PCEP Procedures and Protocol Extensions for
Using PCE as a Central Controller (PCECC) for Segment Routing (SR) MPLS Segment Identifier (SID) Allocation and Distribution.Huawei TechnologiesHuawei Bld., No.156 Beiqing Rd.Beijing 100095Chinalizhenbin@huawei.comHuawei TechnologiesHuawei Bld., No.156 Beiqing Rd.Beijing100095Chinapengshuping@huawei.comRtBrick IncN-17L, 18th Cross Rd, HSR LayoutBangaloreKarnataka560102Indiamahend.ietf@gmail.comEtheric Networks1009 S CLAREMONT STSAN MATEOCA94402USAqzhao@ethericnetworks.comHPEchaozhou_us@yahoo.com
Routing
PCE Working GroupThe Path Computation Element (PCE) is a core component of Software-Defined Networking (SDN) systems. It can compute optimal paths for
traffic across a network and can also update the paths to reflect
changes in the network or traffic demands.PCE was developed to derive paths for MPLS Label Switched Paths
(LSPs), which are supplied to the head end of the LSP using the Path
Computation Element Communication Protocol (PCEP). But SDN has a
broader applicability than signaled (G)MPLS traffic-engineered (TE)
networks, and the PCE may be used to determine paths in a range of
use cases. PCEP has been proposed as a control protocol for use in
these environments to allow the PCE to be fully enabled as a central
controller.A PCE-based Central Controller (PCECC) can simplify the processing of
a distributed control plane by blending it with elements of SDN and
without necessarily completely replacing it. Thus, the LSP can be
calculated/set up/initiated and the label forwarding entries can also
be downloaded through a centralized PCE server to each network
device along the path while leveraging the existing PCE technologies
as much as possible.This document specifies the procedures and PCEP extensions
when a PCE-based controller is also responsible for configuring the
forwarding actions on the routers, in addition to computing the paths
for packet flows in a segment routing (SR) network and telling the edge
routers what instructions to attach to packets as they enter the
network. PCECC is further enhanced for SR-MPLS SID (Segment Identifier) allocation and distribution.The Path Computation Element (PCE) was developed to offload
the path computation function from routers in an MPLS traffic-engineered
network. Since then, the role and function of the PCE has grown to
cover a number of other uses (such as GMPLS ) and to allow
delegated control and PCE-initiated use of network
resources .According to , Software-Defined Networking (SDN) refers to a
separation between the control elements and the forwarding components
so that software running in a centralized system, called a
controller, can act to program the devices in the network to behave
in specific ways. A required element in an SDN architecture is a
component that plans how the network resources will be used and how
the devices will be programmed. It is possible to view this
component as performing specific computations to place traffic flows
within the network given knowledge of the availability of network
resources, how other forwarding devices are programmed, and the way
that other flows are routed. This is the function and purpose of a
PCE, and the way that a PCE integrates into a wider network control
system (including an SDN system) is presented in .In early PCE implementations, where the PCE was used to derive paths
for MPLS Label Switched Paths (LSPs), paths were requested by network
elements (known as Path Computation Clients (PCCs)), and the results
of the path computations were supplied to network elements using the
Path Computation Element Communication Protocol (PCEP) .
This protocol was later extended to allow a PCE to send unsolicited
requests to the network for LSP establishment . introduces the architecture for PCE as a central
controller as an extension of the architecture described in
and assumes the continued use of PCEP as the protocol used between
PCE and PCC. further examines the motivations and applicability
for PCEP as a Southbound Interface (SBI), and introduces the implications for the
protocol. describes the use cases for
the PCE-based Central Controller (PCECC) architecture. As described in , PCECC simplifies the processing of a distributed IGP based control plane by blending it with elements of SDN, without replacing it. specify the procedures and PCEP extensions for
using the PCE as the central controller for static LSPs, where
LSPs can be provisioned as explicit label instructions at each
hop on the end-to-end path.Segment Routing (SR) technology leverages the source routing and tunneling paradigms.
