Patent Description:
<NPL>, describes extensions to the Path Computation Element Protocol (PCEP) that allow a PCE to compute and instantiate service function paths in the unified source routing based service function chaining context.

A Segment Routing (SR) technology leverages the source routing and tunneling paradigms. It enables any head-end node, i.e., the source node, to choose a path without relying on hop-by-hop signaling protocols in the Multiprotocol Label Switching (MLPS) network, such as Label Distribution Protocol (LDP) or Resource Reservation Protocol-Traffic engineered (RSVP-TE). Each path is specified as a set of "segments" advertised by link-state routing Protocols. A Segment Routed Path can be derived from a variety of mechanisms, including an IGP Shortest Path Tree (SPT), explicit configuration, or calculated by a Path Computation Element (PCE). Such paths may be chosen by a suitable network planning tool or provisioned on the ingress node.

Reference is made to the Internet Engineering Task Force (IETF) Network Working Group Internet-Draft "Segment Routing Architecture", draft-filsfils-rtgwg-segment-routing-<NUM>, for introduction to the SR architecture. The draft-filsfils-rtgwg-segment-routing-<NUM> defines an "IGP Segment or IGP SID" as a segment attached to a piece of information advertised by a link-state routing protocols, e.g. an IGP prefix or an IGP adjacency. Several types of segments are defined. An IGP-Node Segment represents an IGP-Prefix Segment which identifies a specific router (e.g. a loopback). The terms "Node Segment" or "Node-SID" are often used as an abbreviation. An IGP-Adjacency Segment or Adjacency Segment or Adj-SID represents an IGP segment attached to an unidirectional adjacency or a set of unidirectional adjacencies. An Adjacency Segment is local to the node which advertises it. Both Node segments and Adjacency segments can be used for SR Traffic Engineering (SR-TE).

SR may be performed by using extensions to Intermediate System-to-Intermediate System (IS-IS) and Open Shortest Path First (OSPF) protocols. Segment Routing can operate with the MPLS data plane or an IPv6 data plane, and Segment Routing integrates with multiple service capabilities of the MPLS, including Layer <NUM> virtual private network (L3VPN), Virtual Private Wire Service (VPWS), Virtual Private LAN Service (VPLS), and Ethernet VPN (EVPN).

The SR architecture can be applied to the MPLS forwarding plane without any change, in which case an SR path corresponds to an MPLS Label Switching Path (LSP). The SR is applied to IPV6 forwarding plane using Segment Routing Header (SRH) as specified in the Internet-draft [I D. ietf-6man-segment-routing-header].

Reference is also made to IETF Internet-Draft draft-ietf-isis-segment-routing-extensions, e.g. draft-ietf-isis-segment-routing-extensions-<NUM>, "IS-IS Extensions for Segment Routing". Further, for OSPF Extensions for Segment Routing, reference is made to IETF Internet-Draft draft-ietf-ospf-segment-routing-extensions, e.g. draft-ietf-ospf-segment-routing-extensions-<NUM>, "OSPF Extensions for Segment Routing".

Reference is also made to IETF Internet-Draft draft -ietf-pce-segment-routing-<NUM>, "PCEP Extensions for Segment Routing", April <NUM>, which provides further details on segment routing to support Segment routing by MPLS data plane. This document defines a new ERO subobject denoted by "SR-ERO subobject" capable of carrying a Segment Identifier (SID) as well as a node/adjacency identifier (NAI) associated with the SID. The SR-capable PCEP speakers (i.e., PCC and PCE) are able to generate and/or process such ERO subobject.

Thus, draft-ietf-pce-segment-routing-<NUM> specifies extensions to the Path Computation Element Protocol (PCEP) extensions for supporting a SR-TE 1sp for MPLS forwarding plane, that allow a stateful PCE to compute and initiate Traffic Engineering (TE) paths, as well as a PCC to request a path subject to certain constraint(s) and optimization criteria in SR networks.

IETF Internet-Draft draft-ietf-6man-segment-routing-header-<NUM>, "IPv6 Segment Routing Header (SRH)", discloses that Segment Routing can be applied to the IPv6 data plane with the addition of a new type of Routing Extension Header.

