets. The Endpoint Behavior code point for
this SRv6 SID as per the IANA subregistry called "SRv6 Endpoint
Behaviors", created by [RFC8986]. When the field is set with the
value 0, the endpoint behavior is considered unknown.
o The following fields are used to advertise the length of each
individual part of the SRv6 SID as defined in [RFC8986]:
* LB Length: 1 octet. SRv6 SID Locator Block length in bits.
* LN Length: 1 octet. SRv6 SID Locator Node length in bits.
* Function Length: 1 octet. SRv6 SID Function length in bits.
* Argument Length: 1 octet. SRv6 SID Arguments length in bits.
5. Operation
The binding value is allocated by the PCC and reported to a PCE via
PCRpt message. If a PCE does not recognize the TE-PATH-BINDING TLV,
it would ignore the TLV in accordance with [RFC5440]. If a PCE
recognizes the TLV but does not support the TLV, it MUST send PCErr
with Error-Type = 2 (Capability not supported).
Multiple TE-PATH-BINDING TLVs are allowed to be present in the same
LSP object. This signifies the presence of multiple binding SIDs for
the given LSP. In the case of multiple TE-PATH-BINDING TLVs,
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existing instances of TE-PATH-BINDING TLVs MAY be included in the LSP
object. In case of an error condition, the whole message is rejected
and the resulting PCErr message MAY include the offending TE-PATH-
BINDING TLV in the PCEP-ERROR object.
If a PCE recognizes an invalid binding value (e.g., label value from
the reserved MPLS label space), it MUST send a PCErr message with
Error-Type = 10 ("Reception of an invalid object") and Error Value =
2 ("Bad label value") as specified in [RFC8664].
For SRv6 BSIDs, it is RECOMMENDED to always explicitly specify the
SRv6 Endpoint Behavior and SID Structure in the TE-PATH-BINDING TLV
by setting the BT (Binding Type) to 3. This enables the sender to
have control of the SRv6 Endpoint Behavior and SID Structure. A
sender MAY choose to set the BT to 2, in which case the receiving
implementation chooses how to interpret the SRv6 Endpoint Behavior
and SID Structure according to local policy.
If a PCC wishes to withdraw a previously reported binding value, it
MUST send a PCRpt message with the specific TE-PATH-BINDING TLV with
R flag set to 1. If a PCC wishes to modify a previously reported
binding, it MUST withdraw the old binding value (with R flag set in
the old TE-PATH-BINDING TLV) and include a new TE-PATH-BINDING TLV
containing the new binding value. Note that, other instances of TE-
PATH-BINDING TLVs that are unchanged MAY also be included.
If a PCE requires a PCC to allocate a specific binding value(s), it
may do so by sending a PCUpd or PCInitiate message containing a TE-
PATH-BINDING TLV(s). If the value(s) can be successfully allocated,
the PCC reports the binding value(s) to the PCE. If the PCC
considers the binding value specified by the PCE invalid, it MUST
send a PCErr message with Error-Type = TBD2 ("Binding label/SID
failure") and Error Value = TBD3 ("Invalid SID"). If the binding
value is valid, but the PCC is unable to allocate the binding value,
it MUST send a PCErr message with Error-Type = TBD2 ("Binding label/
SID failure") and Error Value = TBD4 ("Unable to allocate the
specified binding value"). Note that in case of an error, the PCC
rejects the PCUpd or PCInitiate message in its entirety and can carry
the offending TE-PATH-BINDING TLV in the PCEP-ERROR object.
If a PCE wishes to request withdrawal of a previously reported
binding value, it MUST send a PCUpd message with the specific TE-
PATH-BINDING TLV with R flag set to 1. If a PCE wishes to modify a
previously requested binding value, it MUST request withdrawal of the
old binding value (with R flag set in the old TE-PATH-BINDING TLV)
and include a new TE-PATH-BINDING TLV containing the new binding
value.
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In some cases, a stateful PCE can request the PCC to allocate any
binding value. It instructs the PCC by sending a PCUpd message
containing an empty TE-PATH-BINDING TLV, i.e., no binding value is
specified (making the length field of the TLV as 4). A PCE can also
request PCC to allocate a binding value at the time of initiation by
sending a PCInitiate message with an empty TE-PATH-BINDING TLV. Only
one such instance of empty TE-PATH-BINDING TLV SHOULD be included in
the LSP object and others ignored on receipt. If the PCC is unable
to allocate a new binding value as per the specified BT, it MUST send
a PCErr message with Error-Type = TBD2 ("Binding label/SID failure")
and Error-Value = TBD5 ("Unable to allocate a new binding label/
SID").