A source node can choose a path without relying on hop-by-hop
signaling protocols such as LDP or RSVP-TE. Each path is specified
as a set of "segments" advertised by link-state routing protocols
(IS-IS or OSPF). provides an
introduction to SR architecture. The corresponding IS-IS and OSPF extensions are
specified in and
, respectively.
It relies on a series of
forwarding instructions being placed in the header of a packet.
The segment routing architecture supports operations that can be used
to steer packet flows in a network, thus providing a form of traffic
engineering. specify the SR specific PCEP
extensions.
PCECC may further use PCEP for SR SID (Segment Identifier) allocation and distribution to all the SR nodes
with some benefits. The SR nodes continue to rely on IGP for distributed computation (nexthop selection, protection etc) where PCE (and PCEP) does only the allocation and distribution of SIDs in the network. Note that the topology at PCE is still learned via existing mechanisms. This document specifies the procedures and PCEP extensions when
a PCE-based controller is also responsible for configuring
the forwarding actions on the routers (i.e. the SR SID allocation and distribution in this case), in addition to computing
the SR paths for packet flows in a segment routing network and telling the edge routers
what instructions to attach to packets as they enter the network as described in .
Only SR using MPLS dataplane (SR-MPLS) is in the scope of this document. Refer for use of PCECC technique for SR in IPv6 (SRv6) dataplane.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 when, and only when, they
appear in all capitals, as shown here.Terminologies used in this document is the same as described in the draft
and . specifies extensions to
PCEP that allow a stateful PCE to
compute, update, or initiate SR-TE paths. An ingress node of an SR-TE path appends
all outgoing packets with a list of MPLS labels (SIDs). This is encoded in
SR-ERO subobject, capable of carrying a label (SID) as well as the identity of the
node/adjacency label (SID).The notion of segment and SID is defined in
, which fits the MPLS architecture
as the label which
is managed by a local allocation process of LSR (similarly to
other MPLS signaling protocols) .
The SR information such as node/adjacency label (SID) is flooded via IGP as specified in and
. examines the motivations and applicability for
PCECC and use of PCEP as an SBI. Section 3.1.5. of
highlights the use of PCECC for configuring the forwarding actions on the routers and
assume responsibility for managing the label space. It simplifies the processing of a distributed
control plane by blending it with elements of SDN and without
necessarily completely replacing it. This allows the operator to introduce
the advantages of SDN (such as programmability) into the network. Further Section 3.3. of describes some of the scenarios where the PCECC technique could be useful. Section 4 of
also describe the implications on the protocol when used as an SDN SBI. The operator needs to evaluate the advantages offered by PCECC against the operational and scalability needs of the PCECC.