However, none of these documents define any mechanism for establishing an SRv6 tunnel based on Segment Routing (SR) forIPv6 data-plane/forwarding plane.

Thus, there exists a dire need to a mechanism in a PCE managed Software Defined Network (SDN), to support Segment Routing for IPv6.

This summary is provided to introduce concepts related to a method for establishing a segment routing tunnel, and the same are further described below in the detailed description.

An objective of the present disclosure is to provide PCEP extensions for establishing a Segment Routing tunnel by PCE managed SDN based on IPv6 data-plane. The Segment Routing for IPv6 (SRv6) tunnel can be configured in PCC or initiated by PCE.

Another objective of the present disclosure is to provide a PCC or PCE indicating its ability to support IPv6 SR-Path during the PCEP session Initialization phase via a new flag bit in the SR-PCE-CAPABILITY TLV.

In a first aspect of the present invention, a method implemented by a path computation element (PCE) includes the features defined in claim <NUM>.

In a second aspect of the present invention, a method implemented by a path computation client (PCC) includes the features defined in claim <NUM>.

In one implementation of the second aspect, before receiving the third PCEP message, the method of the second aspect comprises the steps of sending, by the PCC, a first PCEP message to the PCE; receiving, by the PCC, a second PCEP message from the PCE; wherein, the first PCEP message and the second PCEP message are used to set up an SRv6 capable PCEP session between the first PCC and the PCE, each of the first PCEP message and the second PCEP message carries an SRv6-CAPABILITY Type Length Value (TLV) field, wherein the Type field of the SRv6-CAPABILITY TLV field is used to indicate that both the PCE and the first PCC support SRv6 forwarding.

Significantly, an SID field and indication information can be carried by an Explicit Route Object (ERO) subobject supporting variable length SID for SR IPv6. The ERO subobject in the present application can also be known as SRv6-ERO Subobject. The indicating information can be a bit, i.e. an I-bit of the SRv6-ERO Subobject, modified to support variable length SID for SR IPv6. It indicates that the SID is variable length (i.e. <NUM> bytes to encode IPv6 Prefix) unlike <NUM> bytes in old subobjects. The ERO subobjects can be carried in at least one or more of PCUpd message, Reinitiate message and PCRep message to convey an explicit-path to the PCC from the PCE.

Optionally, the third PCEP message, which can be a Reinitiate message, or a PCRep message, also comprises a PATH-SETUP-TLV field, where the Type field of the PATH-SETUP-TLV field indicates that the tunnel is established by SRv6 technique. The first PCEP message, which can be a PCReq Message, also comprises a SRv6-CAPABILITY Type Length Value (TLV) field, where the Type field of the SRv6-CAPABILITY TLV field indicates that the first PCC supports SRv6 forwarding. The second PCEP message, which can be a PCRep Message, also comprises an SRv6-CAPABILITY Type Length Value (TLV) field, where the Type field of the SRv6-CAPABILITY TLV field indicates that the PCE supports SRv6 forwarding.

Optionally, the PCC configured to send a Path Computation Report (PCRpt) message for updating Link-State-Database (LSDB) to the PCE. The PCE determines IPv6 LSDB through path computation element protocol link state (PCEPLS) or Border Gateway Protocol link state (BGPLS) or Interior Gateway Protocols (IGP) or any combination thereof. The PCE configured to modify said path and sends an update message (PCUpd) message to the PCC.

At the outset, both PCC and PCE exchange SRv6 capability TLV through an Open message, for establishing SRv6 capability during the PCEP session. The PCC first sends an Open message to PCE to indicate that it is capable of establishing a SRv6 session. In reply, the PCE sends an Open message to PCC to indicate that it is also capable of establishing a SRv6 session. A Route Record object (RRO) carried in PCRpt message and/or PCReq message sent by PCC, conveys the actual-path from PCC to PCE.

Thus, in the prior art, a forwarding node can compute the SRv6 tunnel path, however it is limited to intra area and optimal inter-area/inter-AS tunnels cannot be setup. In various embodiments of the present invention, the PCE may optimally set up intra-area, inter-area and inter-AS SRv6 tunnels. Thus, segment routing tunnel setup can be achieved by the IPv6 data plane with PCE even if the forwarding network does not support the MPLS.

