One document matched: draft-ietf-pce-pcep-domain-sequence-02.xml
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<rfc ipr="trust200902" category="exp" docName="draft-ietf-pce-pcep-domain-sequence-02" obsoletes="" updates="" submissionType="IETF" xml:lang="en">
<front>
<title abbrev="DOMAIN SEQ">Standard Representation Of Domain-Sequence</title>
<author initials="D" surname="Dhody" fullname="Dhruv Dhody">
<organization>Huawei Technologies India Pvt Ltd</organization>
<address>
<postal>
<street>Leela Palace</street>
<city>Bangalore</city>
<region>Karnataka</region>
<code>560008</code>
<country>INDIA</country>
</postal>
<email>dhruv.dhody@huawei.com</email>
</address>
</author>
<author initials="U" surname="Palle" fullname="Udayasree Palle">
<organization>Huawei Technologies India Pvt Ltd</organization>
<address>
<postal>
<street>Leela Palace</street>
<city>Bangalore</city>
<region>Karnataka</region>
<code>560008</code>
<country>INDIA</country>
</postal>
<email>udayasree.palle@huawei.com</email>
</address>
</author>
<author initials="R" surname="Casellas" fullname="Ramon Casellas">
<organization>CTTC - Centre Tecnologic de Telecomunicacions de Catalunya</organization>
<address>
<postal>
<street>Av. Carl Friedrich Gauss n7</street>
<city>Castelldefels</city>
<region>Barcelona </region>
<code>08860</code>
<country>SPAIN</country>
</postal>
<email>ramon.casellas@cttc.es </email>
</address>
</author>
<date month="Feb" year="2013" />
<area>Routing</area>
<workgroup>PCE Working Group</workgroup>
<abstract>
<t>The ability to compute shortest constrained Traffic Engineering Label Switched Paths (TE LSPs) in Multiprotocol Label Switching (MPLS) and Generalized MPLS (GMPLS) networks across multiple domains has been identified as a key requirement for P2P and P2MP scenarios. In this context, a domain is a collection of network elements within a common sphere of address management or path computational responsibility such as an IGP area or an Autonomous Systems. This document specifies a standard representation and encoding of a Domain-Sequence, which is defined as an ordered sequence of domains traversed to reach the destination domain. This document also defines new subobjects to be used to encode domain identifiers. </t>
</abstract>
</front>
<middle>
<section title="Introduction" toc="default">
<t>A PCE may be used to compute end-to-end paths across multi-domain environments using a per-domain path computation technique <xref target="RFC5152"/>. The so called backward recursive path computation (BRPC) mechanism <xref target="RFC5441"/> defines a PCE-based path computation procedure to compute inter-domain constrained (G)MPLS TE LSPs. However, both per-domain and BRPC techniques assume that the sequence of domains to be crossed from source to destination is known, either fixed by the network operator or obtained by other means. For inter-domain point-to-multi-point (P2MP) tree, <xref target="PCE-P2MP-PROCEDURES"/> assumes the domain-tree is known.</t>
<t>The list of domains (domain-sequence) in a point-to-point (P2P) path or a point-to-multi-point (P2MP) tree is usually a constraint in the path computation request. The PCE determines the next PCE to forward the request based on the domain-sequence.</t>
<t>In a multi-domain path computation, a PCC MAY indicate the sequence of domains to be traversed using the Include Route Object (IRO) defined in <xref target="RFC5440"/>. </t>
<t>When the sequence of domains is not known in advance, the Hierarchical PCE <xref target="RFC6805"/> architecture and mechanisms can be used to determine the end-to-end Domain-Sequence.</t>
<t>This document defines a standard way to represent and encode a Domain-Sequence in various deployment scenarios including P2P, P2MP and Hierarchical PCE (H-PCE) <xref target="RFC6805"/>. </t>
<t>The Domain-Sequence (the set of domains traversed to reach the destination domain) is either administratively predetermined or discovered by some means (H-PCE) that is outside of the scope of this document.</t>
<t><xref target="RFC5440"/> defines the Include Route Object (IRO) and the Explicit Route Object (ERO); <xref target="RFC5521"/> defines the Exclude Route Object (XRO) and the Explicit Exclusion Route Subobject (EXRS); The use of Autonomous Number (AS) (2-Byte) as an abstract node representing domain is defined in <xref target="RFC3209"/>, This document specifies new subobjects to include or exclude domains such as an IGP area or an Autonomous Systems (4-Byte).</t>
<section title="Requirements Language" toc="default">
<t>The key words "MUST", "MUST NOT", "REQUIRED", "SHALL", "SHALL NOT", "SHOULD", "SHOULD NOT", "RECOMMENDED", "MAY", and "OPTIONAL" in this document are to be interpreted as described in <xref target="RFC2119"/>.</t>
</section>
</section>
<section title="Terminology" toc="default">
<t>The following terminology is used in this document.</t>
<t>
<list style="hanging">
<t hangText="ABR:">OSPF Area Border Router. Routers used to connect two IGP areas.</t>
<t hangText="AS:">Autonomous System.</t>
<t hangText="ASBR:">Autonomous System Boundary Router.</t>
<t hangText="BN:">Boundary Node, Can be an ABR or ASBR.</t>
<t hangText="BRPC:">Backward Recursive Path Computation</t>
<t hangText="Domain:">As per <xref target="RFC4655"/>, any collection of network elements within a common sphere of address management or path computational responsibility. Examples of domains include Interior Gateway Protocol (IGP) areas and Autonomous Systems (ASs).</t>
<t hangText="Domain-Sequence:">An ordered sequence of domains traversed to reach the destination domain.</t>
<t hangText="ERO:">Explicit Route Object</t>
<t hangText="H-PCE:">Hierarchical PCE</t>
<t hangText="IGP:">Interior Gateway Protocol. Either of the two routing protocols, Open Shortest Path First (OSPF) or Intermediate System to Intermediate System (IS-IS).</t>
<t hangText="IRO:">Include Route Object</t>
<t hangText="IS-IS:">Intermediate System to Intermediate System.</t>
<t hangText="OSPF:">Open Shortest Path First.</t>
<t hangText="PCC:">Path Computation Client: any client application requesting a path computation to be performed by a Path Computation Element.</t>
<t hangText="PCE:">Path Computation Element. An entity (component, application, or network node) that is capable of computing a network path or route based on a network graph and applying computational constraints.</t>
<t hangText="P2MP:">Point-to-Multipoint</t>
<t hangText="P2P:">Point-to-Point</t>
<t hangText="RSVP:">Resource Reservation Protocol</t>
<t hangText="TE LSP:">Traffic Engineering Label Switched Path.</t>
</list>
</t>
</section>
<section title="Detail Description" toc="default">
<section title="Domains" toc="default">
<t><xref target="RFC4726"/> and <xref target="RFC4655"/> define domain as a separate administrative or geographic environment within the network. A domain may be further defined as a zone of routing or computational ability. Under these definitions a domain might be categorized as an Autonomous System (AS) or an Interior Gateway Protocol (IGP) area. Each AS can be made of several IGP areas. In order to encode a Domain-Sequence, it is required to uniquely identify a domain in the Domain-Sequence. A domain can be uniquely identified by area-id or AS or both.</t>
</section>
<section title="Domain-Sequence" toc="default">
<t>A domain-sequence is an ordered sequence of domains traversed to reach the destination domain. </t>
<t>A domain-sequence can be applied as a constraint and carried in path computation request to PCE(s). A domain-sequence can also be the result of a path computation. For example, in the case of H-PCE <xref target="RFC6805"/> Parent PCE MAY send the Domain-Sequence as a result in a path computation reply. </t>