Thus, PCE as a central controller can allocate and provision the node/prefix/adjacency label (SID) via PCEP. The rest of the
processing is similar to existing stateful PCE with SR mechanism.For the purpose
of this document, it is assumed that the label/SID range to be used by a PCE
is set on both PCEP peers. The PCC MUST NOT make allocations from the label space set aside for the PCE to avoid overlap and collisions of label allocations. Further, a global label/SID range is assumed to be
set on all PCEP peers in the SR domain. A future extension could add the capability to
advertise this range via a possible PCEP extension as well (see ). This document also allows a case where the label/SID space is maintained by PCC itself, and the labels/SID are
allocated by the PCC, in this case, the PCE should request the allocation from
PCC as described in .Following key requirements for PCECC-SR should be considered when`
designing the PCECC-based solution:A PCEP speaker supporting this draft needs to have the capability to
advertise its PCECC-SR capability to its peers.PCEP procedures need to allow for PCC-based label/SID allocations.PCEP procedures need means to update (or clean up) the label-map entry to the PCC.PCEP procedures need to provide a mean to synchronize the SR labels/SIDs allocations between
the PCE to the PCC via PCEP messages.Active stateful PCE is described in . PCE
as a Central Controller (PCECC) reuses the existing active stateful PCE
mechanism as much as possible to control the LSPs.Several new functions are required in PCEP to support PCECC as described in . This document reuses the existing messages to support PCECC-SR.The PCEP messages PCRpt, PCInitiate, PCUpd are used to send
LSP Reports, LSP setup, and LSP update respectively. The extended PCInitiate message described in
is used to download
or clean up central controller's instructions (CCIs) (SR SID in the scope of this document). The extended PCRpt message described in
is also used to report
the CCIs (SR SIDs) from PCC to PCE. specify an object called CCI for the encoding of the central controller's instructions for Label. This document extends the CCI by defining a new object-type for SR-MPLS. The PCEP messages are extended in this document to handle the PCECC operations for SR.During PCEP Initialization Phase, PCEP Speakers (PCE or PCC)
advertise their support of PCECC extensions. A PCEP Speaker includes
the "PCECC Capability" sub-TLV, described in
.A new S-bit is added in the PCECC-CAPABILITY sub-TLV to indicate support for
PCECC-SR for MPLS dataplane. A PCC MUST set the S-bit in the PCECC-CAPABILITY sub-TLV and include
the SR-PCE-CAPABILITY sub-TLV () in the OPEN Object
(inside the PATH-SETUP-TYPE-CAPABILITY TLV)
to support the PCECC SR-MPLS extensions defined in this document. If
the S-bit is set in the PCECC-CAPABILITY sub-TLV and the SR-PCE-CAPABILITY sub-TLV is not
advertised in the OPEN Object, PCE SHOULD send a PCErr message with
Error-Type=19 (Invalid Operation) and Error-value=TBD4 (SR capability
was not advertised) and terminate the session.The rest of the processing is as per .A PCE may construct its Traffic Engineering Database (TED) by participating in the IGP (
and for MPLS-TE; and for GMPLS). An
alternative is offered by BGP-LS or
.A PCEP speaker could use any local IP address while creating a TCP
session. It is important to link the session IP address with the
Router ID in TED for successful PCECC operations.During PCEP Initialization Phase, the PCC SHOULD advertise the TE mapping
information by including the "Node Attributes TLV"
with "IPv4/IPv6 Router-ID of Local Node",
in the OPEN Object for this purpose.
describes the usage as auxiliary Router-IDs that the IGP might be
using, e.g., for TE purposes. If there are more than one auxiliary
Router-ID of a given type, then multiple TLVs are used to encode
them.If "IPv4/IPv6 Router-ID" TLV is not present, the TCP session IP
address is directly used for mapping purpose.[Editor's Note: "Node Attributes TLV" could be moved to this document if the progresses of is lagging. This needs to be handled before the WG LC.] specify the PCEP extension to allow a stateful PCE
to compute and initiate SR-TE paths, as well as a PCC to request a
path subject to certain constraint(s) and optimization criteria in SR
networks.The Path Setup Type for segment routing (PST=1) is used on the PCEP session with the Ingress as per
.Segment Routing (SR) as described in
depends on "segments" that are
advertised by Interior Gateway Protocols (IGPs). The SR-node
allocates and advertises the SID (node, adj, etc) and flood them via the
IGP. This document proposes a new mechanism where PCE allocates the
SID (label/index/SID) centrally and uses PCEP to distribute them to all nodes. In some
deployments, PCE (and PCEP) are better suited than IGP because of
the centralized nature of PCE and direct TCP based PCEP sessions to all the
