Path Computation Element Communication Protocol (PCEP) Extensions for Native IP Networks

Generally, Multiprotocol Label Switching Traffic Engineering (MPLS-TE) requires the corresponding network devices to support Resource ReSerVation Protocol (RSVP)/Label Distribution Protocol (LDP) protocols to ensure the End-to-End (E2E) traffic performance. But in native IP network scenarios described in , there will be no such signaling protocol to synchronize the actions among different network devices. It is feasible to use the central control mode described in to correlate the forwarding behavior among different network devices. describes the architecture and solution philosophy for the E2E traffic assurance in the Native IP network via multiple Border Gateway Protocol (BGP) sessions-based solution. It requires only the PCE to send the instructions to the PCCs, to build multiple BGP sessions, distribute different prefixes on the established BGP sessions and assign the different paths to the BGP next hops. This document describes the corresponding Path Computation Element Communication Protocol (PCEP) extensions to transfer the key information about BGP peer, peer prefix advertisement, and the explicit peer route on on-path routers.

The keywords "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "NOT RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in BCP 14 when, and only when, they appear in all capitals, as shown here.

The message formats in this document are illustrated using Routing Backus-Naur Form (RBNF) encoding, as specified in . The use of RBNF is illustrative only and may elide certain important details; the normative specification of messages is found in the prose description. If there is any divergence between the RBNF and the prose, the prose is considered authoritative.

This document uses the following terms defined in : PCC, PCE, PCEP. The following terminology is used in this document: BPI: BGP Peer Info CCDR: Central Control Dynamic Routing CCI: Central Controller Instructions, defined in E2E: End-to-End EPR: Explicit Peer Route PCECC: PCE as a Central Controller, defined in PPA: Peer Prefix Advertisement PST: Path Setup Type, defined in SRP: Stateful PCE Request Parameters, defined in RR: Route Reflector

During the PCEP Initialization Phase, PCEP Speakers (PCE or PCC) advertise their support of Native IP extensions. This document defines a new Path Setup Type (PST) for Native-IP, as follows: PST = 4: Path is a Native IP TE path as per . A PCEP speaker MUST indicate its support of the function described in this document by sending a PATH-SETUP-TYPE-CAPABILITY TLV in the OPEN object with this new PST included in the PST list. defined the PCECC-CAPABILITY sub-TLV to exchange information about their PCECC capability. A new flag is defined in PCECC-CAPABILITY sub-TLV for Native IP: N (NATIVE-IP-TE-CAPABILITY - 1 bit - 30): If set to 1 by a PCEP speaker, it indicates that the PCEP speaker is capable of TE in a Native IP network as specified in this document. The flag MUST be set by both the PCC and PCE to support this extension. If a PCEP speaker receives the PATH-SETUP-TYPE-CAPABILITY TLV with the newly defined path setup type, but without the N bit set in PCECC-CAPABILITY sub-TLV, it MUST: send a PCErr message with Error-Type=10 (Reception of an invalid object) and Error-Value=39 (PCECC NATIVE-IP-TE-CAPABILITY bit is not set). terminate the PCEP session If a PCEP speaker receives the PATH-SETUP-TYPE-CAPABILITY TLV with the newly defined path setup type, but without the PCECC-CAPABILITY sub-TLV, it MUST: send a PCErr message with Error-Type=10(Reception of an invalid object) and Error-Value=33 (Missing PCECC Capability sub-TLV). terminate the PCEP session If one or both speakers (PCE and PCC) have not indicated support and willingness to use the PCEP extensions for Native-IP, the PCEP extensions for the Native-IP MUST NOT be used. If a Native-IP operation is attempted when both speakers have not agreed on the OPEN messages, the receiver of the message MUST: send a PCErr message with Error-Type=19 (Invalid Operation) and Error-value=TBD1 (Attempted Native-IP operations when the capability was not advertised) and terminate the PCEP session.

PCECC Native IP TE solution uses the existing PCE Label Switched Path (LSP) Initiate Request message (PCInitiate) , and PCE Report message (PCRpt) to accomplish the multiple BGP sessions establishment, E2E Native-IP TE path deployment, and route prefixes advertisement among different BGP sessions. A new PST for Native-IP is used to indicate the path setup based on TE in Native IP networks. The extended PCInitiate message described in is used to download or remove the central controller's instructions (CCIs). specifies an object called CCI for the encoding of the central controller's instructions. This document specifies a new CCI Object-Type for Native IP. The PCEP messages are extended in this document to handle the PCECC operations for Native IP. Three new PCEP Objects (BGP Peer Info (BPI) Object, Explicit Peer Route (EPR) Object, and Peer Prefix Advertisement (PPA) Object) are defined in this document. Refer to for detailed object definitions. All PCEP procedures specified in continue to apply unless specified otherwise.