As previously noted, if a message contains an invalid TE-PATH-BINDING
TLV that leads to an error condition, the whole message is rejected
including any other valid instances of TE-PATH-BINDING TLVs, if any.
The resulting error message MAY include the offending TE-PATH-BINDING
TLV in the PCEP-ERROR object.
If a PCC receives a TE-PATH-BINDING TLV in any message other than
PCUpd or PCInitiate, it MUST close the corresponding PCEP session
with the reason "Reception of a malformed PCEP message" (according to
[RFC5440]). Similarly, if a PCE receives a TE-PATH-BINDING TLV in
any message other than a PCRpt or if the TE-PATH-BINDING TLV is
associated with any object other than an LSP or PCEP-ERROR object,
the PCE MUST close the corresponding PCEP session with the reason
"Reception of a malformed PCEP message" (according to [RFC5440]).
If a TE-PATH-BINDING TLV is absent in the PCRpt message and no
binding values were reported before, the PCE MUST assume that the
corresponding LSP does not have any binding. Similarly, if TE-PATH-
BINDING TLV is absent in the PCUpd message and no binding values were
reported before, the PCC's local policy dictates how the binding
allocations are made for a given LSP.
6. Binding SID in SR-ERO
In PCEP messages, LSP route information is carried in the Explicit
Route Object (ERO), which consists of a sequence of subobjects.
[RFC8664] defines a new ERO subobject "SR-ERO subobject" capable of
carrying a SID as well as the identity of the node/adjacency (NAI)
represented by the SID. The NAI Type (NT) field indicates the type
and format of the NAI contained in the SR-ERO. In case of binding
SID, the NAI MUST NOT be included and NT MUST be set to zero. So as
per Section 5.2.1 of [RFC8664], for NT=0, the F bit is set to 1, the
S bit needs to be zero and the Length is 8. Further, the M bit is
set. If these conditions are not met, the entire ERO MUST be
considered invalid and a PCErr message is sent by the PCC with Error-
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Type = 10 ("Reception of an invalid object") and Error-Value = 11
("Malformed object").
7. Binding SID in SRv6-ERO
[I-D.ietf-pce-segment-routing-ipv6] defines a new ERO subobject
"SRv6-ERO subobject" for an SRv6 SID. As stated in Section 6, in
case of binding SID, the NAI is not included and NT is set to zero
i.e., NT=0, the F bit is set to 1, the S bit needs to be zero and the
Length is 24 [I-D.ietf-pce-segment-routing-ipv6]. As per [RFC8664],
if these conditions are not met, the entire ERO is considered invalid
and a PCErr message is sent by the PCC with Error-Type = 10
("Reception of an invalid object") and Error-Value = 11 ("Malformed
object").
8. PCE Allocation of Binding label/SID
Section 5 already includes the scenario where a PCE requires a PCC to
allocate a specified binding value by sending a PCUpd or PCInitiate
message containing a TE-PATH-BINDING TLV. This section specifies an
OPTIONAL feature for the PCE to allocate the binding label/SID on its
own accord in the case where the PCE also controls the label space of
the PCC and can make the label allocation on its own as described in
[RFC8283]. Note that the act of requesting a specific binding value
(Section 5) is different from the act of allocating a binding label/
SID as described in this section.
[RFC8283] introduces the architecture for PCE as a central controller
as an extension of the architecture described in [RFC4655] and
assumes the continued use of PCEP as the protocol used between PCE
and PCC. [I-D.ietf-pce-pcep-extension-for-pce-controller] specifies
the procedures and PCEP extensions for using the PCE as the central
controller.
For an implementation that supports PCECC operations as per
[I-D.ietf-pce-pcep-extension-for-pce-controller], the binding label/
SID MAY also be allocated by the PCE itself. Both peers need to
exchange the PCECC capability as described in
[I-D.ietf-pce-pcep-extension-for-pce-controller] before the PCE can
allocate the binding label/SID on its own.
A new P flag in the LSP object [RFC8231] is introduced to indicate
the allocation needs to be made by the PCE:
o P (PCE-allocated binding label/SID): If the bit is set to 1, it
indicates that the PCC requests PCE to make allocations for this
LSP. The TE-PATH-BINDING TLV in the LSP object identifies that
the allocation is for binding label/SID. A PCC would set this bit
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to 1 and include a TE-PATH-BINDING TLV in the LSP object to
request for allocation of binding label/SID by the PCE in the PCEP
message. A PCE would also set this bit to 1 and include a TE-
PATH-BINDING TLV to indicate that the binding label/SID is
allocated by PCE and encoded in the PCEP message towards PCC.