nodes. Note that only the SID allocation and distribution is done by the PCEP, all other SR operations (nexthop selection, protection, etc) are still done by the node (and the IGPs).Each node (PCC) is allocated a node-SID by the PCECC. The
PCECC sends PCInitiate message to update the label map of each node to all
the nodes in the domain. The TE router ID is determined from the
TED or from "IPv4/IPv6 Router-ID" Sub-TLV
, in the OPEN Object .It is RECOMMENDED that PCEP session with PCECC-SR capability to use a
different session IP address during TCP session establishment than
the node Router ID in TEDB, to make sure that the PCEP session does
not get impacted by the SR Node/Prefix Label maps ().If a node (PCC) receives a PCInitiate message with a CCI object-type=TBD6 encoding a SID, out
of the range set aside for the SR Global Block (SRGB), it MUST send a PCErr message with Error-type=TBD
(PCECC failure) and Error-value=TBD (Label out of range) (defined in ) and MUST include the
SRP object to specify the error is for the corresponding central control instruction via the PCInitiate message.On receiving the label map, each node (PCC) uses the local
routing information via IGP to determine the next-hop and download the label
forwarding instructions accordingly as shown in . The PCInitiate message in this
case does not use the LSP object but uses a new FEC object defined in .The forwarding behavior and the end result is similar to IGP based
"Node-SID" in SR. Thus, from anywhere in the domain, it enforces the
ECMP-aware shortest-path forwarding of the packet towards the related
node as per .PCE relies on the Node/Prefix Label clean up using the same PCInitiate
message as per .The above example depicts the FEC and PCEP speakers that uses IPv4 address. Similarly an IPv6 address (such as 2001:db8::1) can be used during PCEP session establishment in the FEC object as described in this specification.In the case where the label/SID allocation is made by the PCC itself (see ), the PCE could request an allocation to be made by the PCC, and where the PCC would send a PCRpt with the allocated
label/SID encoded in the CC-ID object as shown in .It should be noted that in this example (), the request is made to the node 192.0.2.1 with C bit set in the CCI object to indicate that the allocation needs to be done by this PCC and it responds with the allocated label/SID to the PCE. The PCE would further inform the other nodes (PCCs) in the network about the label-map allocation without setting the C bit as before.All other distributed operations such as nexthop change, protection, etc is handled by the local node as before.For PCECC-SR, apart from node-SID, Adj-SID is used where each adjacency
is allocated an Adj-SID by the PCECC. The PCECC sends
the PCInitiate message to update the label map of each adjacency to all
the nodes in the domain as shown in . Each node (PCC) download the label forwarding
instructions accordingly. Similar to SR Node/Prefix Label allocation, the
PCInitiate message in this case does not use the LSP object but uses
the new FEC object defined in this document. The forwarding behavior and the end result is similar to IGP based
"Adj-SID" in SR. The Adj-SID is distributed to all nodes to enable SR-TE and TI-LFA.PCE relies on the Adj SID/label clean up using the same PCInitiate
message as per .The above example () depicts FEC object and PCEP speakers that uses an IPv4 address. Similarly an IPv6 address (such as 2001:db8::1, 2001:db8::2) can be used during the PCEP session establishment in the FEC object as described in this specification.The handling of adjacencies on the LAN subnetworks is specified in . PCECC MUST assign Adj-SID for every pair of routers in the LAN. The rest of the protocol mechanism remains the same.In the case where the label/SID map allocation is made by the PCC itself (see ), the PCE could request an allocation to be made by the PCC, and where the PCC would send a PCRpt with the allocated
label/SID encoded in the CC-ID object as shown in .In this example (), the request is made to the node 192.0.2.1 with the C bit set in the CCI object to indicate that the allocation needs to be done by this PCC for the adjacency (198.51.100.1 - 198.51.100.2) and it responds with the allocated label/SID to the PCE. The PCE further distribute this to other nodes without setting the C bit as before. describes the synchronization
mechanism between the stateful PCEs. The SR SIDs allocated by a PCE MUST also be
synchronized among PCEs for PCECC SR state synchronization. Note that the SR SIDs
are independent of the SR-TE LSPs, and remains intact till any topology
change. The redundant PCEs MUST have a common view of all SR SIDs allocated in the
domain.
describes the action
needed for CCIs for the static LSPs on a terminated
session. Same holds true for the CCI Object-Type=TBD6 for SR SID as well. describes the synchronization of Central Controller's Instructions (CCI) via LSP state synchronization
as described in and
.