The PCInitiate Message defined in and extended in is further extended to support Native-IP CCI. The format of the extended PCInitiate message is as follows:

::=

Where: is defined in [RFC5440] ::= [] ::= (| | ) ::=

::= [||] [] ]]>

Where: <PCE-initiated-lsp-instantiation> and <PCE-initiated-lsp-deletion> are as per [RFC8281]. The LSP and SRP objects are defined in [RFC8231]. When the PCInitiate message is used for Native IP instructions, i.e. When the CCI Object-Type is 2, the SRP, LSP and CCI objects MUST be present. The error handling for missing SRP, LSP or CCI objects is as per . Furthermore, one, and only one, object among BPI, EPR or PPA objects MUST be present. The PLSP-ID and Symbolic Path Name TLVs are set as per the existing rules in , , and . The Symbolic Path Name is used by the PCE/PCC to uniquely identify the E2E native IP TE path. The related Native-IP instructions with BPI, EPR or PPA objects are identified by the same Symbolic Path Name. If none of the BPI, EPR or PPA objects are present, the receiving PCC MUST send a PCErr message with Error-type=6 (Mandatory Object missing) and Error-value=19 (Native IP object missing). If there is more than one instance of BPI, EPR or PPA object present, the receiving PCC MUST send a PCErr message with Error-type=19 (Invalid Operation) and Error-value=22 (Only one BPI, EPR or PPA object can be included in this message). When the PCInitiate message is not used for Native IP instructions, i.e. When CCI Object-Type is not equal to 2, the BPI, EPR and PPA objects SHOULD NOT be present. If present, they MUST be ignored by the receiver. To clean up the existing Native IP instructions, the SRP object MUST set the R (remove) bit.

The PCRpt message is used to acknowledge the Native-IP instructions received from the central controller (PCE) as well as during the State Synchronization phase. The format of the PCRpt message is as follows:

::=

Where: ::= [] ::= (| ) ::= []

::= []

::= [||] [] ]]>

Where: <path> is as per [RFC8231] and the LSP and SRP objects are also defined in [RFC8231]. The error handling for missing CCI objects is as per . Furthermore, one, and only one, object among BPI, EPR or PPA object MUST be present. If none of the BPI, EPR or PPA objects are present, the receiving PCE MUST send a PCErr message with Error-type=6 (Mandatory Object missing) and Error-value=19 (Native IP object missing). If there are more than one instance of BPI, EPR or PPA objects present, the receiving PCE MUST send a PCErr message with Error-type=19 (Invalid Operation) and Error-value=22 (Only one BPI, EPR or PPA object can be included in this message). When the PCInitiate message is not used for Native IP instructions, i.e. When CCI Object-Type is not equal to 2, the BPI, EPR and PPA objects SHOULD NOT be present. If present, they MUST be ignored by the receiver.

The detailed procedures for the TE in the native IP environment are described in the following sections.

The PCInitiate and PCRpt message pair is used to exchange the configuration parameters for a BGP peer session. This pair of PCEP messages are exchanged between a PCE and each BGP peer (acting as PCC) which needs to establish a BGP session. After the BGP peer session has been initiated via this pair of PCEP messages, the BGP session establishes and operates in a normal fashion. The BGP peers can be used for External BGP (EBGP) peers or Internal BGP (IBGP) peers. For IBGP connection topologies, the Route Reflector (RR) is required. The PCInitiate message should be sent to PCC which is acting as BGP router and/or RR. The RR topology for a single Autonomous System (AS) is shown in Figure 1. The BGP routers R1, R3, and R7 are within a single AS. R1 and R7 are BGP RR clients, and R3 is a RR. The PCInitiate message should be sent to the BGP routers R1, R3 and R7 that need to establish a BGP session. PCInitiate message creates an auto-configuration function for these BGP peers by providing the indicated Peer AS and the Local/Peer IP Address. When the PCC receives the BPI and CCI object (with the R bit set to 0 in the SRP object) in the PCInitiate message, the PCC should try to establish the BGP session with the indicated Peer as per AS and Local/Peer IP address. During the establishment procedure, the PCC should report to the PCE the status of the BGP session via the PCRpt message, with the status field in the BPI object set to the appropriate value and the corresponding SRP and CCI objects included. When the PCC receives this message with the R bit set to 1 in the SRP object in the PCInitiate message, the PCC should clear the BGP configuration and tear down the BGP session that is indicated by the BPI object. When the PCC clears successfully the specified BGP session configuration, it should report the result via the PCRpt message, with the BPI object included, and the corresponding SRP and CCI objects.

