PCEP Extensions for Stateful PCE
draft-ietf-pce-stateful-pce-07
The information below is for an old version of the document.
Document | Type |
This is an older version of an Internet-Draft that was ultimately published as RFC 8231.
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Authors | Edward Crabbe , Jan Medved , Ina Minei , Robert Varga | ||
Last updated | 2013-10-08 | ||
Replaces | draft-crabbe-pce-stateful-pce, draft-crabbe-pce-stateful-pce-mpls-te | ||
RFC stream | Internet Engineering Task Force (IETF) | ||
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GENART Last Call review
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by Joel Halpern
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Additional resources | Mailing list discussion | ||
Stream | WG state | WG Document | |
Document shepherd | (None) | ||
IESG | IESG state | Became RFC 8231 (Proposed Standard) | |
Consensus boilerplate | Unknown | ||
Telechat date | (None) | ||
Responsible AD | (None) | ||
Send notices to | (None) |
draft-ietf-pce-stateful-pce-07
#x27;s PCEP session with a PCE terminates unexpectedly, the PCC MUST wait the time interval specified in Redelegation Timeout Interval before revoking LSP delegations to that PCE and attempting to redelegate LSPs to an alternate PCE. If a PCEP session with the original PCE can be reestablished before the Redelegation Timeout Interval timer expires, LSP delegations to the PCE remain intact. Likewise, when a PCC's PCEP session with a PCE terminates unexpectedly, the PCC MUST wait for the State Timeout Interval before flushing any LSP state associated with that PCE. Note that the State Timeout Interval timer may expire before the PCC has redelegated the LSPs to another PCE, for example if a PCC is not connected to any active stateful PCE or if no connected active stateful PCE accepts the delegation. In this case, the PCC SHALL flush any LSP state set by the PCE upon expiration of the State Timeout Interval and revert to operator-defined default parameters. This operation SHOULD be done in a make-before-break fashion. The State Timeout Interval SHOULD be greater than or equal to the Crabbe, et al. Expires April 11, 2014 [Page 17] Internet-Draft PCEP Extensions for Stateful PCE October 2013 Redelegation Timeout Interval and MAY be set to infinity (meaning that until the PCC specifically takes action to change the parameters set by the PCE, they will remain intact). 5.5.3. Returning a Delegation A PCE that no longer wishes to update an LSP's parameters SHOULD return the LSP delegation back to the PCC by sending an empty LSP Update Request which has the Delegate flag set to 0. Note that in order to keep a delegation, the PCE MUST set the Delegate flag to 1 on each LSP Update Request sent to the PCC. +-+-+ +-+-+ |PCC| |PCE| +-+-+ +-+-+ | | |---PCRpt, Delegate=1--->| LSP delegated | . | | . | | . | |<--PCUpd, Delegate=0----| Delegation returned | | |---PCRpt, Delegate=0--->| No delegation for LSP | | Figure 6: Returning a Delegation If a PCC cannot delegate an LSP to a PCE (for example, if a PCC is not connected to any active stateful PCE or if no connected active stateful PCE accepts the delegation), the LSP delegation on the PCC will time out within a configurable Redelegation Timeout Interval and the PCC MUST flush any LSP state set by a PCE at the expiration of the State Timeout Interval. 5.5.4. Redundant Stateful PCEs In a redundant configuration where one PCE is backing up another PCE, the backup PCE may have only a subset of the LSPs in the network delegated to it. The backup PCE does not update any LSPs that are not delegated to it. In order to allow the backup to operate in a hot-standby mode and avoid the need for state synchronization in case the primary fails, the backup receives all LSP State Reports from a PCC. When the primary PCE for a given LSP set fails, after expiry of the Redelegation Timeout Interval, the PCC SHOULD delegate to the redundant PCE all LSPs that had been previously delegated to the failed PCE. Assuming that the State Timeout Interval had been configured to be larger than the Redelegation Timeout Interval (as recommended), this delegation change will not cause any changes to Crabbe, et al. Expires April 11, 2014 [Page 18] Internet-Draft PCEP Extensions for Stateful PCE October 2013 the LSP parameters. 5.5.5. Redelegation on PCE Failure On failure, the goal is to: 1) avoid any traffic loss on the LSPs that were updated by the PCE that crashed 2) minimize the churn in the network in terms of ownership of the LSPs, 3) not leave any "orphan" (undelegated) LSPs and 4) be able to control when the state that was set by the PCE can be changed or purged. The values chosen for the Redelegation Timeout and State Timeout values affect the ability to accomplish these goals. This section summarizes the behaviour with regards to LSP delegation and LSP state on a PCE failure. If the PCE crashes but recovers within the Redelegation Timeout, both the delegation state and the LSP state are kept intact. If the PCE crashes but does not recover within the Redelegation Timeout, the delegation state is returned to the PCC. If the PCC can redelegate the LSPs to another PCE, and that PCE accepts the delegations, there will be no change in LSP state. If the PCC cannot redelegate the LSPs to another PCE, then upon expiration of the State Timeout Interval, the state set by the PCE is flushed, which may cause change in the LSP state. Note that an operator may choose to use an infinite State Timeout Interval if he wishes to maintain the PCE state indefinetely. Note also that flushing the state should be implemented using make-before-break to avoid traffic loss. If there is a standby PCE, the Redelegation Timeout may be set to 0 through policy on the PCC, causing the LSPs to be redelegated immediately to the PCC, which can delegate them immediately to the standby PCE. Assuming the State Timeout Interval is larger than the Redelegation Timeout, the LSP state will be kept intact. 