Same procedures are applied for the CCI for SR SID as well.
The PCE can request the PCC to allocate the label/SID using the
PCInitiate message. The C flag in the
CCI object is set to 1 to indicate that the allocation needs to be done by the PCC.
The PCC would allocate the SID/Label/Index
and would report to the PCE using the PCRpt
message.
If the value of the SID/Label/Index is 0 and the C flag is set to 1, it
indicates that the PCE is requesting the allocation to be done by the PCC. If the
SID/Label/Index is 'n' and the C flag is set to 1 in the CCI object, it
indicates that the PCE requests a specific value 'n' for the SID/Label/Index.
If
the allocation is successful, the PCC should report
via PCRpt message with the CCI object. Else, it MUST send a PCErr message with Error-Type =
TBD ("PCECC failure") and Error Value = TBD ("Invalid CCI") (defined in ). If
the value of the SID/Label/Index in the CCI object is valid, but the PCC is unable to
allocate it, it MUST send a PCErr message with Error-Type =
TBD ("PCECC failure") and Error Value = TBD ("Unable to
allocate the specified CCI") (defined in ).
If the PCC wishes to withdraw or modify the previously assigned label/SID, it MUST send a PCRpt message without any SID/Label/Index
or with the SID/Label/Index containing the new value respectively in
the CCI object. The PCE would further trigger the removal of the
central controller instruction as per this document.A PCECC can allocate and
provision the node/prefix/adjacency label (SID) via PCEP. Another SID called binding SID is described in , the PCECC mechanism can also be used to allocate the binding SID.A procedure for binding label/SID allocation is described in and is applicable for all path setup types (including SR paths).As defined in , a PCEP message consists of a common header
followed by a variable-length body made of a set of objects that can
be either mandatory or optional. An object is said to be mandatory
in a PCEP message when the object must be included for the message to
be considered valid. For each PCEP message type, a set of rules is
defined that specify the set of objects that the message can carry.
An implementation MUST form the PCEP messages using the object
ordering specified in this document.Message formats in this section are presented
using Routing Backus-Naur Format (RBNF) as specified in .The PCInitiate message defined in and extended in
is further extended to support SR based central control instructions. The format of the extended PCInitiate message is as follows:
When the PCInitiate message is used to distribute SR SIDs, the SRP, the FEC and the CCI object of object-type=TBD6 MUST be present. The error handling for missing SRP or CCI object is as per . If the FEC object is missing, the receiving PCC MUST send a PCErr message with Error-type=6
(Mandatory Object missing) and Error-value=TBD5 (FEC object missing).To clean up, the R (remove) bit in the SRP object and the corresponding FEC and the CCI object are included.The PCRpt message can be used to report the SR central controller instructions received from the PCECC during the state synchronization phase or as an acknowledgment to the PCInitiate message.The format of the PCRpt message is as follows:
When PCRpt message is used to report the label map allocations, the FEC and CCI object of object-type=TBD6 MUST be present.
The error handling for the missing CCI object is as per . If the FEC object is
missing, the receiving PCE MUST send a PCErr message with Error-type=6
(Mandatory Object missing) and Error-value=TBD5 (FEC object missing). defined
the PCECC-CAPABILITY sub-TLV.A new S-bit is added in PCECC-CAPABILITY sub-TLV for PCECC-SR:[Editor's Note - The above figure is included for ease of the reader but should be removed before publication.]S (PCECC-SR-CAPABILITY - 1 bit - TBD1): If set to 1 by a PCEP speaker, it
indicates that the PCEP speaker is capable of PCECC-SR capability
and the PCE allocates the Node and Adj label/SID on this session.The PATH-SETUP-TYPE TLV is defined in .
