Internet DRAFT - draft-hsd-pce-sr-p2mp-policy
draft-hsd-pce-sr-p2mp-policy
Network Working Group H. Bidgoli, Ed.
Internet-Draft Nokia
Intended status: Standards Track V. Voyer
Expires: November 26, 2021 Bell Canada
S. Rajarathinam
Nokia
E. Hemmati
Cisco System
T. Saad
Juniper Networks
S. Sivabalan
Ciena
May 25, 2021
PCEP extensions for p2mp sr policy
draft-hsd-pce-sr-p2mp-policy-03
Abstract
SR P2MP policies are set of policies that enable architecture for
P2MP service delivery. This document specifies extensions to the
Path Computation Element Communication Protocol (PCEP) that allow a
stateful PCE to compute and initiate P2MP paths from a Root to a set
of Leaves.
Status of This Memo
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Copyright Notice
Copyright (c) 2021 IETF Trust and the persons identified as the
document authors. All rights reserved.
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Table of Contents
1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . 3
2. Conventions used in this document . . . . . . . . . . . . . . 4
3. Overview of PCEP Operation in SR P2MP Network . . . . . . . . 4
3.1. High level view of P2MP Policy Objects . . . . . . . . . 5
3.1.1. Shared Tree vs Non-Shared Replication Segment . . . . 6
3.2. Existing drafts used for defining a P2MP Policy . . . . . 7
3.2.1. Existing Documents used by this draft . . . . . . . . 7
3.2.2. P2MP Policy Identification . . . . . . . . . . . . . 8
3.2.3. Replication Segment Identification . . . . . . . . . 9
3.2.4. PCECC Use in Replication Segment . . . . . . . . . . 9
3.3. High Level Procedures for P2MP SR LSP Instantiation . . . 9
3.3.1. PCE-Init Procedure . . . . . . . . . . . . . . . . . 9
3.3.2. PCC-Init Procedure . . . . . . . . . . . . . . . . . 10
3.3.3. Common Procedure . . . . . . . . . . . . . . . . . . 10
3.3.4. Global Optimization of the Candidate Path . . . . . . 11
3.3.5. Fast Reroute . . . . . . . . . . . . . . . . . . . . 12
3.3.6. Connecting Replication Segment via Segment List . . . 13
3.4. SR P2MP Policy and Replication Segment TLVs and Objects . 13
3.4.1. SR P2MP Policy Objects . . . . . . . . . . . . . . . 13
3.4.2. Replication Segment Objects . . . . . . . . . . . . . 14
3.4.3. P2MP Policy and Replication Segment general
considerations . . . . . . . . . . . . . . . . . . . 14
4. Object Format . . . . . . . . . . . . . . . . . . . . . . . . 15
4.1. Open Message and Capability Exchange . . . . . . . . . . 15
4.1.1. PCECC Path Setup Capability . . . . . . . . . . . . . 15
4.1.2. Association Type Capability . . . . . . . . . . . . . 16
4.2. Symbolic Name in PCInit Message from PCC . . . . . . . . 16
4.3. P2MP Policy Specific Objects and TLVs . . . . . . . . . . 16
4.3.1. P2MP Policy Association Group for P2MP Policy . . . . 16
4.3.1.1. P2MP SR Policy Association Group Policy
Identifiers TLV . . . . . . . . . . . . . . . . . 16
4.3.1.2. P2MP SR Policy Association Group Candidate Path
Identifiers TLV . . . . . . . . . . . . . . . . . 17
4.3.1.3. P2MP SR Policy Association Group Candidate Path
Attributes TLV . . . . . . . . . . . . . . . . . 18
4.3.2. P2MP-END-POINTS Object . . . . . . . . . . . . . . . 18
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4.4. P2MP Policy and Replication Segment Identifier Object and
TLV . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
4.4.1. Extension of the LSP Object, SR-P2MP-LSPID-TLV . . . 21
4.5. Replication Segment . . . . . . . . . . . . . . . . . . . 22
4.5.1. The format of the replication segment message . . . . 23
4.5.2. PCECC . . . . . . . . . . . . . . . . . . . . . . . . 23
4.5.3. Label action rules in replicating segment . . . . . . 26
4.5.4. SR-ERO Rules . . . . . . . . . . . . . . . . . . . . 27
4.5.4.1. SR-ERO subobject changes . . . . . . . . . . . . 27
5. Tree Deletion . . . . . . . . . . . . . . . . . . . . . . . . 28
6. Fragmentation . . . . . . . . . . . . . . . . . . . . . . . . 28
7. Example Workflows . . . . . . . . . . . . . . . . . . . . . . 28
8. IANA Consideration . . . . . . . . . . . . . . . . . . . . . 33
9. Security Considerations . . . . . . . . . . . . . . . . . . . 34
10. Acknowledgments . . . . . . . . . . . . . . . . . . . . . . . 34
11. References . . . . . . . . . . . . . . . . . . . . . . . . . 34
11.1. Normative References . . . . . . . . . . . . . . . . . . 34
11.2. Informative References . . . . . . . . . . . . . . . . . 34
Authors' Addresses . . . . . . . . . . . . . . . . . . . . . . . 35
1. Introduction
The draft [draft-ietf-pim-sr-p2mp-policy] defines a variant of the SR
Policy [draft-ietf-spring-segment-routing-policy] for constructing a
P2MP segment to support multicast service delivery.
A Point-to-Multipoint (P2MP) Policy connects a Root node to a set of
Leaf nodes, optionally through a set of intermediate replication
nodes. A Replication segment
[draft-ietf-spring-sr-replication-segment], which corresponds to the
state of a P2MP segment on a particular node which provide forwarding
instructions for the segment.
A P2MP Policy is relevant on the root of the P2MP Tree and it
contains candidate paths. The candidate paths are made of path-
instances and each path-instance is constructed via replication
segments. These replication segments are programmed on the root,
leaves and optionally intermediate replication nodes.
A replication segments MAY be connected directly, or they MAY be
connected or steered via unicast SR segment or a segment list.
For a P2MP Tree, a controller may be used to compute paths from a
Root node to a set of Leaf nodes, optionally via a set of replication
nodes. A packet is replicated at the root node and optionally on
Replication nodes towards each Leaf node.
There are two types of a P2MP Tree: Spray and Replication.
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A Point-to-Multipoint service delivery could be via Ingress
Replication, known as Spray. The root unicasts individual copies of
traffic to each leaf. The corresponding P2MP Policy consists of
replication segments only for the root and the leaves and they are
connected via a unicast SR Segment.
A Point-to-Multipoint service delivery could also be via Downstream
Replication, known as Replication. The root and some downstream
replication nodes replicate the traffic along the way as it traverses
closer to the leaves.