5.6. LSP Operations Crabbe, et al. Expires April 11, 2014 [Page 19] Internet-Draft PCEP Extensions for Stateful PCE October 2013 5.6.1. Passive Stateful PCE Path Computation Request/Response +-+-+ +-+-+ |PCC| |PCE| +-+-+ +-+-+ | | 1) Path computation |----- PCReq message --->| request sent to | |2) Path computation PCE | | request received, | | path computed | | |<---- PCRep message ----|3) Computed paths | (Positive reply) | sent to the PCC | (Negative reply) | 4) LSP Status change| | event | | | | 5) LSP Status Report|----- PCRpt message --->| sent to all | . | stateful PCEs | . | | . | 6) Repeat for each |----- PCRpt message --->| LSP status change| | | | Figure 7: Passive Stateful PCE Path Computation Request/Response Once a PCC has successfully established a PCEP session with a passive stateful PCE and the PCC's LSP state is synchronized with the PCE (i.e. the PCE knows about all PCC's existing LSPs), if an event is triggered that requires the computation of a set of paths, the PCC sends a path computation request to the PCE ([RFC5440], Section 4.2.3). Upon receiving a path computation request from a PCC, the PCE triggers a path computation and returns either a positive or a negative reply to the PCC ([RFC5440], Section 4.2.4). Upon receiving a positive path computation reply, the PCC receives a set of computed paths and starts to setup the LSPs. For each LSP, it sends an LSP State Report carried on a PCRpt message to the PCE, indicating that the LSP's status is 'Pending'. Once an LSP is up, the PCC sends an LSP State Report carried on a PCRpt message to the PCE, indicating that the LSP's status is 'Up'. If the LSP could not be set up, the PCC sends an LSP State Report indicating that the LSP is "Down' and stating the cause of the failure. Note that due to timing constraints, the LSP status may Crabbe, et al. Expires April 11, 2014 [Page 20] Internet-Draft PCEP Extensions for Stateful PCE October 2013 change from 'Pending' to 'Up' (or 'Down') before the PCC has had a chance to send an LSP State Report indicating that the status is 'Pending'. In such cases, the PCC may choose to only send the PCRpt indicating the latest status ('Up' or 'Down'). Upon receiving a negative reply from a PCE, a PCC may decide to resend a modified request or take any other appropriate action. For each requested LSP, it also sends an LSP State Report carried on a PCRpt message to the PCE, indicating that the LSP's status is 'Down'. There is no direct correlation between PCRep and PCRpt messages. For a given LSP, multiple LSP State Reports will follow a single PCRep message, as a PCC notifies a PCE of the LSP's state changes. A PCC sends each LSP State Report to each stateful PCE that is connected to the PCC. Note that a single PCRpt message MAY contain multiple LSP State Reports. The passive stateful PCE is the model for stateful PCEs is described in [RFC4655], Section 6.8. 5.6.2. Active Stateful PCE LSP Update +-+-+ +-+-+ |PCC| |PCE| +-+-+ +-+-+ | | 1) LSP State |-- PCRpt, Delegate=1 -->| Synchronization | . | or add new LSP | . |2) PCE decides to | . | update the LSP | | |<---- PCUpd message ----|3) PCUpd message sent | | to PCC | | | | 4) LSP Status Report|---- PCRpt message ---->| sent(->Pending) | . | | . | | . | 5) LSP Status Report|---- PCRpt message ---->| sent (->Up|Down) | | | | Figure 8: Active Stateful PCE Crabbe, et al. Expires April 11, 2014 [Page 21] Internet-Draft PCEP Extensions for Stateful PCE October 2013 Once a PCC has successfully established a PCEP session with an active stateful PCE, the PCC's LSP state is synchronized with the PCE (i.e. the PCE knows about all PCC's existing LSPs) and LSPs have been delegated to the PCE, the PCE can modify LSP parameters of delegated LSPs. A PCE sends an LSP Update Request carried on a PCUpd message to the PCC. The LSP Update Request contains a variety of objects that specify the set of constraints and attributes for the LSP's path. Each LSP Update Request has a unique identifier, the SRP-ID-number, carried in the SRP (Stateful PCE Request Parameters) Object described in Section 7.2. The SRP-ID-number is used to correlate errors and state reports to LSP Update Requests. A single PCUpd message MAY contain multiple LSP Update Requests. Upon receiving a PCUpd message the PCC starts to setup LSPs specified in LSP Update Requests carried in the message. For each LSP, it sends an LSP State Report carried on a PCRpt message to the PCE, indicating that the LSP's status is 'Pending'. If the PCC decides that the LSP parameters proposed in the PCUpd message are unacceptable, it MUST report this error by including the LSP-ERROR- CODE TLV (Section 7.3.3) with LSP error-value="Unacceptable parameters" in the LSP object in the PCRpt message to the PCE. Based on local policy, it MAY react further to this error by revoking the delegation. If the PCC receives a PCUpd message for an LSP object identified with a PLSP-ID that does not exist on the PCC, it MUST generate a PCErr with error-type 19 (Invalid Operation), error-value 3, (Attempted LSP Update Request for an LSP identified by an unknown PSP-ID) (see Section 8.4). Once an LSP is up, the PCC sends an LSP State Report (PCRpt message) to the PCE, indicating that the LSP's status is 'Up'. If the LSP could not be set up, the PCC sends an LSP State Report indicating that the LSP is 'Down' and stating the cause of the failure. A PCC may choose to compress LSP State Reports to only reflect the most up to date state, as discussed in the previous section. A PCC sends each LSP State Report to each stateful PCE that is connected to the PCC. PCErr and PCRpt messages triggered as a result of a PCUpd message MUST include the SRP-ID-number from the PCUpd. This provides correlation of requests and errors and acknowledgement of state processing. The PCC may choose to compress state when processing PCUpd. In this case, receipt of a higher SRP-ID-number implicitly acknowledges processing all the earlier updates for the specific LSP. A PCC MUST NOT send to any PCE a Path Computation Request for a Crabbe, et al. Expires April 11, 2014 [Page 22] Internet-Draft PCEP Extensions for Stateful PCE October 2013 delegated LSP. Should the PCC decide it wants to issue a Path Computation Request on a delegated LSP, it MUST perform Delegation Revocation procedure first. 5.7. LSP Protection LSP protection and interaction with stateful PCE, as well as the extensions necessary to implement this functionality will be discussed in a separate draft. 5.8. Transport A permanent PCEP session MUST be established between a stateful PCE and the PCC. In the case of session failure, session reestablishment MUST be re-attempted per the procedures defined in [RFC5440]. 6. PCEP Messages As defined in [RFC5440], 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. 6.1. The PCRpt Message A Path Computation LSP State Report message (also referred to as PCRpt message) is a PCEP message sent by a PCC to a PCE to report the current state of an LSP. A PCRpt message can carry more than one LSP State Reports. A PCC can send an LSP State Report either in response to an LSP Update Request from a PCE, or asynchronously when the state of an LSP changes. The Message-Type field of the PCEP common header for the PCRpt message is set to [TBD]. The format of the PCRpt message is as follows: Crabbe, et al. Expires April 11, 2014 [Page 23] Internet-Draft PCEP Extensions for Stateful PCE October 2013 <PCRpt Message> ::= <Common Header> <state-report-list> Where: <state-report-list> ::= <state-report>[<state-report-list>] <state-report> ::= [<SRP>] <LSP> <path> Where: <path>::= <ERO><attribute-list>[<RRO>] Where: <attribute-list> is defined in [RFC5440] and extended by PCEP extensions. The SRP object (see Section 7.2) is optional. If the PCRpt message is not in response to a PCupd message, the SRP object MAY be omitted. When the PCC does not include the SRP object, the PCE treats this as an SRP object with an SRP-ID-number equal to the reserved value 0x00000000. The reserved value 0x00000000 indicates that the state reported is not as a result of processing a PCUpd