A PST value of 1 is used
when Path is setup via SR mode as per . The procedure for SR-TE path setup as specified in remains unchanged.The Central Control Instructions (CCI) Object used by the PCE to specify the controller instructions is defined in .
This document defines another object-type for SR-MPLS purpose. CCI Object-Type is TBD6 for SR-MPLS as below -
The field CC-ID is as described in . Following new fields are defined for CCI Object-Type TBD6 -
Multi-Topology ID (as defined in ). Single octet identifying the algorithm the SID is associated with. See . is used to carry any additional information
pertaining to the CCI. The following bits are defined -
L-Bit (Local/Global): If set, then the value/index
carried by the CCI object has local significance. If not set,
then the value/index carried by this object has global
significance.V-Bit (Value/Index): If set, then the CCI carries
an absolute value. If not set, then the CCI carries an
index.E-Bit (Explicit-Null): If set, any upstream neighbor of the node
that advertised the SID MUST replace the SID with the
Explicit-NULL label (0 for IPv4) before forwarding the packet.N-Bit (No-PHP): If set, then the penultimate hop MUST
NOT pop the SID before delivering packets to the node
that advertised the SID.C-Bit (PCC Allocation): If the bit is set to 1, it indicates that
the SR SID/label allocation needs to be done by the PCC for this central
controller instruction. A PCE set this bit to request the PCC to
make an allocation from its SR label/ID space. A PCC would set
this bit to indicate that it has allocated the SR SID/label and report it
to the PCE.Following bits are applicable when the SID represents an Adj-SID only, it MUST be ignored for others -
G-Bit (Group): When set, the G-Flag indicates that
the Adj-SID refers to a group of adjacencies (and
therefore MAY be assigned to other adjacencies as well).P-Bit (Persistent): When set, the P-Flag indicates
that the Adj-SID is persistently allocated, i.e., the
Adj-SID value remains consistent across router restart
and/or interface flap.B-Bit (Backup): If set, the Adj-SID refers to an
adjacency that is eligible for protection (e.g., using IP
Fast Reroute or MPLS-FRR (MPLS-Fast Reroute) as described
in Section 2.1 of .All unassigned bits MUST be set to zero at transmission and ignored at receipt. According to the V and L flags, it contains
either:A 32-bit index defining the offset in the SID/Label space
advertised by this router.A 24-bit label where the 20 rightmost bits are used for
encoding the label value.The FEC Object is used to specify the FEC information and MAY be
carried within PCInitiate or PCRpt message.FEC Object-Class is TBD3.The FEC objects are as follows:IPv4 Node ID: where IPv4 Node ID is specified as an IPv4 address of
the Node. FEC Object-type is 1, and the Object-Length is 4 in
this case.IPv6 Node ID: where IPv6 Node ID is specified as an IPv6 address of
the Node. FEC Object-type is 2, and the Object-Length is 16 in
this case.IPv4 Adjacency: where Local and Remote IPv4 address is specified as
pair of IPv4 addresses of the adjacency. FEC Object-type is 3, and
the Object-Length is 8 in this case.IPv6 Adjacency: where Local and Remote IPv6 address is specified as
pair of IPv6 addresses of the adjacency. FEC Object-type is 4, and
the Object-Length is 32 in this case.Unnumbered Adjacency with IPv4 NodeID: where a pair of Node ID /
Interface ID tuple is used. FEC Object-type is 5, and the
Object-Length is 16 in this case.Linklocal IPv6 Adjacency: where a pair of (global IPv6
address, interface ID) tuple is used. FEC object-type is 6, and the
Object-Length is 40 in this case.[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
. 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 , "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".The PCE function was developed in the ONOS open source platform. This extension was implemented on a private version as a proof of concept for PCECC.