The leaves and the root can be explicitly configured on the PCE or
PCC can update the PCE with the information of the discovered root
and leaves. As an example Multicast protocols like MVPN procedures
[RFC6513] or PIM can be used to discovery the leaves and roots on the
PCC and update the PCE with these relevant information. The
controller can calculate the P2MP Policy and any of its associated
replication segments with these info.
This document defines PCEP objects, TLVs and the procedures to
instantiate a P2MP Policy and Replication Segments.
2. Conventions used in this document
The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT",
"SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this
document are to be interpreted as described in RFC 2119 [RFC2119].
3. Overview of PCEP Operation in SR P2MP Network
After discovering the root and the leaves on the PCE (via different
mechanism mentioned in previous sections), the PCE computes the P2MP
Tree and identifying the relevant Replication routers, then it
programs the PCCs with relevant information needed to create a P2MP
Tree.
As per draft [draft-ietf-pim-sr-p2mp-policy] a P2MP Policy is defined
by Root-ID, Tree-ID and a set of leaves. A P2MP policy is a variant
of SR policy as such it uses the same concept as draft
[draft-ietf-pce-segment-routing-policy-cp]. A P2MP policy is
composed of a collection of SR P2mp Candidate Paths. Candidate paths
are computed by the PCE and can be used for P2MP Tree redundancy.
Only a single candidate path may be active at each time. Each
candidate paths can be globally optimized, therefore it is consists
of multiple path-instances. A path-instance can be considered to a
P2MP LSP. If a candidate path needs to be globally optimized two
path-instances can be programmed on the root node and via make before
break procedures the candidate path can be switched from path-
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instance 1 to the 2nd path-instance. The forwarding states of these
path-instances are build via replication segments, in short each
path-instance initiated on the root has its own set of replication
segments on the Root, Transit and Leaf nodes.
A replication segment is set of forwarding instructions on a specific
node. Each instruction may be a PUSH or SWAP operation before
forwarding out of an interface, or a POP action on bud and leaf
nodes.
PCE could also calculate and download additional information for the
replication segments, such as protections next-hops for link
protection (FRR).
3.1. High level view of P2MP Policy Objects
o SR P2MP Policy
* Is only relevant on the Root of the P2MP path and is a policy
on PCE. It is downloaded only on the rootnode and is
identified via <Root-ID, Tree-ID> It contains the following
information:
+ Root node of the P2MP Segment
+ Leaf nodes of the P2MP Segment
+ Tree-ID, which is a unique identifier of the P2MP tree on
the Root
+ A set of Candidate paths belonging to the policy
+ Optional Constraints used to build these candidate paths
o Candidate Path:
* Is used for P2MP Tree redundancy where the candidate path with
the highest preference is the active path.
* It can contain two path-instance for global optimization
procedures (i.e. make before break)
* Contains information regarding protocol-id, originator,
discriminator, preference, path-instances
o Replication Segment:
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* Is the forwarding information needed on each node for building
the forwarding path for each path-instance of the P2MP
Candidate path.
* Explained further in upcoming sections, there are 2 ways to
identify the replication segment, depending if they are shared
and non-shared
+ It is identified via Tree-ID and Root-ID and path-instance
for non-shared replication segment.
+ It is identified via Node-ID, Replication-ID, for shared
replication segment
+ Contains forwarding instructions, in the form of a list of
outgoing segments each of which may be a list
+ On the forwarding plane the Replication Segment is
identified via the incoming Replication SID.
+ Replication segment information is downloaded on Root,
Transit and Leaf nodes respectively.
3.1.1. Shared Tree vs Non-Shared Replication Segment
A non-shared Replication Segment is used when the label field of the
PMSI Tunnel Attribute (PTA) is set to zero as per
[draft-parekh-bess-mvpn-sr-p2mp]. This is used when there is no
upstream assigned label in the PTA (provider tunnel attribute) and
aggregate of MVPNs into a single P-Tunnel is not desired.
An alternative shared Replication Segment is used when the label
field of the PTA is not set to Zero and there is an upstream assigned
label in the PTA. In this case multiple MVPNs (VRFs) can be
aggregate into a single Provider Tunnel and the upstream assigned
label distinguishes the MVPNs context.
It should be noted that the shared Replication Segment can also be
used to build a bypass tunnel for the purpose of fast re-route. This
might be desirable if the bypass tunnel is build via the PCE and
downloaded to the PCC for link protection. In doing so, multiple
non-shared Replication Segments can use the shared replication
segment as their bypass tunnel for link protection. The replication
segments used in this bypass tunnel should only create a unicast
bypass tunnel to protect the link between two replication segments on
the primary path.
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3.2. Existing drafts used for defining a P2MP Policy
This document attempts to leverage existing IETF draft and RFC
documents which define PCEP objects, to update the PCE with Root and
Leaves information when PCC Initiated method is used. Similarly,
existing documents are utilized where feasible to update the PCC with
relevant information to build the P2MP Policy and its Replication
Segments. This document introduces new TLVs and Objects specific to
a programing P2MP policy and its replication segment.
3.2.1. Existing Documents used by this draft
o [RFC8231] The bases for a stateful PCE, and reuses the following
objects or a variant of them
* <SRP Object>
* <LSP Object>
* A variation of the LSP identifier TLV is defined in this draft,
to support P2MP LSP Identifier
o [RFC8236] P2MP capabilities advertisement
o [draft-ietf-pce-segment-routing-policy-cp] Candidate paths for
P2MP Policy is used for Tree Redundancy. As an example, a P2MP
Policy can have multiple candidate paths. Each protecting the
primary candidate path. The active path is chosen via the
preference of the candidate path.
o [RFC3209] Defines the instance-ID, instance-ID is used for global
optimization of a candidate path with in a P2MP policy. Each
Candidate path can have 2 path-instances. These path-instances
are equivalent to sub-lsps (instance-IDs). There are used for MBB
and global optimization procedures. instance-ID is equivalent to
LSP ID
o [draft-ietf-spring-segment-routing-policy] Segment-list, used for
connecting two non-adjacent replication policy via a unicast
binding SID or Segment-list.
o [RFC8306] P2MP End Point objects, used for the PCC to update the
PCE with discovered Leaves.
o [draft-ietf-pce-pcep-extension-for-pce-controller] for programming
and identifying the Replication Segment. A new PCE CC Capability
sub Tlv is introduced to indicated the support to handle PCE CC
based label download for SR P2MP.
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o [draft-ietf-pce-multipath] Forwarding instruction for a P2MP LSP
is defined by a set of SR-ERO sub-objects in the ERO object, ERO-
ATTRIBUTES object and MULTIPATH-BACKUP TLV as defined in this
draft.
o [RFC8664] SR-ERO Sub Object used in the multipath.
It should be noted that the [draft-dhs-spring-sr-p2mp-policy-yang]
can provide further details of the high level P2MP Policy Model.