message. If the PCRpt message is in response to a PCUpd message, the SRP object SHOULD be included and the value of the SRP-ID-number in the SRP Object MUST be the same as that sent in the PCUpd message that triggered the state that is reported. If the PCC compressed several PCUpd messages for the same LSP by only processing the latest one, then it should use the SRP-ID-number of that request. No state compression is allowed for state reporting, e.g. PCRpt messages MUST NOT be pruned from the PCC's egress queue even if subsequent operations on the same LSP have been completed before the PCRpt message has been sent to the TCP stack. The PCC MUST explicitly report state changes (including removal) for paths it manages. The LSP object (see Section 7.3) is mandatory, and it MUST be included in each LSP State Report on the PCRpt message. If the LSP object is missing, the receiving PCE MUST send a PCErr message with Error-type=6 (Mandatory Object missing) and Error-value=[TBD] (LSP object missing). If the LSP transitioned to non-operational state, the PCC SHOULD include the LSP-ERROR-TLV (Section 7.3.3) with the relevant LSP Error Code to report the error to the PCE. The RRO SHOULD be included by the PCC when the path is up, but MAY be omitted if the path is down due to a signaling error or another failure. Crabbe, et al. Expires April 11, 2014 [Page 24] Internet-Draft PCEP Extensions for Stateful PCE October 2013 A PCE may choose to implement a limit on the resources a single PCC can occupy. If a PCRpt is received that causes the PCE to exceed this limit, it MUST send a PCErr message with error-type 19 (invalid operation) and error-value 4 (indicating resource limit exceeded) in response to the PCRpt message triggering this condition and MAY terminate the session. 6.2. The PCUpd Message A Path Computation LSP Update Request message (also referred to as PCUpd message) is a PCEP message sent by a PCE to a PCC to update attributes of an LSP. A PCUpd message can carry more than one LSP Update Request. The Message-Type field of the PCEP common header for the PCUpd message is set to [TBD]. The format of a PCUpd message is as follows: <PCUpd Message> ::= <Common Header> <udpate-request-list> Where: <update-request-list> ::= <update-request>[<update-request-list>] <update-request> ::= <SRP> <LSP> <path> Where: <path>::= <ERO><attribute-list> Where: <attribute-list> is defined in [RFC5440] and extended by PCEP extensions. There are three mandatory objects that MUST be included within each LSP Update Request in the PCUpd message: the SRP Object (see Section 7.2), the LSP object (see Section 7.3) and the ERO object (as defined in [RFC5440]. If the SRP object is missing, the receiving PCC MUST send a PCErr message with Error-type=6 (Mandatory Object missing) and Error-value=10 (SRP object missing). If the LSP object is missing, the receiving PCC MUST send a PCErr message with Error- type=6 (Mandatory Object missing) and Error-value=8 (LSP object missing). If the ERO object is missing, the receiving PCC MUST send a PCErr message with Error-type=6 (Mandatory Object missing) and Error-value=9(ERO object missing). A PCC only acts on an LSP Update Request if permitted by the local policy configured by the network manager. Each LSP Update Request that the PCC acts on results in an LSP setup operation. An LSP Update Request MUST contain all LSP parameters that a PCE wishes to Crabbe, et al. Expires April 11, 2014 [Page 25] Internet-Draft PCEP Extensions for Stateful PCE October 2013 be set for the LSP. A PCC MAY set missing parameters from locally configured defaults. If the LSP specified in the Update Request is already up, it will be re-signaled. The PCC SHOULD minimize the traffic interruption, and MAY use the make-before-break procedures described in [RFC3209] in order to achieve this goal. If the make-before-break procedures are used, two paths will briefly co-exist. The PCC MUST send separate PCRpt messages for each, identified by the LSP-IDENTIFIERS TLV. When the old path is torn down after the head end switches over the traffic, this event MUST be reported by sending a PCRpt message with the LSP- IDENTIFIERS-TLV of the old path and the R bit set. The SRP-ID-number that the PCE associates with this PCRpt MUST be 0x00000000. Thus, a make-before-break operation will typically result in at least two PCRpt messages, one for the new path and one for the removal of the old path (more messages may be possible if intermediate states are reported). A PCC MUST respond with an LSP State Report to each LSP Update Request it processed to indicate the resulting state of the LSP in the network (even if this processing did not result in changing the state of the LSP). The SRP-ID-number included in the PCRpt MUST match that in the PCUpd. A PCC MAY respond with multiple LSP State Reports to report LSP setup progress of a single LSP. In that case, the SRP-ID-number MUST be included for the first message, for subsequent messages the reserved value 0x00000000 SHOULD be used. Note that a PCC MUST process all LSP Update Requests - for example, an LSP Update Request is sent when a PCE returns delegation or puts an LSP into non-operational state. The protocol relies on TCP for message-level flow control. If the rate of PCUpd messages sent to a PCC for the same target LSP exceeds the rate at which the PCC can signal LSPs into the network, the PCC MAY perform state compression on its ingress queue. The compression algorithm is based on the fact that each PCUpd request contains the complete LSP state the PCE wishes to be set and works as follows: when the PCC starts processing a PCUpd message at the head of its ingress queue, it may search the queue forward for more recent PCUpd messages pertaining that particular LSP, prune all but the latest one from the queue and process only the last one as that request contains the most up-to-date desired state for the LSP. The PCC MUST NOT send PCRpt nor PCErr messages for requests which were pruned from the queue in this way. This compression step may be performed only while the LSP is not being signaled, e.g. if two PCUpd arrive for the same LSP in quick succession and the PCC started the signaling of the changes relevant to the first PCUpd, then it MUST wait until the signaling finishes (and report the new state via a Crabbe, et al. Expires April 11, 2014 [Page 26] Internet-Draft PCEP Extensions for Stateful PCE October 2013 PCRpt) before attempting to apply the changes indicated in the second PCUpd. Note also that it is up to the PCE to handle inter-LSP dependencies; for example, if ordering of LSP set-ups is required, the PCE has to wait for an LSP State Report for a previous LSP before starting the update of the next LSP. If the PCUpd cannot be satisfied (for example due to unsupported object or TLV), the PCC MUST respond with a PCErr message indicating the failure (see Section 7.3.3). 