In a third aspect of the present invention, a PCE includes the features defined in claim <NUM>.

In a fourth aspect of the present invention, a PCC includes the features defined in claim <NUM>.

Embodiments include the features defined in the dependent claims.

The various options and preferred embodiments referred to above are also applicable in relation to the other implementations.

The same numbers are used throughout the drawings to refer like features and components.

It is to be understood that the attached drawings are for purposes of illustrating the concepts of the application and may not be to scale.

The application can be implemented in numerous ways, as a process, an apparatus, a system, a composition of matter, a computer readable medium such as a computer readable storage medium or a computer network wherein program instructions are sent over optical or electronic communication links. In this specification, these implementations, or any other form that the application may take, may be referred to as techniques. In general, the order of the steps of disclosed processes may be altered within the scope of the application.

A detailed description of one or more embodiments of the application is provided below along with accompanying figures that illustrate the principles of the application. The application is described in connection with such embodiments, but the application is not limited to any embodiment. The scope of the application is limited only by the claims and the application encompasses numerous alternatives, modifications and equivalents. Numerous specific details are set forth in the following description in order to provide a thorough understanding of the application. These details are provided for the purpose of example and the application may be practiced according to the claims without some or all of these specific details. For the purpose of clarity, technical material that is known in the technical fields related to the application has not been described in detail so that the application is not unnecessarily obscured.

In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the application. However, it will be understood by those skilled in the art that the present application may be practiced without these specific details. In other instances, well-known methods, procedures, and components, modules, units and/or circuits have not been described in detail so as not to obscure the application.

Although embodiments of the application are not limited in this regard, discussions utilizing terms such as, for example, "processing," "computing," "calculating," "determining," "establishing", "analyzing", "checking", or the like, may refer to operation(s) and/or process(es) of a computer, a computing platform, a computing system, or other electronic computing device, that manipulates and/or transforms data represented as physical (e.g., electronic) quantities within the computer's registers and/or memories into other data similarly represented as physical quantities within the computer's registers and/or memories or other information non-transitory storage medium that may store instructions to perform operations and/or processes.

Although embodiments of the application are not limited in this regard, the terms "plurality" and "a plurality" as used herein may include, for example, "multiple" or "two or more". The terms "plurality" or "a plurality" may be used throughout the specification to describe two or more components, devices, elements, units, parameters, or the like. Unless explicitly stated, the method embodiments described herein are not constrained to a particular order or sequence. Additionally, some of the described method embodiments or elements thereof can occur or be performed simultaneously, at the same point in time, or concurrently.

Embodiments of the present invention teach a method for setting up a segment routing tunnel based on IPv6 data plane by using Path Computation Element Protocol (PCEP) extensions. The Path Computation Element Protocol (PCEP) runs on a Path Computation Client (PCC) and a Path Computation Element (PCE) to establish the communication between the PCC and the PCE. A PCE is capable of computing a network path or route based on a network graph and applying computational constraints.

While aspects are described for a method for establishing a segment routing tunnel based on IPv6 data plane by extending PCEP, the present application may be implemented in any number of different computing systems, environments, and/or configurations, the embodiments are describe in the context of the following exemplary systems, devices/nodes/apparatus, and methods.

Henceforth, embodiments of the present disclosure are explained with the help of exemplary diagrams and one or more examples. However, such exemplary diagrams and examples are provided for the illustration purpose for better understanding of the present disclosure and should not be construed as limitation on scope of the present disclosure.

The method is applied in a system including a PCC and a PCE, wherein the PCC and the PCE run the PCEP and communication with each other.

The IETF Internet-Draft document (RFC5440), "Path Computation Element (PCE) Communication Protocol (PCEP)", which describes PCEP for communication between a PCC and a PCE or between one a pair of PCEs. In the present invention, the basic PCEP operation in SR networks are followed as in the Internet-draft document, draft-ietf-pce-segment routing. SR-IPv6 LSPs computed by a PCE can be represented in one of the following forms:.