3.2.2. P2MP Policy Identification
A P2MP Policy and its candidate path can be identified on the root
via the P2MP LSP Object. This Object is a variation of the LSP ID
Object defined in [RFC8231] and is as follow:
o PLSP-ID: [RFC8231], is assigned by PCC and is unique per candidate
path. It is constant for the lifetime of a PCEP session. Stand-
by candidate paths will be assigned a new PLSP-ID by PCC. Stand-
by candidate paths can co-exist with the active candidate path.
* Note: Every candidate path in the SR-P2MP Policy is unique with
its own unique PLSP-ID and Instance-ID. But the same Tree-ID
is used for all candidate paths as they are part of the same
P2MP Tree.
o Root-ID: is equivalent to the first node on the P2MP path, as per
[RFC3209], Section 4.6.2.1
o Tree-ID: is equivalent to Tunnel Identifier color which identifies
a unique P2MP Policy at a ROOT and is advertised via the PTA in
the BGP AD route or can be assigned manually on the root. Tree-ID
needs to be unique on the root.
o Instance-ID: LSP ID Identifier as defined in RFC 3209, is the
path-instance identifier and is assigned by the PCC. As it was
mentioned the candidate path can have up to two path-instance for
global optimization. Note that the Root-ID, Tree-ID and Instance-
ID are part of a new SR- P2MP-LSP-IDENTIFIER TLV which will be
identified in this draft.
* Note: each Path-instance on the Root node is assigned a unique
Instance-ID
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3.2.3. Replication Segment Identification
The key to identify a replication segment is also a P2MP LSP Object.
With varying encoding rules for the SR-P2MP-LSP- IDENTIFIER TLV which
will be explained in later sections.
3.2.4. PCECC Use in Replication Segment
PCECC and a variant of CCI object is used in Replication Segment to
identify a cross connect. A cross connect is a incoming SID and set
of outgoing interfaces and their corresponding SID. The CCI objects
contains the incoming SID while the outgoing interfaces are presented
via the ERO objects, which each may contain a list of segments.
3.3. High Level Procedures for P2MP SR LSP Instantiation
A P2MP policy can be instantiated via the PCC or the PCE depending on
how the root and the leaves are discovered. This document describes
two way to discover the root and the leaves:
o They can be configured and identified on the controller and are
considered PCE initiated.
o They can be discovered on the PCC via MVPN procedures [RFC6513] or
legacy multicast protocols like PIM or IGMP etc... and are
considered PCC initiated.
3.3.1. PCE-Init Procedure
o PCE is informed of the P2MP request through its API or
configuration mechanism to instantiate a P2MP tunnel.
o PCE will initiate the P2MP Policy for the request, by sending a
PCInitiate message to the Root.
o Root in response to the PCInitiate message, will generate PLSP-ID
for the candidate paths and an Instance-ID for the Path-Instance
(LSP-ID) contained with in the candidate path. The tree-id for
the P2MP Policy is also filled. PCC will reports back the PLSP-
ID, Instance-ID and tree-id via PCRpt message
* Optionally, the Root can add any additional leaves that were
discovered by multicast procedures in this PCRpt message.
o PCE will send a PCInitiate message to the Root, Transit and the
Leaf nodes to download the Replication Segment information. These
messages will utilize the CCI object to encode the forwarding
instruction information.
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o PCE will then send a PCUpdate to the root indicating the
association information (Candidate path) , and implicitly indicate
it to bind to the latest CCI information downloaded.
3.3.2. PCC-Init Procedure
After Root (PCC) discovers the leaves (as an example via MVPN
Procedures or other mechanism), the following communication happens
between the PCE and PCCs
o Root sends a PCRpt message for P2MP policy to PCE including the
Root-ID, Tree-ID, PLSP-ID, Instance-ID, symbolic-path-name, and
any leaves discovered until then.
o PCE on receiving of this report, will compute the P2MP Policy and
its replication segments.
* PCE will send a PCInitiate message to the Root, Transit and the
Leaf nodes to download the Replication Segment information.
These messages will utilize the CCI object to encode the
forwarding instruction information.
* PCE will then send a PCUpdate to the root indicating the
association information (Candidate path) , and implicitly
indicate it to bind to the latest CCI information downloaded.
3.3.3. Common Procedure
The following procedures are the same for PCE or PCC Init.
o PCE will download the replication segments for the Candidate-
path's path-instances to all the leaves and transit nodes using
PCInitiate message with PLSP-ID = 0, Instance-ID =0, symbolic path
name, Root-address, Tree-id(assigned by the root). This
PCInitiate message includes the EROs needed for the replication
segments. These messages will utilize the CCI object to encode
the forwarding instruction information.
o Any new candidate path for the P2MP Policy is downloaded by PCE to
the Root by sending a PCInitiate message
* it should be noted, PLSP-ID, Path-Instance ID and the Tree-ID
are generated by the PCC for these new candidate paths and
their Path-instances
* Any update to the Candidate Paths or Replication Segments is
done via the PCUpd message. Association object need to be
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present for Candidate Path updates and CCI object for the
replication segment updates.
o The PCE will also download the necessary replication segment for
the candidate path and its path-instances to the root, leaves and
the transit nodes via a PCInit message
o New leaves can be discovered via Multicast procedures, and new
replication segments can be instantiated or existing one updated
to reach these leaves
* If these leaves reside on routers that are part of the P2MP LSP
path, then PCUpd is sent from PCE to necessary PCCs (LEAVES,
TRANSIT or ROOT) with the correct PLSP-ID, Instance-ID, Tree-ID
and CC-ID.
* If the new leaves are residing on routers that are not part of
the P2MP Tree yet, then a PCInitiate message is sent down with
PLSP- ID=0 and Instance-ID=0 on the corresponding routers.
o The active candidate-path is indicated by the PCC through the
operational bits(Up/Active) of the LSP object in the PCRpt
message. If a candidate path needs to be removed, PCE sends PC
Initiate message, setting the R-flag in the LSP object and R bit
in the SRP-object.
o To remove the entire P2MP-LSP, PCE needs to send PCInitiate remove
messages for every candidate path of the P2MP POLICY to the root
and send PCInitiate remove messages for every Replication Regment
on all the PCCs on the P2MP Tree. The R bit in the LSP Object as
defined in [RFC8231], refers to the removal of the LSP as
identified by the SR-P2MP-POLICY-ID-TLV (defined in this
document). An all zero (SR-P2MP-LSP-ID-TLV defines to remove all
the state of the corresponding PLSP-ID.
o A candidate path is made active based on the preference of the
path. If the Root is programed with multiple candidate paths from
different sources, as an example PCE and CLI, based on its tie-
breaking rules, if it selects the CLI path, it will send a report
to PCE for the PCE path indicating the status of label-download
and sets operational bit of the LSP object to UP and Not Active .
At any instance, only one path will be active
3.3.4. Global Optimization of the Candidate Path
When a P2MP LSP needs to be optimized for any reason (i.e. it is
taking a FRR tunnel or new routers are added to the network) a global
optimization of the candidate path is possible.