6.3. The PCErr Message If the stateful PCE capability has been advertised on the PCEP session, the PCErr message MAY include the SRP object. If the error reported is the result of an LSP update request, then the SRP-ID- number MUST be the one from the PCUpd that triggered the error. If the error is unsolicited, the SRP object MAY be omitted. This is equivalent to including an SRP object with SRP-ID-number equal to the reserved value 0x00000000. The format of a PCErr message from [RFC5440] is extended as follows: <PCErr Message> ::= <Common Header> ( <error-obj-list> [<Open>] ) | <error> [<error-list>] <error-obj-list>::=<PCEP-ERROR>[<error-obj-list>] <error>::=[<request-id-list> | <stateful-request-id-list>] <<<< new <error-obj-list> <request-id-list>::=<RP>[<request-id-list>] <stateful-request-id-list>::=<SRP>[<stateful-request-id-list>] <<< new <error-list>::=<error>[<error-list>] 7. Object Formats The PCEP objects defined in this document are compliant with the PCEP object format defined in [RFC5440]. The P flag and the I flag of the PCEP objects defined in this document MUST always be set to 0 on transmission and MUST be ignored on receipt since these flags are exclusively related to path computation requests. Crabbe, et al. Expires April 11, 2014 [Page 27] Internet-Draft PCEP Extensions for Stateful PCE October 2013 7.1. OPEN Object This document defines two new optional TLVs for use in the OPEN Object. 7.1.1. Stateful PCE Capability TLV The STATEFUL-PCE-CAPABILITY TLV is an optional TLV for use in the OPEN Object for stateful PCE capability advertisement. Its format 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type=[TBD] | Length=4 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Flags |U| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 9: STATEFUL-PCE-CAPABILITY TLV format The type of the TLV is [TBD] and it has a fixed length of 4 octets. The value comprises a single field - Flags (32 bits): U (LSP-UPDATE-CAPABILITY - 1 bit): if set to 1 by a PCC, the U Flag indicates that the PCC allows modification of LSP parameters; if set to 1 by a PCE, the U Flag indicates that the PCE is capable of updating LSP parameters. The LSP-UPDATE-CAPABILITY Flag must be advertised by both a PCC and a PCE for PCUpd messages to be allowed on a PCEP session. Unassigned bits are considered reserved. They MUST be set to 0 on transmission and MUST be ignored on receipt. Advertisement of the stateful PCE capability implies support of LSPs that are signaled via RSVP, as well as the objects, TLVs and procedures defined in this document. 7.2. SRP Object The SRP (Stateful PCE Request Parameters) object MUST be carried within PCUpd messages and MAY be carried within PCRpt, PCNtf and PCErr messages. The SRP object is used to correlate between update requests sent by the PCE and the error reports and state reports sent by the PCC. SRP Object-Class is [TBD]. Crabbe, et al. Expires April 11, 2014 [Page 28] Internet-Draft PCEP Extensions for Stateful PCE October 2013 SRP Object-Type is 1. The format of the SRP object body is shown in Figure 10: 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Flags | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | SRP-ID-number | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | // Optional TLVs // | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 10: The SRP Object format The SRP object body has a variable length and may contain additional TLVs. The SYMBOLIC-PATH-NAME TLV MAY be included as one of the optional TLVs. Flags (32 bits): None defined yet. SRP-ID-number (32 bits): The SRP-ID-number value in the scope of the current PCEP session uniquely identify the operation that the PCE has requested the PCC to perform on a given LSP. The SRP-ID-number is incremented each time a new request is sent to the PCC, and may wrap around. The values 0x00000000 and 0xFFFFFFFF are reserved. Every request to update an LSP receives a new SRP-ID-number. This number is unique per PCEP session and is incremented each time an operation is requested from the PCE. Thus, for a given LSP there may be more than one SRP-id-number unacknowledged at a given time. The value of the SRP-ID-number is echoed back by the PCC in PCErr and PCRpt messages to allow for correlation between requests made by the PCE and errors or state reports generated by the PCC. If the error or report were not as a result of a PCE operation (for example in the case of a link down event), the reserved value of 0x00000000 is used for the SRP-ID-number. The absence of the SRP object is equivalent to an SRP object with the reserved value of 0x00000000. An SRP-ID- number is considered unacknowledged and cannot be reused until a PCErr or PCRpt arrives with an SRP-ID-number equal or higher for the same LSP. A PCRpt with state "Pending" is not considered as an acknowledgement. Crabbe, et al. Expires April 11, 2014 [Page 29] Internet-Draft PCEP Extensions for Stateful PCE October 2013 7.3. LSP Object The LSP object MUST be present within PCRpt and PCUpd messages. The LSP object contains a set of fields used to specify the target LSP, the operation to be performed on the LSP, and LSP Delegation. It also contains a flag indicating to a PCE that the LSP state synchronization is in progress. This document focuses on LSPs that are signaled with RSVP, many of the TLVs used with the LSP object mirror RSVP state. LSP Object-Class is [TBD]. LSP Object-Type is 1. The format of the LSP object body is shown in Figure 11: 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | PLSP-ID | Flags | O|A|R|S|D| +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ // TLVs // | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 11: The LSP Object format PLSP-ID (20 bits): A PCEP-specific identifier for the LSP. A PCC creates a unique PLSP-ID for each LSP that is constant for the life time of a PCEP session. The mapping of the Symbolic Path Name to PLSP-ID is communicated to the PCE by sending a PCRpt message containing the SYMBOLIC-PATH-NAME TLV. All subsequent PCEP messages then address the LSP by the PLSP-ID. The values of 0 and 0xFFFFF are reserved. Note that the PLSP-ID is a value that is constant for the life time of the PCEP session, during which time for an RSVP-signaled LSP there might be a different RSVP identifiers (LSP-id, tunnel-id) allocated it. Flags (12 bits): D (Delegate - 1 bit): on a PCRpt message, the D Flag set to 1 indicates that the PCC is delegating the LSP to the PCE. On a PCUpd message, the D flag set to 1 indicates that the PCE is confirming the LSP Delegation. To keep an LSP delegated to the PCE, the PCC must set the D flag to 1 on each PCRpt message for the duration of the delegation - the first PCRpt with the D flag set to 0 revokes the delegation. To keep the delegation, the PCE must set the D flag to 1 on each PCUpd message for the duration of Crabbe, et al. Expires April 11, 2014 [Page 30] Internet-Draft PCEP Extensions for Stateful PCE October 2013 the delegation - the first PCUpd with the D flag set to 0 returns the delegation. S (SYNC - 1 bit): the S Flag MUST be set to 1 on each PCRpt sent from a PCC during State Synchronization. The S Flag MUST be set to 0 in other PCRpt messages sent from the PCC. R(Remove - 1 bit): On PCRpt messages the R Flag indicates that the LSP has been removed from the PCC and the PCE SHOULD remove all state from its database. Upon receiving an LSP State Report with the R Flag set to 1 for an RSVP-signaled LSP, the PCE SHOULD remove all state for the path identified by the LSP Identifiers TLV from its database. When the all-zeros LSP-IDENTIFIERS-TLV is used, the PCE SHOULD remove all state for the PLSP-ID from its database. A(Administrative - 1 bit): On PCRpt messages, the A Flag indicates the PCC's target operational status for this LSP. On PCUpd messages, the A Flag indicates the LSP status that the PCE desires for this LSP. In both cases, a value of '1' means that the desired operational state is active, and a value of '0' means that the desired operational state is inactive. A PCC ignores the A flag on a PCUpd message unless the operator's policy allows the PCE to control the corresponding LSP's administrative state. O(Operational - 3 bits): On PCRpt messages, the O Field represents the operational status of the LSP. The following values are defined: 0 - DOWN: not active. 1 - UP: signalled. 2 - ACTIVE: up and carrying traffic. 3 - GOING-DOWN: LSP is being torn down, resources are being released. 4 - GOING-UP: LSP is being signalled. 5-7 - Reserved: these values are reserved for future use. Unassigned bits are considered reserved. They MUST be set to 0 on transmission and MUST be ignored on receipt. TLVs that may be included in the LSP Object are described in the following sections. Crabbe, et al. Expires April 11, 2014 [Page 31] Internet-Draft PCEP Extensions for Stateful PCE October 2013 7.3.1. LSP Identifiers TLVs The LSP Identifiers TLV MUST be included in the LSP object in PCRpt messages for RSVP-signaled LSPs. If the TLV is missing, the PCE will generate an error with error-type 6 (mandatory object missing) and error-value 11 (LSP-IDENTIFIERS TLV missing) and close the session. The LSP Identifiers TLV MAY be included in the LSP object in PCUpd messages for RSVP-signaled LSPs. The special value of all zeros for this TLV is used to refer to all paths pertaining to a particular PLSP-ID. There are two LSP Identifiers TLVs, one for IPv4 and one for IPv6. It is the responsibility of the PCC to send to the PCE the identifiers for each RSVP incarnation of the tunnel. For exmple, in a make-before-break scenario, the PCC MUST send a separate PCRpt for the old and for the reoptimized paths, and explicitly report removal of any of these paths using the R bit in the LSP object. The format of the IPV4-LSP-IDENTIFIERS 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type=[TBD] | Length=12 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | IPv4 Tunnel Sender Address | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | LSP ID | Tunnel ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Extended Tunnel ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | IPv4 Tunnel Endpoint Address | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 12: IPV4-LSP-IDENTIFIERS TLV format The type of the TLV is [TBD] and it has a fixed length of 12 octets. The value contains the following fields: IPv4 Tunnel Sender Address: contains the sender node's IPv4 address, as defined in [RFC3209], Section 4.6.2.1 for the LSP_TUNNEL_IPv4 Sender Template Object. LSP ID: contains the 16-bit 'LSP ID' identifier defined in [RFC3209], Section 4.6.2.1 for the LSP_TUNNEL_IPv4 Sender Template Object. Crabbe, et al. Expires April 11, 2014 [Page 32] Internet-Draft PCEP Extensions for Stateful PCE October 2013 Tunnel ID: contains the 16-bit 'Tunnel ID' identifier defined in [RFC3209], Section 4.6.1.1 for the LSP_TUNNEL_IPv4 Session Object. Tunnel ID remains constant over the life time of a tunnel. Extended Tunnel ID: contains the 32-bit 'Extended Tunnel ID' identifier defined in [RFC3209], Section 4.6.1.1 for the LSP_TUNNEL_IPv4 Session Object. IPv4 Tunnel Endpoint Address: contains the egress node's IPv4 address, as defined in [RFC3209], Section 4.6.1.1 for the LSP_TUNNEL_IPv4 Sender Template Object. The format of the IPV6-LSP-IDENTIFIERS TLV is shown in l 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type=[TBD] | Length=36 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + + | IPv6 tunnel sender address | + (16 octets) + | | + + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | LSP ID | Tunnel ID | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + + | Extended Tunnel ID | + (16 octets) + | | + + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + + | IPv6 tunnel endpoint address | + (16 octets) + | | + + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 13: IPV6-LSP-IDENTIFIERS TLV format Crabbe, et al. Expires April 11, 2014 [Page 33] Internet-Draft PCEP Extensions for Stateful PCE October 2013 The type of the TLV is [TBD] and it has a fixed length of 36 octets. The value contains the following fields: IPv6 Tunnel Sender Address: contains the sender node's IPv6 address, as defined in [RFC3209], Section 4.6.2.2 for the LSP_TUNNEL_IPv6 Sender Template Object. LSP ID: contains the 16-bit 'LSP ID' identifier defined in [RFC3209], Section 4.6.2.2 for the LSP_TUNNEL_IPv6 Sender Template Object. Tunnel ID: contains the 16-bit 'Tunnel ID' identifier defined in [RFC3209], Section 4.6.1.2 for the LSP_TUNNEL_IPv6 Session Object. Tunnel ID remains constant over the life time of a tunnel. However, when Global Path Protection or Global Default Restoration is used, both the primary and secondary LSPs have their own Tunnel IDs. A PCC will report a change in Tunnel ID when traffic switches over from primary LSP to secondary LSP (or vice versa). Extended Tunnel ID: contains the 128-bit 'Extended Tunnel ID' identifier defined in [RFC3209], Section 4.6.1.2 for the LSP_TUNNEL_IPv6 Session Object. IPv6 Tunnel Endpoint Address: contains the egress node's IPv6 address, as defined in [RFC3209], Section 4.6.1.2 for the LSP_TUNNEL_IPv6 Session Object. 7.3.2. Symbolic Path Name TLV Each LSP (path) MUST have a symbolic name that is unique in the PCC. This symbolic path name MUST remain constant throughout a path's lifetime, which may span across multiple consecutive PCEP sessions and/or PCC restarts. The symbolic path name MAY be specified by an operator in a PCC's configuration. If the operator does not specify a unique symbolic name for a path, the PCC MUST auto-generate one. The SYMBOLIC-PATH-NAME TLV MUST be included in the LSP State Report when during a given PCEP session an LSP is first reported to a PCE. A PCC sends to a PCE the first LSP State Report either during State Synchronization, or when a new LSP is configured at the PCC. The symbolic path name MAY be included in subsequent LSP State Reports for the LSP. The SYMBOLIC-PATH-NAME TLV MAY appear as a TLV in both the LSP Object and the LSPA Object. The format of the SYMBOLIC-PATH-NAME TLV is shown in the following figure: Crabbe, et al. Expires April 11, 2014 [Page 34] Internet-Draft PCEP Extensions for Stateful PCE October 2013 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=[TBD] | Length (variable) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | // Symbolic Path Name // | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 14: SYMBOLIC-PATH-NAME TLV format The type of the TLV is [TBD] and it has a variable length, which MUST be greater than 0. 