| PCE Working Group | C. Barth |
| Internet-Draft | R. Torvi |
| Intended status: Standards Track | Juniper Networks |
| Expires: December 31, 2018 | June 29, 2018 |
PCEP Extensions for RSVP-TE Local-Protection with PCE-Stateful
draft-cbrt-pce-stateful-local-protection-01
Stateful PCE can apply global concurrent optimizations to optimize LSP placement. In a deployment where a PCE is used to compute all the paths, it may be beneficial for the local protection paths to also be computed by the PCE. This document defines extensions needed for the setup and management of RSVP-TE protection paths by the PCE.
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[RFC5440] describes the Path Computation Element Protocol PCEP. PCEP defines the communication between a Path Computation Client (PCC) and a Path Control Element (PCE), or between PCE and PCE, enabling computation of Multi-protocol Label Switching (MPLS) for Traffic Engineering Label Switched Path (TE LSP) characteristics.
Stateful PCE specifies a set of extensions to PCEP to enable stateful control of paths such as MPLS TE LSPs between and across PCEP sessions in compliance with [RFC4657]. It includes mechanisms to effect LSP state synchronization between PCCs and PCEs and allow delegation of control of LSPs to PCEs.
In a network where all LSPs have control delegated to a PCE, the PCE can apply global concurrent optimization to optimize LSP placement. The PCE can also control the timing and sequence of path computation and applying path changes. In a deployment where a PCE is used to compute all the paths, it may be beneficial for the protection paths to also be controlled through the PCE. This document defines extensions needed for the setup and management of protection paths by the PCE.
Benefits of stateful synchronization and control of the protection paths include:
o Better control over traffic after a failure and more deterministic path computation of protection paths. The PCE can optimize the protection path based on data not available to the PCC, for instance the PCE can make sure the protection path will not violate the delay specified by [I-D.ietf-pce-pcep-service-aware].
o Satisfy more complex constraints and diversity requirements, such as maintaining diverse paths for LSPs as well as their local protection paths.
o Given the PCE's global view of network resources, act as a form of LSP admission control into a protection path to ensure links are not overloaded during failure events.
o On a PLR with multiple available protection routes, allows the PCE to map LSPs to all available protection routes versus a single best protection route.
o Most of the benefits stated in the stateful PCE applicability draft [I-D.ietf-pce-stateful-pce-app-04] apply equally to protection paths.
This document uses the following terms defined in [RFC5440] PCC PCE, PCEP Peer.
This document uses the following terms defined in [RFC8231] Stateful PCE, Delegation, Delegation Timeout Interval, LSP State Report, LSP Update Request.
The message formats in this document are specified using Routing Backus-Naur Format (RBNF) encoding as specified in RFC5511.
Local protection refers to the ability to locally route around failure of an LSP. Two types of local protection are possible:
(1) 1:1 protection - the protection path protects a single LSP.
(2) N:1 protection - the protection path protects multiple LSPs traversing the protected resource.
It is assumed that the PCE knows what resources require protection through mechanisms outside the scope of this document. In a PCE controlled deployment, support of 1:1 protection has limited applicability, and can be achieved as a degenerate case of 1:N protection. For this reason, local protection will be discussed only for the N:1 case.
Local protection requires the setup of a bypass at the PLR. This bypass can be PCC-initiated and delegated, or PCE-initiated. In either case, the PLR MUST maintain a PCEP session to the PCE. A bypass identifier (the name of the bypass) is required for disambiguation as multiple bypasses are possible at the PLR. There two types Bypass LSPs mappings:
(1) Independent Bypass LSP Mapping: In this case Bypass LSP mapping is handled by a local policy on PCC and the PCC reports all mappings to the PCE. In other words, bypass LSP(s) are mapped to any protected LSP(s) that satisfy PCC local policy.
(2) Dependent Bypass LSP mapping: Mapping of LSPs to bypass is done through a new TLV, the LOCALLY-PROTECTED-LSPS TLV in the LSP Update message from PCE to PLR. See section Section 4.3. When an LSP requiring protection is set up through the PLR, the PLR checks if it has a mapping to a bypass and only provides protection if such a mapping exists. The status of bypasses and what LSPs are protected by them is communicated to the PCE via LSP Status Report messages.
When provisioning a PCC, the PCE can influence primary to bypass LSP association of the PCC using the preference TLV. Bypass LSPs with a higher preference are used first during primary LSP association. Bypass LSPs with identical preferences are used for primary association according to local PCC selection.
The format of the IPv4 Preference TLV is shown in the following figure:
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 2
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type=[TBD] | Length=8 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MUST be zero | Preference |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 1: IPv4 Preference TLV format
The type of the TLV is [TBD] and it has a fixed length of 8 octets. The value contains the following fields:
Preference (8 bits): The value indicates the bypass LSP preference during the primary LSP selection process of the PCC. A lower preference value is preferred to a higher value with a default value of 255. A value of 0 would indicate that the bypass is not to be selected for any primary LSP associations.