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Each Candidate Path can contain two Path-Instances. The current
unoptimized Path-Instance is the active instance and its replication
segments are forwarding the multicast PDUs from the root to the
leaves. However the second optimized Path-Instance will be setup
with its own unique replication segments throughout the network, from
the Root to the leaves. These two Path-Instances can co-exist. The
two Path-Instances are uniquely identified by their Instance-ID in
the SR-P2MP-POLICY-ID-TLV (defined in this document). After the
optimized LSP has been downloaded successfully PCC MUST send two
reports, reporting UP of the new path indicating the new LSP-ID, and
a second reporting the tear down of the old path with the R bit of
the LSP Object SET with the old Instance-ID in the SR-P2MP-POLICY-ID-
TLV. This MBB procedure will move the multicast PDUs to the
optimized Path-Instance.
The leaf should be able to accept traffic from both Path-Instances to
minimize the traffic outage by the Make Before Break process.
3.3.5. Fast Reroute
Currently this draft identifies the Facility FRR procedures. In
addition, only LINK Protection procedures are defined. How the
Facility Path is built and instantiated is beyond the scope of this
document.
R
| |
T
|
---
| |
L1 L2
Figure 1
R---F1
| |
T---F2
|
---
| |
L1 L2
Figure 2
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As an example, the bypass path (unicast bypass) between the PLR and
MP can be constructed via SR or even via a shared tree (replication
segment).
As an example, in figure 1 the detour path between R and T is the 2nd
fiber between these nodes. As such the bypass path could be setup on
the 2nd fiber. That said in figure 2 the bypass path is traversing
multiple nodes and this example a unicast SR path might be ideal for
setting up the detour path.
In addition, PHP procedure and implicit null label on the bypass path
can be implemented to reduce the PCE programming on the MP PCC.
Optional shared replication segments can be used in networks that do
not have unicast SR turned on. These shared replication segments can
be programmed on the bypass nodes without a P2MP Policy. The
replication segments on primary path can use these shared replication
segments as a protection tunnel to protect links.
3.3.6. Connecting Replication Segment via Segment List
There could be nodes between two replication segment that do not
support P2MP Policy or Replication segment. It is possible to
connect two non-adjacent Replication segments via a unicast segment
routing path via a SID list, comprised of any IGP supported segment
types (ex: Binding, Adjacency, Node) to forward to the next
replicating node. This information is encoded via the SR-ERO sub-
objects and ERO-attributes objects. The last segment in an encoding
SID list MUST be a replication segment
3.4. SR P2MP Policy and Replication Segment TLVs and Objects
3.4.1. SR P2MP Policy Objects
SR P2MP Policy can be constructed via the following objects
<Common Header>
<SRP>
<P2MP LSP>
[<association-list>]
optionally if the root is updating the PCE with end point list the
end-point-list object can be added.
[<end-points-list>]
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3.4.2. Replication Segment Objects
Replication segment can be constructed via the following objects
<Common Header>
<SRP>
<P2MP LSP>
(<cci-list>|
(<CCI><intended-path>))
<cci-list> ::= <CCI>
[<cci-list>]
<intended-path> ::= ((<PATH-ATTRIB><ERO>)
[<intended-path>])
Path-attribute as per [draft-ietf-pce-multipath]
3.4.3. P2MP Policy and Replication Segment general considerations
The above new objects and TLV's defined in this document can be
included in PCRpt, PcInitiate and PcUpd messages.
It should be noted that every PcRpt, PcInitiate and PCUpd messages
will contain full list of the Leaves and segment and forwarding
information that is needed to build the Candidate path and its
Replication segments. They will never send the delta information
related to the new leaves or forwarding information that need to be
added or updated. This is necessary to ensure that PCE or any new
PCE is in sync with the PCC.
When a PCRpt, PCInitiate and PCUpd messages is sent via PCEP it
maintains the previous ERO Path IDs and generates new Path IDs for
new instructions, as per [draft-ietf-pce-multipath]. The PATH IDs
are maintained for each specific forwarding instructions until the
instructions are deleted. For example: When the first leaf is added,
the PCE will update with PathI ID 1 to the PCC. When the second leaf
is added, according to the path calculated, PCE might just append the
existing instruction Path ID 1 with a new Path ID 2 to construct the
new PCUpd message.
The CCI Object is used to identify the entire cross connect of
incoming segment and the set of outgoing Interfaces and their
corresponding SIDs/SIDList. Any modification to the cross connect
should use this CCI ID to identify the cross connect uniquely.
Leaves and their corresponding Path IDs can be removed from the cross
connect identified via the CCI. The CC-ID is assigned by the PCE.
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4. Object Format
4.1. Open Message and Capability Exchange
Format of the open Object:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Ver | Flags | Keepalive | DeadTimer | SID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
// Optional TLVs //
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
All the nodes need to establish a PCEP connection with the PCE.
During PCEP Initialization Phase, PCEP Speakers need to set flags N,
M, P in the STATEFUL-PCE-CAPABILITY TLV as defined in
[draft-ietf-pce-stateful-pce-p2mp] section-5.2
This draft extends the PCEP OPEN object by defining an optional TLV
to indicate the PCE's capability to perform SR-P2MP path computations
with a new IANA capability type.
The inclusion of this TLV in an OPEN object indicates that the sender
can perform SR-P2MP path computations. This will be similar to the
P2MP-CAPABILITY defined in [RFC8306] section-3.1.2 and a new value
needs to be defined for SR-P2MP.
4.1.1. PCECC Path Setup Capability
A PST of PCECC is also added as per
[draft-ietf-pce-pcep-extension-for-pce-controller].
This document also introduces a new bit S in the SR PCECC capacity
Sub TLV indicating the support to handle PCECC based label download
for Replication segment.
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type=1 | Length=4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags |S|M|L|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Also, the N,M,P bits in STATEFUL-PCE-CAPABILITY TLV should be SET.
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4.1.2. Association Type Capability
A Assoc-Type-List TLV as per [RFC8697] section 3.4 should be send via
PCEP open object with following association type
+-------------------+----------------------------+------------------+
| Association Type | Association Name | Reference |
| Value | | |
+-------------------+----------------------------+------------------+
| TBD1 | P2MP SR Policy Association | This document |
+-------------------+----------------------------+------------------+
OP-CONF-Assoc-RANGE (Operator-configured Association Range)should not
be set for this association type and must be ignored.
The open message MUST include the MULTIPATH CAPABILITY TLV as defined
in [draft-ietf-pce-multipath]
4.2. Symbolic Name in PCInit Message from PCC
As per [RFC8231] section 7.3.2. a Symbolic Path Name TLV should
uniquely identify the P2MP path on the PCC. This symbolic path name
is a human-readable string that identifies an P2MP LSP in the
network. It needs to be constant through the lifetime of the P2MP
path.