<t>In this context, the ordered nature of a domain-sequence is important. In a P2P path, the domains listed appear in the order that they are crossed. In a P2MP path, the domain tree is represented as list of domain sequences. </t>
<t>A domain-sequence enables a PCE to select the next PCE to forward the path computation request based on the domain information. </t>
<t>A PCC or PCE MAY add an additional constraints covering which Boundary Nodes (ABR or ASBR) or Border links (Inter-AS-link) MUST be traversed while defining a Domain-Sequence. </t>
<t>Thus a Domain-Sequence MAY be made up of one or more of -</t>
<t>
<list style="symbols">
<t>AS Number</t>
<t>Area ID</t>
<t>Boundary Node ID</t>
<t>Inter-AS-Link Address</t>
</list>
</t>
<t>Consequently, a Domain-Sequence can be used: </t>
<t>
<list style="numbers">
<t>by a PCE in order to discover or select the next PCE in a collaborative path computation, such as in BRPC <xref target="RFC5441"/>; </t>
<t>by the Parent PCE to return the Domain-Sequence when unknown, this can further be an input to BRPC procedure <xref target="RFC6805"/>;</t>
<t>by a PCC (or PCE) to constraint the domains used in a H-PCE path computation, explicitly specifying which domains to be expanded;</t>
<t>by a PCE in per-domain path computation model <xref target="RFC5152"/> to identify the next domain(s);</t>
</list>
</t>
</section>
<section title="Standard Representation" toc="default">
<t>Domain-Sequence MAY appear in PCEP Messages, notably in - </t>
<t>
<list style="symbols">
<t>Include Route Object (IRO): As per <xref target="RFC5440"/>, used to specify set of network elements that MUST be traversed. These subobjects are used to specify the domain-sequence that MUST be traversed to reach the destination. </t>
<t>Exclude Route Object (XRO): As per <xref target="RFC5521"/>, used to specify certain abstract nodes that MUST be excluded from whole path. These subobjects are used to specify certain domains that MUST be avoided to reach the destination. </t>
<t>Explicit Exclusion Route Subobject (EXRS): As per <xref target="RFC5521"/>, used to specify exclusion of certain abstract nodes between a specific pair of nodes. EXRS are a subobject inside the IRO. These subobjects are used to specify the domains that must be excluded between two abstract nodes.</t>
<t>Explicit Route Object (ERO): As per <xref target="RFC5440"/>,used to specify a computed path in the network. </t>
</list>
</t>
</section>
<section title="Include Route Object (IRO)" toc="default" anchor="sec_iro_sub">
<t>As per <xref target="RFC5440"/>, IRO (Include Route Object) can be used to specify that the computed path MUST traverse a set of specified network elements or abstract nodes.</t>
<section title="Subobjects" toc="default" >
<t>Some subobjects are defined in <xref target="RFC3209"/>, <xref target="RFC3473"/>, <xref target="RFC3477"/> and <xref target="RFC4874"/>, but new subobjects related to Domain-Sequence are needed.</t>
<t>The following subobject types are used in IRO.</t>
<figure title="" suppress-title="false" align="left" alt="" width="" height="">
<artwork xml:space="preserve" name="" type="" align="left" alt="" width="" height=""><![CDATA[
The following subobject types are used.
Type Subobject
1 IPv4 prefix
2 IPv6 prefix
4 Unnumbered Interface ID
32 Autonomous system number (2 Byte)
33 Explicit Exclusion (EXRS)
]]></artwork>
</figure>
<t>This document extends the above list to support 4-Byte AS numbers and IGP Areas.</t>
<figure title="" suppress-title="false" align="left" alt="" width="" height="">
<artwork xml:space="preserve" name="" type="" align="left" alt="" width="" height=""><![CDATA[
The following subobject types are used.
Type Subobject
TBD Autonomous system number (4 Byte)
TBD OSPF Area id
TBD ISIS Area id
]]></artwork>
</figure>
<t>- Autonomous system</t>
<t><xref target="RFC3209"/> already defines 2 byte AS number.</t>
<t>To support 4 byte AS number as per <xref target="RFC4893"/> following subobject is defined: </t>
<t>
<figure title="" suppress-title="false" align="left" alt="" width="" height="">
<artwork xml:space="preserve" name="" type="" align="left" alt="" width="" height=""><![CDATA[
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|L| Type | Length | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| AS Id (4 bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
]]></artwork>
</figure>
</t>
<t>L: The L bit is an attribute of the subobject as define in <xref target="RFC3209"/>. </t>
<t>Type: (TBA by IANA) indicating 4 byte AS Number. </t>
<t>Length: 8 (Total length of the subobject in bytes). </t>
<t>Reserved: Zero at transmission, Ignored at receipt. </t>
<t>AS-ID: The 4 byte AS Number. Note that if 16-bit AS numbers are in use, the low order bits (16 through 31) should be used and the high order bits (0 through 15) should be set to zero. </t>
<t>- IGP Area</t>
<t>Since the length and format of Area-id is different for OSPF and ISIS, following two subobjects are defined: </t>
<t>
<figure title="" suppress-title="false" align="left" alt="" width="" height="">
<artwork xml:space="preserve" name="" type="" align="left" alt="" width="" height=""><![CDATA[ For OSPF, the area-id is a 32 bit number. The Subobject looks
0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|L| Type | Length | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OSPF Area Id (4 bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
]]></artwork>
</figure>
</t>
<t>L: The L bit is an attribute of the subobject as define in <xref target="RFC3209"/>. </t>
<t>Type: (TBA by IANA) indicating 4 byte OSPF Area ID. </t>
<t>Length: 8 (Total length of the subobject in bytes). </t>
<t>Reserved: Zero at transmission, Ignored at receipt. </t>
<t>OSPF Area Id: The 4 byte OSPF Area ID. </t>
<t> </t>
<t>For IS-IS, the area-id is of variable length and thus the length of the Subobject is variable. The Area-id is as described in IS-IS by ISO standard <xref target="ISO 10589"/>.</t>
<t>
<figure title="" suppress-title="false" align="left" alt="" width="" height="">
<artwork xml:space="preserve" name="" type="" align="left" alt="" width="" height=""><![CDATA[ 0 1 2 3
0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1 2 3 4 5 6 7 8 9 0 1
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|L| Type | Length | Area-Len | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
// IS-IS Area ID //
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
]]></artwork>
</figure>
</t>
<t>L: The L bit is an attribute of the subobject as define in <xref target="RFC3209"/>. </t>
<t>Type: (TBA by IANA) indicating IS-IS Area ID. </t>
<t>Length: Variable (Total length of the subobject in bytes including padding). The Length MUST be at least 4, and MUST be a multiple of 4.</t>
<t>Area-Len: Variable (Length of the actual (non-padded) IS-IS Area Identifier in octets; Valid values are from 2 to 11 inclusive). </t>
<t>Reserved: Zero at transmission, Ignored at receipt. </t>
<t>IS-IS Area Id: The variable-length IS-IS area identifier. Padded with trailing zeroes to a four-byte boundary. </t>
</section>
<section title="Option (A): New IRO Object Type" toc="default">
<t><xref target="RFC5440"/> in its description of IRO does not require the subobjects to be in a given particular order. When considering a Domain-Sequence, the domain relative ordering is a basic criterion and, as such, this option suggest a new IRO object type.</t>
<t>
<figure title="" suppress-title="false" align="left" alt="" width="" height="">
<artwork xml:space="preserve" name="" type="" align="left" alt="" width="" height=""><![CDATA[ IRO Object-Class is 10.