Organization: HuaweiImplementation: Huawei's PoC based on ONOSDescription: PCEP as a southbound plugin was added to ONOS. To support PCECC-SR, an earlier version of this I-D was implemented. Refer https://wiki.onosproject.org/display/ONOS/PCEP+ProtocolMaturity Level: PrototypeCoverage: PartialContact: satishk@huawei.comAs per , the security considerations for a PCE-based controller is a little
different from those for any other PCE system. That is, the
operation relies heavily on the use and security of PCEP, so
consideration should be given to the security features discussed in
and the additional mechanisms described in . It further lists the vulnerability of a central controller architecture, such as a central
point of failure, denial-of-service, and a focus for
interception and modification of messages sent to individual NEs.The PCECC extension builds on the existing PCEP messages and thus the security considerations described in , ,
, and continue to apply.As per , it is RECOMMENDED that these PCEP extensions
only be activated on mutually-authenticated and encrypted sessions across
PCEs and PCCs belonging to the same administrative authority,
using Transport Layer Security (TLS) as per the
recommendations and best current practices in (unless
explicitly set aside in ). A PCE or PCC implementation SHOULD allow to configure to
enable/disable PCECC SR capability as a global configuration. The implementation SHOULD also allow setting the local IP address used by the PCEP session. describes the PCEP MIB, this MIB can be extended to get the
PCECC SR capability status.The PCEP YANG module could be extended
to enable/disable PCECC SR capability.Mechanisms defined in this document do not imply any new liveness
detection and monitoring requirements in addition to those already
listed in .Mechanisms defined in this document do not imply any new operation
verification requirements in addition to those already listed in
, , and .PCEP extensions defined in this document do not put new requirements
on other protocols.PCEP extensions defined in this document allow SR SID Label allocation to be done from a central controller and thus simplifying the initial network operations. defines the
PCECC-CAPABILITY sub-TLV and requests that IANA to create a new sub-registry to
manage the value of the PCECC-CAPABILITY sub-TLV's Flag field. IANA
is requested to allocate a new bit in the PCECC-CAPABILITY sub-TLV Flag
Field sub-registry, as follows:BitDescriptionReferenceTBD1SR-MPLSThis documentIANA is requested to allocate new code-points for the new FEC object and a new Object-Type for CCI object in "PCEP Objects" sub-registry as follows:Object-Class ValueNameObject-TypeReferenceTBD3FEC1: IPv4 Node IDThis document2: IPv6 Node IDThis document3: IPv4 AdjacencyThis document4: IPv6 AdjacencyThis document5: Unnumbered Adjacency with IPv4 NodeIDThis document6: Linklocal IPv6 AdjacencyThis documentTBDCCITBD6: SR-MPLSThis documentIANA is requested to allocate a new error-value within
the "PCEP-ERROR Object Error Types and Values" sub-registry of the
PCEP Numbers registry for the following errors:
MeaningMandatory Object missing.
FEC object missingInvalid operation.
SR capability was not advertisedThe Reference is marked as "This document".IANA is requested to create a new sub-registry to manage the Flag field
of the CCI Object-Type=TBD6 for SR called "CCI Object Flag Field for SR". New
values are to be assigned by Standards Action . Each bit
should be tracked with the following qualities:Bit number (counting from bit 0 as the most significant bit)Capability descriptionDefining RFCFollowing bits are defined for the CCI Object flag field for SR in this document as follows:BitDescriptionReference0-7UnassignedThis document8B-Bit - BackupThis document9P-Bit - PersistentThis document10G-Bit - GroupThis document11C-Bit - PCC AllocationThis document12N-Bit - No-PHPThis document13E-Bit - Explicit-NullThis document14V-Bit - Value/IndexThis document15L-Bit - Local/GlobalThis documentWe would like to thank Robert Tao, Changjing Yan, Tieying Huang, Avantika, and Aijun Wang for
their useful comments and suggestions.Further thanks to Stephane Litkowski, Robert Sawaya, Zafar Ali, and Mike Koldychev for useful discussion and ideas to improve the document.