Further, a PCE would set this bit to 0 and include a TE-PATH-
BINDING TLV in the LSP object to indicate that the binding label/
SID should be allocated by the PCC as described in Section 5.
Note that -
o A PCE could allocate the binding label/SID on its own accord for a
PCE-initiated or delegated LSP, and inform the PCC in the
PCInitiate message or PCUpd message by setting P=1 and including
TE-PATH-BINDING TLV in the LSP object.
o To let the PCC allocates the binding label/SID, a PCE could set
P=0 and include an empty TE-PATH-BINDING TLV ( i.e., no binding
value is specified) in the LSP object in PCInitiate/PCUpd message.
o A PCC could request that the PCE allocate the binding label/SID by
setting P=1, D=1, and including an empty TE-PATH-BINDING TLV in
PCRpt message. The PCE would allocate it and respond to the PCC
with PCUpd message including the allocated binding label/SID in
the TE-PATH-BINDING TLV and P=1, D=1 in the LSP object.
o If both peers have not exchanged the PCECC capabilities as per
[I-D.ietf-pce-pcep-extension-for-pce-controller] and a PCEP peer
receives P=1 in the LSP object, it needs to act as per
[I-D.ietf-pce-pcep-extension-for-pce-controller]:
* Send a PCErr message with Error-Type=19 (Invalid Operation) and
Error-Value=16 (Attempted PCECC operations when PCECC
capability was not advertised)
* Terminate the PCEP session
It is assumed that the label range to be used by a PCE is known and
set on both PCEP peers. The exact mechanism is out of scope of
[I-D.ietf-pce-pcep-extension-for-pce-controller] or this document.
Note that the specific BSID could be from the PCE-controlled or the
PCC-controlled label space. The PCE can directly allocate the label
from the PCE-controlled label space using P=1 as described above,
whereas the PCE can request for the allocation of a specific BSID
from the PCC-controlled label space with P=0 as described in
Section 5.
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9. Implementation Status
[Note to the RFC Editor - remove this section before publication, as
well as remove the reference to RFC 7942.]
This section records the status of known implementations of the
protocol defined by this specification at the time of posting of this
Internet-Draft, and is based on a proposal described in [RFC7942].
The description of implementations in this section is intended to
assist the IETF in its decision processes in progressing drafts to
RFCs. Please note that the listing of any individual implementation
here does not imply endorsement by the IETF. Furthermore, no effort
has been spent to verify the information presented here that was
supplied by IETF contributors. This is not intended as, and must not
be construed to be, a catalog of available implementations or their
features. Readers are advised to note that other implementations may
exist.
According to [RFC7942], "this will allow reviewers and working groups
to assign due consideration to documents that have the benefit of
running code, which may serve as evidence of valuable experimentation
and feedback that have made the implemented protocols more mature.
It is up to the individual working groups to use this information as
they see fit".
9.1. Huawei
o Organization: Huawei
o Implementation: Huawei's Router and Controller
o Description: An experimental code-point is used and plan to
request early code-point allocation from IANA after WG adoption.
o Maturity Level: Production
o Coverage: Full
o Contact: chengli13@huawei.com
9.2. Cisco
o Organization: Cisco Systems
o Implementation: Head-end and controller.
o Description: An experimental code-point is currently used.
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o Maturity Level: Production
o Coverage: Full
o Contact: mkoldych@cisco.com
10. Security Considerations
The security considerations described in [RFC5440], [RFC8231],
[RFC8281] and [RFC8664] are applicable to this specification. No
additional security measure is required.
As described [RFC8664], SR allows a network controller to instantiate
and control paths in the network. A rogue PCE can manipulate binding
SID allocations to move traffic around for some other LSP that uses
BSID in its SR-ERO.
Thus, as per [RFC8231], it is RECOMMENDED that these PCEP extensions
only be activated on authenticated and encrypted sessions across PCEs
and PCCs belonging to the same administrative authority, using
Transport Layer Security (TLS) [RFC8253], as per the recommendations
and best current practices in BCP195 [RFC7525] (unless explicitly set
aside in [RFC8253]).
11. Manageability Considerations
All manageability requirements and considerations listed in
[RFC5440], [RFC8231], and [RFC8664] apply to PCEP protocol extensions
defined in this document. In addition, requirements and
considerations listed in this section apply.
11.1. Control of Function and Policy
A PCC implementation SHOULD allow the operator to configure the
policy based on which PCC needs to allocates the binding label/SID.