IRO Object-Type is TBD. (2 suggested value to IANA)
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
// (Subobjects) //
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
]]></artwork>
</figure>
</t>
<t>Subobjects: The IRO is made of subobjects identical to the ones defined in <xref target="RFC3209"/>, <xref target="RFC3473"/>, and <xref target="RFC3477"/>, where the IRO subobject type is identical to the subobject type defined in the related documents. Some new subobjects related to Domain-Sequence are also added in this document as mentioned in <xref target="sec_iro_sub"/>. </t>
<t><xref target="RFC3209"/> defines subobjects for IPv4, IPv6 and unnumbered Interface ID, which in the context of domain-sequence is used to specify Boundary Node (ABR/ASBR) and Inter-AS-Links. The subobjects for AS Number (2 or 4 Byte) and IGP Area is used to specify the domains in the domain-sequence.</t>
<t>The new IRO Object-Type used to define the domain-sequence would handle the L bit (Loose / Strict) in the subobjects similar to <xref target="RFC3209"/>. </t>
<t>Further we have following options:</t>
<t>* Option (A.1): New IRO Object Type for Domain-Sequence object only</t>
<t>A new IRO Object Type is used to specify the ordered sequence of domains (Domain-Sequence) only. The PCReq message is modified to allow encoding of both types of IRO; one with IRO Type 1 <xref target="RFC5440"/> used to specify the intra-domain abstract nodes and resources and the second IRO Type with the new subobjects as described in this section to specify the domain-sequence. </t>
<t>All other rules of PCEP objects and message processing (ex. P bit handling of Common Object Header) is as per <xref target="RFC5440"/>. </t>
<t>* Option (A.2): New IRO Object Type for both intra and inter-domain (domain-sequence)</t>
<t>A new IRO Object Type is used to include both intra nodes and inter-domains nodes but the sequence of domain is strict. The intra-domain nodes can still be ordered.</t>
<t>In case of inter-domain path computation, only the new IRO type is used which contains the specific intra domain network nodes as well as inter-domain abstract nodes or domains. The inter-domain abstract nodes are encoded in the sequence they must be traversed but the intra-domain elements MAY be an unordered set.</t>
<section title="Handling of the Domain-Sequence IRO object" toc="default">
<t>An IRO object containing Domain-Sequence subobjects constraints or defines the domains involved in a multi-domain path computation, typically involving two or more collaborative PCEs. </t>
<t>A Domain-Sequence can have varying degrees of granularity; it is possible to have a Domain-Sequence composed of, uniquely, AS identifiers. It is also possible to list the involved areas for a given AS.</t>
<t>In any case, the mapping between domains and responsible PCEs is not defined in this document. It is assumed that a PCE that needs to obtain a "next PCE" from a Domain-Sequence is able to do so (e.g. via administrative configuration, or discovery).</t>
<t>A PCC builds a Domain-Sequence IRO to encode the Domain-Sequence, that is all domains that it wishes the cooperating PCEs to traverse in order to compute the end to end path. </t>
<t>For each inclusion, the PCC clears the L-bit to indicate that the PCE is required to include the domain, or sets the L-bit to indicate that the PCC simply desires that the domain be included in the domain-sequence. </t>
<t>When a PCE receives a PCEP Request message with an IRO, it looks for a Domain-Sequence IRO (new type) to see if a domain-sequence is specified. If the message contains more than one Domain-Sequence IRO (new type), it MUST use the first one in the message and MUST ignore subsequent instances.</t>
<t>If a PCE does not recognize the Domain-Sequence IRO (new type), it MUST return a PCErr message with Error-Type "Unknown Object" and Error-value "Unrecognized object Type" as described in <xref target="RFC5440"/>. </t>
<t>If a PCE is unwilling or unable to process the Domain-Sequence IRO (new type), it MUST return a PCErr message with the Error-Type "Not supported object" and follow the relevant procedures described in <xref target="RFC5440"/>.</t>
<t>If a PCE that supports the Domain-Sequence IRO (new type) and encounters a subobject that it does not support or recognize, it MUST act according to the setting of the L-bit in the subobject. If the L-bit is clear, the PCE MUST respond with a PCErr with Error-Type "Unrecognized subobject" and set the Error-Value to the subobject type code. If the L-bit is set, the PCE MAY respond with a PCErr as already stated or MAY ignore the subobject: this choice is a local policy decision.</t>
<t>If a PCE parses a Domain-Sequence IRO (new type), it MUST act according to the requirements expressed in the subobject. That is, if the L-bit is clear, the PCE(s) MUST produce a path that follows domain-sequence nodes in order identified by the subobjects in the path. If the L-bit is set, the PCE(s) SHOULD produce a path along the Domain-Sequence unless it is not possible to construct a path complying with the other constraints expressed in the request.</t>
<t>A successful path computation reported in a PCEP response message MUST include an ERO to specify the path that has been computed as specified in <xref target="RFC5440"/> following the sequence of domains.</t>
<t>In a PCEP response message, PCE MAY also supply a Domain-Sequence IRO (new type) with the NO-PATH object indicating that the set of elements of the request's Domain-Sequence IRO prevented the PCE from finding a path.</t>
<t>Subobject types for AS and IGP Area affect the next domain selection as well as finding the PCE serving that domain.</t>
<t>Note that a particular domain in the domain-sequence can be identified by :- </t>
<t>
<list style="symbols">
<t>A single IGP Area: Only the IGP (OSPF or ISIS) Area subobject is used to identify the next domain. (Refer <xref target="fig1"/>)</t>
<t>A single AS: Only the AS subobject is used to identify the next domain. (Refer <xref target="fig2"/>)</t>
<t>Both an AS and an IGP Area: Combination of both AS and Area are used to identify the next domain. In this case the order is AS Subobject followed by Area. (Refer <xref target="fig3"/>)</t>
</list>
</t>
<t>Subobject of other types representing Boundary Node or Inter-AS-Link do not pay any role in the selection of next domain, but they MUST be applied during the final path computation procedure as before.</t>
</section>
</section>
<section title="Option B: Existing IRO Object Type" toc="default">