The present invention extends the "SR-ERO subobject" as defined in I-D. ietf-pce-segment-routing, to carry IPv6 SID(s) (IPv6 Addresses). The SRH-capable PCEP speakers should be able to generate and/or process such ERO subobject. An ERO containing SR-ERO subobjects can be included in the PCEP Path included in the PCEP Path Computation Reply (PCRep) message defined in [RFC5440], the PCEP LSP Initiate Request message (PCInitiate) as defined in the Internet Draft document I-D. ietf-pce-pce-initiated-lsp, as well as in the PCEP LSP Update Request (PCUpd) and PCEP LSP State Report (PCRpt) messages defined in defined in Stateful PCE [I-D. ietf-pce-stateful-pce].

The extensions specified in the present invention complement the existing PCEP specifications to support SRH path. As such, the PCEP messages (E. , Path computation Request, Path computation Reply, Path Computation Report, Path Computation.

Update, Path Computation Initiate, etc.) must be formatted according to the IETF Internet-Draft document (RFC5440), Internet draft I-D. ietf-pce-stateful-pce, Internet draft I-D. ietf-pce-pce-initiated-lsp, and any other applicable PCEP specifications.

The present invention uses the following terms which are as follows:.

The Path Computation Client (PCC) and the PCE according to the embodiment of the present invention, includes a processor, a memory, and an interconnection mechanism coupling the memory and a transceiver respectively. The processor may be implemented as one or more microprocessors, microcomputers, microcontrollers, digital signal processors, central processing units, state machines, logic circuitries, and/or any devices that manipulate signals based on operational instructions. Among other capabilities, at least one processor is configured to fetch and execute computer-readable instructions stored in the memory to implement the method of present invention.

The memory may include any computer-readable medium known in the art including, for example, volatile memory, such as static random access memory (SRAM) and dynamic random access memory (DRAM), and/or nonvolatile memory, such as read only memory (ROM), erasable programmable ROM, flash memories, hard disks, optical disks, and magnetic tapes.

The Path Computation Element (PCE) ane the PCC includes a transceiving unit and a processing unit. The transceiving unit is used to perform the action of receiving and sending in the method of the present invention, and the processing unit is used to perform the other actions except the transceiving action in the method of the present invention. For example, the processing unit of the PCE is configured to generate a first path computation element communication protocol (PCEP) message, wherein the first PCEP message comprises an indicating information and a segment identifier (SID) field, the SID field comprises multiple SIDs and the indicating information is used to indicate that each of the multiple SIDs is an IPv6 prefix of a node in a tunnel respectively; and the transceiving unit of the PCE is configured to send the first PCEP message to a first path computation client (PCC) to establish a segment routing for IPv6 (SRv6) tunnel from the first PCC to a second PCC according to the SIDs and the indicating information. For another example, the transceiving unit of the PCC is configured to receive a first path computation element communication protocol (PCEP) message from a path computation element (PCE), wherein the first PCEP message comprises an indicating information and a segment identifier (SID) field, the SID field comprises multiple SIDs and the indicating information is used to indicate that each of the multiple SIDs is an IPv6 Prefix of a node in tunnel respectively; and the processing unit of the PCC is configured to establish a segment routing for IPv6 (SRv6) tunnel from the first PCC to a second PCC according to the SIDs and the indicating information.

Although the present subject matter is explained considering that the present invention is implemented as the PCC or PCE, it may be understood that the PCC or PCE may also be implemented in a variety of computing systems, such as a laptop computer, a desktop computer, a notebook, a workstation, a mainframe computer, a server, a network server, and the like. It will be understood that the PCC or PCE may be accessed by multiple users through one or more user devices (not shown), collectively referred to as user hereinbefore/after, or applications residing on the user devices. Examples of the PCC or PCE may include, but are not limited to, a router, a switch, a controller in a SDN, a portable computer, a personal digital assistant, a handheld device, and a workstation. The PCC and PCE are communicatively coupled to with each other through a network.