11.2. Information and Data Models
The PCEP YANG module [I-D.ietf-pce-pcep-yang] could be extended to
include policy configuration for binding label/SID allocation.
11.3. Liveness Detection and Monitoring
Mechanisms defined in this document do not imply any new liveness
detection and monitoring requirements in addition to those already
listed in [RFC5440].
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11.4. Verify Correct Operations
Mechanisms defined in this document do not imply any new operation
verification requirements in addition to those already listed in
[RFC5440], [RFC8231], and [RFC8664].
11.5. Requirements On Other Protocols
Mechanisms defined in this document do not imply any new requirements
on other protocols.
11.6. Impact On Network Operations
Mechanisms defined in [RFC5440], [RFC8231], and [RFC8664] also apply
to PCEP extensions defined in this document. Further, the mechanism
described in this document can help the operator to request control
of the LSPs at a particular PCE.
12. IANA Considerations
IANA maintains the "Path Computation Element Protocol (PCEP) Numbers"
registry. This document requests IANA actions to allocate code
points for the protocol elements defined in this document.
12.1. PCEP TLV Type Indicators
This document defines a new PCEP TLV; IANA is requested to confirm
the following early allocations from the "PCEP TLV Type Indicators"
subregistry of the PCEP Numbers registry, as follows:
Value Description Reference
55 TE-PATH-BINDING This document
12.1.1. TE-PATH-BINDING TLV
IANA is requested to create a new subregistry "TE-PATH-BINDING TLV BT
field" to manage the value of the Binding Type field in the TE-PATH-
BINDING TLV. Initial values for the subregistry are given below.
New values are assigned by Standards Action [RFC8126].
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Value Description Reference
0 MPLS Label This document
1 MPLS Label Stack This document
Entry
2 SRv6 SID This document
3 SRv6 SID with This document
Behavior and
Structure
4-255 Unassigned This document
IANA is requested to create a new subregistry "TE-PATH-BINDING TLV
Flag field" to manage the Flag field in the TE-PATH-BINDING TLV. New
values are to be assigned by Standards Action [RFC8126]. Each bit
should be tracked with the following qualities:
o Bit number (count from 0 as the most significant bit)
o Description
o Reference
Bit Description Reference
0 R (Removal) This document
1-7 Unassigned This document
12.2. LSP Object
IANA is requested to confirm the early allocation for a new code-
point in the "LSP Object Flag Field" sub-registry for the new P flag
as follows:
Bit Description Reference
0 PCE-allocated binding This document
label/SID
12.3. PCEP Error Type and Value
This document defines a new Error-type and Error-Values for the PCErr
message. IANA is requested to allocate new error-type and error-
values within the "PCEP-ERROR Object Error Types and Values"
subregistry of the PCEP Numbers registry, as follows:
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Error-Type Meaning Error-value Reference
TBD2 Binding label/SID This
failure document
TBD3: Invalid SID This
document
TBD4: Unable to allocate the This
specified binding value document
TBD5: Unable to allocate a This
new binding label/SID document
13. Acknowledgements
We like to thank Milos Fabian, Mrinmoy Das, Andrew Stone, Tom Petch,
Aijun Wang, Olivier Dugeon, and Adrian Farrel for their valuable
comments.
14. References
14.1. Normative References
[RFC2119] Bradner, S., "Key words for use in RFCs to Indicate
Requirement Levels", BCP 14, RFC 2119,
DOI 10.17487/RFC2119, March 1997,
<https://www.rfc-editor.org/info/rfc2119>.
[RFC3032] Rosen, E., Tappan, D., Fedorkow, G., Rekhter, Y.,
Farinacci, D., Li, T., and A. Conta, "MPLS Label Stack
Encoding", RFC 3032, DOI 10.17487/RFC3032, January 2001,
<https://www.rfc-editor.org/info/rfc3032>.
[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>.
[RFC5462] Andersson, L. and R. Asati, "Multiprotocol Label Switching
(MPLS) Label Stack Entry: "EXP" Field Renamed to "Traffic
Class" Field", RFC 5462, DOI 10.17487/RFC5462, February
2009, <https://www.rfc-editor.org/info/rfc5462>.
[RFC7525] Sheffer, Y., Holz, R., and P. Saint-Andre,
"Recommendations for Secure Use of Transport Layer
Security (TLS) and Datagram Transport Layer Security
(DTLS)", BCP 195, RFC 7525, DOI 10.17487/RFC7525, May
2015, <https://www.rfc-editor.org/info/rfc7525>.