7.3.3. LSP Error Code TLV The LSP Error code TLV is an optional TLV for use in the LSP object to convey error information. When an LSP Update Request fails, an LSP State Report MUST be sent to report the current state of the LSP, and SHOULD contain the LSP-ERROR-CODE TLV indicating the reason for the failure. Similarly, when a PCRpt is sent as a result of an LSP transitioning to non-operational state, the LSP-ERROR-CODE TLV SHOULD be included to indicate the reason for the transition. The format of the LSP-ERROR-CODE 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type=[TBD] | Length=4 | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | LSP Error Code | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 15: LSP-ERROR-CODE TLV format The type of the TLV is [TBD] and it has a fixed length of 4 octets. The value contains an error code that indicates the cause of the failure. The following LSP Error Codes are defined: Crabbe, et al. Expires April 11, 2014 [Page 35] Internet-Draft PCEP Extensions for Stateful PCE October 2013 Value Meaning 1 Unknown reason 2 Limit reached for PCE-controlled LSPs 3 Too many pending LSP update requests 4 Unacceptable parameters 5 Internal error 6 LSP administratively brought down 7 LSP preempted 8 RSVP signaling error 7.3.4. RSVP Error Spec TLV The RSVP-ERROR-SPEC TLV is an optional TLV for use in the LSP object to carry RSVP error information. It includes the RSVP ERROR_SPEC or USER_ERROR_SPEC Object ([RFC2205] and [RFC5284]) which were returned to the PCC from a downstream node. If the set up of an LSP fails at a downstream node which returned an ERROR_SPEC to the PCC, the PCC SHOULD include in the PCRpt for this LSP the LSP-ERROR-CODE TLV with LSP Error Code = "RSVP signaling error" and the RSVP-ERROR-SPEC TLV with the relevant RSVP ERROR-SPEC or USER_ERROR_SPEC Object. The format of the RSVP-ERROR-SPEC 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 +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | Type=[TBD] | Length (variable) | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ | | + RSVP ERROR_SPEC or USER_ERROR_SPEC Object + | | +-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+ Figure 16: RSVP-ERROR-SPEC TLV format The type of the TLV is [TBD] and it has a variable length. The value contains the RSVP ERROR_SPEC or USER_ERROR_SPEC object, including the object header. 7.4. Optional TLVs for the LSPA Object TLVs that may be included in the LSPA Object are described in the following sections and in separate technology-specific documents. Crabbe, et al. Expires April 11, 2014 [Page 36] Internet-Draft PCEP Extensions for Stateful PCE October 2013 7.4.1. Symbolic Path Name TLV See section Section 7.3.2. 8. IANA Considerations This document requests IANA actions to allocate code points for the protocol elements defined in this document. Values shown here are suggested for use by IANA. 8.1. PCEP Messages This document defines the following new PCEP messages: Value Meaning Reference 10 Report This document 11 Update This document 8.2. PCEP Objects This document defines the following new PCEP Object-classes and Object-values: Object-Class Value Name Reference 32 LSP This document Object-Type 1 33 SRP This document Object-Type 1 8.3. LSP Object This document requests that a registry is created to manage the Flags field of the LSP object. New values are to be assigned by Standards Action [RFC5226]. Each bit should be tracked with the following qualities: o Bit number (counting from bit 0 as the most significant bit) o Capability description o Defining RFC The following values are defined in this document: Crabbe, et al. Expires April 11, 2014 [Page 37] Internet-Draft PCEP Extensions for Stateful PCE October 2013 Bit Description Reference 25-27 Operational (3 bits) This document 28 Administrative This document 29 Remove This document 30 SYNC This document 31 Delegate This document 8.4. PCEP-Error Object This document defines new Error-Type and Error-Value for the following new error conditions: Error-Type Meaning 6 Mandatory Object missing Error-value=8: LSP Object missing Error-value=9: ERO Object missing Error-value=10: SRP Object missing Error-value=11: LSP-IDENTIFIERS TLV missing 19 Invalid Operation Error-value=1: Attempted LSP Update Request for a non- delegated LSP. The PCEP-ERROR Object is followed by the LSP Object that identifies the LSP. Error-value=2: Attempted LSP Update Request if active stateful PCE capability was not advertised. Error-value=3: Attempted LSP Update Request for an LSP identified by an unknown PLSP-ID. Error-value=4: A PCE indicates to a PCC that it has exceeded the resource limit allocated for its state, and thus it cannot accept and process its LSP State Report message. 20 LSP State synchronization error. Error-value=1: A PCE indicates to a PCC that it can not process (an otherwise valid) LSP State Report. The PCEP-ERROR Object is followed by the LSP Object that identifies the LSP. Error-value=5: A PCC indicates to a PCE that it can not complete the state synchronization, 8.5. PCEP TLV Type Indicators This document defines the following new PCEP TLVs: Crabbe, et al. Expires April 11, 2014 [Page 38] Internet-Draft PCEP Extensions for Stateful PCE October 2013 Value Meaning Reference 16 STATEFUL-PCE-CAPABILITY This document 17 SYMBOLIC-PATH-NAME This document 18 IPV4-LSP-IDENTIFIERS This document 19 IPV6-LSP-IDENTIFIERS This document 20 LSP-ERROR-CODE This document 21 RSVP-ERROR-SPEC This document 8.6. STATEFUL-PCE-CAPABILITY TLV This document requests that a registry is created to manage the Flags field in the STATEFUL-PCE-CAPABILITY TLV in the OPEN object. New values are to be assigned by Standards Action [RFC5226]. Each bit should be tracked with the following qualities: o Bit number (counting from bit 0 as the most significant bit) o Capability description o Defining RFC The following values are defined in this document: Bit Description Reference 31 LSP-UPDATE-CAPABILITY This document 8.7. LSP-ERROR-CODE TLV This document requests that a registry is created to manage the value of the LSP error code field in this TLV. This field specifies the reason for failure to update the LSP. Value Meaning 1 Unknown reason 2 Limit reached for PCE-controlled LSPs 3 Too many pending LSP update requests 4 Unacceptable parameters 5 Internal error 6 LSP administratively brought down 7 LSP preempted 8 RSVP signaling error 9. Manageability Considerations All manageability requirements and considerations listed in [RFC5440] apply to PCEP protocol extensions defined in this document. In Crabbe, et al. Expires April 11, 2014 [Page 39] Internet-Draft PCEP Extensions for Stateful PCE October 2013 addition, requirements and considerations listed in this section apply. 