<t>The IRO (Include Route Object) <xref target="RFC5440"/> is an optional object used to specify a set of network elements that the computed path MUST traverse.</t>
<t>The new subobjects denoting the domain-sequence are carried in the same IRO Type 1, and all the rules of processing as specified in <xref target="RFC5440"/> are applied.</t>
<t>Note the following differences :- </t>
<t>
<list style="symbols">
<t>Order: Since there is no inherent order specified in the encoding of the subobjects in IRO Type 1 <xref target="RFC5440"/>, it is the job of the PCE to figure out the optimal order of the domains to be crossed to reach the destination domain. Note that in case of doubt, or when applicable, the PCE can still apply the ordering as specified in the request message. Further PCE may have to crankback and try multiple permutations before figuring out the correct sequence.</t>
<t>Loose / Strict (L-Bit): <xref target="RFC5440"/> state that the L bit of the subobjects within an IRO Type 1 <xref target="RFC5440"/> has no meaning. This will be applicable for subobjects denoting domain-sequence as well.</t>
<t>Scope: Coexistence of intra-domain nodes, boundary nodes and domain nodes in the same IRO List. It is the job of PCE to figure out the scope and apply the processing rules accordingly. The nodes in the IRO which are recognized by the PCE are handled locally and others are forwarded to next PCE hoping they would handle them, the aggregating PCE (Ingress PCE or Parent) would make sure that all nodes in IRO are handled correctly.</t>
</list>
</t>
</section>
</section>
<section title="Exclude Route Object (XRO)" toc="default">
<t>The Exclude Route Object (XRO) <xref target="RFC5521"/> is an optional object used to specify exclusion of certain abstract nodes or resources from the whole path.</t>
<section title="Subobjects" toc="default">
<t>The following subobject types are defined to be used in XRO as defined in <xref target="RFC3209"/>, <xref target="RFC3477"/>, <xref target="RFC4874"/>, and <xref target="RFC5521"/>. </t>
<t>
<figure title="" suppress-title="false" align="left" alt="" width="" height="">
<artwork xml:space="preserve" name="" type="" align="left" alt="" width="" height=""><![CDATA[
Type Subobject
1 IPv4 prefix
2 IPv6 prefix
4 Unnumbered Interface ID
32 Autonomous system number (2 Byte)
34 SRLG
64 IPv4 Path Key
65 IPv6 Path Key
]]></artwork>
</figure>
</t>
<t>This document extends the above list to support 4-Byte AS numbers and IGP Areas.</t>
<t>
<figure title="" suppress-title="false" align="left" alt="" width="" height="">
<artwork xml:space="preserve" name="" type="" align="left" alt="" width="" height=""><![CDATA[
Type Subobject
TBD Autonomous system number (4 Byte)
TBD OSPF Area id
TBD ISIS Area id
]]></artwork>
</figure>
</t>
<section title="Autonomous system" toc="default">
<t>The new subobjects to support 4 byte AS and IGP (OSPF / ISIS) Area MAY also be used in the XRO to specify exclusion of certain domains in the path computation procedure.</t>
<t>
<figure title="" suppress-title="false" align="left" alt="" width="" height="">
<artwork xml:space="preserve" name="" type="" align="left" alt="" width="" height=""><![CDATA[
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|X| Type | Length | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| AS Id (4 bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
]]></artwork>
</figure>
</t>
<t>The X-bit indicates whether the exclusion is mandatory or desired. </t>
<t> 0 indicates that the AS specified MUST be excluded from the path computed by the PCE(s). </t>
<t> 1 indicates that the AS specified SHOULD be avoided from the inter-domain path computed by the PCE(s), but MAY be included subject to PCE policy and the absence of a viable path that meets the other constraints.</t>
<t>All other fields are consistent with the definition in <xref target="sec_iro_sub"/>.</t>
</section>
<section title="IGP Area" toc="default">
<t>Since the length and format of Area-id is different for OSPF and ISIS, following two subobjects are defined: </t>
<t>For OSPF, the area-id is a 32 bit number. The subobject is encoded as follows: </t>
<t>
<figure title="" suppress-title="false" align="left" alt="" width="" height="">
<artwork xml:space="preserve" name="" type="" align="left" alt="" width="" height=""><![CDATA[
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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|X| Type | Length | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OSPF Area Id (4 bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
]]></artwork>
</figure>
</t>
<t>The X-bit indicates whether the exclusion is mandatory or desired. </t>
<t> 0 indicates that the OSFF Area specified MUST be excluded from the path computed by the PCE(s). </t>
<t> 1 indicates that the OSFF Area specified SHOULD be avoided from the inter-domain path computed by the PCE(s), but MAY be included subject to PCE policy and the absence of a viable path that meets the other constraints.</t>
<t>All other fields are consistent with the definition in <xref target="sec_iro_sub"/>.</t>
<t>For IS-IS, the area-id is of variable length and thus the length of the subobject is variable. The Area-id is as described in IS-IS by ISO standard <xref target="ISO 10589"/>. The subobject is encoded as follows:</t>
<t>
<figure title="" suppress-title="false" align="left" alt="" width="" height="">
<artwork xml:space="preserve" name="" type="" align="left" alt="" width="" height=""><![CDATA[ 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|X| Type | Length | Area-Len | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
// IS-IS Area ID //
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
]]></artwork>
</figure>
</t>
<t>The X-bit indicates whether the exclusion is mandatory or desired. </t>
<t> 0 indicates that the ISIS Area specified MUST be excluded from the path computed by the PCE(s). </t>
<t> 1 indicates that the ISIS Area specified SHOULD be avoided from the inter-domain path computed by the PCE(s), but MAY be included subject to PCE policy and the absence of a viable path that meets the other constraints.</t>
<t>All other fields are consistent with the definition in <xref target="sec_iro_sub"/>.</t>
<t>If a PCE that supports XRO and encounters a subobject that it does not support or recognize, it MUST act according to the setting of the X-bit in the subobject. If the X-bit is clear, the PCE MUST respond with a PCErr with Error-Type "Unrecognized subobject" and set the Error-Value to the subobject type code. If the X-bit is set, the PCE MAY respond with a PCErr as already stated or MAY ignore the subobject: this choice is a local policy decision.</t>