As an example in the case of P2MP LSP the symbolic name can be p2mp
policy name + candidate path name of the LSP.
4.3. P2MP Policy Specific Objects and TLVs
4.3.1. P2MP Policy Association Group for P2MP Policy
Two ASSOCIATION object types for IPv4 and IPv6 are defined in
[RFC8697]. The ASSOCIATION object includes "Association type"
indicating the type of the association group. This document adds a
new Association type. Association type = TBD1 "P2MP SR Policy
Association Type" for SR Policy Association Group (P2MP SRPAG). As
per [draft-barth-pce-segment-routing-policy-cp] section 5, three new
TLVs are identified to carry association information: P2MP-SRPAG-
POL-ID-TLV, P2MP-SRPAG-CPATH-ID-TLV, P2MP-SRPAG-CPATH-ATTR-TLV
4.3.1.1. P2MP SR Policy Association Group Policy Identifiers TLV
The P2MP-SRPOLICY-POL-ID TLV is a mandatory TLV for the P2MP-SRPAG
Association. Only one P2MP-SRPOLICY-POL-ID TLV can be carried and
only the first occurrence is processed and any others MUST be
ignored.
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0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type | Length |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Root |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| TREE-ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: TBD2 for "P2MP-SR-POLICY-POL-ID" TLV.
Length: 8 or 20, depending on length of End-point (IPv4 or IPv6)
Tunnel Sender Address : Can be either IPv4 or IPv6, this value is the
value of the root loopback IP.
Tree-ID: Tree ID that the replication segment is part of as per
draft-ietf-spring-sr-p2mp-policy
4.3.1.2. P2MP SR Policy Association Group Candidate Path Identifiers
TLV
The P2MP-SRPOLICY-CPATH-ID TLV is a mandatory TLV for the P2MPSRPAG
Association. Only one P2MP-SRPOLICY-CPATH-ID TLV can be carried and
only the first occurrence is processed and any others MUST be
ignored.
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Proto. Origin |Flags |A| Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Originator ASN |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Originator Address |
| |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Discriminator |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: TBD3 for "P2MP-SR-POLICY-CPATH-ID" TLV.
Length: 28.
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Protocol Origin: 8-bit value that encodes the protocol origin, as
specified in [I-D.ietf-spring-segment-routing-policy] Section 2.3.
Flags : A: This candidate path is active. At any instance only one
candidate path can be active. PCC indicates the active candidate
path to PCE through this bit. Reserved: MUST be set to zero on
transmission and ignored on receipt.
Originator ASN: Represented as 4 byte number, part of the originator
identifier, as specified in
[draft-ietf-spring-segment-routing-policy] Section 2.4.
Originator Address: Represented as 128 bit value where IPv4 address
are encoded in lowest 32 bits, part of the originator identifier, as
specified in [draft-ietf-spring-segment-routing-policy] Section 2.4.
Discriminator: 32-bit value that encodes the Discriminator of the
candidate path.
4.3.1.3. P2MP SR Policy Association Group Candidate Path Attributes TLV
The P2MP-SRPOLICY-CPATH-ATTR TLV is an optional TLV for the SRPAG
Association. Only one P2MP-SRPOLICY-CPATH-ATTR TLV can be carried
and only the first occurrence is processed and any others MUST be
ignored.
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 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Preference |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Type: TBD4 for "P2MP-SRPOLICY-CPATH-ATTR" TLV.
Length: 4. Preference: Numerical preference of the candidate path,
as specified in [draft-ietf-spring-segment-routing-policy]
Section 2.7.
If the TLV is missing, a default preference of 100 as specified in
[draft-ietf-spring-segment-routing-policy] is used.
4.3.2. P2MP-END-POINTS Object
In order for the Root to indicate operations of its
leaves(Add/Remove/Modify/DoNotModify), the PC Report message is
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extended to include P2MP End Point <P2MP End-points> Object which is
defined in [RFC8306]
The format of the PC Report message is as follow:
<Common Header>
[<SRP>]
<LSP>
[<association-list>]
[<end-points-list>]
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IPV4-P2MP END-POINTS:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Leaf type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Source IPv4 address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Destination IPv4 address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ ... ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Destination IPv4 address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
IPV6-P2MP END-POINTS:
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Leaf type |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Source IPv6 address (16 bytes) |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Destination IPv6 address (16 bytes) |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
~ ... ~
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
| Destination IPv6 address (16 bytes) |
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Leaf Types (derived from [RFC8306] section 3.3.2) :
1. New leaves to add (leaf type = 1)
2. Old leaves to remove (leaf type = 2)
3. Old leaves whose path can be modified/reoptimized (leaf type =
3), Future reserved not used for tree SID as of now.
4. Old leaves whose path must be left unchanged (leaf type = 4)
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5. the entire pce leaf list is overwritten and replaced with the new
leaf list (leaf type = 5)
A given P2MP END-POINTS object gathers the leaves of a given type.
Note that a P2MP report can mix the different types of leaves by
including several P2MP END-POINTS objects. The END-POINTS object
body has a variable length. These are multiples of 4 bytes for IPv4,
multiples of 16 bytes, plus 4 bytes, for IPv6.
4.4. P2MP Policy and Replication Segment Identifier Object and TLV
As it was mentioned previously both P2MP Policy and Replication
Segment are identified via the LSP object and more precisely via the
SR-P2MP-LSPID-TLV
The P2MP Policy uses the PLSP-ID to identify the Candidate Paths and
the Instance-ID to identify a Path-Instance with in the Candidate
path.
On other hand the Replication Segment uses the SR-P2MP-LSPID-TLV to
identify and correlate a Replication Segment to a P2MP Policy
As it was noted previously on the Root, the P2MP Policy and the
Replication Segment is downloaded via the same PCUpd message.
4.4.1. Extension of the LSP Object, SR-P2MP-LSPID-TLV
The LSP Object is defined in Section 7.3 of [RFC8231]. It specifies
the PLSP-ID to uniquely identify an LSP that is constant for the life
time of a PCEP session. Similarly, for a P2MP tunnel, the PLSP-ID
identify a Candidate Path uniquely with in the P2MP policy.
The LSP Object MUST include the new SR-P2MP-POLICY-ID-TLV (IPV4/IpV6)
defined in this document below. This is a variation to the P2MP
object defined in [draft-ietf-pce-stateful-pce-p2mp]
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SR-IPV4-P2MP-POLICY-ID TLV:
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=TBD | Length=10 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Root |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Tree-ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Path-Instance-ID | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
SR-IPV6-P2MP-POLICY-ID TLV :
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=TBD | Length=22 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
+ +
| Root |
+ (16 octets) +
| |
+ +
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Tree-ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Path-Instance-ID | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
The type (16-bit) of the TLV is TBD (need allocation by IANA).