In the present invention, in order to support SRv6 tunnel, the PCEP is extended to support IPv6 capability (in Open Object/open message), IPv6 prefix SR-Stack (in SR-ERO subobject) and a new path-setup-type (in RP/SRP object). With these extensions, a PCC can create tunnel or a PCE can send request to a PCC for creating a tunnel based on SRv6 (e.g. IPv6 tunnel based on SRH technique defined in IETF draft-ietf-6man-segment-routing-header-<NUM>).

In SR networks, an ingress node of an SR path appends all outgoing packets with an SR header (SRH) consisting of a list of SIDs (i.e., IPv6 prefix in case of SRH-IPv6). The header has all necessary information to guide the packets from the ingress node to the egress node of the path, and hence there is no need for any signaling protocol. The present invention describes extensions to SR path for IPv6 forwarding-plane. SR-path (i.e., ERO object) consists of an ordered set of SIDs. A PCC or PCE indicates its ability to support IPv6 SR-path during the PCEP session Initialization phase via a new flag in the SR-PCE-CAPABILITY TLV format.

Referring to <FIG>, which illustrates the process flow of a method for establishing a Segment Routing tunnel over an IPv6 data-plane (SRv6) configured at a PCC or initiated by PCE, according to an embodiment of the present invention. In one method, when PCC configures the tunnel, then before the PCE sending the first PCEP message, receives a second PCEP message from the PCC, wherein the second PCEP message can be PCReq MESSAGE. And the PCE sends a third PCEP message to PCC. The third PCEP message is PCRep MESSAGE.

In the embodiment, the method <NUM> includes the following steps for sending data packets in a communications network through SRv6 tunnel:
Step <NUM>: generating, by a path computation element (PCE), a first path computation element communication protocol (PCEP) message, wherein the first PCEP message comprises an indicating information and a segment identifier (SID) field, the SID field comprises multiple SIDs and the indicating information is used to indicate that each of the multiple SIDs is an IPv6 prefix of a node in a tunnel respectively. Optionally, The first PCEP message can includes an ERO object to carry the indicating information and the SID field. The indicating information can be a bit, but the present invention does not limit to this.

Step <NUM>: sending, by the said PCE, the first PCEP message to a first PCC to establish a SRv6tunnel from the first PCC to a second PCC according to the SIDs and the indication information.

Step <NUM>: Receiving, by a first path computation client (PCC), a first path computation element communication protocol (PCEP) message from a path computation element (PCE), wherein the first PCEP message comprises an indicating information and a segment identifier (SID) field, the SID field comprises multiple SIDs and the indicating information is used to indicate that each of the multiple SIDs is an IPv6 Prefix of a node in tunnel respectively.

Step <NUM>: establishing, by the first PCC, a segment routing for IPv6 forwarding plane (SR-IPv6) tunnel from the first PCC to a second PCC according to the SIDs and the indicating information.

In the various embodiments of the present invention, the first PCEP message can be selected from a Path Computation Initiate (PCInitiate) message, the second PCEP message can be selected from a Path Computation Request (PCReq) message, and the third PCEP message can be selected from a Path Computation Reply (PCRep) message. The PCEP message can also be selected from an update message (PCUpd) or LSP State Report (PCRpt).

Referring to <FIG>, which illustrates the flow chart diagram of a method <NUM> for configuring SRv6 tunnel initiated by a PCC. It illustrates the followings steps:.

<FIG> illustrates the flow chart diagram of a method <NUM> for configuring SRv6 tunnel initiated by a PCE. The flow chart diagram of SRv6 tunnel initiated by PCE, according to second embodiment of the present invention. It illustrates the following steps:.

The SRv6 tunnel setup by PCE schematic is shown <FIG>. The PCE send a first PCEP message to the first PCC node (Ingress node). The message contains the ERO according to the format as shown in <FIG>.

Referring to <FIG> which illustrates the schematic of SRv6 packet forwarding, based on SRv6 data plane, in accordance with an embodiment of the present subject matter. As shown in the figure, at ingress, PCC downloads SRv6 IPv6 Prefix SIDS as SRv6 Next Headers List. At each transit node, Destination Address (DA) is updated. PCE updates ingress node with SRv6 ERO. On receiving packet at ingress, it applies SRv6 ERO as SRv6 next headers and forwards the packet to A, DA [1A1] (i.e. from the bottom of the next-headers). At A, DA is updated to [A2B1] and packet is forwarded to B. At B, DA is updated to [B2C1] and packet is forwarded to C. At C, DA is updated to [C2D1] and packet is forwarded to E (i.e. Final Destination).