PCE <----------+ | +--------^---------+ | | | | | PCInitiate/PCRpt | | | | | +----v--+ | +---------------+ R3(RR)+-----------------+ | +-------+ | PCInitiate/PCRpt PCInitiate/PCRpt | | +v-+ +--+ +--+ +-v+ |R1+----------+R5+----------+R6+---------+R7| ++-+ +-++ +--+ +-++ | | | | +--+ +--+ | +------------+R2+----------+R4+-----------+ +--+ +--+ Figure 1: BGP Session Establishment Procedures(R3 act as RR) ]]> The message peers, message type, message key parameters and procedures in the above figures are shown below:

| | | | |BPI Object(Peer AS, Local_IP=R1_A, Peer_IP=R3_A)| +--------+ | | | | (For R1/R3 BGP Session on R3) | | |<--PCInitiate,CC-ID=Y1,Symbolic Path Name=Class A-----| | | BPI Object(Peer AS, Local_IP=R3_A, Peer_IP=R1_A)| | |---PCRpt,CC-ID=Y1,Symbolic Path Name=Class A--------->| | | BPI Object(Peer AS, Local_IP=R3_A, Peer_IP=R1_A)| | | | | | (For R3/R7 BGP Session on R3) | | |<--PCInitiate,CC-ID=Y2,Symbolic Path Name=Class A-----| | | BPI Object(Peer AS, Local_IP=R3_A, Peer_IP=R7_A) | | |----PCRpt,CC-ID=Y2,Symbolic Path Name=Class A-------->| | | BPI Object(Peer AS, Local_IP=R3_A, Peer_IP=R7_A) | | | | (For R3/R7 BGP Session on R7) | |<--PCInitiate,CC-ID=Z,Symbolic Path Name=Class A--------------| | BPI Object(Peer AS, Local_IP=R7_A, Peer_IP=R3_A) | |---PCRpt,CC-ID=Z,Symbolic Path Name=Class A------------------>| | BPI Object(Peer AS, Local_IP=R7_A, Peer_IP=R3_A) | Figure 2: Message Information and Procedures ]]> The Local/Peer IP address MUST be dedicated to the usage of the native IP TE solution, and MUST NOT be used by other BGP sessions that are established manually or in other ways. If the Local IP Address or Peer IP Address within the BPI object is used in other existing BGP sessions, the PCC MUST report such an error situation via a PCErr message with: Error-type=33 (Native IP TE failure) and Error-value=1 (Local IP is in use), or Error-type=33 (Native IP TE failure )and Error-value=2 (Remote IP is in use). The detailed Error-Types and Error-Values are defined in If the established BGP session is broken, the PCC MUST report such information via PCRpt message with the status field set to "BGP session down" in the associated BPI Object. The error code field within the BPI object should indicate the reason that leads to the BGP session being down. In the future, when the BGP session is up again, the PCC MUST report that as well via the PCRpt message with the status field set to "BGP Session Established".

The explicit route establishment procedures can be used by PCE to install a route on the PCC, using the PCInitiate and PCRpt message pair. Such explicit routes operate the same as static routes installed by network management protocols (Network Configuration Protocol (NETCONF)/YANG). The procedures of such explicit route addition and removal must be controlled by the PCE in a specific order so that the pathways are established without loops. The PCInitiate message should be sent to every router on the path. In the example, for the explicit route from R1 to R7, the PCInitiate message should be sent to R1, R2 and R4, as shown in Figure 3. For the explicit route from R7 to R1, the PCInitiate message should be sent to R7, R4 and R2, as shown in Figure 5. When the PCC receives the EPR and the CCI object (with the R bit set to 0 in the SRP object) in the PCInitiate message, the PCC should install the explicit route to the peer in the RIB/FIB. When the PCC installs successfully the explicit route to the peer, it should report the result via the PCRpt messages, with the EPR object and the corresponding SRP and CCI objects included. When the PCC receives the EPR and the CCI object with the R bit set to 1 in the SRP object in the PCInitiate message, the PCC MUST remove the explicit route to the peer that is indicated by the EPR object. When the PCC has removed the explicit route that is indicated by this object, it should report the result via the PCRpt message, with the EPR object included, and the corresponding SRP and CCI object.