Root: Source Router IP Address
Tree-ID: Unique Identifier of this P2MP LSP on the Root.
Instance-ID : Contains 16 Bit instance ID.
4.5. Replication Segment
As per [draft-ietf-spring-sr-replication-segment] a replication
segment has a next-hop-group which MAY contain a single outgoing
replication SID or a list of SIDs (sr-policy-sid-list) In either case
there needs to be a replication SID at the bottom of the stack. This
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means two replication segments can be directly connected or connected
via a SR domain.
4.5.1. The format of the replication segment message
The format of a Replication Segment message encoding is similar to
P2MP Policy. However, the P2MP Policy contains the association
object and the replication segment message does not contain the
association object. In addition the replication segment uses the CCI
object to identify a P2MP cross connect. The replication segment is
downloaded individually to the root, transit and leaf nodes without
the P2MP Policy. The P2MP Policy is a Root Concept. The replication
segment uses SR-P2MP-LSPID-TLV as its identifier. The TLV is coded
differently for shared and non-shared case.
o In the case of a replication segment being shared, the Tree-ID in
the SR-P2MP-POLICY Identifier TLV is the replication-id of the
Replication Segment and Root = 0, Instance-Id = 0. When
downloading a shared replication segment from PCE through a
PcInitiate message, the SR-P2MP-POLICY Identifier TLV is all 0,
and on the report back from PCC, PCC generates PLSP-ID,
Replication-id (Tree-id field will be populated with replication-
id). Instance-id will be 0.
4.5.2. PCECC
The CCI Object as defined in
[draft-ietf-pce-pcep-extension-for-pce-controller] is used to
identify a forwarding instruction in the Replication Segment. A
forwarding instruction is incoming SID and a set of outgoing
branches. The CCI Object-Type of 1 is used for the MPLS Label. The
label in the CCI Object is the incoming SID. The outgoing SIDs are
defined by the ERO Objects.
The CCI Object can be include in Reports, initiate and Update
messages for Replication Segments.
The PCInitiate message defined in [RFC8281] and extended in
[draft-ietf-pce-pcep-extension-for-pce-controller] is further
extended to support SR-P2MP replication segment based central control
instructions.
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The format of the extended PCInitiate message is as follows:
<PCInitiate Message> ::= <Common Header>
<PCE-initiated-lsp-list>
Where:
<Common Header> is defined in [RFC5440]
<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><intended-path>))
<cci-list> ::= <CCI>
[<cci-list>]
<intended-path> ::= ((<PATH-ATTRIB><ERO>)
[<intended-path>])
Where:
<PCE-initiated-lsp-instantiation> and
<PCE-initiated-lsp-deletion> are as per
[RFC8281].
The LSP and SRP object is defined in [RFC8231]. The <intended-path>
is as per [RFC8281] [draft-ietf-pce-multipath] (PATH-ATTRIB and ERO).
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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><intended-path>))
<cci-list> ::= <CCI>
[<cci-list>]
Where:
<path> is as per [RFC8231] and the LSP and SRP object are
also defined in [RFC8231].
The <intended-path> is as per [draft-ietf-pce-multipath] (PATH-ATTRIB
and ERO).
This document extends the use of PCUpd message with SR-P2MP CCI as
follows:
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<PCUpd Message> ::= <Common Header>
<update-request-list>
Where:
<update-request-list> ::= <update-request>[<update-request-list>]
<update-request> ::= (<lsp-update-request>|
<central-control-update>)
<lsp-update-request> ::= <SRP>
<LSP>
<path>
<central-control-update> ::= <SRP>
<LSP>
(<CCI><intended-path>)
Where:
<path> is as per [RFC8231] and the LSP and SRP object are
also defined in [RFC8231].
The <intended-path> is as per [draft-ietf-pce-multipath] (PATH-ATTRIB
and ERO).
4.5.3. Label action rules in replicating segment
The node action and role of ingress, transit, leaf or bud, is
indicated via a new Node Role TLV. This document introduces a new
SR-P2MP-NODE-ROLE TLV (Type To be assigned by IANA) that will be
present in the PATH-ATTRIB object.
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=TBD | Length=4 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Role Type | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
o ingress, role type = 1
o transit, role type = 2
o leaf, role type = 3
o bud, role type = 4
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4.5.4. SR-ERO Rules
Forwarding information of a replication segment can be configured and
steered via many different mechanisms.
As an example a replication SID can be steered via:
1. Replication SID steered with an IPv4/IPv6 directly connected
nexthop
* In this case there will two SR-ERO in the ERO Object, with the
Replication SID SR-ERO at the bottom and the IPv4/IPv6 SR-ERO
on the top.
2. Replication SID steered with an IPv4/IPv6 loopback address that
reside on the directly connected router.
* In this case there will two SR-ERO in the ERO Object, with the
Replication SID SR-ERO at the bottom and the IPv4/IPv6 SR-ERO
on the top.
* In addition a new flag D is added to the SR-ERO to signal that
the Loopback nexthop is connected to the directly attached
router.
3. Replication SID steered with unnumbered IPv4/IPv6 directly
connected Interface
4. Replication SID steered via a SR adjacency or node SID
* In this case even a sid-list can be used to traffic engineer
the path between two Replication Segment
* The Replication SID SR-ERO is at the bottom while the segments
describing the path are on top in order.
4.5.4.1. SR-ERO subobject changes
SR-ERO from RFC 8664 is used to construct the forwarding information
needed for Replication Segment.
A new D flag was added to indicate a loopback nexthop that is
residing on the directly attached router. It should be noted that
this flag should be set only for the loopback case and not for a
local interface as a nexthop.
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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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|L| Type=36 | Length | NT | Flags |D|F|S|C|M|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| SID (optional) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// NAI (variable, optional) //
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Flags : F, S, C, M are already defined in rfc8664.
This document defines a new flag D: If the next-hop in NAI field is
system IP or loopback, this bit indicates whether the system IP /
loopback is directly connected router or not. If set indicates
directly connected address. When this bit is set, F bit should be 0
(meaning NAI should be present)
5. Tree Deletion
To delete the entire tree (P2MP LSP), Root send a PCRpt message with
the R bit of the LSP object set and all the fields of the SR-P2MP-
LSP-ID TLV set to 0(indicating to remove all state associated with
this P2MP tunnel). The PCE in response sends a PCInitiate message
with R bit in the SRP object SET to all nodes along the path to
indicate deletion of the entries.