9.1. Control Function and Policy In addition to configuring specific PCEP session parameters, as specified in [RFC5440], Section 8.1, a PCE or PCC implementation MUST allow configuring the stateful PCEP capability and the LSP Update capability. A PCC implementation SHOULD allow the operator to specify multiple candidate PCEs for and a delegation preference for each candidate PCE. A PCC SHOULD allow the operator to specify an LSP delegation policy where LSPs are delegated to the most-preferred online PCE. A PCC MAY allow the operator to specify different LSP delegation policies. A PCC implementation which allows concurrent connections to multiple PCEs SHOULD allow the operator to group the PCEs by administrative domains and it MUST NOT advertise LSP existence and state to a PCE if the LSP is delegated to a PCE in a different group. A PCC implementation SHOULD allow the operator to specify whether the PCC will advertise LSP existence and state for LSPs that are not controlled by any PCE (for example, LSPs that are statically configured at the PCC). A PCC implementation SHOULD allow the operator to specify both the Redelegation Timeout Interval and the State Timeout Interval. The default value of the Redelegation Timeout Interval SHOULD be set to 30 seconds. An operator MAY also configure a policy that will dynamically adjust the Redelegation Timeout Interval, for example setting it to zero when the PCC has an established session to a backup PCE. The default value for the State Timeout Interval SHOULD be set to 60 seconds. After the expiration of the State Timeout Interval, the LSP reverts to operator-defined default parameters. A PCC implementation MUST allow the operator to specify the default LSP parameters. To achieve a behavior where the LSP retains the parameters set by the PCE until such time that the PCC makes a change to them, a State Timeout Interval of infinity SHOULD be used. Any changes to LSP parameters SHOULD be done in make-before-break fashion. A PCC implementation SHOULD allow the operator to specify delegation priority for PCEs. This effectively defines the primary PCE and one or more backup PCEs to which primary PCE's LSPs can be delegated when the primary PCE fails. Policies defined for stateful PCEs and PCCs should eventually fit in Crabbe, et al. Expires April 11, 2014 [Page 40] Internet-Draft PCEP Extensions for Stateful PCE October 2013 the Policy-Enabled Path Computation Framework defined in [RFC5394], and the framework should be extended to support Stateful PCEs. 9.2. Information and Data Models PCEP session configuration and information in the PCEP MIB module SHOULD be extended to include advertised stateful capabilities, synchronization status, and delegation status (at the PCC list PCEs with delegated LSPs). 9.3. Liveness Detection and Monitoring PCEP protocol extensions defined in this document do not require any new mechanisms beyond those already defined in [RFC5440], Section 8.3. 9.4. Verifying Correct Operation Mechanisms defined in [RFC5440], Section 8.4 also apply to PCEP protocol extensions defined in this document. In addition to monitoring parameters defined in [RFC5440], a stateful PCC-side PCEP implementation SHOULD provide the following parameters: o Total number of LSP updates o Number of successful LSP updates o Number of dropped LSP updates o Number of LSP updates where LSP setup failed A PCC implementation SHOULD provide a command to show for each LSP whether it is delegated, and if so, to which PCE. A PCC implementation SHOULD allow the operator to manually revoke LSP delegation. 9.5. Requirements on Other Protocols and Functional Components PCEP protocol extensions defined in this document do not put new requirements on other protocols. 9.6. Impact on Network Operation Mechanisms defined in [RFC5440], Section 8.6 also apply to PCEP protocol extensions defined in this document. Additionally, a PCEP implementation SHOULD allow a limit to be placed Crabbe, et al. Expires April 11, 2014 [Page 41] Internet-Draft PCEP Extensions for Stateful PCE October 2013 on the number of LSPs delegated to the PcE and on the rate of PCUpd and PCRpt messages sent by a PCEP speaker and processed from a peer. It SHOULD also allow sending a notification when a rate threshold is reached. A PCC implementation SHOULD allow a limit to be placed on the rate of LSP Updates to the same LSP to avoid signaling overload discussed in Section 10.3. 10. Security Considerations 10.1. Vulnerability This document defines extensions to PCEP to enable stateful PCEs. The nature of these extensions and the delegation of path control to PCEs results in more information being available for a hypothetical adversary and a number of additional attack surfaces which must be protected. The security provisions described in [RFC5440] remain applicable to these extensions. However, because the protocol modifications outlined in this document allow the PCE to control path computation timing and sequence, the PCE defense mechanisms described in [RFC5440] section 7.2 are also now applicable to PCC security. As a general precaution, it is RECOMMENDED that these PCEP extensions only be activated on authenticated and encrypted sessions across PCEs and PCCs belonging to the same administrative authority. The following sections identify specific security concerns that may result from the PCEP extensions outlined in this document along with recommended mechanisms to protect PCEP infrastructure against related attacks. 10.2. LSP State Snooping The stateful nature of this extension explicitly requires LSP status updates to be sent from PCC to PCE. While this gives the PCE the ability to provide more optimal computations to the PCC, it also provides an adversary with the opportunity to eavesdrop on decisions made by network systems external to PCE. This is especially true if the PCC delegates LSPs to multiple PCEs simultaneously. Adversaries may gain access to this information by eavesdropping on unsecured PCEP sessions, and might then use this information in various ways to target or optimize attacks on network infrastructure. For example by flexibly countering anti-DDoS measures being taken to Crabbe, et al. Expires April 11, 2014 [Page 42] Internet-Draft PCEP Extensions for Stateful PCE October 2013 protect the network, or by determining choke points in the network where the greatest harm might be caused. PCC implementations which allow concurrent connections to multiple PCEs SHOULD allow the operator to group the PCEs by administrative domains and they MUST NOT advertise LSP existence and state to a PCE if the LSP is delegated to a PCE in a different group. 10.3. Malicious PCE The LSP delegation mechanism described in this document allows a PCC to grant effective control of an LSP to the PCE for the duration of a PCEP session. While this enables PCE control of the timing and sequence of path computations within and across PCEP sessions, it also introduces a new attack vector: an attacker may flood the PCC with PCUpd messages at a rate which exceeds either the PCC's ability to process them or the network's ability to signal the changes, either by spoofing messages or by compromising the PCE itself. A PCC is free to revoke an LSP delegation at any time without needing any justification. A defending PCC can do this by enqueueing the appropriate PCRpt message. As soon as that message is enqueued in the session, the PCC is free to drop any incoming PCUpd messages without additional processing. 