PCE + | +----^-----------^-+ | | | | | | | | +------+ | +---------------|-+R3(RR)+--|-------------+ PCInitiate/PCRpt | +------+ | | | | | | +v-+ +--+ | | +--+ +--+ |R1+------+R5+---+-----------|---+R6+----+R7| ++-+ +--+ | | +--+ +-++ | PCInitiate/PCRpt PCInitiate/PCRpt | | | | | | +--v--+ +--v-+ | +------------+- R2 +-----+ R4 +-----------+ +--+--+ +--+-+ Figure 3: Explicit Route Establish Procedures(From R1 to R7) ]]> The message peers, message type, message key parameters and procedures in the above figures are shown below:

| | | | | EPR Object(Peer Address=R7_A, Next Hop=R7_A)| +--------+ | | | | (EPR route on R2) | | |<--PCInitiate,CC-ID=Y,Symbolic Path Name=Class A-----| | | EPR Object(Peer Address=R7_A, Next Hop=R4_A) | | |----PCRpt,CC-ID=Y,Symbolic Path Name=Class A-------->| | | EPR Object(Peer Address=R7_A, Next Hop=R4_A) | | | | | | | (EPR route on R1) | |<--PCInitiate,CC-ID=X,Symbolic Path Name=Class A-------------| | EPR Object(Peer Address=R7_A, Next Hop=R2_A) | |---PCRpt,CC-ID=X1(Symbolic Path Name=Class A)--------------->| | EPR Object(Peer Address=R7_A, Next Hop=R2_A) | Figure 4: Message Information and Procedures ]]>

The message peers, message type, message key parameters and procedures in the above figures are shown below:

| | | | | EPR Object(Peer Address=R1_A, Next Hop=R1_A) | +--------+ | | | | (EPR route on R4) | | |<--PCInitiate,CC-ID=Y,Symbolic Path Name=Class A-----| | | EPR Object(Peer Address=R1_A, Next Hop=R2_A) | | |----PCRpt,CC-ID=Y,Symbolic Path Name=Class A-------->| | | EPR Object(Peer Address=R1_A, Next Hop=R2_A) | | | | | | | (EPR route on R7) | |<--PCInitiate,CC-ID=Z,Symbolic Path Name=Class A-------------| | EPR Object(Peer Address=R1_A, Next Hop=R4_A) | |---PCRpt,CC-ID=Z,Symbolic Path Name=Class A----------------->| | EPR Object(Peer Address=R1_A, Next Hop=R4_A) | Figure 6: Explicit Route Establish Procedures(From R7 to R1) ]]> To avoid the transient loop while deploying the explicit peer route, the EPR object should be sent to the PCCs in the reverse order of the E2E path. To remove the explicit peer route, the EPR object should be sent to the PCCs in the same order as the E2E path. To accomplish ECMP effects, the PCE can send multiple EPR/CCI objects to the same node, with the same route priority and peer address value but a different next-hop address. The PCC should verify that the next hop address is reachable. In case of failure, the PCC MUST send the corresponding error via PCErr message, with the error information: Error-type=33 (Native IP TE failure), Error-value=3 (Explicit Peer Route Error). When the peer info is not the same as the peer info that is indicated in the BPI object in PCC for the same path that is identified by Symbolic Path Name TLV, a PCErr message MUST be reported, with the error information: Error-type=33 (Native IP TE failure), Error-value=4, EPR/BPI Peer Info Mismatch. Note that the same error can be used in case no BPI is received at the PCC. If the PCE needs to update the path, it should first instruct the new CCI with updated EPR corresponding to the new next hop to use and then instruct the removal of the older CCI.

The detailed procedures for BGP prefix advertisement are shown below, using the PCInitiate and PCRpt message pair. The PCInitiate message should be sent to PCC that acts as a BGP peer edge router only. In the example, it should be sent to R1 and R7 respectively. When the PCC receives the PPA and the CCI object (with the R bit set to 0 in the SRP object) in the PCInitiate message, the PCC should send the prefixes indicated in this object to the identified BGP peer via the corresponding BGP session . When the PCC has successfully sent the prefixes to the appointed BGP peer, it should report the result via the PCRpt messages, with the PPA object and the corresponding SRP and CCI objects included. When the PCC receives the PPA and the CCI object with the R bit set to 1 in the SRP object in the PCInitiate message, the PCC MUST withdraw the prefixes advertisement to the peer indicated by this object. When the PCC withdraws successfully the prefixes that are indicated by this object, it should report the result via the PCRpt message, with the PPA object included, and the corresponding SRP and CCI objects.