<t>All the other processing rules are as per <xref target="RFC5521"/>.</t>
</section>
</section>
</section>
<section title="Explicit Exclusion Route Subobject (EXRS)" toc="default">
<t>Explicit Exclusion Route Subobject (EXRS) <xref target="RFC5521"/> is used to specify exclusion of certain abstract nodes between a specific pair of nodes. </t>
<t>The EXRS subobject may carry any of the subobjects defined for inclusion in the XRO, thus the new subobjects to support 4 byte AS and IGP (OSPF / ISIS) Area MAY also be used in the EXRS. The meanings of the fields of the new XRO subobjects are unchanged when the subobjects are included in an EXRS, except that scope of the exclusion is limited to the single hop between the previous and subsequent elements in the IRO.</t>
<t>All the processing rules are as per <xref target="RFC5521"/>.</t>
</section>
<section title="Explicit Route Object (ERO)" toc="default">
<t>The Explicit Route Object (ERO) <xref target="RFC5440"/> is used to specify a computed path in the network. PCEP ERO subobject types correspond to RSVP-TE ERO subobject types as defined in <xref target="RFC3209"/>, <xref target="RFC3473"/>, <xref target="RFC3477"/>, <xref target="RFC4873"/>, <xref target="RFC4874"/>, and <xref target="RFC5520"/>.</t>
<t>
<figure title="" suppress-title="false" align="left" alt="" width="" height="">
<artwork xml:space="preserve" name="" type="" align="left" alt="" width="" height=""><![CDATA[
Type Subobject
1 IPv4 prefix
2 IPv6 prefix
3 Label
4 Unnumbered Interface ID
32 Autonomous system number (2 Byte)
33 Explicit Exclusion (EXRS)
37 Protection
64 IPv4 Path Key
65 IPv6 Path Key
]]></artwork>
</figure>
</t>
<t>This document extends the above list to support 4-Byte AS numbers and IGP Areas.</t>
<t>
<figure title="" suppress-title="false" align="left" alt="" width="" height="">
<artwork xml:space="preserve" name="" type="" align="left" alt="" width="" height=""><![CDATA[
Type Subobject
TBD Autonomous system number (4 Byte)
TBD OSPF Area id
TBD ISIS Area id
]]></artwork>
</figure>
</t>
<t>The new subobjects to support 4 byte AS and IGP (OSPF / ISIS) Area MAY also be used in the ERO to specify an abstract node (a group of nodes whose internal topology is opaque to the ingress node of the LSP). Using this concept of abstraction, an explicitly routed LSP can be specified as a sequence of domains. </t>
<t>In case of Hierarchical PCE <xref target="RFC6805"/>, a Parent PCE MAY be requested to find the domain-sequence. Refer example in <xref target="sec_hpce"/>.</t>
<t>The format of the new ERO subobjects is similar to new IRO subobjects, refer <xref target="sec_iro_sub"/>.</t>
</section>
</section>
<section title="Other Considerations" toc="default">
<section title="Inter-Area Path Computation" toc="default">
<t>In an inter-area path computation where the ingress and the egress nodes belong to different IGP areas within the same AS, the Domain-Sequence MAY be represented using a ordered list of Area subobjects. The AS number MAY be skipped, as area information is enough to select the next PCE.</t>
<t>
<figure title="Inter-Area Path Computation" anchor="fig1" suppress-title="false" align="left" alt="" width="" height="">
<artwork xml:space="preserve" name="" type="" align="left" alt="" width="" height=""><![CDATA[ +-------------------+ +-------------------+
| | | |
| +--+ | | +--+ |
| +--+ | | | | | | |
| | | +--+ | | +--+ +--+ |
| +--* + + | | |
| | | +--+ |
| *--+ + + |
| | | | | +--+ |
| +--+ | | | | |
| |+--------------------------+| +--+ |
| ++++ +-++ |
| |||| +--+ | || |
| Area 2 ++++ | | +-++ Area 4 |
+-------------------+| +--+ |+-------------------+
| |
| +--+ |
| +--+ | | |
| | | +--+ |
| +--+ |
| |
| |
| |
| |
| +--+ |
| | | |
| +--+ |
+------------------+| |+--------------------+
| ++-+ +-++ |
| || | | || |
| ++-+ Area 0 +-++ |
| |+--------------------------+| +--+ |
| +--+ | | | | |
| | | | | +--+ |
| +--+ +--+ | | |
| | | + + +--+ |
| +--+ | | | | |
| + + +--+ |
| +--+ | | |
| | | | | +--+ |
| +--+ | | | | |
| | | +--+ |
| | | |
| Area 1 | | Area 5 |
+------------------+ +--------------------+
AS Number is 100.]]></artwork>
</figure>
</t>
<t>
<figure title="" suppress-title="false" align="left" alt="" width="" height="">
<artwork xml:space="preserve" name="" type="" align="left" alt="" width="" height=""><![CDATA[This could be represented in the <IRO> as:
+---------+ +---------+ +---------+ +---------+
|IRO | |Sub | |Sub | |Sub |
|Object | |Object | |Object | |Object |
|Header | |Area 2 | |Area 0 | |Area 4 |
| | | | | | | |
| | | | | | | |
+---------+ +---------+ +---------+ +---------+
+---------+ +---------+ +---------+ +---------+ +---------+
|IRO | |Sub | |Sub | |Sub | |Sub |
|Object | |Object AS| |Object | |Object | |Object |
|Header | |100 | |Area 2 | |Area 0 | |Area 4 |
| | | | | | | | | |
| | | | | | | | | |
+---------+ +---------+ +---------+ +---------+ +---------+
AS is optional and it MAY be skipped. PCE should be able to
understand both notations. ]]></artwork>
</figure>
</t>
</section>
<section title="Inter-AS Path Computation" toc="default">
<t>In inter-AS path computation, where ingress and egress belong to different AS, the Domain-Sequence is represented using an ordered list of AS subobjects. The Domain-Sequence MAY further include decomposed area information in Area subobjects.</t>
<section title="Example 1" toc="default">
<t>As shown in <xref target="fig2"/>, where AS to be made of a single area, the area subobject MAY be skipped in the Domain-Sequence as AS is enough to uniquely identify the next domain and PCE.</t>
<t>
<figure title="Inter-AS Path Computation" anchor="fig2" suppress-title="false" align="left" alt="" width="" height="">
<artwork xml:space="preserve" name="" type="" align="left" alt="" width="" height=""><![CDATA[ +---------------------------------+
|AS 200 |
| +------+ |
| | | |
+------------------------+ | | | +------+ |
| AS 100 | | +------+ | | |
| +------+ | | +------+ | | |
| | +-+-----+-+ | +------+ |
| | | | | | | |
| +------+ | | +------+ |
| +------+ | | +------+ |
| | | | | | | |
| | | | | | | |
| +------+ | | +------+ |
| | | |
| +------+ | | +------+ |
| | +-+-----+-+ | +------+ |
| | | | | | | | | |
| +------+ | | +------+ | | |
| | | +------+ |
| | | |
| | | |
| +------+ | | +------+ |
| | | | | | | |
| |PCE | | | |PCE | |
| +------+ | | +------+ |
| | | |
+------------------------+ | |
+---------------------------------+
Both AS are made of Area 0.
