One document matched: draft-ietf-pce-pcep-domain-sequence-06.xml
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<rfc ipr="trust200902" category="exp" docName="draft-ietf-pce-pcep-domain-sequence-06" 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</organization>
<address>
<postal>
<street>Leela Palace</street>
<city>Bangalore</city>
<region>Karnataka</region>
<code>560008</code>
<country>INDIA</country>
</postal>
<email>dhruv.ietf@gmail.com</email>
</address>
</author>
<author initials="U" surname="Palle" fullname="Udayasree Palle">
<organization>Huawei Technologies</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</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="October" year="2014" />
<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.
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
Interior Gateway Protocol (IGP) area or an Autonomous Systems (AS). 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
to be used by Path Computation Elements (PCEs) to compute inter-domain shortest
constrained paths across a predetermined sequence of domains . 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. Also for inter-domain point-to-multi-point (P2MP)
tree computation, <xref target="RFC7334"/> assumes the domain-tree is known
in priori.</t>
<t>The list of domains (domain-sequence) in a point-to-point (P2P) path or a
point-to-multipoint (P2MP) tree is usually a constraint in the path computation
request. A PCE determines the next PCE to forward the request based on the domain-sequence.
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 (H-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 H-PCE. </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 System (AS)
(albeit with a 2-Byte AS number) 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 as per
<xref target="RFC4893"/>).</t>
<t>Further, the domain
identifier may simply act as delimiter to specify where the domain boundary
starts and ends.</t>
<t>This is a companion document to Resource ReserVation Protocol -
Traffic Engineering (RSVP-TE)
extensions for the domain identifiers <xref target="DOMAIN-SUBOBJ"/>. </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>
<t hangText="XRO:">Exclude Route Object</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 AS or an 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 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.
The subobjects in IRO 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. The subobjects in XRO 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. 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 using ERO.</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[
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[
Type Subobject
TBD1 Autonomous system number (4 Byte)
TBD2 OSPF Area id
TBD3 ISIS Area id
]]></artwork>
</figure>
<section title="Autonomous system" toc="default" >
<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>
<list style="hanging">
<t hangText="L:">The L bit is an attribute of the subobject
as defined in <xref target="RFC3209"/> and usage in IRO subobject
updated in <xref target="IRO-UPDATE"/>.</t>
<t hangText="Type:">(TBD1 by IANA) indicating a 4-Byte AS Number.</t>
<t hangText="Length:">8 (Total length of the subobject in bytes).</t>
<t hangText="Reserved:">Zero at transmission, ignored at receipt.</t>
<t hangText="AS-ID:">The 4-Byte AS Number. Note that if 2-Byte 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>
</list>
</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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|L| Type | Length | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| OSPF Area Id (4 bytes) |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
]]></artwork>
</figure>
</t>
<t>
<list style="hanging">
<t hangText="L:">The L bit is an attribute of the subobject as
defined in <xref target="RFC3209"/> and usage in IRO subobject
updated in <xref target="IRO-UPDATE"/>.</t>
<t hangText="Type:">(TBD2 by IANA) indicating a 4-Byte OSPF Area ID.</t>
<t hangText="Length:">8 (Total length of the subobject in bytes).</t>
<t hangText="Reserved:">Zero at transmission, ignored at receipt.</t>
<t hangText="OSPF Area Id:">The 4-Byte OSPF Area ID.</t>
</list>
</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="ISO10589"/>. 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
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
|L| Type | Length | Area-Len | Reserved |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
| |
// IS-IS Area ID //
| |
+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+-+
]]></artwork>
</figure>
</t>
<t>
<list style="hanging">
<t hangText="L:">The L bit is an attribute of the subobject as defined
in <xref target="RFC3209"/> and usage in IRO subobject
updated in <xref target="IRO-UPDATE"/>.</t>
<t hangText="Type:">(TBD3 by IANA) indicating IS-IS Area ID.</t>
<t hangText="Length:">Variable. As per <xref target="RFC3209"/>, the
total length of the subobject in bytes, including the L, Type and Length
fields. The Length MUST be at least 4, and MUST be a multiple of 4.</t>
<t hangText="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 hangText="Reserved:">Zero at transmission, ignored at receipt.</t>
<t hangText="IS-IS Area Id:">The variable-length IS-IS area identifier.
Padded with trailing zeroes to a four-byte boundary.</t>
</list>
</t>
</section>
</section>
<section title="Update in IRO specification" toc="default" anchor="SEC_IRO_UPD">
<t><xref target="RFC5440"/> describes IRO as an optional object used to specify
that the computed path MUST traverse a set of specified network
elements. It further state that the L bit of such sub-object has
no meaning within an IRO. It did not mention if IRO is an ordered or
un-ordered list of sub-objects. </t>
<t>An update to IRO specification <xref target="IRO-UPDATE"/> makes IRO as
an ordered list as well as support for loose bit (L-bit).</t>
<t>The use IRO for domain-sequence assumes the updated specification for
IRO as per <xref target="IRO-UPDATE"/>.