PCE <-----------+ | +------------------+ | | +--+ | +------------------+R3+-------------------+ PCInitiate/PCRpt +--+ PCInitiate/PCRpt | | +v-+ +--+ +--+ +-v+ |R1+----------+R5+----------+R6+---------+R7| ++-+ +--+ +--+ +-++ (BGP Router) (BGP Router) | | | | | +--+ +--+ | +------------+R2+----------+R4+-----------+ +--+ +--+ Figure 7: BGP Prefix Advertisement Procedures ]]> The message peers, message type, message key parameters and procedures in the above figures are shown below:

| | | PPA Object(Peer IP=R7_A, Prefix=1_A) | | | | (Instruct R7 to advertise Prefix 7_A to R1 ) | |<--PCInitiate,CC-ID=Z,Symbolic Path Name=Class A-----| | PPA Object(Peer IP=R1_A, Prefix=7_A) | |----PCRpt,CC-ID=Z,Symbolic Path Name=Class A-------->| | PPA Object(Peer IP=R1_A, Prefix=7_A) | | | Figure 8: Message Information and Procedures ]]> The AFI/SAFI for the corresponding BGP session should match the Peer Prefix Advertisement Object-Type, AFI/SAFI should be 1/1 for the IPv4 prefix and 2/1 for the IPv6 prefix. In case of mismatch, an error: Error-type=33 (Native IP TE failure), Error-value=5 (BPI/PPA address family mismatch) SHOULD be reported via PCErr message. When the peer info is not the same as the peer info that is indicated in the BPI object in PCC for the same path that is identified by Symbolic Path Name TLV, an error: Error-type=33 (Native IP TE failure), Error-value=6 (PPA/BPI peer info mismatch) SHOULD be reported via the PCErr message. Note that the same error can be used in case no BPI is received at the PCC.

Normally, when the above procedures are finished, the user traffic will be forwarded via the appointed path, but the forwarding will be based solely on the destination of user traffic. If there is traffic from different attached points to the same destination coming into the network, they could share the priority path which may not be the initial desire. For example, as illustrated in Figure 1, the initial aim is to ensure traffic that enters the network via R1 and exits the network at R7 via R5-R6-R7. If some traffic enters the network via the R2 router, passes through R5 and exits at R7, they may share the priority path among R5-R6-R7, which may not be the desired effect. The above normal traffic forwarding behavior is clarified as a Raw mode forwarding strategy. Such a mode can achieve only the moderate traffic path control effect. To achieve the strict traffic path control effect, the entry point should tunnel the user traffic from the entry point of the network to the exit point of the network, which is also between the BGP peer established via . Such forwarding behavior is called the Tunnel mode forwarding strategy. For simplicity, the IPinIP tunnel type is used between the BGP peers by default. The selection of Raw mode and Tunnel mode forwarding strategies are controlled via the "T" bit in BPI Object that is defined in

To remove the Native-IP state from the PCC, the PCE MUST send explicit CCI cleanup instructions for PPA, EPR and BPI objects respectively with the R flag set in the SRP object. If the PCC receives a PCInitiate message but does not recognize the Native-IP information in the CCI, the PCC MUST generate a PCErr message with Error-Type=19 (Invalid operation) and Error-value=TBD2 (Unknown Native-IP Info) and MUST include the SRP object to specify the error is for the corresponding cleanup (via a PCInitiate message).

The handling of the state synchronization, redundant PCEs, re-delegation and clean up is the same as other CCIs as specified in .

One new CCI Object type and three new PCEP objects are defined in this document. All new PCEP objects are as per .

The Central Control Instructions (CCI) Object (defined in ) is used by the PCE to specify the forwarding instructions. This document defines another object type for Native-IP procedures. CCI Object-Type is 2 for Native-IP as below:

The field CC-ID is as described in . The following fields are defined for CCI Object-Type 2 2 Bytes, is set to zero while sending and ignored on receipt. 2 Bytes, is used to carry any additional information about the Native-IP CCI. Currently, no flag bits are defined. Unassigned flags are set to zero while sending and ignored on receipt. Optional TLVs may be included within the CCI object body. The Symbolic Path Name TLV MUST be included in the CCI Object-Type 2 to identify the E2E TE path in the Native IP environment.