]]></artwork>
</figure>
</t>
<t>
<figure title="" suppress-title="false" align="left" alt="" width="" height="">
<artwork xml:space="preserve" name="" type="" align="left" alt="" width="" height=""><![CDATA[
This could be represented in the <IRO> as:
+---------+ +---------+ +---------+
|IRO | |Sub | |Sub |
|Object | |Object AS| |Object AS|
|Header | |100 | |200 |
| | | | | |
| | | | | |
+---------+ +---------+ +---------+
+---------+ +---------+ +---------+ +---------+ +---------+
|IRO | |Sub | |Sub | |Sub | |Sub |
|Object | |Object AS| |Object | |Object AS| |Object |
|Header | |100 | |Area 0 | |200 | |Area 0 |
| | | | | | | | | |
| | | | | | | | | |
+---------+ +---------+ +---------+ +---------+ +---------+
Area subobject is optional and it MAY be skipped. PCE should be
able to understand both notations. ]]></artwork>
</figure>
</t>
</section>
<section title="Example 2" toc="default">
<t>As shown in <xref target="fig3"/>, where AS 200 is made up of multiple areas and multiple domain-sequence exist, PCE MAY include both AS and Area subobject to uniquely identify the next domain and PCE.</t>
<t>
<figure title="Inter-AS Path Computation" anchor="fig3" suppress-title="false" align="left" alt="" width="" height="">
<artwork xml:space="preserve" name="" type="" align="left" alt="" width="" height=""><![CDATA[
|
| +-------------+ +----------------+
| |Area 2 | |Area 4 |
| | +--+| | +--+ |
| | | || | | | |
| | +--+ +--+| | +--+ +--+ |
| | | | | | | | |
| | *--+ | | +--+ |
| | / +--+ | | +--+ |
| |/ | | | | | | |
| / +--+ | | +--+ +--+ |
| /| +--+ |+--------------+| | | |
|/ | | | ++-+ +-++ +--+ |
+-------------+/ | +--+ || | | || |
| /| | ++-+ +-++ |
| +--*|| +-------------+| |+----------------+
| | ||| | +--+ |
| +--+|| | | | |
| +--+ || | +--+ |
| | | || | |
| +--+ || | |
| || | +--+ |
|+--+ || | | | |
|| | || | +--+ |
|+--+ || | |
| || | +--+ |
| +--+ || +------------+ | | | |+----------------+
| | | || |Area 3 +-++ +--+ +-++ Area 5 |
| +--+ || | | || | || |
| || | +-++ +-++ |
| +--+|| | +--+ | | Area 0 || +--+ |
| | ||| | | | | +--------------+| | | |
| +--*|| | +--+ | | +--+ |
| \| | | | +--+ |
|Area 1 |\ | +--+ | | +--+ | | |
+-------------+|\ | | | | | | | +--+ |
| \| +--+ +--+ | +--+ |
| \ | | | |
| |\ +--+ | +--+ |
| | \ +--+ | | | | |
| | \| | | | +--+ |
| | *--+ | | |
| | | | |
| +------------+ +----------------+
|
|
AS 100 | AS 200
|
]]></artwork>
</figure>
</t>
<t>
<figure title="" suppress-title="false" align="left" alt="" width="" height="">
<artwork xml:space="preserve" name="" type="" align="left" alt="" width="" height=""><![CDATA[The Domain-Sequence can be carried in the IRO as shown below:
+-------+ +-------+ +-------+ +-------+ +-------+ +-------+ +-------+
|IRO | |Sub | |Sub | |Sub | |Sub | |Sub | |Sub |
|Object | |Object | |Object | |Object | |Object | |Object | |Object |
|Header | |AS 100 | |Area 1 | |AS 200 | |Area 3 | |Area 0 | |Area 4 |
| | | | | | | | | | | | | |
+-------+ +-------+ +-------+ +-------+ +-------+ +-------+ +-------+
]]></artwork>
</figure>
</t>
<t>The combination of both an AS and an Area uniquely identify a domain in the Domain-Sequence. </t>
<t>Note that an Area domain identifier always belongs to the previous AS that appears before it or, if no AS subobjects are present, it is assumed to be the current AS.</t>
<t>If the area information cannot be provided, PCE MAY forward the path computation request to the next PCE based on AS alone. If multiple PCEs are responsible, PCE MAY apply local policy to select the next PCE. </t>
</section>
</section>
<section title="Boundary Node and Inter-AS-Link" toc="default">
<t>A PCC or PCE MAY add additional constraints covering which Boundary Nodes (ABR or ASBR) or Border links (Inter-AS-link) MUST be traversed while defining a Domain-Sequence. In which case the Boundary Node or Link MAY be encoded as a part of the domain-sequence using the existing subobjects. </t>
<t>Boundary Nodes (ABR / ASBR) can be encoded using the IPv4 or IPv6 prefix subobjects usually the loopback address of 32 and 128 prefix length respectively. An Inter-AS link can be encoded using the IPv4 or IPv6 prefix subobjects or unnumbered interface subobjects. </t>
<t>For <xref target="fig1" />, an ABR to be traversed can be specified as:</t>
<t>
<figure title="" suppress-title="false" align="left" alt="" width="" height="">
<artwork xml:space="preserve" name="" type="" align="left" alt="" width="" height=""><![CDATA[
+---------+ +---------+ +---------++---------+ +---------+
|IRO | |Sub | |Sub ||Sub | |Sub |
|Object | |Object | |Object ||Object | |Object |
|Header | |Area 2 | |IPv4 ||Area 0 | |Area 4 |
| | | | |x.x.x.x || | | |
| | | | | || | | |
+---------+ +---------+ +---------++---------+ +---------+
]]></artwork>
</figure>
</t>
<t>For <xref target="fig2" />, an inter-AS-link to be traversed can be specified as:</t>
<t>
<figure title="" suppress-title="false" align="left" alt="" width="" height="">
<artwork xml:space="preserve" name="" type="" align="left" alt="" width="" height=""><![CDATA[
+---------+ +---------+ +---------+ +---------+ +---------+
|IRO | |Sub | |Sub | |Sub | |Sub |
|Object | |Object AS| |Object | |Object | |Object AS|
|Header | |100 | |IPv4 | |IPv4 | |200 |
| | | | |x.x.x.x | |x.x.x.x | | |
| | | | | | | | | |
+---------+ +---------+ +---------+ +---------+ +---------+
]]></artwork>
</figure>
</t>
</section>
<section title="PCE serving multiple domains" toc="default">
<t>A single PCE MAY be responsible for multiple domains; for example PCE function deployed on an ABR. A PCE which can support 2 adjacent domains can internally handle this situation without any impact on the neighboring domains. </t>
</section>
<section title="P2MP" toc="default">
<t>In case of inter-domain P2MP path computation, (Refer <xref target="PCE-P2MP-PROCEDURES"/>) the path domain tree is nothing but a series of Domain Sequences, as shown in the below figure:</t>
<t>
<figure title="" suppress-title="false" align="left" alt="" width="" height="">
<artwork xml:space="preserve" name="" type="" align="left" alt="" width="" height=""><![CDATA[ D1-D3-D6, D1-D3-D5 and D1-D2-D4.