</t>
</section>
<section title="IRO for domain-sequence" toc="default">
<t>Some subobjects for IRO are defined in <xref target="RFC3209"/>,
<xref target="RFC3473"/>, <xref target="RFC3477"/> and
<xref target="RFC4874"/>, further some new subobjects
related to Domain-Sequence are also added in this document as mentioned
in <xref target="sec_iro_sub"/>. </t>
<t>The subobjects for IPv4, IPv6 and unnumbered
Interface ID can be 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 domain identifiers in
the domain-sequence.</t>
<t>The IRO MAY have both intra-domain (from the context of the ingress PCC)
and inter-domain (domain-sequence) subobjects in a sequence in which they
must be traversed in the computed path.</t>
<t>Thus an IRO comprising of subobjects that represents a domain-sequence
may constraints or define
the domains involved in an inter-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 an IRO to encode the Domain-Sequence, that the
cooperating PCEs should compute an inter-domain shortest constrained paths across the
specified sequence of domains.</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>If a PCE
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 TBD4 "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>PCE 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 reply message (PCRep)
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 PCRep, PCE MAY also supply IRO (with domain sequence information)
with the NO-PATH object indicating
that the set of
elements (domains) of the request's IRO prevented the PCEs
from finding a path.</t>
<t>The Subobject types for domains (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>The Subobjects representing an internal node, a Boundary Node or an
Inter-AS-Link MAY influence the selection of the path as well.</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
TBD1 Autonomous system number (4 Byte)
TBD2 OSPF Area id
TBD3 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>
<list style="hanging">
<t hangText="0:">indicates that the AS specified MUST be excluded from the
path computed by the PCE(s).</t>
<t hangText="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>
</list>
</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>
<list style="hanging">
<t hangText="0:">indicates that the OSFF Area specified MUST be excluded
from the path computed by the PCE(s).</t>
<t hangText="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>
</list>
</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="ISO10589"/>. 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>
<list style="hanging">
<t hangText="0:">indicates that the ISIS Area specified MUST be excluded
from the path computed by the PCE(s).</t>
<t hangText="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>
</list>
</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 TBD4 "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
TBD1 Autonomous system number (4 Byte)
TBD2 OSPF Area id
TBD3 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">
<t>The examples in this section are for illustration purposes only; to show
how the new subobjects may be encoded.</t>
<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 |
+------------------+ +--------------------+
]]></artwork>
</figure>
</t>
<t>AS Number is 100.</t>
<t>This could be represented in the <IRO> 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 |
|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 |
| | | | | | | | | |
| | | | | | | | | |
+---------+ +---------+ +---------+ +---------+ +---------+
]]></artwork>
</figure>
</t>
<t>AS is optional and it MAY be skipped. PCE should be able to
understand both notations.</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 | |
| +------+ | | +------+ |
| | | |
+------------------------+ | |
+---------------------------------+
]]></artwork>
</figure>
</t>
<t>Both AS are made of Area 0.</t>
<t>This could be represented in the <IRO> 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 |
|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 |
| | | | | | | | | |
| | | | | | | | | |
+---------+ +---------+ +---------+ +---------+ +---------+
]]></artwork>
</figure>
</t>
<t>Area subobject is optional and it MAY be skipped. PCE should be
able to understand both notations. </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>The Domain-Sequence can be carried in the IRO as shown below:</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 | |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 neighbouring domains. </t>
</section>
<section title="P2MP" toc="default">
<t>In case of inter-domain P2MP path computation,
(Refer <xref target="RFC7334"/>) 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>
</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
PCReq message (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 AS but with a 2-Byte AS Number. </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) in RSVP-TE.</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="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
TBD1 4 byte AS number [This I.D.]
TBD2 OSPF Area ID [This I.D.]
TBD3 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
TBD4 "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>In case of per-domain path computation <xref target="RFC5152"/>,
where the full path of an inter-domain TE LSP cannot be or is not
determined at the ingress node, and signaling message may use
domain identifiers. The Subobjects defined in this document
SHOULD be supported by RSVP-TE. <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 Sandeep Boina and Avantika
for their useful comments and suggestions.</t>
</section>
</middle>
<back>
<references title="Normative References">
<?rfc include="reference.RFC.2119.xml" ?>
<?rfc include="reference.RFC.5440.xml" ?>
<?rfc include="reference.RFC.5441.xml" ?>
<?rfc include="reference.RFC.5521.xml" ?>
<?rfc include="reference.RFC.6805.xml" ?>
</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.5520.xml" ?>
<?rfc include="reference.RFC.5886.xml" ?>
<?rfc include="reference.RFC.7334.xml" ?>
<!--PCEP-MIB-->
<reference anchor="PCEP-MIB">
<front>
<title>PCE communication protocol(PCEP) Management Information Base. (draft-ietf-pce-pcep-mib)</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="September" year="2014" />
</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="September" year="2014" />
</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="July" year="2014" />
</front>
</reference>
<!--IRO-SURVEY-->
<reference anchor="IRO-SURVEY">
<front>
<title>Informal Survey into Include Route Object (IRO) Implementations in Path
Computation Element communication Protocol (PCEP). (draft-dhody-pce-iro-survey-01)</title>
<author initials="D" surname="Dhody" fullname="Dhody D">
<organization />
</author>
<date month="October" year="2014" />
</front>
</reference>
<!--IRO-UPDATE-->
<reference anchor="IRO-UPDATE">
<front>
<title>Update to Include Route Object
(IRO) specification in Path Computation Element communication
Protocol (PCEP. (draft-dhody-pce-iro-update-00)</title>
<author initials="D" surname="Dhody" fullname="Dhody D">
<organization />
</author>
<date month="October" year="2014" />
</front>
</reference>
<!--ISO-->
<reference anchor="ISO10589">
<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>
<date month="" year="1992"/>
</front>
<seriesInfo name="ISO/IEC" value="10589:2002"/>
</reference>
</references>
</back>
</rfc>
| PAFTECH AB 2003-2026 | 2026-04-23 14:29:26 |