If the Preference TLV is included, then the LSPA object MUST also carry the SYMBOLIC-PATH-NAME TLV as one of the optional TLVs. Failure to include the mandatory SYMBOLIC-PATH-NAME TLV MUST trigger PCErr of type 6 (Mandatory Object missing) and value TBD (SYMBOLIC-PATH-NAME TLV missing for bypass LSP).
The facility backup method creates a bypass tunnel to protect a potential failure point. The bypass tunnel protects a set of LSPs with similar backup constraints [RFC4090].
A PCC can delegate a bypass tunnel to PCE control or a PCE can provision the bypass tunnel via a PCC. The procedures for bypass instantiation rely on the extensions defined in [RFC8281] and will be detailed in a future version of this document.
A subscription multiplier can be used to influence the local PCC admission control during primary LSP association. This allows for under subscription or oversubscription policy to be applied to the bandwidth attribute of the bypass LSP.
The Bypass TLV carries information about the bypass tunnel. It is included in the LSPA Object in LSP State Report and LSP Update Request messages.
The format of the IPv4 Bypass TLV is shown in the following figure:
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 2
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type=[TBD] | Length=8 |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MUST be zero | Flags |I|N|
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Bypass IPv4 Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Subscription Multiplier |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 2: IPv4 Bypass TLV format
The type of the TLV is [TBD] and it has a fixed length of 8 octets. The value contains the following fields:
Flags (16 bit)
N (Node Protection - 1 bit): The N flag indicates whether the Bypass is used for node-protection. If the N flag is set to 1, the Bypass is used for node-protection. If the N flag is 0, the Bypass is used for link-protection.
I (Local Protection In Use - 1 bit): The I Flag indicates that local repair mechanism is in use.
Bypass IPv4 address: The Bypass IPv4 Address is the next-hop address of the protected link in the paths of the protected LSPs.
Subscription Multiplier (32 bits): An optional multiplier represented as a floating point number. The value may be used to influence CAC during primary LSP association. For example, a bypass may reserved 50M but the PCC may want to admit up to (multiplier * reserved bandwidth) to the bypass LSP.
If the Bypass TLV is included, then the LSPA object MUST also carry the SYMBOLIC-PATH-NAME TLV as one of the optional TLVs. Failure to include the mandatory SYMBOLIC-PATH-NAME TLV MUST trigger PCErr of type 6 (Mandatory Object missing) and value TBD (SYMBOLIC-PATH-NAME TLV missing for bypass LSP)
The IPV4-LOCALLY-PROTECTED-LSPS TLV in the LSPA Object contains a list of LSPs protected by the bypass tunnel.
The format of the Locally protected LSPs TLV is shown in the following figure:
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 2
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Type=[TBD] | Length (variable) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv4 tunnel end point address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags |R| Tunnel ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Extended Tunnel ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv4 Tunnel Sender Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MUST be zero | LSP ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
// .... //
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv4 tunnel end point address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Flags |R| Tunnel ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| Extended Tunnel ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| IPv4 Tunnel Sender Address |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| MUST be zero | LSP ID |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
Figure 3: IPv4 Locally protected LSPs TLV format
The type of the TLV is [TBD] and it is of variable length.The value contains one or more LSP descriptors including the following fields filled per [RFC3209]
IPv4 Tunnel end point address: As defined in [RFC3209], Section 4.6.1.1
Flags (16 bit)
R(Remove - 1 bit): The R flag indicates that the LSP has been removed from the list of LSPs protected by the bypass tunnel.
Tunnel ID: As defined in [RFC3209], Section 4.6.1.1
Extended Tunnel ID: As defined in [RFC3209], Section 4.6.2.1
IPv4 Tunnel Sender address: As defined in [RFC3209], Section 4.6.2.1
LSP ID: As defined in RFC 3209
This document defines new Error-Type and Error-Value for the following new error conditions:
Error-Type Meaning 6 Mandatory Object missing Error-value=TBD: SYMBOLIC-PATH-NAME TLV missing for a path where the S-bit is set in the LSPA object. Error-value=TBD: SYMBOLIC-PATH-NAME TLV missing for a bypass path.
This document defines the following new PCEP TLVs:
| Value # | Meaning | Reference |
|---|---|---|
| ??? | Bypass | This Document |
| ??? | Weight | This Document |
| ??? | LOCALLY-PROTECTED-LSPS | This Document |
The same security considerations apply at the PLR as those describe for the head end in PCE Initiated LSPs.
The following people have substantially contributed to the editing of this document:
Harish Sitaraman, Juniper Networks, hsitaraman@juniper.net
Vishnu Pavan Beeram, Juniper Networks, vbeeram@juniper.net
Chandrasekar Ramachandran, Juniper Networks, csekar@juniper.net
Ambrose Kwong, Juniper Networks, akwong@juniper.net
Phil Bedard, bedard.phil@gmail.com
This becomes an Appendix.