D1
/ \
D2 D3
/ / \
D4 D5 D6]]></artwork>
</figure>
</t>
<t>All rules of processing as applied to P2P can be applied to P2MP as well.</t>
<t>In case of P2MP, different destinations MAY have different Domain-Sequence within the domain tree, it requires domain-sequence to be attached per destination. (Refer <xref target="PCE-P2MP-PER-DEST"/>)</t>
</section>
<section title="Hierarchical PCE" toc="default" anchor="sec_hpce">
<t>As per <xref target="RFC6805"/>, consider a case as shown in <xref target="fig4"/> consisting of multiple child PCEs and a parent PCE. </t>
<t>
<figure title="Hierarchical PCE" anchor="fig4" suppress-title="false" align="left" alt="" width="" height="">
<artwork xml:space="preserve" name="" type="" align="left" alt="" width="" height=""><![CDATA[
+--------+
| Parent |
| PCE |
+--------+
+-------------------+ +-------------------+
| +--+ | | +--+ |
| +--+ | | | | | | |
| | | +--+ | | +--+ +--+ |
| +--* + + | | |
| | | +--+ |
| *--+ + + |
| | | | | +--+ |
| +--+ | | | | |
| |+--------------------------+| +--+ |
| ++++ +-++ |
| |||| +--+ | || |
| Area 2 ++++ | | +-++ Area 4 |
+-------------------+| +--+ |+-------------------+
| +--+ |
| +--+ | | |
| | | +--+ |
| +--+ |
| |
| +--+ |
| | | |
| +--+ |
+------------------+| |+--------------------+
| ++-+ +-++ |
| || | | || |
| ++-+ Area 0 +-++ |
| |+--------------------------+| +--+ |
| +--+ | | | | |
| | | | | +--+ |
| +--+ +--+ | | |
| | | + + +--+ |
| +--+ | | | | |
| + + +--+ |
| +--+ | | |
| | | | | +--+ |
| +--+ | | | | |
| | | +--+ |
| Area 1 | | Area 5 |
+------------------+ +--------------------+
]]></artwork>
</figure>
</t>
<t>In H-PCE, the Ingress PCE PCE(1) can request the parent PCE to determine the Domain-Sequence and return it in the PCEP response, using the ERO Object. The ERO can contain an ordered sequence of subobjects such as AS and Area (OSPF/ISIS) subobjects. In this case, the Domain-Sequence appear as:</t>
<t>
<figure title="" suppress-title="false" align="left" alt="" width="" height="">
<artwork xml:space="preserve" name="" type="" align="left" alt="" width="" height=""><![CDATA[
+---------+ +---------+ +---------+ +---------+
|ERO | |Sub | |Sub | |Sub |
|Object | |Object | |Object | |Object |
|Header | |Area 2 | |Area 0 | |Area 4 |
| | | | | | | |
| | | | | | | |
+---------+ +---------+ +---------+ +---------+
+---------+ +---------+ +---------+ +---------+ +---------+
|ERO | |Sub | |Sub | |Sub | |Sub |
|Object | |Object AS| |Object | |Object | |Object |
|Header | |100 | |Area 2 | |Area 0 | |Area 4 |
| | | | | | | | | |
| | | | | | | | | |
+---------+ +---------+ +---------+ +---------+ +---------+
]]></artwork>
</figure>
</t>
<t>Note that, in the case of ERO objects, no new PCEP object type is required since the ordering constraint is assumed.</t>
</section>
<section title="Relationship to PCE Sequence" toc="default">
<t>Instead of a domain-sequence, a sequence of PCEs MAY be enforced by policy on the PCC, and this constraint can be carried in the PCEP path computation request (as defined in <xref target="RFC5886"/>).</t>
<t>Note that PCE-Sequence can be used along with domain-sequence in which case PCE-Sequence SHOULD have higher precedence in selecting the next PCE in the inter-domain path computation procedures. Note that Domain-Sequence IRO constraints should still be checked as per the rules of processing IRO.</t>
</section>
<section title="Relationship to RSVP-TE" toc="default">
<t><xref target="RFC3209"/> already describes the notion of abstract nodes, where an abstract node is a group of nodes whose internal topology is opaque to the ingress node of the LSP. It further defines a subobject for Autonomous Systems (AS) (2-Byte). </t>
<t><xref target="DOMAIN-SUBOBJ"/> extends the notion of abstract nodes by adding new subobjects for IGP Areas and 4-byte AS numbers. These subobjects MAY be included in Explicit Route Object (ERO), Exclude Route object (XRO) or Explicit Exclusion Route Subobject (EXRS).</t>
<t>In any case subobject type defined in RSVP-TE are identical to the subobject type defined in the related documents in PCEP.</t>
</section>
</section>
<section title="IANA Considerations" toc="default">
<section title="PCEP Objects" toc="default">
<t>The "PCEP Parameters" registry contains a subregistry "PCEP Objects". IANA is requested to make the following allocations from this registry.</t>
<t>
<figure title="" suppress-title="false" align="left" alt="" width="" height="">
<artwork xml:space="preserve" name="" type="" align="left" alt="" width="" height=""><![CDATA[
Object Name Reference
Class
10 IRO [RFC5440]
Object-Type
(TBA): Domain-Sequence [This I.D.]
]]></artwork>
</figure>
</t>
</section>
<section title="New Subobjects" toc="default">
<t>The "PCEP Parameters" registry contains a subregistry "PCEP Objects" with an entry for the Include Route Object (IRO), Exclude Route Object (XRO) and Explicit Route Object (ERO). IANA is requested to add further subobjects as follows:</t>
<t>
<figure title="" suppress-title="false" align="left" alt="" width="" height="">
<artwork xml:space="preserve" name="" type="" align="left" alt="" width="" height=""><![CDATA[
7 ERO
10 IRO
17 XRO
Subobject Type Reference
TBA 4 byte AS number [This I.D.]
TBA OSPF Area ID [This I.D.]
TBA IS-IS Area ID [This I.D.]
]]></artwork>
</figure>
</t>
</section>
<section title="Error Object Field Values" toc="default">
<t>The "PCEP Parameters" registry contains a subregistry "Error Types and Values". IANA is requested to make the following allocations from this subregistry</t>
<t>
<figure title="" suppress-title="false" align="left" alt="" width="" height="">
<artwork xml:space="preserve" name="" type="" align="left" alt="" width="" height=""><![CDATA[
ERROR Meaning Reference
Type
TBA "Unrecognized subobject" [This I.D.]