In the embodiment, before generating a first PCEP message, the SRv6 capable PCEP session is establish between PCC and PCE by an OPEN message. In the present invention, a SRv6-PCE-CAPABILITY TLV is introduced, but it's an optional TLV associated with the OPEN Object to exchange SR IPv6 capability of PCEP speakers. The PCE and PCC exchange an open message to establish SRv6 capable PCEP session. PCC or PCE must encode the SRv6-PCE-CAPABILITY TLV in the open message. When a PCEP session between a PCC and a PCE is established, both PCEP speakers to exchange their capabilities to indicate their ability to support SRH specific functionality.

The <FIG> illustrates the updated format of SRv6 capability TLV in accordance with an embodiment of the present subject matter. This TLV is for SR based on iPv6 data plane not TE existing one is for SR-TE. The format of the SRv6-PCE-CAPABILITY TLV is shown in the figure. The code point for the TLV type is TBD as defined by IANA. The TLV length is <NUM> octets and is variable length. The <NUM>-bit value is formatted as follows. The MAX-SL is "Maximum SID Depth" (<NUM> octet) field (MSD) specifies the maximum number of SIDs a PCC is capable of imposing as MPLS labels. The "SRH MSD" (<NUM> octets) field (SRH MSD) specifies the maximum number of SIDs a PCC is capable of imposing as next headers in SRH. "Flags" field is <NUM> octet long, and the present invention defines the following flag:
L-flag: A PCC sets this flag to <NUM> to indicate that it does not impose any limit on MSD.

The exchanging of SR capability is same as described in the Internet draft-ietf-pce-segment-routing of the prior art. Therefore, the same is not repeated herein to maintain brevity.

In the embodiment, the PCE learns IPv6 LSDB via PCEPLSBGPLS/IGP protocols. The IPv6PrefixSIDs are advertised by IGP for each IPv6 adjacency. PCC and PCE must have BGPLS/IGP or PCEPLS (capability), so PCC can update Link-State-Database (LSDB) to PCE. PCE updates network topology based on LSDB received and uses the same to compute path.

In the embodiment PCE encodes SRv6_ERO in PCRep (i.e. if PCReq message is send from PCC to PCE), in PCUpd (i.e. if LSP is delegated from PCC to PCE), in PCInitiate (i.e. if tunnel is initiated by PCE). PCC encodes SRv6_RRO in PCRpt (i.e. in Path Computation Report send from PCC to PCE).

In one embodiment of the present invention, in order to set up a tunnel with IPv6 SRH technique is utilized by PCE to support tunnel setup based on SRv6. The PCC configure Tunnel with path-setup-type SRv6 (i.e. PST=<NUM>). A PATH-SETUP-TYPE (<NUM>) is defined in PATH-SETUP-TYPE TLV. <FIG> illustrates the format of path setup type TLV (PST Type <NUM> is added). This TLV is encoded in RP/SRP object as specified in Internet-draft document draft-ietf-pce-lsp-setup-type, SRP object can be encoded in PCUpd (to identify the transaction from PCE) and PCRpt (i.e. to match the transaction received from PCE) message.

Referring to <FIG> and <FIG>, which illustrate a SRv6- Explicit Route Object (ERO) Subobject and SRv6- Route Record object (RRO) Subobject, respectively, in accordance with an embodiment of the present invention, whereby SID is the Segment Identifier and Node or Adjacency Identifier (NAI) contains the NAI associated with the SID.

In the embodiment, SR-ERO/SR-RRO subobject is modified to support variable length SID for SR IPv6. Indicating information, i.e., a bit (I), is introduced, which indicates SID is variable length (i.e. <NUM> bytes to encode IPv6 Prefix) unlike <NUM> bytes in old subobjects. ERO object is encoded in PCUpd, PCInitiate or PCRep message, to convey the explicit-path to PCC from PCE. RRO object is encoded in PCRpt message to convey the actual-path to PCE from PCC, RRO object also can be encoded in PCReq message.