6. Fragmentation
The Fragmentation bit in the LSP object (F bit) can be used to
indicate a fragmented PCEP message
7. Example Workflows
PCC-Initiated Workflow
+-------+ +-------+
|PCC | | PCE |
|Root | +-------+
+------| | |
| PCC +-------+ |
| Transit| | |
+------| | |---PCRpt,PLSP-ID=1,D=1-------------->| PCECC LSP
|PCC +--------+ | N=1,root-addr,tree-id=a, | SR-Policy
| | | | instance-id =b, | Report to
|Leaf | | | p2mp-end-points(LeafType=5) | PCE
+--------+ | | |
| | | |
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| | |<--PCUpdate,PLSP-ID=1, SRP-ID =1, | Update
| | | root-addr,tree-id=a,instance-id=b,| CP
| | | p2mp-end-points, association-obj |
| | | |
| | |-------PCRpt,PLSP-ID=1, SRP-ID = 1,->|
| | | root-addr,tree-id=a,instance-id=b,|
| | | p2mp-end-points(LeafType=5) |
| | | association-object, |
| | | |
|<---------------PCInitiate,PLSP-ID=0, -------------| Download
| | | root-addr,tree-id=a,instance-id=0,| Leaf
| | | CC-ID=Z,C=0, | Replication
| | | O=0,L=z,path-attribute,ERO,SR-ERO | Segment(RS)
| | | |
|---------------------PCRpt,PLSP-ID=1-------------->|
| | | root-addr,tree-id=a,instance-id=b,|
| | | CC-ID=Z,Label=z,O=0, |
| | | path-attribute,ERO,SR-ERO |
| | | |
| |<-------PCInitiate,PLSP-ID=0, -------------| Download
| | | root-addr,tree-id=a,instance-id=0,| Transit
| | | CC-ID=Y,C=0, | RS
| | | O=0,L=y,path-attribute,ERO,SR-ERO |
| | | |
| |-------------PCRpt,PLSP-ID=2-------------->|
| | | root-addr,tree-id=a,instance-id=c,|
| | | CC-ID=Y,Label=y,O=0, |
| | | path-attribute,ERO,SR-ERO |
| | | |
| | |<--PCInitiate,PLSP-ID=1, | Download
| | | root-addr,tree-id=a,instance-id=b,| Root
| | | CC-ID=X,C=0, | RS
| | | O=0,L=x,p2mp-end- |
| | | points(LeafType=5),path-attribute,|
| | | ERO,SR-ERO |
| | | |
| | |-------PCRpt,PLSP-ID=1-------------->|
| | | root-addr,tree-id=a,instance-id=b,|
| | | CC-ID=X,Label=x,O=0, |
| | | p2mp-end-points(LeafType=5) |
| | | path-attriute,ERO,SR-ERO |
| | | |
| | |<--PCUpdate,PLSP-ID=1, SRP-ID =2, |
| | | root-addr,tree-id=a,instance-id=b,| Activate
| | | p2mp-end-points | CP to last
| | | | RS
| | |-------PCRpt,PLSP-ID=1, SRP-ID =2, ->|
| | | root-addr,tree-id=a,instance-id=b,|
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| | | p2mp-end-points(LeafType=5) |
| | | |
Note that on transit / leaf Initiate is with PLSP-ID = 0. Therefore
PLSP-ID is locally unique to a node. It should be noted that the CC-
ID does not need to be constant across all nodes that make up the
path.
PCE-Initiated workflow
+-------+ +-------+
|PCC | | PCE |
|Root | +-------+
+------| | |
| PCC +-------+ |
| Transit| | |
+------| | | | PCECC LSP
|PCC +--------+ | |
| | | | |
|Leaf | | | |
+--------+ | | |
|<---------------PCInitiate,PLSP-ID=0, -------------| Download
| | | root-addr,tree-id=a,instance-id=0,| Leaf RS
| | | CC-ID=Z,C=0, |
| | | O=0,L=z,path-attribute,ERO,SR-ERO |
| | | |
|---------------------PCRpt,PLSP-ID=1-------------->|
| | | root-addr,tree-id=a,instance-id=b,|
| | | CC-ID=Z,Label=z,O=0, |
| | | path-attribute,ERO,SR-ERO |
| | | |
| |<-------PCInitiate,PLSP-ID=0, -------------| Download
| | | root-addr,tree-id=a,instance-id=0,| Transit RS
| | | CC-ID=Y,C=0, |
| | | O=0,L=y,path-attribute,ERO,SR-ERO |
| | | |
| |-------------PCRpt,PLSP-ID=2-------------->|
| | | root-addr,tree-id=a,instance-id=c,|
| | | CC-ID=Y,Label=y,O=0, |
| | | path-attribute,ERO,SR-ERO |
| | | |
| | |<--PCInitiate,PLSP-ID=0, | Initiate
| | | root-addr,tree-id=0,instance-id=0,| CP
| | | p2mp-end-points, association-obj |
| | | |
| | |-------PCRpt,PLSP-ID=1,------------->|
| | | root-addr,tree-id=a,instance-id=b,|
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| | | p2mp-end-points(LeafType=5) |
| | | association-object, |
| | | |
| | |<--PCInitiate,PLSP-ID=1, | Download
| | | root-addr,tree-id=a,instance-id=b,| Root RS
| | | CC-ID=X,C=0, |
| | | O=0,L=x,p2mp-end- |
| | | points(LeafType=5),path-attribute,|
| | | ERO,SR-ERO |
| | | |
| | |-------PCRpt,PLSP-ID=1-------------->|
| | | root-addr,tree-id=a,instance-id=b,|
| | | CC-ID=X,Label=x,O=0, |
| | | p2mp-end-points(LeafType=5) |
| | | path-attriute,ERO,SR-ERO |
| | | |
| |<-------PCInitiate,PLSP-ID=0, -------------|
| | | root-addr,tree-id=a,instance-id=0,|
| | | CC-ID=Y,C=0, |
| | | O=0,L=y,path-attribute,ERO,SR-ERO |
| | | |
| |-------------PCRpt,PLSP-ID=2-------------->|
| | | root-addr,tree-id=a,instance-id=c,|
| | | CC-ID=Y,Label=y,O=0, |
| | | path-attribute,ERO,SR-ERO |
| | | |
| | |<--PCUpdate,PLSP-ID=1, SRP-ID =1, | Bind and
| | | root-addr,tree-id=a,instance-id=b,| Activate
| | | p2mp-end-points, | CP to last
| | | | RS
| | |-------PCRpt,PLSP-ID=1, SRP-ID = 1,->|
| | | root-addr,tree-id=a,instance-id=b,|
| | | p2mp-end-points(LeafType=5) |
MBB Workflow:
Common (PCE-INIT, PCC-INIT) MBB
+-------+ +-------+
|PCC | | PCE |
|Root | +-------+
+------| | |
| PCC +-------+ |
| Transit| | |
+------| | | | PCECC LSP
|PCC +--------+ | |
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| | | | |
|Leaf | | | |
+--------+ | | |
|<---------------PCInitiate,PLSP-ID=1, -------------| Download