Error-Value: type code
]]></artwork>
</figure>
</t>
</section>
</section>
<section title="Security Considerations" toc="default">
<t>This document specifies a standard representation of Domain-Sequence and new subobjects, which MAY be used in inter-domain PCE scenarios as explained in other RFC and drafts. The new subobjects and Domain-Sequence mechanisms defined in this document allow finer and more specific control of the path computed by a cooperating PCE(s). Such control increases the risk if a PCEP message is intercepted, modified, or spoofed because it allows the attacker to exert control over the path that the PCE will compute or to make the path computation impossible. Therefore, the security techniques described in <xref target="RFC5440"/> are considered more important. </t>
<t>Note, however, that the Domain-Sequence mechanisms also provide the operator with the ability to route around vulnerable parts of the network and may be used to increase overall network security.</t>
</section>
<section title="Manageability Considerations" toc="default">
<section title="Control of Function and Policy" toc="default">
<t>Several local policy decisions should be made at the PCE. Firstly, the exact behavior with regard to desired inclusion and exclusion of domains must be available for examination by an operator and may be configurable. Second, the behavior on receipt of an unrecognized subobjects with the L or X-bit set should be configurable and must be available for inspection. The inspection and control of these local policy choices may be part of the PCEP MIB module.</t>
</section>
<section title="Information and Data Models" toc="default">
<t>A MIB module for management of the PCEP is being specified in a separate document <xref target="PCEP-MIB"/>. That MIB module allows examination of individual PCEP messages, in particular requests, responses and errors. The MIB module MUST be extended to include the ability to view the domain-sequence extensions defined in this document.</t>
</section>
<section title="Liveness Detection and Monitoring" toc="default">
<t>Mechanisms defined in this document do not imply any new liveness detection and monitoring requirements in addition to those already listed in <xref target="RFC5440"/>.</t>
</section>
<section title="Verify Correct Operations" toc="default">
<t>Mechanisms defined in this document do not imply any new operation verification requirements in addition to those already listed in <xref target="RFC5440"/>.</t>
</section>
<section title="Requirements On Other Protocols" toc="default">
<t>The Subobjects defined in this document SHOULD be supported by RSVP especially for per-domain path computation <xref target="RFC5152"/> where the domains need to encoded in the RSVP messages. <xref target="DOMAIN-SUBOBJ"/> extends the notion of abstract nodes by adding new subobjects for IGP Areas and 4-byte AS numbers.</t>
<t>Apart from this, mechanisms defined in this document do not imply any requirements on other protocols in addition to those already listed in <xref target="RFC5440"/>.</t>
</section>
<section title="Impact On Network Operations" toc="default">
<t>Mechanisms defined in this document do not have any impact on network operations in addition to those already listed in <xref target="RFC5440"/>.</t>
</section>
</section>
<section title="Acknowledgments" toc="default">
<t>We would like to thank Adrian Farrel, Pradeep Shastry, Suresh Babu, Quintin Zhao, Fatai Zhang, Daniel King, Oscar Gonzalez, Chen Huaimo, Venugopal Reddy, Reeja Paul and Sandeep Boina for their useful comments and suggestions.</t>
</section>
</middle>
<back>
<references title="Normative References">
<?rfc include="reference.RFC.2119.xml" ?>
<!--ISO-->
<reference anchor="ISO 10589">
<front>
<title>
Intermediate system to Intermediate system routing information
exchange protocol for use in conjunction with the Protocol for
providing the Connectionless-mode Network Service (ISO
8473)
</title>
<author fullname="ISO">
<organization >ISO</organization>
</author>
</front>
<seriesInfo name="ISO/IEC" value="10589:2002"/>
</reference>
</references>
<references title="Informative References">
<?rfc include="reference.RFC.3209.xml" ?>
<?rfc include="reference.RFC.3473.xml" ?>
<?rfc include="reference.RFC.3477.xml" ?>
<?rfc include="reference.RFC.4655.xml" ?>
<?rfc include="reference.RFC.4726.xml" ?>
<?rfc include="reference.RFC.4873.xml" ?>
<?rfc include="reference.RFC.4874.xml" ?>
<?rfc include="reference.RFC.4893.xml" ?>
<?rfc include="reference.RFC.5152.xml" ?>
<?rfc include="reference.RFC.5440.xml" ?>
<?rfc include="reference.RFC.5441.xml" ?>
<?rfc include="reference.RFC.5520.xml" ?>
<?rfc include="reference.RFC.5521.xml" ?>
<?rfc include="reference.RFC.5886.xml" ?>
<?rfc include="reference.RFC.6805.xml" ?>
<!--PCE-P2MP-PROCEDURES-->
<reference anchor="PCE-P2MP-PROCEDURES">
<front>
<title>PCE-based Computation Procedure To Compute Shortest Constrained P2MP Inter-domain Traffic Engineering Label Switched Paths (draft-ietf-pce-pcep-inter-domain-p2mp-procedures)</title>
<author initials="Q" surname="Zhao" fullname="Zhao Q">
<organization />
</author>
<author initials="D" surname="Dhody" fullname="Dhody D">
<organization />
</author>
<author initials="Z" surname="Ali" fullname="Ali Z">
<organization />
</author>
<author initials="T" surname="Saad," fullname="Saad T">
<organization />
</author>
<author initials="S" surname="Sivabalan," fullname="Sivabalan S">
<organization />
</author>
<author initials="R" surname="Casellas" fullname="Casellas R">
<organization />
</author>
<date month="February" year="2012" />
</front>
</reference>
<!--PCEP-MIB-->
<reference anchor="PCEP-MIB">
<front>
<title>PCE communication protocol(PCEP) Management Information Base</title>
<author initials="A" surname="Koushik" fullname="Koushik A">
<organization />
</author>
<author initials="S" surname="Emile" fullname="Emile S">
<organization />
</author>
<author initials="Q" surname="Zhao" fullname="Quintin Zhao">
<organization />
</author>
<author initials="D" surname="King" fullname="Daniel King">
<organization />
</author>
<author initials="J" surname="Hardwick" fullname="Hardwick J">
<organization />
</author>
<date month="July" year="2012" />
</front>
</reference>
<!--PCE-P2MP-PER-DEST-->
<reference anchor="PCE-P2MP-PER-DEST">
<front>
<title>Supporting explicit inclusion or exclusion of abstract nodes for a subset of P2MP destinations in Path Computation Element Communication Protocol (PCEP). (draft-dhody-pce-pcep-p2mp-per-destination)</title>
<author initials="D" surname="Dhody" fullname="Dhody D">
<organization />
</author>
<author initials="U" surname="Palle" fullname="Palle U">
<organization />
</author>
<author initials="V" surname="Kondreddy" fullname="Kondreddy V">
<organization />
</author>
<date month="Oct" year="2012" />
</front>
</reference>
<!--DOMAIN-SUBOBJ-->
<reference anchor="DOMAIN-SUBOBJ">
<front>
<title>Domain Subobjects for Resource ReserVation Protocol - Traffic Engineering (RSVP-TE). (draft-dhody-ccamp-rsvp-te-domain-subobjects)</title>
<author initials="D" surname="Dhody" fullname="Dhody D">
<organization />
</author>
<author initials="U" surname="Palle" fullname="Palle U">
<organization />
</author>
<author initials="V" surname="Kondreddy" fullname="Kondreddy V">
<organization />
</author>
<author initials="R" surname="Casellas" fullname="Casellas R">
<organization />
</author>
<date month="Sept" year="2012" />
</front>
</reference>
</references>
</back>
</rfc>| PAFTECH AB 2003-2026 | 2026-04-23 14:32:51 |