In one embodiment, for supporting IPv6 SID(s), indicating information, i.e., a new bit (I), is set in existing SR-ERO sub object. If I bit is set, then SR-ERO sub object consists of a <NUM>-bit header followed by the IPv6 SID and the NAI associated with theIPv6 SID. If I-bit is set, length field is variable unlike defined in the Internet Draft document, I-D. ietf-pce-segment-routing. The SR-ERO Subobject format is shown in <FIG>. The fields in the SR-ERO Subobject are as follows:.

Flags is used to carry any additional information pertaining to SID. In the embodiment of the present invention, new bit(I) is defined.

M: When this bit is set, the SID value represents an MPLS label stack entry as specified in [RFC5462] where only the label value is specified by the PCE.

I: When this bit is set, the SID value represents an IPv6 SRH stack entry as specified in [I-D. ietf-6man-segment-routing-header]. If M bit is set I bit MUST not be set and vice-versa, otherwise PCEP speaker MUST send a PCErr message with Error-Type = <NUM> ("Reception of an invalid object") and Error Value = TBD ("Bad SID format").

Other bits are as defined in draft-ietf-pce-segment-routing.

In the embodiment, the ERO processing remains same except processing for new flag bit(I) defined and variable SID(i.e.PrefixSID), if a PCEP speaker does not support PrefixSID it MUST send PCErr message with Error-Type = <NUM> (Not supported object) and Error-Value = <NUM> (Not supported object Type). If M bit is set I bit MUST not be set and vice-versa, otherwise PCEP speaker MUST send a PCErr message with Error-Type = <NUM> ("Reception of an invalid object") and Error Value = TBD ("Bad SID Format").

In order to support SRH only SR-ERO sub-object is modified, other RRO related sub-objects and processing must follow as specified in the Internet Draft I-D. ietf-pce-segment-routing. A SRIPv6-ERO subobject consists of a <NUM>-bit header followed by the variable (SID) PrefixSID and the NAI associated with the PrefixSID.

In the embodiment, a PCEP speaker that does not support the SR PCEP capability cannot recognize the SR-ERO or SR-RRO subobjects with new (I) flag MUST send a PCEP error with Error-Type = <NUM> (Not supported object) and Error- Value = <NUM> (Not supported object Type) as per [RFC5440].

Accordingly, some of the noteworthy features of the present invention is as follows:.

Although implementations for method for establishing ipv6 segment routing (srv6) tunnel by extending PCEP have been described in language specific to structural features and/or methods, it is to be understood that the appended claims are not necessarily limited to the specific features or methods described. Rather, the specific features and methods are disclosed as examples of implementations of the method for establishing ipv6 segment routing (srv6) tunnel by extending PCEP.

The embodiments of the present invention provides a PCE in a network. <FIG> is schematic diagram of the PCE according to an embodiment of the present invention. Other parts of the PCE can refer to the existing technology of PCE and not be described in the present invention.

As shown in <FIG>, the PCE includes a transceiving unit <NUM> and a processing unit <NUM>. Wherein, the transceiving unit <NUM> is configure to perform the receiving action and sending action performed by the PCE in the method <NUM>, <NUM> or <NUM> as shown in <FIG>, and the processing unit <NUM> is configured to perform the other actions except the receiving action and the sending action in the method <NUM>, <NUM> or <NUM>. For example, the processing unit <NUM> is configured to generate a first path computation element communication protocol (PCEP) message, wherein the first PCEP message comprises an indicating information and a segment identifier (SID) field, the SID field comprises multiple SIDs and the indicating information is used to indicate that each of the multiple SIDs is an IPv6 prefix of a node in a tunnel respectively; and the transceiving unit <NUM> is configured to send the first PCEP message to a first path computation client (PCC) to establish a segment routing for IPv6 (SRv6) tunnel from the first PCC to a second PCC according to the SIDs and the indicating information. The detailed description refer to the above method embodiments and details are not described herein again.