10.4. Malicious PCC A stateful session also result in increased attack surface by placing a requirement for the PCE to keep an LSP state replica for each PCC. It is RECOMMENDED that PCE implementations provide a limit on resources a single PCC can occupy. A PCE implementing such a limit MUST send a PCErr message with error-type 19 (invalid operation) and error-value 4 (indicating resource limit exceeded) upon receiving an LSP state report causing it to exceed this threshold. Delegation of LSPs can create further strain on PCE resources and a PCE implementation MAY preemptively give back delegations if it finds itself lacking the resources needed to effectively manage the delegation. Since the delegation state is ultimately controlled by the PCC, PCE implementations SHOULD provide throttling mechanisms to prevent strain created by flaps of either a PCEP session or an LSP delegation. 11. Acknowledgements We would like to thank Adrian Farrel, Cyril Margaria and Ramon Casellas for their contributions to this document. Crabbe, et al. Expires April 11, 2014 [Page 43] Internet-Draft PCEP Extensions for Stateful PCE October 2013 We would like to thank Shane Amante, Julien Meuric, Kohei Shiomoto, Paul Schultz and Raveendra Torvi for their comments and suggestions. Thanks also to Cyril Margaria, Jon Hardwick, Dhruv Dhoddy, Ramon Casellas, Oscar Gonzales de Dios, Tomas Janciga, Stefan Kobza, Kexin Tang, Matej Spanik, Jon Parker, Marek Zavodsky, Ambrose Kwong, Ashwin Sampath, Calvin Ying and Xian Zhang for helpful comments and discussions. 12. References 12.1. Normative References [I-D.ietf-pce-gmpls-pcep-extensions] Margaria, C., Dios, O., and F. Zhang, "PCEP extensions for GMPLS", draft-ietf-pce-gmpls-pcep-extensions-08 (work in progress), July 2013. [RFC2119] Bradner, S., "Key words for use in RFCs to Indicate Requirement Levels", BCP 14, RFC 2119, March 1997. [RFC2205] Braden, B., Zhang, L., Berson, S., Herzog, S., and S. Jamin, "Resource ReSerVation Protocol (RSVP) -- Version 1 Functional Specification", RFC 2205, September 1997. [RFC3209] Awduche, D., Berger, L., Gan, D., Li, T., Srinivasan, V., and G. Swallow, "RSVP-TE: Extensions to RSVP for LSP Tunnels", RFC 3209, December 2001. [RFC3473] Berger, L., "Generalized Multi-Protocol Label Switching (GMPLS) Signaling Resource ReserVation Protocol-Traffic Engineering (RSVP-TE) Extensions", RFC 3473, January 2003. [RFC4090] Pan, P., Swallow, G., and A. Atlas, "Fast Reroute Extensions to RSVP-TE for LSP Tunnels", RFC 4090, May 2005. [RFC5088] Le Roux, JL., Vasseur, JP., Ikejiri, Y., and R. Zhang, "OSPF Protocol Extensions for Path Computation Element (PCE) Discovery", RFC 5088, January 2008. [RFC5089] Le Roux, JL., Vasseur, JP., Ikejiri, Y., and R. Zhang, "IS-IS Protocol Extensions for Path Computation Element (PCE) Discovery", RFC 5089, January 2008. [RFC5226] Narten, T. and H. Alvestrand, "Guidelines for Writing an IANA Considerations Section in RFCs", BCP 26, RFC 5226, May 2008. Crabbe, et al. Expires April 11, 2014 [Page 44] Internet-Draft PCEP Extensions for Stateful PCE October 2013 [RFC5284] Swallow, G. and A. Farrel, "User-Defined Errors for RSVP", RFC 5284, August 2008. [RFC5440] Vasseur, JP. and JL. Le Roux, "Path Computation Element (PCE) Communication Protocol (PCEP)", RFC 5440, March 2009. [RFC5511] Farrel, A., "Routing Backus-Naur Form (RBNF): A Syntax Used to Form Encoding Rules in Various Routing Protocol Specifications", RFC 5511, April 2009. 12.2. Informative References [I-D.ietf-pce-stateful-pce-app] Zhang, X. and I. Minei, "Applicability of Stateful Path Computation Element (PCE)", draft-ietf-pce-stateful-pce-app-01 (work in progress), September 2013. [I-D.minei-pce-stateful-sync-optimizations] Crabbe, E., Medved, J., Minei, I., Varga, R., Zhang, X., and D. Dhody, "Optimizations of State Synchronization Procedures for Stateful PCE", draft-minei-pce-stateful-sync-optimizations-00 (work in progress), October 2013. [I-D.sivabalan-pce-disco-stateful] Sivabalan, S., Medved, J., and X. Zhang, "IGP Extensions for Stateful PCE Discovery", draft-sivabalan-pce-disco-stateful-02 (work in progress), July 2013. [MPLS-PC] Chaieb, I., Le Roux, JL., and B. Cousin, "Improved MPLS-TE LSP Path Computation using Preemption", Global Information Infrastructure Symposium, July 2007. [MXMN-TE] Danna, E., Mandal, S., and A. Singh, "Practical linear programming algorithm for balancing the max-min fairness and throughput objectives in traffic engineering", pre- print, 2011. [NET-REC] Vasseur, JP., Pickavet, M., and P. Demeester, "Network Recovery: Protection and Restoration of Optical, SONET- SDH, IP, and MPLS", The Morgan Kaufmann Series in Networking, June 2004. [RFC2702] Awduche, D., Malcolm, J., Agogbua, J., O'Dell, M., and J. McManus, "Requirements for Traffic Engineering Over MPLS", Crabbe, et al. Expires April 11, 2014 [Page 45] Internet-Draft PCEP Extensions for Stateful PCE October 2013 RFC 2702, September 1999. [RFC3031] Rosen, E., Viswanathan, A., and R. Callon, "Multiprotocol Label Switching Architecture", RFC 3031, January 2001. [RFC3346] Boyle, J., Gill, V., Hannan, A., Cooper, D., Awduche, D., Christian, B., and W. Lai, "Applicability Statement for Traffic Engineering with MPLS", RFC 3346, August 2002. [RFC3630] Katz, D., Kompella, K., and D. Yeung, "Traffic Engineering (TE) Extensions to OSPF Version 2", RFC 3630, September 2003. [RFC4655] Farrel, A., Vasseur, J., and J. Ash, "A Path Computation Element (PCE)-Based Architecture", RFC 4655, August 2006. [RFC4657] Ash, J. and J. Le Roux, "Path Computation Element (PCE) Communication Protocol Generic Requirements", RFC 4657, September 2006. [RFC5305] Li, T. and H. Smit, "IS-IS Extensions for Traffic Engineering", RFC 5305, October 2008. [RFC5394] Bryskin, I., Papadimitriou, D., Berger, L., and J. Ash, "Policy-Enabled Path Computation Framework", RFC 5394, December 2008. [RFC5557] Lee, Y., Le Roux, JL., King, D., and E. Oki, "Path Computation Element Communication Protocol (PCEP) Requirements and Protocol Extensions in Support of Global Concurrent Optimization", RFC 5557, July 2009. Authors' Addresses Edward Crabbe Google, Inc. 1600 Amphitheatre Parkway Mountain View, CA 94043 US Email: edc@google.com Crabbe, et al. Expires April 11, 2014 [Page 46] Internet-Draft PCEP Extensions for Stateful PCE October 2013 Jan Medved Cisco Systems, Inc. 170 West Tasman Dr. San Jose, CA 95134 US Email: jmedved@cisco.com Ina Minei Juniper Networks, Inc. 1194 N. Mathilda Ave. Sunnyvale, CA 94089 US Email: ina@juniper.net Robert Varga Pantheon Technologies SRO Mlynske Nivy 56 Bratislava 821 05 Slovakia Email: robert.varga@pantheon.sk Crabbe, et al. Expires April 11, 2014 [Page 47]