The BGP Peer Info object is used to specify the information about the peer with which the PCC should establish the BGP session. This object should only be included and sent to the source and destination router of the E2E path in case there is no Route Reflection (RR) involved. If the RR is used between the source and destination routers, then such information should be sent to the source router, RR and destination router respectively. By default, the Local/Peer IP address MUST be dedicated to the usage of the native IP TE solution, and MUST NOT be used by other BGP sessions that are established by manual or other configuration mechanisms. BGP Peer Info Object-Class is 46 BGP Peer Info Object-Type is 1 for IPv4 and 2 for IPv6 The format of the BGP Peer Info object body for IPv4 (Object-Type=1) is as follows:

The format of the BGP Peer Info object body for IPv6 (Object-Type=2) is as follows:

Peer AS Number: 4 Bytes, to indicate the AS number of Remote Peer. Note that if 2-byte AS numbers are in use, the low-order bits (16 through 31) MUST be used, and the high-order bits (0 through 15) MUST be set to zero. ETTL: 1 Byte, EBGP Time To Live, to indicate the multi-hop count for the EBGP session. It should be 0 and ignored when Local AS and Peer AS are the same. Status: 1 Byte, Indicate BGP session status between the peers. Its values are defined below: 0: Reserved 1: BGP Session Established 2: BGP Session Establishment In Progress 3: BGP Session Down 4-255: Reserved Error Code: 1 Byte, Indicate the reason that the BGP session can't be established. 0: Unspecific 1: ASes do not match, BGP Session Failure 2: Peer IP can't be reached, BGP Session Failure 3-255: Reserved Flag: 1 Byte. Currently, only bit 7 (T bit) is defined. When the T bit is set, the traffic should be sent in the IPinIP tunnel (Tunnel source is Local IP Address, tunnel destination is Peer IP Address). When the T bit is cleared, the traffic is sent via its original source and destination address. The Tunnel mode(T bit is set) is used when the operator wants to ensure only the traffic from the specified (entry, exit) pair, and the Raw mode (T bit is clear) is used when the operator wants to ensure traffic from any entry to the specified destination. Unassigned flags are set to zero while sending and ignored on receipt. Local IP Address(4/16 Bytes): IP address of the local router, used to peer with another end router. When Object-Type is 1, the length is 4 bytes; when Object-Type is 2, the length is 16 bytes. Peer IP Address(4/16 Bytes): IP address of the peer router, used to peer with the local router. When Object-Type is 1, the length is 4 bytes; when Object-Type is 2, the length is 16 bytes; Optional TLVs: TLVs that are associated with this object, can be used to convey other necessary information for dynamic BGP session establishment. No TLVs are currently defined. When the PCC receives a BPI object, with Object-Type=1, it should try to establish a BGP session with the peer in AFI/SAFI=1/1. When the PCC receives a BPI object with Object-Type=2, it should try to establish a BGP session with the peer in AFI/SAFI=2/1.

The Explicit Peer Route object is defined to specify the explicit peer route to the corresponding peer address on each device that is on the E2E Native-IP TE path. This Object should be sent to all the devices on the path that is calculated by the PCE. Although the object is named as “Explicit Peer Route”, it can be seen that the routes it installs are simply host routes. The use of this object to install host routes for any purpose other than reaching the corresponding peer address on each device that is on the E2E Native-IP TE path is outside the scope of this specification. It is RECOMMENDED that the path established by this object should have higher priority than the other paths calculated by dynamic IGP protocol, but should have lower priority than the static route configured by manual or NETCONF or any other static means. Explicit Peer Route Object-Class is 47. Explicit Peer Route Object-Type is 1 for IPv4 and 2 for IPv6 The format of the Explicit Peer Route object body for IPv4 (Object-Type=1) is as follows:

The format of the Explicit Peer Route object body for IPv6 (Object-Type=2) is as follows:

Route Priority: 2 Bytes; the priority of this explicit route. The higher priority should be preferred by the device. This field is used to indicate the preferred path at each hop. Reserved: is set to zero while sending, ignored on receipt. Peer (IPv4/IPv6) Address: Peer Address for the BGP session (4/16 Bytes). Next Hop (IPv4/IPv6) Address to the Peer: To indicate the next hop address (4/16 Bytes) to the corresponding peer address. Optional TLVs: TLVs that are associated with this object, can be used to convey other necessary information for explicit peer path establishment. No TLVs are currently defined.