Corresponding to the method shown in <FIG>, an embodiment of the present invention further provides a PCE <NUM>. Referring to a schematic diagram shown in <FIG>, the PCE may include: a processor <NUM>, a memory <NUM>, a transceiver <NUM>, and a bus system504, where.

As shown in <FIG>, the PCC includes a transceiving unit <NUM> and a processing unit <NUM>. Wherein, the transceiving unit <NUM> is configure to perform the receiving action and sending action performed by the PCC in the method <NUM>, <NUM> or <NUM> as shown in <FIG>, and the processing unit <NUM> is configured to perform the other actions except the receiving action and the sending action in the method <NUM>, <NUM> or <NUM>. For example, the transceiving unit <NUM> is configured to receive a first path computation element communication protocol (PCEP) message from a path computation element (PCE), wherein the first PCEP message comprises an indicating information and a segment identifier (SID) field, the SID field comprises multiple SIDs and the indicating information is used to indicate that each of the multiple SIDs is an IPv6 Prefix of a node in tunnel respectively; and the processing unit <NUM> is configured to establish a segment routing for IPv6 (SRv6) tunnel from the first PCC to a second PCC according to the SIDs and the indicating information. The detailed description refer to the above method embodiments and details are not described herein again.

Corresponding to the method shown in <FIG>, an embodiment of the present invention further provides a PCC <NUM>. Referring to a schematic diagram shown IN <FIG>, the PCC may include: a processor <NUM>, a memory <NUM>, a transceiver <NUM>, and a bus system604, where.

The processor in the present invention may be implemented as one or more microprocessors, microcomputers, microcontrollers, digital signal processors, central processing units, state machines, logic circuitries, and/or any devices that manipulate signals based on operational instructions. Among other capabilities, at least one processor is configured to fetch and execute computer-readable instructions stored in the memory to implement the method of present invention.

A system is provided, where the system includes: a PCE according to any one of the above PCE and a PCC according to any one of the above PCC.

From the foregoing descriptions of the implementation manners, a person skilled in the art may clearly understand that some or all steps of the methods in the embodiments may be implemented by software in addition to a universal hardware platform. Based on such an understanding, the technical solutions of the present invention essentially or the part contributing to the prior art may be implemented in a form of a software product. The software product may be stored in a storage medium, such as a read-only memory (English: read-only memory, ROM for short), a RAM, a magnetic disk, or an optical disc, and includes several instructions for instructing a computer device (which may be a personal computer, a server, or a network device such as media gateway) to perform the methods described in the embodiments or some parts of the embodiments of the present invention.

It should be noted that the embodiments in this specification are all described in a progressive manner, for same or similar parts in the embodiments, reference may be made to these embodiments, and each embodiment focuses on a difference from other embodiments. Especially, network device and system embodiments are basically similar to a method embodiment, and therefore are described briefly; for related parts, reference may be made to partial descriptions in the method embodiment. The described network device embodiment is merely exemplary. The units described as separate parts may or may not be physically separate, and parts displayed as units may or may not be physical units, may be located in one position, or may be distributed on multiple network units. Some or all of the modules may be selected according to actual needs to achieve the objectives of the solutions of the embodiments. A person of ordinary skill in the art may understand and implement the embodiments of the present invention without creative efforts.

Embodiment can include the following features:.

Claim 1:
A method implemented by a path computation element, PCE, and comprising:
receiving, from a path computation client, PCC, a first Path Computation Element Communication Protocol, PCEP, message that is an OPEN message, the first PCEP message comprising a first Segment Routing over IPv6, SRv6, capability type-length-value, TLV, indicating that the PCC supports SRv6;
sending, to the PCC, a second PCEP message that is an OPEN message, the second PCEP message comprising a second SRv6 capability TLV indicating that the PCE supports SRv6; and
after receiving the first PCEP message and sending the second PCEP message, sending (<NUM>), to the PCC, a third PCEP message comprising an explicit route object, ERO, for establishing a SRv6 tunnel,
wherein the ERO comprises an SRv6-ERO subobject, and
wherein the SRv6-ERO subobject comprises an SRv6 segment identifier, SID.