| | | root-addr,tree-id=a,instance-id=b,| new RS on
| | | CC-ID=Z1,C=0, | Leaf
| | | O=0,L=z1,path-attribute,ERO,SR-ERO |
| | | |
|---------------------PCRpt,PLSP-ID=1-------------->|
| | | root-addr,tree-id=a,instance-id=b,|
| | | CC-ID=Z1,Label=z1,O=0, |
| | | path-attribute,ERO,SR-ERO |
| | | |
| |<-------PCInitiate,PLSP-ID=2, -------------| Download
| | | root-addr,tree-id=a,instance-id=c,| new RS on
| | | CC-ID=Y1,C=0, | Transit
| | | O=0,L=y1,path-attribute,ERO,SR-ERO |
| | | |
| |-------------PCRpt,PLSP-ID=2-------------->|
| | | root-addr,tree-id=a,instance-id=c,|
| | | CC-ID=Y1,Label=y1,O=0, |
| | | path-attribute,ERO,SR-ERO |
| | | |
| | |<--PCInitiate,PLSP-ID=1, | Download
| | | root-addr,tree-id=a,instance-id=b,| new RS on
| | | CC-ID=X1,C=0, | Root
| | | O=0,L=x1,p2mp-end- |
| | | points(LeafType=5),path-attribute,|
| | | ERO,SR-ERO |
| | | |
| | |-------PCRpt,PLSP-ID=1-------------->|
| | | root-addr,tree-id=a,instance-id=b,|
| | | CC-ID=X1,Label=x1,O=0, |
| | | p2mp-end-points(LeafType=5) |
| | | path-attriute,ERO,SR-ERO |
| | | |
| | |<--PCUpdate,PLSP-ID=1, SRP-ID =1, | Bind and
| | | root-addr,tree-id=a,instance-id=b,| Activate
, | | | p2mp-end-points, | CP to last
| | | | RS
| | |-------PCRpt,PLSP-ID=1, SRP-ID = 1,->|
| | | root-addr,tree-id=a,instance-id=b,|
| | | p2mp-end-points(LeafType=5) |
| | | |
| | |<--PCInitiate,PLSP-ID=1,R=1 | Remove
| | | root-addr,tree-id=a,instance-id=b,| the old RS
| | | CC-ID=X1,C=0 | from Leaf
| | | O=0,L=x1,p2mp-end- |
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| | | points(LeafType=5),path-attribute,|
| | | ERO,SR-ERO |
| | | |
| | |-------PCRpt,PLSP-ID=1, R=1--------->|
| | | root-addr,tree-id=a,instance-id=b,|
| | | CC-ID=X1,Label=x1,O=0, |
| | | p2mp-end-points(LeafType=5) |
| | | path-attriute,ERO,SR-ERO |
| | | |
| |<-------PCInitiate,PLSP-ID=2, R=1----------| Remove the
| | | root-addr,tree-id=a,instance-id=c,| old RS from
| | | CC-ID=Y1,C=0, | Transit
| | | O=0,L=y1,path-attribute,ERO,SR-ERO |
| | | |
| |-------------PCRpt,PLSP-ID=2, R=1--------->|
| | | root-addr,tree-id=a,instance-id=c,|
| | | CC-ID=Y1,Label=y1,O=0, |
| | | path-attribute,ERO,SR-ERO |
| | | |
|<---------------PCInitiate,PLSP-ID=1,R=1-----------| Remove the
| | | root-addr,tree-id=a,instance-id=b,| old RS from
| | | CC-ID=Z1,C=0, | Root
| | | O=0,L=z1,path-attribute,ERO,SR-ERO |
| | | |
|---------------------PCRpt,PLSP-ID=1,R=1---------->|
| | | root-addr,tree-id=a,instance-id=b,|
| | | CC-ID=Z1,Label=z1,O=0, |
| | | path-attribute,ERO,SR-ERO |
8. IANA Consideration
1. This draft extends the PCEP OPEN object by defining an optional
TLV to indicate the PCE's capability to perform SR-P2MP path
computations with a new IANA capability type (TBD).
2. PCEP open object with a new association type " P2MP SR Policy
Association " value (TBD).
3. A new Association type. Association type = TBD1 "P2MP SR Policy
Association Type" for SR Policy Association Group (P2MP SRPAG)
1. three new TLVs are identified to carry association
information: P2MP-SRPAG- POL-ID-TLV, P2MP-SRPAG-CPATH-ID-TLV,
P2MP-SRPAG-CPATH-ATTR-TLV
4. Two new TLVs for Identifying the P2MP Policy and the Replication
segment SR-IPV4-P2MP-POLICY-ID TLV and SR-IPV6-P2MP-POLICY-ID TLV
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5. A new SR-P2MP-NODE-ROLE TLV (Type To be assigned by IANA) that
will be present in the PATH-ATTRIB object
9. Security Considerations
TBD
10. Acknowledgments
The authors would like to thank Tanmoy Kundu and Stone Andrew at
Nokia for their feedback and major contribution to this draft.
11. References
11.1. 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>.
11.2. Informative References
[draft-barth-pce-segment-routing-policy-cp]
.
[draft-dhs-spring-sr-p2mp-policy-yang]
.
[draft-ietf-pce-multipath]
.
[draft-ietf-pce-pcep-extension-for-pce-controller]
.
[draft-ietf-pce-segment-routing-policy-cp]
.
[draft-ietf-pce-stateful-pce-p2mp]
.
[draft-ietf-pim-sr-p2mp-policy]
"D. Yoyer, C. Filsfils, R.Prekh, H.bidgoli, Z. Zhang,
"draft-voyer-pim-sr-p2mp-policy"", October 2019.
[draft-ietf-spring-segment-routing-policy]
.
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[draft-ietf-spring-sr-replication-segment]
"D. Yoyer, C. Filsfils, R.Prekh, H.bidgoli, Z. Zhang,
"draft-voyer-pim-sr-p2mp-policy "draft-voyer-spring-sr-
replication-segment"", July 2020.
[draft-parekh-bess-mvpn-sr-p2mp]
.
[draft-sivabalan-pce-binding-label-sid]
.
[RFC3209] .
[RFC5440] .
[RFC6513] .
[RFC8231] .
[RFC8236] .
[RFC8281] .
[RFC8306] .
[RFC8664] .
[RFC8697] .
Authors' Addresses
Hooman Bidgoli (editor)
Nokia
Ottawa
Canada
Email: hooman.bidgoli@nokia.com
Daniel Voyer
Bell Canada
Montreal
Canada
Email: daniel.yover@bell.ca
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Saranya Rajarathinam
Nokia
Mountain View
US
Email: saranya.Rajarathinam@nokia.com
Ehsan Hemmati
Cisco System
San Jose
USA
Email: ehemmati@cisco.com
Tarek Saad
Juniper Networks
Ottawa
Canada
Email: tsaad@juniper.com
Siva Sivabalan
Ciena
Ottawa
Canada
Email: ssivabal@ciena.com
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