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[RFC7942] Sheffer, Y. and A. Farrel, "Improving Awareness of Running
Code: The Implementation Status Section", BCP 205,
RFC 7942, DOI 10.17487/RFC7942, July 2016,
<https://www.rfc-editor.org/info/rfc7942>.
[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>.
[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>.
[RFC8402] Filsfils, C., Ed., Previdi, S., Ed., Ginsberg, L.,
Decraene, B., Litkowski, S., and R. Shakir, "Segment
Routing Architecture", RFC 8402, DOI 10.17487/RFC8402,
July 2018, <https://www.rfc-editor.org/info/rfc8402>.
[RFC8664] Sivabalan, S., Filsfils, C., Tantsura, J., Henderickx, W.,
and J. Hardwick, "Path Computation Element Communication
Protocol (PCEP) Extensions for Segment Routing", RFC 8664,
DOI 10.17487/RFC8664, December 2019,
<https://www.rfc-editor.org/info/rfc8664>.
[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>.
[RFC8986] Filsfils, C., Ed., Camarillo, P., Ed., Leddy, J., Voyer,
D., Matsushima, S., and Z. Li, "Segment Routing over IPv6
(SRv6) Network Programming", RFC 8986,
DOI 10.17487/RFC8986, February 2021,
<https://www.rfc-editor.org/info/rfc8986>.
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[I-D.ietf-pce-pcep-extension-for-pce-controller]
Li, Z., Peng, S., Negi, M., Zhao, Q., and C. Zhou, "PCEP
Procedures and Protocol Extensions for Using PCE as a
Central Controller (PCECC) of LSPs", draft-ietf-pce-pcep-
extension-for-pce-controller-10 (work in progress),
January 2021.
14.2. Informative References
[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>.
[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>.
[RFC8669] Previdi, S., Filsfils, C., Lindem, A., Ed., Sreekantiah,
A., and H. Gredler, "Segment Routing Prefix Segment
Identifier Extensions for BGP", RFC 8669,
DOI 10.17487/RFC8669, December 2019,
<https://www.rfc-editor.org/info/rfc8669>.
[I-D.ietf-spring-segment-routing-policy]
Filsfils, C., Talaulikar, K., Voyer, D., Bogdanov, A., and
P. Mattes, "Segment Routing Policy Architecture", draft-
ietf-spring-segment-routing-policy-09 (work in progress),
November 2020.
[I-D.ietf-pce-pcep-yang]
Dhody, D., Hardwick, J., Beeram, V., and J. Tantsura, "A
YANG Data Model for Path Computation Element
Communications Protocol (PCEP)", draft-ietf-pce-pcep-
yang-15 (work in progress), October 2020.
[I-D.ietf-pce-segment-routing-ipv6]
Li, C., Negi, M., Sivabalan, S., Koldychev, M.,
Kaladharan, P., and Y. Zhu, "PCEP Extensions for Segment
Routing leveraging the IPv6 data plane", draft-ietf-pce-
segment-routing-ipv6-08 (work in progress), November 2020.
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Appendix A. Contributor Addresses
Jonathan Hardwick
Metaswitch Networks
33 Genotin Road
Enfield
United Kingdom
EMail: Jonathan.Hardwick@metaswitch.com
Dhruv Dhody
Huawei Technologies
Divyashree Techno Park, Whitefield
Bangalore, Karnataka 560066
India
EMail: dhruv.ietf@gmail.com
Mahendra Singh Negi
RtBrick India
N-17L, Floor-1, 18th Cross Rd, HSR Layout Sector-3
Bangalore, Karnataka 560102
India
EMail: mahend.ietf@gmail.com
Mike Koldychev
Cisco Systems, Inc.
2000 Innovation Drive
Kanata, Ontario K2K 3E8
Canada
Email: mkoldych@cisco.com
Zafar Ali
Cisco Systems, Inc.
Email: zali@cisco.com
Authors' Addresses
Siva Sivabalan
Ciena Corporation
EMail: msiva282@gmail.com
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Clarence Filsfils
Cisco Systems, Inc.
Pegasus Parc
De kleetlaan 6a, DIEGEM BRABANT 1831
BELGIUM
EMail: cfilsfil@cisco.com
Jeff Tantsura
Juniper Networks
EMail: jefftant.ietf@gmail.com
Stefano Previdi
Huawei Technologies
EMail: stefano@previdi.net
Cheng Li
Huawei Technologies
Huawei Campus, No. 156 Beiqing Rd.
Beijing 100095
China
EMail: c.l@huawei.com
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