The Peer Prefix Advertisement object is defined to specify the IP prefixes that should be advertised to the corresponding peer. This object should only be included and sent to the source/destination router of the E2E path. The prefix information included in this object MUST only be advertised to the indicated peer, and MUST NOT be advertised to other BGP peers. Peer Prefix Advertisement Object-Class is 48 Peer Prefix Advertisement Object-Type is 1 for IPv4 and 2 for IPv6 The format of the Peer Prefix Advertisement object body is as follows:

Peer IPv4 Address: 4 Bytes. Identifies the peer IPv4 address that the associated prefixes will be sent to. No. of Prefix: 1 Byte. Identifies the number of prefixes that are advertised to the peer in the PPA object. Reserved: 3 Bytes. MUST be set to zero while sending and MUST be ignored on receipt. IPv4 Prefix: 4 Bytes. Identifies the prefix that will be sent to the peer identified by Peer IPv4 Address. Prefix Len: 1 Byte. Identifies the length of the prefix. Optional TLVs: TLVs that are associated with this object, can be used to convey other necessary information for prefix advertisement. No TLVs are currently defined. For IPv6: Peer IPv6 Address: 16 Bytes. Identifies the peer IPv6 address that the associated prefixes will be sent to. IPv6 Prefix: Identifies the prefix that will be sent to the peer identified by Peer IPv6 Address. If in the future, a requirement is identified to advertise IPv4 prefixes toward an IPv6 peering address, or IPv6 prefixes towards an IPv4 peering address, then a new Peer Prefix Advertisement Object-Types can be defined for these purposes.

A PCEP-ERROR object is used to report a PCEP error and is characterized by an Error-Type that specifies that type of error and an Error-value that provides additional information about the error. An additional Error-Type and several Error-values are defined to represent the errors related to the newly defined objects that are related to Native IP TE procedures.

This document defines the procedures and objects to create the BGP sessions and advertise the associated prefixes dynamically. Only the key information, for example, peer IP addresses, and peer AS numbers are exchanged via the PCEP protocol. Other parameters that are needed for the BGP session setup should be derived from their default values. When the PCE sends out the PCInitiate message with the BPI object embedded to establish the BGP session between the PCC peers, the PCC should report the BGP session status. For instance, the PCC could respond with "BGP Session Establishment In Progress" initially and on session establishment send another PCRpt message with the state updated to "BGP Session Established". If there is any error during the BGP session establishment, the PCC should indicate the reason with the appropriate status value set in the BPI object. Upon receiving such key information, the BGP module on the PCC should try to accomplish the task appointed by the PCEP protocol and report the successful status to the PCEP modules after the session is set up. There is no influence on the current implementation of BGP Finite State Machine (FSM). The PCEP focuses only on the success and failure status of the BGP session and acts upon such information accordingly. The error-handling procedures related to incorrect BGP parameters are specified in , , and .

The information transferred in this document is mainly used for the BGP session setup, explicit route deployment and the prefix distribution. The planning, allocation and distribution of the peer addresses within IGP should be accomplished in advance and they are out of the scope of this document. The communication of PCE and PCC described in this document SHOULD follow the state synchronization procedures described in , treat the three newly defined objects (BPI, EPR and PPA) associated with the same symbolic path name as the attribute of the same path in the LSP-DB (LSP State Database). When PCE detects one or some of the PCCs are out of its control, it should recompute and redeploy the traffic engineering path for native IP on the currently active PCCs. The PCE should ensure the avoidance of the possible transient loop in such node failure when it deploys the explicit peer route on the PCCs. In case of a PCE failure, a new PCE can gain control over the central controller instructions as described in . As per the PCEP procedures in , the State Timeout Interval timer is used to ensure that a PCE failure does not result in automatic and immediate disruption for the services. Similarly, as per , the central controller instructions are not removed immediately upon PCE failure. Instead, they could be re-delegated to the new PCE before the expiration of this timer, or be cleaned up on the expiration of this timer. This allows for network clean up without manual intervention. The PCC supports the removal of CCI as one of the behaviors applied on the expiration of the State Timeout Interval timer.

A PCE or PCC implementation SHOULD allow the PCECC Native-IP capability to be enabled/disabled as part of the global configuration.

describes the PCEP MIB; this MIB could be extended to get the PCECC Native-IP capability status. The PCEP YANG module could be extended to enable/disable the PCECC Native-IP capability.

Mechanisms defined in this document do not imply any new liveness detection and monitoring requirements in addition to those already listed in . The operator relies on existing IP liveness detection and monitoring.

Verification of the mechanisms defined in this document can be built on those already listed in , and . Further, the operator needs to be able to verify the status of BGP sessions and prefix advertisements.

Mechanisms defined in this document require the interaction with BGP. describes in detail the considerations regarding the BGP. During the BGP session establishment, the Local/Peer IP address MUST be dedicated to the usage of the native IP TE solution, and MUST NOT be used by other BGP sessions that are established manually or in other ways.

describes the various deployment considerations in CCDR architecture and their impact on network operations.

[Note to the RFC Editor - remove this section before publication, as well as remove the reference to RFC 7942.] This section records the status of known implementations of the protocol defined by this specification at the time of posting of this Internet-Draft, and is based on a proposal described in [RFC7942]. The description of implementations in this section is intended to assist the IETF in its decision processes in progressing drafts to RFCs. Please note that the listing of any individual implementation here does not imply endorsement by the IETF. Furthermore, no effort has been spent to verify the information presented here that was supplied by IETF contributors. This is not intended as, and must not be construed to be, a catalog of available implementations or their features. Readers are advised to note that other implementations may exist. According to , "This will allow reviewers and working groups to assign due consideration to documents that have the benefit of running code, which may serve as evidence of valuable experimentation and feedback that has made the implemented protocols more mature. It is up to the individual working groups to use this information as they see fit".

At the time of posting the -26 version of this document, there are no known implementations of this mechanism. A proof of concept for the overall design has been verified using another SBI protocol on the Open Daylight (ODL) controller.

ZTE is preparing an implementation of this document at the time of posting the -29 version of this document.

In this setup, the BGP sessions, prefix advertisement, and explicit peer route establishment are all controlled by the PCE. See for security consideration of classical BGP implementation, and for classical BGP vulnerabilities analysis. Security considerations in for basic PCEP protocol, for PCEP extension for stateful PCE and for PCE-Initiated LSP setup should be considered. To prevent a bogus PCE from sending harmful messages to the network nodes, the network devices should authenticate the validity of the PCE and ensure a secure communication channel between them. Thus, the mechanisms described in for the usage of TLS for PCEP and for malicious PCE should be used. If suitable default values as discussed in aren't enough and securing the BGP transport is required(for example, the TCP-AO , it can be provided through the addition of optional TLVs to the BGP Peer Info object that conveys the necessary additional information (for example, a key chain name).

created a sub-registry within the "Path Computation Element Protocol (PCEP) Numbers" registry called "PCEP Path Setup Types". IANA is requested to allocate a new code point within this sub-registry, as follows:

created a sub-registry within the "Path Computation Element Protocol (PCEP) Numbers" registry to manage the value of the PCECC-CAPABILITY sub-TLV's 32-bit Flag field. IANA is requested to allocate a new bit position within this registry, as follows:

IANA is requested to allocate new codepoints in the "PCEP Objects" sub-registry as follows:

IANA is requested to allocate new error types and error values within the "PCEP-ERROR Object Error Types and Values" sub-registry of the PCEP Numbers registry for the following errors:

The reference for the new Error-type/value should be set to this document.

IANA is requested to create a new sub-registry to manage the 16-bits Flag field of the new CCI Object called "CCI Object Flag Field for Native-IP". New values are to be assigned by IETF review . Each bit should be tracked with the following qualities: bit number (counting from bit 0 as the most significant bit, and bit 15 as the lest significant bit) capability description defining RFC Currently, no flags are assigned.

IANA is requested to create a new sub-registry "BPI Object Status Code Field" within the "Path Computation Element Protocol (PCEP) Numbers". New values are assigned by IETF review . Each value should be tracked with the following qualities: value, meaning, and defining RFC. The following values are defined in this document:

IANA is requested to create a new sub-registry "BPI Object Error Code Field" within the "Path Computation Element Protocol (PCEP) Numbers". New values are assigned by IETF review . Each value should be tracked with the following qualities: value, meaning, and defining RFC. The following values are defined in this document:

IANA is requested to create a new sub-registry "BPI Object Flag Field" within the "Path Computation Element Protocol (PCEP) Numbers". New values are to be assigned by IETF review . Each bit should be tracked with the following qualities: bit number (counting from bit 0 as the most significant bit) capability description defining RFC The following values are defined in this document:

Dhruv Dhody has contributed to this document.

Thanks Mike Koldychev, Susan Hares, Siva Sivabalan and Adam Simpson for their valuable suggestions and comments.